higher chemistry unit 2 nature’s chemistry. what you should know… that molecular structure and...

Higher Chemistry

Unit 2

Nature’s Chemistry

What you should know…• That molecular structure and physical properties of hydrocarbons are related.

• The names, molecular and structural formula of straight and branched chain alkanes, alkenes and cycloalkanes.

• How to identify isomers and draw their structural formulae.

• What is meant by saturated and unsaturated carbon compounds and how they can be distinguished.

• Addition reactions

• The name of the functional group present in alcohols and the properties of alcohols

• The names, molecular and structural formula of straight and branched chain alcohols

• The name of the functional group present in carboxylic acids and the properties of carboxylic acids

• The names, molecular and structural formula of straight and branched chain carboxylic acids

Originally, chemical compounds were divided into 2 classes:Inorganic or Organic

Organic compounds were derived from living things. It was believed that they contained a ‘vital force’ and couldnot be made from inorganic compounds (non-living sources).

Organic chemistry is the study of carbon compounds

Organic Chemistry

•Organic molecules may be as simple as methane, CH4

or as complicated as cholesterol

HO

L.I. To learn about esters Section 1 (a)

S.C. By the end of this lesson you should be able to…

• State the name ending present in all esters.• State the name of the functional group present in an ester.• Draw the functional group present in an ester.• State the two types of molecules which contribute to the name

of an ester.• Draw the structural formula for an ester when given its name.• Draw the structural formula for an ester when given the name of

the parent alcohol and carboxylic acid.• Describe the characteristic smell of an ester.

Fruit Flavours (a) Esters

An ester can be identified by the name endings ‘-yl –oate’.

Esters contain the carboxylate functional group (–COO-)…

Carboxylate group

C O

O

Naming Esters

An ester can be named given the name of the parent alcohol and carboxylic acid or from shortened and full structural formulae.

The parent alkanol gives the start of the name ending in -yl. The parent acid gives the second part of the name ending in -oate.

So the ester formed by reacting ethanol with propanoic acid would be ethyl propanoate…

• Workbook activities

Name of alcohol Name of carboxylic acid

Name of ester Full structural formula of ester

Ethanol Propanoic acid Ethyl propanoate

Propanol

Methanoic acid Propyl methanoate

Methanol

Butanoic acid Methyl butanoate

Propanol

Ethanoic acid Propyl ethanoate

Butanol

Methanoic acid Butyl methanoate

Ethanol

Butanoic acid Ethyl butanoate

1. Methanol + Ethanoic acid Methyl ethanoate

+

2. Butan-1-ol + Ethanoic acid Butyl ethanoate

+

L.I. To learn about making esters (b)


• State the name of the reaction in which esters are formed from carboxylic acids and alcohols.

• State the definition of a condensation reaction.• State how an ester linkage can be formed by the condensation

reaction between a hydroxyl group and a carboxyl group, using full structural formulae.

(b) Making Esters

• In condensation reactions small molecules join together to form a bigger molecule by the elimination of water.

• Esters are formed by the reaction of a carboxylic acid and an alcohol

• Carboxylic acids contain the functional group carboxyl (-COOH)

• Alcohols contain the functional group hydroxyl (-OH)

Acids and carboxylic acids can react by condensation reactions to form esters.

Alcohol + Acid ⇌ Ester + Water

R O H H OC R'

O

+ R OC R'

O+ H2O

alcohol carboxylic acid ester

The ester link is formed by the reaction of a hydroxyl group with a carboxyl group. The reaction is reversible - an equilibrium is set up.

If the water is removed the equilibrium is shifted to the side of the products . Concentrated sulphuric acid has a high affinity for water and is used to remove it and shift the equilibrium to the right.

Carry out the experiment to make an ester in the lab (Workcard 1) …

What is the purpose of the wet paper towel? Why is the reaction mixture heated in a water bath? Why is the reaction mixture poured onto sodium

hydrogen carbonate solution? Observation:

The paper towel acts as a condenser to prevent volatile gases escaping (it cools them down).

To increase the temperature of the reaction and make the reaction happen faster. A Bunsen cannot be used as the reactants are flammable.

It was added to the products to neutralise the sulphuric acid and any excess carboxylic acid.

The product had a strong smell and formed a layer over the water since esters are immicible in water.

Workbook activity…

Carboxylic Acid

Alcohol Name of ester Shortened structural formula of ester

Smell of ester

Ethanoic acid Pentanol Pentyl ethanoateCH3COO(CH2)4CH3

banana

Ethanoic acid

Ethanol

Ethyl ethanoate

CH3COOC2H5

fruity odour

Methanoic acid Ethanol Ethyl methanoate

HCOOCH2CH3

rum-like odour

Methanoic acid

Propanol Propyl methanoate HCOOCH2CH2CH3

plum odour

L.I. To learn about the uses of esters (c)


• Describe the three main uses of esters.

(c) Uses of esters

Esters are oily liquids with generally very pleasant fruity smells and have a range of uses.

Many esters are used as flavourings, in perfumes and as solvents.

Workbook activity

Name Shortened Structural Formula

Odour/Flavour

Pentyl ethanoate CH3COO(CH2)4CH3

Banana

Octyl ethanoate CH3COO(CH2)7CH3

Orange

Methyl Butanoate

CH3CH2CH2COOCH3

Pineapple

3-Methylbutyl Butanoate CH3(CH2)2COO(CH2)2CH(CH3)2

Apple

Propyl ethanoate CH3COOCH2CH2CH3

Pear

Methyl-1-butyl ethanoate

CH3COOCH(CH3)C4H9

Banana

2-Methylpropyl methanoate

HCOOCH2CH(CH3)CH3

Raspberry

Pentyl butanoate C3H7COOC(CH2)4CH3

Apricot, Strawberry

Benzyl ethanoate

CH3COOCH2C6H5

Peach, flowers

Ethyl methanoate

HCOOCH2CH3

Rum

Methyl 2-aminobenzoate

C6H4(NH2)COOCH3

Grapes

Benzyl butanoate C3H7COOCH2C6H5

Cherry

Uses of esters as solvents

Some of the smaller esters are quite volatile and are used as solvents in adhesives, inks and paints – pentyl ethanoate is used in nail varnish for example.

Ethyl ethanoate is one of a number of solvents used to extract caffeine from coffee and tea. De-caffeinated products produced with ethyl ethanoate are often described on the packaging as "naturally decaffeinated" because ethyl ethanoate is a chemical found naturally in many fruits.

