study smart chapter 2 f5

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STUDYSMART

CHEMISTRY FORM 5

CHAPTER 2 : CARBON COMPOUND

2.1 Understanding carbon compounds

2.2 Analysing Alkanes

2.3 Analysing Alkenes

2.4 Synthesising ideas on isomerism

2.5 Analysing Alcohols

2.6 Analysing carboxylic acids

2.7 Analysing esters

2.8 Evaluating fats

2.9 Analysing natural Rubber

2.10 Creating awareness of order in homologous series

2.11 Expressing gratefulness for the variety of organic materials in nature

2.1 UNDERSTANDING CARBON COMPOUNDS

Carbon compound are compound that containing carbonCarbon compound can be classified into inorganic and organic carbon compound.

Examples of inorganic carbon compound (usually non-living things)

- Carbon Monoxide, CO

- Carbon Dioxide, CO2

- Calcium Carbide, CaC2

- Carbonate salts for example Na2CO3, CaCO3, CuCO3

Examples of organic carbon compound (usually living things)

- Urea - Natural rubber

- Glucose - Protein

- Cellulose - Ethanol- Starch - Glucose

Hydrocarbon are organic compound containing hydrogen and carbon only

Organic compound in which some or all of the hydrocarbon atoms have been replaced

other atoms are called non-hydrocarbons.

Hydrocarbon molecules that are made entirely of carbon-carbon single bonds are said

to be saturated hydrocarbon. Hydrocarbon containing at least one carbon-carbon

double or triple bonds is referred as unsaturated hydrocarbon.

Combustion product of organic compounds

- When an organic compound is burnt in excess oxygen, the main product are CO2, and ,

H2O.Example : Combustion of glucose, C6H12O6

C6H12O6 + 6O2 6CO2 + 6H2O


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2.2 ANALYSING ALKANES

Usually in fuels, examples: natural gas, petrol, diesel

Are homologous series

Have a formula of CnH2n+2, where n is a positive integers.

Example : propane has three carbon atom, thus n=3. Then the formula of propane is C3H8

Ends with suffixaneNext alkane formula differ byCH2 atoms. Eg: methane: CH4, ethane: C2H6

Structure of Alkanes

Shows how all atoms in a molecule joined together by drawing lines between atoms to

represent the bonds

Example: butane has a formula of C4H10, therefore the structural formula is:

It has 4 carbon atoms bonded together with 10 hydrogen atoms.

All alkanes are saturated. All alkenes are unsaturated

Name of carbon atoms are shown in table below

Complete the table on left and below

n Name Molecular

Formula

Structural Formula

1 Methane CH4

2 Ethane

Name of carbon atom Root name

1 Meth-

2 Eth-

3 Prop-

4 But-

5 Pent-

6 Hex-

7 Hept-

8 Oct-

9 Non-

10 Dec-


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3 Propane

4 Butane

5 Pentane

6 Hexane

7 Heptane

8 Octane


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9 Nonane

10 Decane

Physical properties of alkanes are :-

- Melting points and boiling points increase as the bonds become larger and heavier which

increases the forces of attraction between molecules so more energy (from heat) is needed to

separate them with the increase of strength of forces of attraction

- Alkanes are insoluble in water but soluble in organic solvents such as tetrachloromethane as a

alkanes are organic compounds

- Alkane density increases down the series; all alkenes are less than 1g/cm3

- Alkanes become more viscous (uneasily flow) going down the series as the longer molecules

tangles together when it flows

- Alkanes become less flammable down the series as B.P. becomes larger

- Alkanes are unreactive with either metals, water, acids or bases because the C C and C H

covalent bonds are harder to break

Alkane Formula Boiling point [C] Melting point [C] Density [gcm3] (at 20C)

Methane CH4 -162 -183 gas

Ethane C2H6 -89 -172 gas

Propane C3H8 -42 -188 gas

Butane C4H10 0 -138 gas

Pentane C5H12 36 -130 0.626(liquid)

Hexane C6H14 69 -95 0.659(liquid)

Heptane C7H16 98 -91 0.684(liquid)

Octane C8H18 126 -57 0.703(liquid)