Caffeine (C8H10N4O2) is an example of a class of compounds called alkaloids which are produced by plants.

The name alkaloid means “alkali-like”, where alkali is a base and hence refers to these basic properties.

Caffeine is more soluble in the organic solvent ethyl ethanoate than in water, so we will extract caffeine into the organic solvent to separate it from glucose, tannins, and other water soluble compounds using a separating funnel.

The ethyl ethanoate portions can be combined and the ethyl ethanoate removed by evaporation to leave the caffeine

Workbook activity

VOC stands for ‘Volatile Organic Compounds’.

Legislation aims to prevent or reduce the direct and indirect effects of emissions of volatile organic compounds (VOCs) on the environment and human health, by setting emission limits for such compounds and laying down operating conditions for installations using organic solvents.

Why?

The emissions of volatile organic compounds * (VOCs) in the atmosphere contribute to the formation of the tropospheric ozone (ozone in the lower atmosphere). Large quantities of this ozone may be harmful to people, vegetation, forests and crops. Sensitive people may suffer irritation of the throat and eyes, as well as respiratory difficulties. Tropospheric ozone is also a greenhouse gas.

L.I. To learn about the hydrolysis of esters (d)


• Describe how an ester can be hydrolysed using full structural formulae.

• State the definition of a hydrolysis reaction.• State the name of the products formed by the hydrolysis of an ester.

In hydrolysis reactions large molecules are broken down into smaller molecules by water.

Esters can be hydrolysed to produce the parent ................... .......... and the parent .................... .

ESTER + WATER ⇌ ACID + ALCOHOL

An alkali is often used to catalyse the reaction and the mixture heated under reflux.

If sodium hydroxide is used a sodium salt of the acid is formed. If this is reacted with a strong acid (eg. Hydrochloric acid) the acid can be displaced from the salt

HCOO- Na+ + HCl HCOOH + NaCl

Sodium + hydrochloric methanoic + sodiummethanoate acid acid chloride

Carry out the experiment to hydrolyse ethyl benzoate (Workcard 2)

Use the equation below to calculate the theoretical mass of benzoic acid expected when 0.033 moles (5g) of ethyl benzoate is hydrolysed.

C6H5COOC2H5 + H2O ⇌ C6H5COOH + C2H5OH

Mass of filter paper (g)

Mass of filter paper + benzoic acid (g)

Mass of benzoic acid formed (g) (actual mass)

Calculate the % Yield using the following equation…

% yield = actual mass x 100 theoretical mass

L.I. To learn about edible fats and oils Section 2 (a)


• State why fats and oils are an essential part of a healthy diet.• Describe the formation and structure of fats and oils.• Explain using full structural formulae how fats and oils are formed.• State the main difference between the structure of saturated and

unsaturated fatty acids.

Natural oils have vegetable and marine (fish) origins Natural fats have ………………………, …………………… or ………………………… origins

Workbook Activity

Name of fat or oil

Source Animal, vegetable or

marineSunflower oil Linseed oil Suet Cod liver oil Lard Castor oil Palm oil Rapeseed oil

Fats and oils are an essential part of the diet. They provide the body with energy.

Fats and oils are a more concentrated source of energy than .................................

Name of fat or oil

Source Animal, vegetable or

marineSunflower oil Sunflower seeds VegetableLinseed oil Flax seeds Vegetable

Suet Beef Animal Cod liver oil Cod fish Marine

Lard Pork Animal Castor oil Castor plant VegetablePalm oil Fruits of palm oil

treesVegetable

Rapeseed oil Rapeseed plant Vegetable

Carry out the experiment to test the unsaturation of fats and oils (Workcard 3)

What does unsaturated mean?

Which sample is the most saturated and which is the most unsaturated?

This comparison is only approximate. How could the method be improved?

Solids fats tend to be saturated

Liquid oils tend to be unsaturated

Fats and oils are naturally occurring esters of the alcohol glycerol and long chain carboxylic acids.

Long chain carboxylic acids are often called ‘fatty acids’

R1, R2, R3 are long carbon chains which can be the same or different

glycerol

Glycerol is a trihydric alcohol – it has three alcohol groups the correct name is .................................... Fats and Oils are formed by combination of ..... moles of fatty acids to .......... mole of glycerol - a

triglyceride. There are .................. ester linkages in the one molecule.

Propan-1,2,3-triol

3 1

3

L.I. To learn about the melting points of fats and oils Section 2 (b)


• State and explain the difference in melting points of fats and oils, in terms of structure, close packing and strength of intermolecular bonds.

• Fats are .................... at room temperature while oils are ...................... .

• The properties of a fat or an oil depend on the fatty acids which are combined with the

glycerol in each triglyceride.

• Most fats and oils in nature are mixtures of triglycerides in which the fatty acid

molecules may or may not be identical. • Fatty acids are saturated or unsaturated straight chain carboxylic acids. They

contain an

even number of carbon atoms and range in size from C4 to C24 carbon atoms, but mainly C16

and C18.

solid liquid

Workbook activity

Complete the table below…

Fatty acid FormulaSaturated or unsaturated

palmitic acid

stearic acid

linoleic acid

oleic acid

Fatty acid FormulaSaturated or unsaturated

palmitic acid

C16H32O2

Saturated

stearic acid C18H36O2

Saturated

linoleic acid C18H32O2

Unsaturated

oleic acid C18H34O2 Unsaturated

Fat and oil molecules are roughly ‘tunning fork’ in shape with three limbs being hydrocarbon chains.

If the chains are saturated, the molecules pack neatly together even at quite high temperature

Fat – higher melting point Oil – lower melting point

If the chains contain one or more double bonds the zig-zag chains become more distorted and the close packing of the molecules is less easy.

How will the close packing of fat molecules affect the strength of the Van der Waal’s (intermolecular) bonds?

What effect will this have on the melting point?

The more closely the molecules can pack together, the stronger the van der Waals forces.

The stronger the van der Waals forces, the more energy is needed to break them and the melting point will be higher.

L.I. To learn about the function of proteins Section 3 (a)


• Describe the role of proteins in the body.

We need protein for ................. and ............... . Foods such as meat and fish are rich in protein.

Proteins are the major structural materials of animal tissues.

Proteins are also involved in the maintenance and regulation of life processes.

Proteins can be classified as fibrous or globular.

growth repair


Give examples of fibrous proteins…

Keratin found in hair and nails

Collagen and elastin found in connective tissue in the body.

Globular proteins have the spiral chains folded into compact units. Globular proteins are involved in the maintenance and regulation of life processes and include enzymes and many hormones.

Fibrous proteins are long and thin and are the major structural materials of animal tissue.


Give examples of globular proteins

Albumin found in blood plasma

Haemoglobin found in blood which carries oxygen around the body

Proteins are chemicals containing the element nitrogen.

Carry out the experiment to heat proteins with soda lime (Workcard 4)

Protein Effect on moist pH paper

When a protein is heated strongly in the presence of soda lime (a mixture of calcium and sodium

hydroxide) an unpleasant smelling alkaline gas is produced which turns moist pH paper blue.

These gases are amines or ammonia - chemicals which contain nitrogen.

Enzymes are proteins, which act as biological catalysts.

They are specific to particular chemical reactions e.g. the enzyme pepsin only catalyses the hydrolysis of proteins and not any other chemical reaction

Certain sequences of amino acids form a region known as the active site. The shape of the active site allows specific reactants known as substrates to attach, like a lock and key.

Incorrect substrates are unable to fit the shape of the active site and are not changed.

Enzyme function is therefore related to the molecular shapes of proteins

Carry out the experiment to find out if pH affects enzyme activity (Workcard 5)

‘normal reaction’ Enzyme reaction Enzyme reaction

Rate

Rate Rate

Temperature

Temperature

pH

If the temperature rises above a critical level the shape of the enzyme molecule becomes irreversibly altered although the peptide links remain intact.

This means that the enzyme is unable to function.

The enzyme is said to be .............................. .

All proteins, not just enzymes, can be denatured by temperature and pH.

1. 2. 3.

denatured

L.I. To learn about amino acids Section 3 (b)


• State the name of the building blocks from which protein molecules are formed.

• Describe the structure of amino acid molecules and how they differ to produce 20 common naturally occurring amino acids.

• Explain why some amino acids are known as essential amino acids.

Amino acids contain an amino group (-NH2) at one end and an acid group (-COOH) at the other end of the molecule. The majority of amino acids found in proteins are of the type

R represents a carbon side chain which may even contain the elements nitrogen and sulphur.

Name R (side chain)

Name R (side chain)

Glycine -H Aspartic Acid -CH2 COOH

Alanine -CH3 Methionine -CH2 CH2 S CH3

Valine -CH CH3 CH3 Phenylalanine -CH2 C6H5

There are 20 or so amino acids which go into making up protein.

The body cannot make all the amino acids required for body proteins and is dependent on dietary protein for the supply of certain ............................. amino acids.essential

L.I. To learn about amide links Section 3 (c)


• State the type of reaction in which many amino acid molecules can link together to form a protein molecule.

• Explain using full structural formulae how an amide (peptide) linkage can be formed by a condensation reaction between amino acids.

• State how the diverse range of proteins needed to fill the different roles in the body is produced from just 20 amino acids.

Proteins specific to body’s needs are built up within the body.

Proteins are ........................... polymers formed by combining amino acids to form long chain molecules of

maybe several thousand amino acid units long.Workbook activity…

The following amino acids react to form a tripeptide. Draw the structure of the product molecule below.

condensation

When amino acids join together an amide link (or peptide link) is formed and water is eliminated.

The amide link is formed by the reaction of an amino group with a carboxyl group.

The structure of a section of protein is based on the constituent amino acids.

The sequence by which the amino acids are joined differs in different protein molecules.

The sequences of amino acids are controlled from information in the nucleus of the cell.

Less complex than the proteins are the peptides.

A tripeptide has 3 amino acid units.

A shorter chain of amino acids, up to 100 units or so is often referred to as a polypeptide.

L.I. To learn about the hydrolysis of proteins Section 3 (d)


• State and explain how proteins can be hydrolysed (digested) to produce amino acids.

• Draw the full structural formulae of the amino acids obtained from the hydrolysis of a given section of a protein.

• Explain how the amino acids present in a sample of hydrolysed protein can be analysed and identified.

During digestion enzymes hydrolyse the proteins in food to amino acids. These can then pass through the

gut wall into the blood stream.

In the stomach, the enzyme pepsin starts the digestion of protein by hydrolysing to smaller polypeptides.

Further enzymes in the gut continue the hydrolysis to the constituent amino acids.

In hydrolysis large molecules are broken down into smaller molecules by water.

PROTEIN + WATER → AMINO ACIDSWorkbook activity

Draw the product molecules as this tripeptide molecule is hydrolysed.

By comparing the position of the spots of the known amino acids with that of the hydrolysed protein, the amino acids in the protein can be identified.

In the lab a protein can be hydrolysed back to its constituent amino acids by refluxing with concentrated hydrochloric acid for several hours.

Amino acids can be identified by the use of paper (or thin layer) chromatography.

A piece of chromatography paper is spotted with some amino acids suspected as being present and also with the hydrolysed protein.

L.I. To learn about flavour in food Section 4 (a)


• Explain why volatile molecules are important in flavour.

• Identify the functional groups present in flavour molecules and explain whether they are likely to be water soluble or oil soluble.

• Make predictions about the boiling point (and volatility) of flavour molecules based on molecular size and the functional groups present.

Many of the flavours in foods are due to the presence of volatile molecules. Normally these molecules

are trapped in the cell. However, during cooking the cell walls can be broken by moisture within the cell

evaporating and rupturing the walls. Also chemicals can damage the walls which are made of a structural

carbohydrate called cellulose. Volatile flavour molecules can then leave the food and enter the air. Also some may dissolve in the

cooking liquid and be lost. So the method and time of cooking is important in preserving flavours.

Flavour molecules can be water-soluble or oil/fat-soluble. You can preserve the flavour by using water for

cooking foods that contain oil/fat-soluble flavours such as green beans and broccoli, and using oil/fat to

cook foods that are richer in water-soluble flavours such as asparagus. Overcooking food using either

method will cause more flavour to be lost.

To recognise flavours we use our sense of smell and sense of taste. Try eating flavoured food without

looking at it, while pinching your nose. It is not as simple are you might think. There are at least five basic

taste qualities: sweet, sour, bitter, salty, and umami. (Umami, or savoury, is the taste we comes from

glutamate, found in chicken broth, meat extracts, and some cheeses.) Our nose can detect more than

10,000 different smells. If there is hydrogen bonding between the molecules responsible to smell, this

will reduce the volatility of the molecule.

To complicate matters some chemical reactions that take place during cooking can result in new,

desirable flavours. The chemistry here is complicated but a simple example to illustrate that more

desirable flavours appear happens when bread is toasted. Bread contains a carbohydrate and its

carbonyl group (>C=O) reacts with amino groups (-NH2) in protein to make this desirable smell.