Nonane C9H20 151 -54 0.718(liquid)Decane C10H22 174 -30 0.730(liquid)
http://en.wikipedia.org/wiki/Methanehttp://en.wikipedia.org/wiki/Ethanehttp://en.wikipedia.org/wiki/Propanehttp://en.wikipedia.org/wiki/Butanehttp://en.wikipedia.org/wiki/Pentanehttp://en.wikipedia.org/wiki/Hexanehttp://en.wikipedia.org/wiki/Heptanehttp://en.wikipedia.org/wiki/Octanehttp://en.wikipedia.org/wiki/Nonanehttp://en.wikipedia.org/wiki/Decanehttp://en.wikipedia.org/wiki/Decanehttp://en.wikipedia.org/wiki/Nonanehttp://en.wikipedia.org/wiki/Octanehttp://en.wikipedia.org/wiki/Heptanehttp://en.wikipedia.org/wiki/Hexanehttp://en.wikipedia.org/wiki/Pentanehttp://en.wikipedia.org/wiki/Butanehttp://en.wikipedia.org/wiki/Propanehttp://en.wikipedia.org/wiki/Ethanehttp://en.wikipedia.org/wiki/Methane


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Chemical properties of alkanes

Alkanes are unreactive compound

Chemical properties of alkanes

COMBUSTION

Alkanes burn in air to ALWAYS form carbon dioxide and water.

2C4H10(g) + 13O2(g)

8CO2(g) + 10 H2O (l)

When there is insufficient oxygen, the product is ALWAYS carbon monoxide and unburnt

carbon.

2CH4 (g) + 3O2 (g) 2CO(g) + 4H2O

CH4 (g) + O2 (g) C(g) + 4H2O

Example: Butane is commonly used camping gas.

High alkanes burn less completely and gives soot (unburnt carbon) and CO

HALOGINATION / SUBSTITUTION REACTION

Reaction of alkanes with halogens (Cl2, Br2, and I2)

Light is needed to break covalent bond between halogens molecule atoms

Substitution reaction the reaction in which one or more atoms replace other atoms in a

moleculeExample : Mixture of methane, CH4 and chlorine is exposed to UV light

CH4 + Cl2 CH3Cl + HCl

monochloromethane

CH3Cl + Cl2 CH2Cl2 + HCl

dichloromethane

CH2Cl2 + Cl2 CHCl3 + HCl

trichloromethane

CHCl3 + Cl2 CCl4 + HCl

tetrachloromethane

2.3 ANALYSING ALKENES

Have general formula CnH2n.

All alkene names end withene.

The formula of one alkene differs from the next byCH2.

Have similar properties like alkane going down the series.

Example : butene has a formula of C4H8, therefore the structural formula is:

It has 4 carbon atoms with a double bond bonded together with 8 hydrogen atoms.

All alkenes are unsaturatedThe Importance of Ethene

- Ethanol solvent & fuel

- poly(ethene) PE plastic variations

- Ethanoic acid vinegar

Complete the table below


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n Name Molecular

Formula

Structural Formula

1 Methane

METHENE IS NOT IN ALKENES GROUP SINCE ITS CONTAIN SINGLE

CARBON ATOM THUS, NO DOUBLE BOND.

2 Ethane

C2H4

3 Propane

4 Butane

5 Pentane

6 Hexane


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7 Heptane

8 Octane

9 Nonane

10 Decane

Physical properties of alkenes are

- cannot conduct electricity

- Less dense than water

- Obeys like dissolve like rule where it dissolve in organic solvent but insoluble in water

- Alkenes have low melting and boiling points

Chemical Reaction of Alkenes

Alkenes are chemically more reactive than alkanes due to the presence of the C = C doublebond.

COMBUSTION

Burns in air to form carbon dioxide and water

Example: Ethene burns in air.

C2H4(g ) + 3O2(g) 2CO2(g) + 2H2O (l)

Incomplete combustion forms soot and CO. Its produced more than alkane


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To differentiate the percentage of carbon in alkene and alkane

C2H4(g ) + 3O2(g) 2CO2(g) + 2H2O (l)

Alkenes burn with sootier flame as compared to alkanes. This is because alkenes have a higher

percentage of carbon in their molecules.