The functional groups present in flavour molecules will give an indication whether they are likely to

be water or oil soluble. The size and functional groups present can be taken into account in

predicting their relative boiling point and hence probable volatility. The important feature here is

whether the functional groups present can hydrogen bond with water, making them water

soluble, or whether they are unable to hydrogen bond with water in which case they will be fat-

or oil-soluble.

Some functional groups are included in the table below for reference. However, the presence of a

particular functional group is no guarantee of the substance being water- or oil-soluble. e.g. a long

hydrocarbon chain (which is non-polar) with a single polar group would be unlikely to be able to

hydrogen bond with water and would make the molecule more likely to be oil-soluble. Functional group name

Functional group structure

Can it form hydrogen bonds?

Water- or oil-soluble

Alkane C-C No oil-soluble

Alkene C=C No oil-soluble

Alkyne C=C No oil-soluble

Hydroxyl -O-H Yes water-soluble

Carbonyl >C=O Yes water-soluble

Carboxylic acid -COOH or Yes water-soluble

Aldehyde -CHO or Yes water-soluble

Amino -NH2 or Yes water-soluble

Phenyl C6H5- No oil-soluble

Amide -CONH- or Yes water-soluble

Ester -COO- or Yes water-soluble

As a general rule, if the molecule contains only C and H atoms is will be non-polar, while if it also

contains O or and N atoms it is more likely to be polar. However, the non-polarity of long hydrocarbon

chains/rings can cancel the effect of a single polar group and make the molecule behave as non-polar. Workbook activity…

The molecular structures below represent the formulae of some common flavours. Examine them and complete the table to show if they are likely to be water or oil soluble.

Molecular Name Flavour Water soluble orOil soluble

Functional groups present in molecule

Nona-2,6-dienal

Cucumber

4-hydroxy-2,5-dimethylfuran-3-one

Strawberry

Propyl pentanoate

Pineapple

Limonene

Orange

1-methyl-1-butylethanoate

Banana

3,7-dimethyloct-2,6-dienal

Lemons

2-methoxy-3-isobutyl-pyrazine

Green peppers

Vanillin

Vanilla

Methyl anthranilate

Pineapple

In general, molecules with a molecular mass of under 300 are likely to be volatile whereas much larger

molecules are not likely to be volatile. The type of bonding present will also have a significant influence

on how volatile the molecule is likely to be. If hydrogen bonding is not present between molecules then

these molecules will be more volatile due to the weak intermolecular forces present.

Watch Heston’s cooking video clips

L.I. To learn about changes in protein structure upon heating Section 4 (b)


• Explain the importance of intermolecular bonding in protein structure.

• State the difference between fibrous and globular proteins.

• State the changes that take place on heating proteins and relate this to the texture of foods such as eggs and meat.

Proteins are complex molecules made from long, amino acid chains which are also branched. The chains are

held together by intermolecular bonding between the side chains of the constituent amino acids. Hydrogen

bonds occur between the amide links and between other groups present in the molecule. Proteins form

three-dimensional structures which are either sheets, spirals or coils. When proteins are heated, during cooking, these intermolecular bonds are broken allowing the proteins to

change shape (denature). These changes alter the texture of foods. For example, egg whites contain many molecules of a globular protein called albumen. When an egg is boiled

or fried, the protein structure is irreversibly changed and a solid is made. During cooking, the protein is

denatured and the protein chains unwind and, as they can now form intermolecular bonds with

neighbouring albumen molecules, a network of interconnected proteins forms causing the egg white to

solidify.

Collagen molecule

The structure of meat changes when cooked. Different temperatures are required for cooking meats with

different levels of connective tissue. Joints containing a lot of connective tissue become tender if cooked

at over 60oC as the collagen forming the tough connective tissue, denatures. The tender lean meat found

in cuts such as fillet steaks have less connective tissue and should not be cooked at too high a

temperature, because in this case the protein molecules start to bunch together resulting in the meat

becoming tougher.


Carry out research and write a short note on the chemistry of browning foods. Use the ipads to help you

answer the following questions... What are Maillard reactions? What reaction takes place during caramelisation? Why do apples brown?

L.I. To learn about the oxidation of alcohols Section 5 (a)


• Draw the structural formula of branched chain alcohols when given the name.

• State the name of branched chain alcohols when given the structural formula.

• State the molecular formula of branched chain alcohols when given the name or structural formula.

• State how to classify alcohols as primary, secondary or tertiary.

• State the product formed when primary alcohols are oxidised.

• State the product formed when secondary alcohols are oxidised.

• State what happens when attempting to oxidise a tertiary alcohol.

• State what is meant by oxidation in terms of the oxygen to hydrogen ratio.

• State the name of common oxidising agents used in the lab and describe the colour changes which occur.

• State the ion equations associated with the oxidation of primary and secondary alcohols.

• State what is meant by the terms ‘dihydric’ and ‘diol’.

• State what is meant by the terms ‘trihydric’ and ‘triol’.

•Draw the structural formulae of dihydric and trihydric alcohols when given the name.

•State the effect of hydrogen bonding on the properties of diols and triols.

Alcohols can be classified according to the position of the –OH group.

• In a primary (1°) alcohol, the carbon which carries the -OH group is only attached to one alkyl group (chain of carbon atoms). Methanol, CH3OH, is counted as a primary alcohol even though there are no alkyl groups attached to the carbon with the -OH group on it.

• In a secondary (2°) alcohol, the carbon with the -OH group attached is joined directly to two alkyl groups, which may be the same or different.

• In a tertiary (3°) alcohol, the carbon atom holding the -OH group is attached directly to three alkyl groups, which may be any combination of same or different.

Structural formula Name 1o 2o 3o

ethanol

2-methylpropan-2-ol

Alcohols burn in oxygen and air to produce carbon dioxide and water.

This is complete oxidation (combustion).

C2H5OH + 3O2 2CO2 + 3H2O

Less vigorous oxidising conditions can be provided by reacting an alcohol with an oxidising agent.

Your teacher will demonstrate the oxidation of alcohols using hot copper oxide (Workcard 6a)

Carry out the experiment using potassium dichromate (Workcard 6b)

The alcohol vapour is passed over hot CuO. The copper oxide is reduced to copper metal and the alcohol is oxidised.

Oxidising alcohol using hot copper oxide

Ethanol + copper oxide ethanoic acid + copper + water

C2H5OH + CuO CH3COOH + Cu + H2O

Oxidising alcohols using potassium dichromate

The dichromate ion is reduced to the Cr3+ ion and the alcohol is oxidised.

Cr2O72- + 14H+ + 6e- → 2Cr3+ + 7H2O

Primary alcohols are oxidised, first to aldehydes and then to carboxylic acids.

Secondary alcohols oxidise to ketones.

Tertiary alcohols are resistant to oxidation

Oxygen to hydrogen ratio

For carbon compounds, oxidation results in an increase in the oxygen to hydrogen ratio and reduction results in a decrease in the oxygen to hydrogen. These are diff erent defi nitions f rom those met previously and only apply in carbon chemistry. oxidation

eg. C2H5OH CH3CHO Oxygen : hydrogen ratio (O:H) 1:6 1:4

Oxidation of ethanol (C2H5OH) to ethanal (CH3CHO) has increased the O:H ratio.

Ethanal can also be reduced back to ethanol and this would be a decrease of the ratio.


Name Formula Oxygen:Hydrogen Ratio

C2H5OH

Ethanal CH3CHO

Ethanoic acid CH3COOH

Name Formula Oxygen:Hydrogen ratio

Ethanol C2H5OH

1:6

Ethanal CH3CHO

1:4

Ethanoic acid CH3COOH

2:4 = 1:2

Now complete the workbook activity by calculating the O:H ratio for each of the compounds given.

Remember to draw the structural formulae of each compound too.

• More than one hydroxyl group

• There are some alcohols that have more than one hydroxyl group in the molecule. For example, glycol, which is used as the antifreeze in car radiators, and glycerol, which you may have eaten as an ingredient in soft ice cream.

• The alcohol used in ordinary car antifreeze has two hydroxyl groups and for this reason is known as a dihydric alcohol or diol. Its common name is glycol, but this says little about its structure. The systematic name is ethane-1,2-diol...

Two numbers are needed in the name to describe the positions of the two hydroxyl groups. Notice that ‘di’ now appears infront of ‘ol’ (‘di’ = 2, ‘ol’ = hydroxyl group).

With two carbon atoms in the molecule, the systematic name is based on ethane. In this case the final ‘e’ of ethane is not dropped in the sysetmatic name because it is not followed by a vowel. The alcohol commonly known as glycerol is found in a variety of foods. It has the systematic name propane-1,2,3-triol.

This molecule has three hydroxyl groups and as a result is known as a trihydric alcohol or triol.

• As the number of hydroxyl groups in a molecule increases, the number of hydrogen bonds between molecules also increases. This will mean that a greater amount of energy is needed to overcome these intermolecular forces of attraction.

• This explains why propane-1,2,3-triol has a higher boiling point than ethane-1,2-diol.

L.I. To learn about aldehydes and ketones Section 5 (b)

S.C. By the end of this lesson you should be able to…• State the name of the functional group present in aldehydes and ketones.

• State the name ending present in aldehydes.

• State the name ending present in ketones.

• State the name of straight chain and branched chain aldehydes when given the

structural formula.

• State the name of straight chain and branched chain ketones when given the structural formula.

• Draw the structural formula of aldehydes and ketones when given the names.

• State the molecular formula of aldehydes and ketones when given the names.

• State and explain the results of a chemical test used to distinguish between

aldehydes and ketones.

• State the name of the products formed when aldehydes (and ketones) are oxidised.

• State the effect of oxidising aldehydes using chemicals such as Benedict’s solution, Tollen’s reagent and acidified potassium dichromate solution.

Both aldehydes and ketones contain the carbonyl group.

In aldehydes a hydrogen atom is bonded to the carbonyl group but in ketones the carbonyl group is

always flanked by carbon atoms:

C O

C

O

H C

O

CC

aldehyde ketone

This structural difference accounts for the fact that aldehydes can undergo mild oxidation to form

carboxylic acids but ketones resist oxidation.

Oxidising agents can therefore be used to distinguish between aldehydes and ketones.

Carry out the experiment to oxidise aldehydes and ketones (Workcard 7)

Benedicts solution

Tollen’s reagent Acidified dichromate (H+/Cr2O7

2-)with compound X Colour change

from blue to orange-red

A solid silver precipitate forms (the silver mirror

effect)

Colour change from orange to

green

with compound Y No reaction

No reaction No reaction

Aldehydes but not ketones can be oxidised by a number of oxidising agents, including

Benedict's solution, Tollen’s reagent and acidified dichromate to carboxylic acids.

Compound X must be ………………………………

Compound Y must be ………………………………..

Aldehydes contain the f unctional group (-CHO)…

Aldehydes can be identified from the ' - al' name ending.

Ketones contain the functional group…

Ketones can be identified from the ' - one' name ending.

Aldehydes have a hydrogen atom joined to the carbonyl group whereas ketones have two carbon atomsjoined to the carbonyl group.

Naming of alkanones is almost exactly the same as for alkanols. e.g. butanone. For longer chain ketones the position of the carbonyl group must be given.

Workbook activities…

1. Draw the full structural formulae and shortened structural formulae for the compounds listed.

2. Draw the full structural formulae and name each of the compounds listed.

L.I. To learn about antioxidants Section 5 (c)


• State how food containing edible oils turns rancid.

• State how to prevent food from turning rancid.

• State the ion-electron equations for the oxidation of antioxidants.

• State the name of carboxylic acids when given the structural formula.

• Draw the structural formula of branched chain carboxylic acids when given the

name.

• State the molecular formula of branched chain carboxylic acids when given the names or structural formula.

• State the products formed when carboxylic acids undergo reduction reactions.

• State the name of the product formed when carboxylic acids react with bases.

Oxygen reacts with edible fats and oils in food giving the food a rancid flavour. For example, butter, a mainly saturated fat, can undergo hydrolysis releasing small quantities of volatile, unpleasant smelling butanoic acid which is responsible for a rancid smell. The reaction with oils is more complex and appears to affect unsaturated fatty acids in the oil. The point of attack is at the C=C double bonds and volatile, smaller molecules such as aldehydes and ketones are released which cause the rancid smell.

Oxidation reactions can produce free radicals. A free radical is a highly reactive species containing an unpaired electron. Free radicals can damage food by removal of an electron.

Antioxidant molecules ‘mop up’ free radicals to protect the foodstuff.

• The antioxidant molecule donates an electron to the potentially damaging free radical.

• A stable electron pair is formed, stabilising the free radical.

• The antioxidant itself becomes oxidised (loses an electron).