For ethane, C2H4

% of carbon = 2 x 12 . x 100%

2(12) + 4(1)

= 24 x 100%

28

= 85.71 %

For ethane, C2H6

% of carbon = 2 x 12 . x 100%

2(12) + 6(1)

= 24 x 100%

30

= 80 %

ADDITION REACTION

I) Addition of hydrogen, H2 / Hydrogenation [ethane ethane]

C2H4 + H2 -----------> C2H6Ethene ------------------------------------> Ethane

II) Addition of halogens (Bromine, Br2)

Ethene + Br2 -----------> 1,2-dibromoethane

III) Addition of hydrogen halides

Ethene + HCl -----------> Chloroethane


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IV) Addition of water, H2O / Hydration [ alkene alcohol ]

V) Addition of hydroxyl groups, -OH

- Acidified potassium manganite (VII), KMnO4

Ethene + H2O + [O] -----------> Ethane-1,2-diol

POLYMERIZATION

The joining of several identical alkene molecules to form a big molecule.


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2.4 SYNTHESISING IDEAS ON ISOMERISM

Isomers are compound with the same molecular formula but different structural formula

Examples :

1. Isomers of pentane

2. Isomers of butane

Naming of each isomer is based on IUPAC. There are several steps before naming an isomers

STEP 1 : Specify the number of carbon atom in the largest continuous carbon chain

STEP 2 : Numbering carbon atoms with 1,2,3,. Starting near functional group / and branch.

STEP 3 : Branch names, -CH3, methyl

-CH2CH3, ethyl

Examples :

Isomer of Pentene

Isomer of Hexane

Isomer of Butane

Isomer of Butene


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2.5 ANALYSING ALCOHOLS

The general formula of alcohol is CnH2n+1OH (n = 1,2,3)

Alcohol contain the hydroxyl group (-OH) as the functional group that covalently bonded to a

carbon atom

Naming of alcohol

- Root denotes the number of carbon atom (meth-, eth-, prop-)- Ending replacee from the name of the alkane withol

NUMBER OF

CARBON

ATOM

MOLECULAR

FORMULA

STRUCTURAL FORMULA NAME

1 CH2OH Methanol

2

3

4

5

6


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Naming alcohol based on IUPAC

STEP 1 : Identify the longest carbon chain containing the hydroxyl group

Root obtain from the number of carbon atom in the longest carbon chain

STEP 2 : Identify the position pf hydroxyl group by numbering the carbon atom in the longest

chain

Beginning at the end nearer to the hydroxyl group

STEP 3 : identify and name that attracted alkyl group (branch)prefix

STEP 4 : Complete the name by combining the three component

Examples :

1. 2

Name : _____________________ Name : _____________________

3. 4.

Name : __________________________________ Name : ____________________________

Isomerism in alcohol exists in the alcohol with three or more carbon atoms

Examples :

1. Propanol (C3H7OH)

2. Butanol


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Preparation of Ethanol

Industrial production of ethanol

i) from sugar and starch by fermentation

ii) from petroleum fractions by hydration

H3PO4

CH2 = CH2 + H2O CH3CH2OH

300oC / 60 atm

Laboratory preparation of ethanol

In the fermentation process, the zymase enzyme decompose the glucose to form ethanol and

carbon dioxide

Equation of the fermentation process :

zymase

C6H12O6 2C2H5OH + 2CO2

30oC -4

oC

Reacting ethane with steam to produce alcohol (fractional distillation)

Ethene and steam are passed over phosphoric acid H3PO4(as a catalyst) under high temperature

of 300oC and pressure of 65 atm.

C2H4(g) + H2O(g) C2H5OH(aq)

Since this is reversible reaction, both ethene and water are produced aside from ethanol.The ethanol is separated by fractional distillation.

Physical properties of alcohol :

A simple alcohol are liquids and very soluble in water

As the number of carbon atoms in their molecules increases, the molecules get bigger, the

forces of attraction between molecules becomes stronger, more energy needed to overcome

the forces of attraction. Thus, melting and boiling points increase gradually.