• Antioxidants are molecules which will prevent oxidation reactions taking place, antioxidants are reducing agents. By undergoing oxidation, the antioxidant provides electrons to prevent the oxidation of fats/oils in food.

• In crisp manufacture, potatoes are typically fried under an atmosphere of steam and packaged under nitrogen to help reduce oxidation.

• Ascorbic acid (or vitamin C), found in many fruits is an antioxidant.

When it behaves as an antioxidant, two of the hydroxyl groups become changed into carbonyl groups as found in ketones. The product has two hydrogen atoms less than the ascorbic acid and is know as dehydroascorbic acid.

It can be seen as an oxidation because there is a increase in the O:H ratio and also that electrons are released in the reaction.

C6H8O6 C6H6O6 + 2H+ + 2e-

When apples are cut, they go brown because of oxidation by the air.

A few drops of lemon juice will prevent this oxidation, though the lemon juice is not an antioxidant.

HOC6H4OH OC6H4O + 2H+ + 2e-

Citric acid and benzoic acid is used in many foods such as jam to prevent oxidation by helping other antioxidants do their work.

Antioxidants in action

Oxidation occurs when the apple is left exposed to air

The apple is protected when dipped in orange juice containing the antioxidant vitamin C

Antioxidant E-number Typical foods

Ascorbic acid (vitamin C) E300

Beers, cut fruits, jams, dried potato. Helps to prevent cut and pulped foods from going brown by preventing oxidation reactions that cause the discolouration. Can be added to foods, such as potato, to replace vitamin C lost in processing.

Tocopherols E306 Oils, meat pies. Obtained from soya beans and maize. Reduces oxidation of fatty acids and some vitamins.

Butylated hydroxyanisole (BHA)

E320 Oils, margarine, cheese, crisps. Helps to prevent the reactions that break down fats and cause the food to go rancid .

Citric acid E330

Jam, tinned fruit, biscuits, alcoholic drinks, cheese, dried soup. Naturally-occuring in citrus fruits like lemons. Helps to increase the anti-oxidant effects of other substances. Helps to reduce the reactions that can discolour fruits. May also be used to regulate pH in jams and jellies.

The table shows some typical antioxidants:

http://www.understandingfoodadditives.org

Carry out the SSERC experiments on antioxidants (Workcard 8)

Now carry out the ‘active talk ‘activity with your group

Carboxylic acids Vinegar is a dilute solution of ethanoic acid which is commonly used in food preservation. Ethanoic acid is a member of the carboxylic acid family. As a homologous series, carboxylic acids all share the same functional group and fit the same general formula (CnH2n+1COOH).

Carboxyl functional group

It is necessary to be able to name and draw structural formulae and molecular formulae for carboxylic acid molecules. This can be done by using the principles we have used before...

• Carry out the workbook activities on naming carboxylic acids and drawing full and shortened structural formulae.

Reactions of carboxylic acidsCarboxylic acids can be reduced in stages back to the original parent aldehyde and alcohol using a reducing agent such as lithium aluminium hydride.

For example...

Ethanoic acid Ethanal Ethanol

(Carboxylic acid) (Aldehyde) (Primary Alcohol)

Workbook activity

Like ordinary acids carboxylic acids can react with bases to form salts.

For example...

Ethanoic acid + Sodium hydroxide Sodium ethanoate + Water

+ NaOH + H2O

Workbook activity* Vitamin C tablets experiment *

L.I. To learn about soaps and emulsions Section 6 (a) making soap


• Explain how soaps are produced by alkaline hydrolysis of fats and oils.

Soaps are produced by the alkaline hydrolysis of fats and oils.

Fats and oils are esters.

The hydrolysis of fats and oils produces fatty acids and glycerol (propane-1,2,3-triol) in the ratio of three moles of fatty acid to one mole of glycerol.

In the presence of an alkali, a water soluble ionic salt of the carboxylic acid is formed.

These salts are the important ingredients of soap - the ones that do the cleaning.

Watch the animation of making a soap on

http://www.educationscotland.gov.uk/highersciences/chemistry/animations/soapformation.asp

L.I. To learn about soaps and emulsions Section 6 (b) cleansing action of soaps

S.C. By the end of this lesson you should be able to…• State what is meant by a hydrophobic tail in a soap molecule.• State what is meant by a hydrophilic head in a soap molecule.• Describe the cleansing action of soaps in terms of the structure of the soap molecule.

Watch the animation to investigate the cleansing action of soaps...

http://www.educationscotland.gov.uk/highersciences/chemistry/animations/cleansingsoap.asp

Cleaning with water alone has little effect if the stains consist of non-polar substances, such as grease and sweat.

Soaps and detergents are ‘emulsifying reagents’. These are simply chemicals which can make oil and water become permanently mixed to produce a stable emulsion.

Soaps and detergents do this job due to the structure of the molecules:

Soap molecules have a long non polar hydrocarbon chain ‘tail’ which is readily soluble in non polar (hydrophobic) compounds and a polar ionic carboxylate ‘head’ which is water soluble.

During cleaning, the hydrophobic tails dissolve in the droplet of grease, whilst the hydrophilic heads face out into the surrounding water, resulting in ball like structures. The following diagrams show how this works.

The dirt or grease is held inside the ball and suspended in the water.

L.I. To learn about soaps and emulsions Section 6 (c) emulsions in food

S.C. By the end of this lesson you should be able to…• State the meaning of the term emulsion.• Explain why emulsifiers are added to food.• State how emulsifiers are made.• Describe how emulsifiers work.

An emulsion contains small droplets of one liquid dispersed in an another liquid.

Emulsions in food are mixtures of oil and water.

To prevent oil and water components separating into layers, a soap-like molecule known as an emulsifier is added.

Emulsifiers for use in food are commonly made by reacting edible oils with glycerol to form molecules in which either one or two fatty acid groups are linked to a glycerol backbone rather than the three normally found in edible oils.

The one or two hydroxyl groups present in these molecules are hydrophilic whilst the fatty acid chains are hydrophobic.

The presence of this emulsifier is shown on packaging by E-numbers, E471 and is one of the most common on food packaging.

Many foods contain emulsions. Mayonnaise is mainly a mixture of vegetable oil and water/vinegar/lemon juice. Egg yolk or a synthetic emulsifier (xanthan gum) can be used to keep the normally immiscible liquid evenly mixed. Without the emulsifier the two liquids would separate and would not appear appetising.

Emulsifiers are added to a very large range of different foods including sauces, bread, biscuits, ice cream, low fat spread and even dried pastas where they help to prevent pasta pieces sticking to each other during cooking.

Watch the animation on emulsions and emulsifiers

http://www.educationscotland.gov.uk/highersciences/chemistry/animations/emulsions.asp

Emulsifiers

Mayonnaise contains oil and water. The emulsifier keeps these mixed and without it the oil and water separate.

L.I. To learn about fragrances Section 7 (a) essential oils


• State what is meant by an essential oil.•State the uses, properties and products of essential oils.•Describe how essential oils can be extracted from plant material.•State the key component in many essential oils.

Essential oils are hydrophobic liquids containing mixtures of volatile aroma compounds that evaporate easily in air giving distinctive fragrances.

The oils have the aroma of the plant from which they are extracted. They include lavender, peppermint, orange, lemon, and eucalyptus oils.

Every essential oil contains a mixture of organic compounds rather than just one pure compound, but it is often the aromatic molecules that provide the distinct fragrances.

Essential oils are extracted from plant material, the difficulty is obtaining the liquid before it evaporates.

Steam DistillationIn this process the volatility of the oil is important so it is carried by the steam. More water can be added from the funnel.

The essential oil collects as a mixture of oil and water, but as the two do not mix, they are easily separated.

In the laboratory extraction can be achieved with the apparatus shown....

Essential oils are used in perfumes, cosmetics, soaps and other products, for flavoring food and drink, and for adding scents to incense and household cleaning products.

Essential oil can contain esters, alcohols, aldehydes and ketones.

An important component in essential oils are known as terpenes.

Modern uses

Essential oils

Cosmetics Flavours

Perfumes Medical

Cleaning

Insect repellents

Dentistry Adhesives

Terpenes are unsaturated compounds formed by joining together isoprene (2-methylbuta-1,3-diene) units.

The basic molecular formulae of terpenes are multiples of that, (C5H8)n where n is the number of linked isoprene units. This is called the isoprene rule.

The isoprene units may be linked together "head to tail" to form linear chains or they may be arranged to form rings. One can consider the isoprene unit as one of nature's common building blocks

Complete the workbook activity to highlight the isoprene units in each molecule.

(Looks like a horse….)

5 carbon molecule….

Terpenes are components in a wide variety of fruit and floral flavours and aromas. Terpenes can be oxidised within plants producing some of the compounds responsible for the distinctive aroma of spices.

Limonene – a cyclic terpene

CH2

CH2C

CH

CH2

CH

CCH2CH3

CH3

Limonene

(skin of citrus fruits)

Menthol – a cyclic terpenoid

CH2

CHCH

CH2CH

CH2

CH3

OH

CHCH3CH3

Menthol

(peppermint)

This terpene has been oxidised to a terpenoid

-Selinene – a cyclic terpene

3 isoprene units

15 carbon atoms

CH2

CH2CH2

CHC

CH2

CH3

C

CC

CH2

CH2

CH2

CH2

CH3

H

-Selinene

β-carotene – a linear terpene

8 isoprene units

40 carbon atoms

CH2

CH2

CH2C

CC

CH3CH3

CHCH

CCH

CHCH

CCH

CHCH

CHC

CHCH

CHC

CHCH

CC

CH2

CH2CH2

CCH3

CH3 CH3CH3 CH3

CH3CH3

CH3

-carotene

Find the horse…

L.I. To learn about skin care products Section 8 (a) effect of UV light


• State the effect of ultraviolet radiation on molecules.•State the effect of ultraviolet radiation on the human body.•Describe how sunblock works.

Image of the sun taken with ultraviolet imaging telescope

Ultraviolet radiation (UV) is a high-energy form of light, present in sunlight.

Exposure to UV light can result in molecules gaining sufficient energy for bonds to be broken. This is the process responsible for sunburn and also contributes to ageing of the skin. Sun-block products prevent UV light reaching the skin.

UV light is divided into UVA, UVB and UVC light. UVA is the highest energy and causes most damage. UVC light does not penetrate the atmosphere and so causes no problems. UVA and UVB cause wrinkles by breaking down collagen, creating substances called free radicals that inhibit the natural the repair of the skin.

UVB light, but not UVA light is stopped by glass. You may notice labels on sunglasses to indicate their effectiveness.

UV Photography reveals the effects of "photoaging", or ageing of skin caused by light.

Photoageing refers to the damage that is done to the skin from prolonged exposure to UV radiation, over a person's lifetime.

Most of the skin changes that occur as we get older are accelerated by sun exposure.

Examples of skin changes from photoaging include dark spots, wrinkles, leathery skin and skin cancer (malignant melanoma).

There’s no such thing as a healthy tan

Skin cancer – malignant melanoma

In the UK, 2,000 people a year die from malignant melanoma, and the number is increasing.

Photoageing caused by UVA

Exposed to sun Not exposed to sun(through car window)

Taxi driver

The effects of UV - ageing of skin

How to protect yourself-Sunscreen

• Sunscreen works by combining organic and inorganic active ingredients.

• Inorganic ingredients like zinc oxide or titanium oxide reflect or scatter ultraviolet (UV) radiation.

• Organic ingredients absorb UV radiation, dissipating it as heat.

L.I. To learn about skin care products Section 8 (b) Free Radical Reactions


• State what is meant by a free radical.• Describe the reactivity of a free radical.• Describe how free radicals are formed.• State what is meant by the terms initiation, propagation and termination.

When UV light breaks bonds free radicals are formed. Free radicals have unpaired electrons and, as a result, are highly reactive. Free radical chain reactions include the following steps: initiation, propagation and termination. Hydrogen and chlorine video clip Hydrogen reacts with explosively with chlorine in the presence of U.V. light. The reaction can be shown as follows:

H2(g) + Cl2(g) → 2HCl(g)

The presence of acid HCl in the product can be shown with moist pH paper. The reaction follows a free radical chain reaction, initiated by U.V. light. For convenience, the reaction can be split into three stages.

1) Initiation

U.V. light provides the energy for the homolytic fission of halogen into reactive halogen atoms or free radicals (atoms with an unpaired electron).

Cl2(g) → Cl.(g) +

.Cl(g)

2) Propagation

In this stage, free radicals collide with other species but the number of free radicals is maintained (hence the term propagation).

H2(g) + .Cl → H

.(g) + HCl(g)

H.(g) + Cl2(g) → HCl(g) + Cl

. (g)

These reactions continue until reactants are used up, or until free radicals are used up by collision with each other.