Physical properties of ethanol are :-

- colourless liquid - sharp smell

- complete miscible with water - boiling point : 78oC at 1atm

Chemical properties of ethanol

COMBUSTION

* Complete combustion of alcohol produces carbon dioxide and water

C2H5OH + 3O2 2CO2 + 3H2O

* Ethanol burns with a non-smoky blue flame


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* Release lots of heat, use as a fuel

C4H9OH + 6O2 4CO2 + 3H2O

OXIDATION

* Alcohol can be easily oxidized to carboxylic acid by using oxidizing agent

* Oxidising agent : acidified potassium manganat(VII) colour turns from purple to green

acidified potassium dichromate(VI) colour turns from orange to green

* Ethanol undergo oxidation reaction to form ethanoic acid

[ -CH2OH group has removed 2 hydrogen atoms and gained an oxygen atom]

C2H5OH + 2[O] CH3COOH + 3H2O

Ethanol carboxylic acid

Draw the structural formula :

DEHYDRATION

* Involves the removal of water by using catalyst such as heated porcelain chips, porous pot,

aluminium oxide, concentrated sulphuric acid

* The dehydration of ethanol produces ethane and water

heated

C2H5OH C2H4 + H2O

Porcelain chips


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Uses of alcohol

As a fuel Volatile, highly flammable and high content

As a solvent and thinner colourless, volatile, miscible with water and good organic solvent

As a raw material to make pharmaceutical products volatile, good solvent, and antiseptic

2.6 ANALYSING CARBOXYLIC ACIDSCommon carboxylic acid in nature are acetic acid in vinegar, lactic acid in sour milk, citric acid in

citrus fruits.

Contain the element carbon, hydrogen and oxygen.

When comparing to alcohols, carboxylic acids contain 2 oxygen atoms

Functional group for carboxylic acid is carboxyl group, -COOH or

General formula of carboxylic acid is CnH2n+1COOH, where n = 0,1,2,3,.

Straight chain carboxylic acids are named with endingoic acid

n Number of C atom (s) Molecular Formula Structural Formula Name

0 1

HCOOH Methanoic Acid

1 2

2 3

3 4

4 5


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5 6

6 7

Naming the branches carboxylic acid

- Identify the longest carbon chain containing the carboxyl group

- Number the carbon atom beginning at the carboxyl groupExamples

___________________ ___________________ ___________________

Making ethanoic acid

Laboratory preparation by the oxidation of ethanol by using oxidizing agent (Acidified KMnO4

or K2Cr2O7 solution)

Physical properties of ethanoic acid

- a colourless liquid at room temperature

- a sour smell

- very soluble in water

Chemical Properties of Carboxylic acids

Ethanoic acid is a weak monoprotic acid. Hydrogen atoms from carboxyl group, -COOH can be

ionize in water to form hydrogen ions

Reaction with reactive metals, bases and carbonates (Act as acid)

CH3COOH + Mg

CH3COOH + NaOH

CH3COOH + Na2CO3


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Reaction with alcohols to form ester and water (Esterification)

A mixture of carboxylic acid and alcohol with a few drops of concentrated sulphuric acid is

heated, an ester is formed.

Example

2.7 ANALYSING ESTERS

General formula of ester is CnH2n+1COOCmH2m+1

Functional group in ester is called carboxylate group, -COO or

Naming ester

Formation of ester

i)

___________________

ii)

_______________ _________________ _____________________

Physical properties of ester

- has sweet pleasant smell (fruity smell)

- a colourless liquid

- low melting and boiling points

- slightly soluble in water but readily dissolve in organic solvent

Carboxylic acid + Alcohol Ester + Water

H2SO4

Ending -yl Ending -oate


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GENERAL CONCLUSION FOR ALKANE, ALKENE, ALCOHOL, CARBOXYLIC ACID AND ESTER

2.8 EVALUATING FATSFats are found in animals which is solid at room temperature. Example : butter, tallow

Oils are found in plants which is liquid at room temperature. Example : palm oil, sunflower oil

Fats and oils are ester formed from glycerol (alcohol with 3 hydroxyl group) and fatty acids

(long-chain carboxylic acids)

Chemical equation :

Saturated and Unsaturated fats

Saturated fats

- saturated alkyl group ( contains single covalent bond only)

- Glycerol and saturated fatty acids, only contain carbon carbon single bond

- Animal fats contain large proportion of saturated esters, have high melting points and solid in

room temperature

- Example : Tristearin, tripalmitin

Unsaturated fats

- unsaturated alkyl group ( contains one or more carbon carbon

double bonds.

- Glycerol and unsaturated fatty acids contain one or more carbon carbon double bonds.

- Plant / vegetable oils contain a large proportion of unsaturated ester, have lower melting

Fermentation

Esterification

Oxidation

dehydration

HydrationHydrogenation

Alkane

CnH2n+2

Alkene

CnH2n

Alcohol

CnH2n+1OH

Glucose

C6H12O6

Carboxylic Acid

CnH2n+1COOH

Ester

CnH2n+1COOCmH2m+1

R1 , R2 , and R3 :

same or different

alkyl group


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points, and liquids at room temperature.

- Example : Triolein

Converting unsaturated fats to saturated fats

- by hydrogenation process

- Margarine is made by hydrogenating some of the carbon carbon double bonds in

polyunsaturated vegetable oil so that the physical state changes from liquid to soft.

Industrial extraction of palm oil

[Refer Textbook]


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2.9 ANALYSING NATURAL RUBBER

A polymer is a large molecules consisting of a long chain. It is made by joining together many

small molecules called monomers

Natural polymers exist naturally. Below are the examples of natural polymers and their

monomers.

Natural rubber is actually poly(isoprene)

Its monomer is 2-methyl-1,3-diene or isoprene with molecular formula C5H8

The isoprene molecules undergo addition polymerization to produce a long chain molecules

called poly(isoprene)

Latex is a white milk-like fluid

Rubber particles is made up of many long-chain rubber molecules enclosed by a protein-like

membrane which is negatively charged

The repulsion between the negatively-charged particles prevents the rubber particles from

coming close to each other. Hence, latex could not coagulate

Latex will coagulate when

- An acid is added. (Methanoic acid or ethanoic acid)

- Exposed to air

Coagulation process of latexa) When an acid is added, the hydrogen ions neutralize the negative charges on the protein

membrane.

b) The rubber particles can now come closer together and collide with one another resulting in

the breakage of the protein membrane

c) The rubber molecules combine with one another and entangle thus causing the latex to

coagulate.

Latex will coagulate when it is exposed to air because the growth and spread of bacteria

produce lactic acid.

Natural Polymer MonomerNatural Rubber Isoprene

Starch Glucose

Cellulose Glucose

Protein Amino Acid


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Latex can be preserved in the liquid by adding ammonia solution. Ammonia solution contain

hydroxide ions that neutralize the acid produced by bacteria

Vulcanization of rubber

Properties of natural rubber :

- Soft

- Elasticity decrease over time

- Sensitive to heat

- Easily oxidized by air

The properties can be improved through vulcanization process.

Vulcanization process can occur when

a) latex is heated with sulphur (industry)

b) rubber products are exposed to disulphur dichloride, S2Cl2 gas (industry)

c) by soaking natural rubber in the solution of disulphur dichloride in methylbenzene.

(Laboratory preparation)

The presence of cross-linkage of sulphur atoms between the rubber molecules improves the

properties of rubber.

Uses of natural rubber

a) making tyres, footwear, rubber threads, rubberized bitumen roads

b) Gloves, tubes and hoses

c) insulator of electrical appliance and cables

Vulcanized rubber Difference Unvulcanized rubber

More elastic Elasticity Less elastic

Harder Hardness Softer

Stronger Tensile strength Weaker

Can withstand highertemperature

Resistance on heat Cannot withstand highertemperature

Hard to be oxidized Resistance to oxidation Easily oxidized

Does not become soft

and sticky easily

Effect of organic solvent Becomes soft and sticky

easily

Limit its uses

study smart chapter 2 f5

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