3) Termination In this stage, free radicals are used up by collision with each other.

H.(g) +

.Cl(g) → HCl(g)

H.(g) +

.H(g) → H2(g)

Cl.(g) +

.Cl(g) → Cl2(g)

Free radical Substitution Methane

Another free radical reaction takes place when a halogen is substituted into an alkane in the presence of UV light. This reaction is not explosive and results in the decolourisation of bromine. Alkanes react with bromine in the presence of U.V. light, though the reaction with bromine is slow. The reaction can be shown as follows:

CH4(g) + Br2(g) → CH3Br(g) + HBr(g)

The presence of acid HBr in the product can be shown with moist pH paper. However, the reaction does not end here and further substitution can occur with hydrogen atoms progressively replaced by halogen atoms.

The slow substitution reaction follows a free radical chain reaction, initiated by U.V. light. Again, the reaction can be split into three stages…

1) Initiation

U.V. light provides the energy for the homolytic fission of halogen into reactive halogen atoms or free radicals (atoms or molecular fragments with an unpaired electron).

Br2(g) → Br.(g) + .Br(g)

2) Propagation

In this stage, free radicals collide with other species but the number of free radicals is maintained (hence the term propagation).

CH3-H(g) + .Br → CH3.(g) + HBr(g)

CH3.(g) + Br2(g) → CH3-Br(g) + Br. (g)

These reactions continue until reactants are used up, or until free radicals are used up by collision with each other.

3) Termination

In this stage, free radicals are used up by collision with each other.

Br.(g) +

.Br(g) → Br2(g)

CH3

.(g) +

.Br(g) → CH3-Br(g)

CH3

.(g) +

.CH3(g) → CH3-CH3(g)

The product of the last equation is ethane. However, to minimise the range of possible products, an excess of the original alkane is used and the products separated from the excess alkane by distillation. Evidence to support this mechanism

The reaction is initiated by U.V. light and, once started, can continue in the dark. Other substitution products are made such as CH2Br2, CHBr3, CBr4 together with longer alkanes (and smaller amounts of substitution products of these alkanes.However, these other substitution products can be minimised by using an excess of the original alkane to try to ensure collision of the relatively small number of free radicals produced by sunlight quickly uses up the bromine.

L.I. To learn about skin care products Section 8 (c) Free Radical Scavengers

S.C. By the end of this lesson you should be able to…• State the effect that free radicals have on the body.• Describe how free radical scavengers work.• State examples of natural free radical scavengers.

Many cosmetic products contain free radical scavengers.These are molecules which can react with free radicals to form stable molecules and prevent chain reactions.

Melatonin and Vitamin E are examples of natural free radical scavengers.

MelatoninAs UV light can cause wrinkling of skin, some skin-care products claim to contain chemicals which prevent wrinkling. These are claimed to be anti-ageing creams.

As free radical scavengers form stable molecules, they help to stop the free radical chain reactions that cause the skin to form wrinkles.

Free radicals remove electrons from skin cells and damage them and wrinkles start to develop.

Watch a selection of adverts for anti-ageing products. Identify the scientific basis of the claims.

Permanent benefits?

Do they work?

There is a range of antioxidants used in anti-wrinkle creams, and some are better at penetrating the skin than others. The antioxidants used in skin care are derived from Vitamins A, E and C

The derivatives of Vitamins A (retinol) and E combat free radicals. Vitamin C is used in the construction of collagen. Other antioxidants work by exfoliating the dead skin on the surface to reveal newer, younger-looking skin underneath. Still others create a barrier to prevent moisture loss fromClaims for retinol derivatives say it can reduce the appearance of lines and reduce skin roughness, and blotchiness. There is some research that says retinol can increase the thickness of the epidermis. But as the molecules are large, they can't fit though the skin unless combined with substances that make the holes in the lipid matrix bigger. Vitamin E is the most widely used ingredient in skin care products, used for its moisturising and antioxidant properties.

Free radical scavengers are also added to food products to slow down the rate of oxidation and also to plastics as without them they can break down under the action of UV light and oxygen.

Carry out the experiment to make your own lip balm (Workcard 11).

Butanoic acid has a powerful, unpleasant odour. It is found in rancid butter, Parmesan cheese and vomit.

Can you identify and name the functional group present in butanoic acid?

Carboxyl group

Revision Questions…

Aqueous solutions of methanal are commonly used in embalming to preserve human or animal remains.

Can you identify and name the functional group present in methanal?

Carbonyl group

Is methanal an aldehyde or a ketone? Aldehyde

The molecule below is found in the disinfectant Dettol, which we instantly recognise by its distinctive smell. Dettol (chloroxylenol) helps us fight unwanted bacteria.

Can you identify and name the functional group present in Dettol?

Hydroxyl group

Carboxyl group

Amide group

4-formamidobenzoic acid is used in pharmaceutical compositions.

Can you identify and name two functional groups present on the 4-formamidobenzoic acid molecule?

Cinnamon is a tasty spice used to flavour biscuits, cakes and pies. Cinnamon also has medicinal properties.

Can you identify and name two functional groups in cinnamon?Is cinnamon an aldehyde or a ketone?

Carbonyl group

Carbon-to-carbon double bond

Aldehyde

What is the strongest type of intermolecular force of attraction between cinnamon molecules?

(Hint: Think about the bond polarity of the functional groups present!)

Can you identify and name the two functional groups present in methyl anthranilate?

Amino group

Methyl anthranilate occurs naturally in grapes and is used as grape flavouring in drinks and chewing gum.

Ester link

Can you identify and name three different types of functional group on the structure of vitamin C?

Ester link

Hydroxylgroup

Vitamin C is needed in your diet for the growth and repair of tissues in all parts of your body.

Carbon-to-carbon double bond

Which is the strongest type of intermolecular force of attraction between molecules of vitamin C?

Is vitamin C a polar or a non-polar molecule?

Is vitamin C soluble in water or in hexane?

(Hint: Think about which functional groups are present!)

Glucose is a simple sugar that is used as an energy source by many living organisms.

Is glucose soluble in water or in hexane? Justify your answer with reference to the functional groups present.

2-methylpropane is a branched hydrocarbon that is used as a refrigerant.

Is 2-methylpropane soluble in water or in hexane? Justify your answer with reference to the structure.

higher chemistry unit 2 nature’s chemistry. what you should know… that molecular structure and...

Documents

parent acid

structural formula of

functional group present

structural formulae

natures chemistry slide

ester linkage

ethyl propanoate slide

organic organic compounds