unit 3- organic chemistry - mr. heff's...

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Unit 3-Organic Chemistry

Lesson 1 –Introduction to Organic

Chemistry

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Your First Mission…Drawing upon your own

chemical knowledge and everyday life, come up with the names of five compounds which you think are organic.

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Organic chemistry.

Organic Chemistry

Pull down the molecule structures to identify the importance of each molecule.

Fuel source for combustion engines.

Fuel source for living cells.

Polymer plastic for consumer products.

Antibiotic agent.

Octane Glucose Nylon Ampicillin

Carbon Hydrogen Nitrogen Oxygen

Organic molecules are important for life.

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• The study of molecular compounds containing carbon and hydrogen atoms.

What is organic chemistry?

• Properties of organic compounds result from the covalent bonds within their molecules

•ex. CH4 CH3OH CH3NH2

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Origins of Organic Chemistry• Swedish chemist Jons Jacob Berzelius

Classified compounds in 2 categories1)Organic-obtained from living organisms - most chemists believed organics could only be synthesized in living organisms thus the theory of “vitalism”2)Inorganic-obtained from mineral sources (non-living).

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Origins of Organic Chemistry-German chemist Friedrich Wohler discovered that organic compounds could be synthesized from inorganic compounds.

-Performed experiment with ammonium cyanate to synthesize urea (found in urine of living creatures).

NH4OCN(aq) à (NH2)2CO(s)

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-Acetic acid, CH3COOH; Sucrose, C12H22O11, as well as many others were and are synthesized.

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Uniqueness of Carbon 1. Forms 4 bonds with other atoms

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2. Bond together to form chains, rings, spheres, sheets and tubes of almost any size

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3. Ability to form single, double or triple covalent bonds

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Is this why we have so many organic compounds?

• YES!These unique properties explain why the number of known compounds of carbon far exceed the number of compounds of all other elements combined

Today, over 98% of all known compounds are organic.

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Organic Compounds Inorganic Compounds

covalent bonding (share electrons)

mainly ionic bonding (transfer electrons)

lower melting higher melting

do not conduct electricity conduct electricity

Comparing Inorganic & Organic Compounds

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Natural Sources Organic Compounds1) Carbonized organic matter extractedfrom fossil fuels (once living matter)ex: coal, oil, and natural gas 2)From plants and animals (living organisms)Ex­ penicillin from mold ­ ASA from the bark of a willow tree

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Synthetic organic compounds such as gasoline, solvents, polyesters, synthetic sweeteners, artificial flavors (vanilla flavor), and medicines (antibiotics, aspirin, heart drugs) have been invented by chemists and engineers. These are copies of the natural products produced by plants and animals.

Inorganic can be extracted from mineral sources (non­living).

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Two Classes of Compounds

1) Organic Compounds are compounds that have a combination of carbon and hydrogen Ex : CH4 CH3OH CH3NH2

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• Examplescarbon oxides - COx EX: CO2, CO

carbonate ion - CO32-

bicarbonate ion - HCO3-

cyanide ion - CN -

thiocyanate ion - SCN -

carbides - SiC

2) Inorganic Compounds are compounds that have either carbon or hydrogen. They contained ionic bonds.

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TWO CLASSES OF ORGANIC COMPOUNDS1)Hydrocarbons Organic compounds that contain only carbon and hydrogen atoms (Ex: methane, CH4).

2) Hydrocarbon derivatives Organic compounds in which one or more hydrogen atoms are replaced by another nonmetallic atom (Ex: bromomethane, CH3Br).

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Aliphatics• organic compounds with chain or cyclic (rings) structures of single, double or triple bonds

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are organic compounds with a special group of six carbons ring known as the benzene ring.

Aromatic

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Classifying Organic Compounds

are separated into families and classified according to functional groups.These groups, the sites where reactions usually take place, help explain the many chemical properties of organic compounds.

Functional Group is the characteristic arrangement of atoms within a molecule that determines the most important chemical and physical properties of the compound.

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FAMILYFUNCTIONAL GROUP Alkane ­ C ­ C ­

Alkene ­ C = C ­

Alkyne ­ C ≡ C ­

Aromatic (Benzene )

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Alkanes (CnH2n+2 )• Hydrocarbons that have only

single covalent carbon-to-carbon bonds

•General Formula: CnH2n+2

alkanes containing any number of carbon atoms in a straight chain

Continuous Chain Alkanes

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Naming Alkanes•Ex1: What is the name of a compound with the molecular formula CH4

C

H

H

H

H

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Naming Continuous Chain Alkanes

Step 1 Use prefix as the first syllable to indicate the number of carbon atoms in the molecule

[These prefixes are used in naming all organic compounds]

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IUPAC Prefix SystemNumber of Carbons Prefix1 meth­2 eth­3 prop­4 but­5 pent­6 hex­7 hept­8 oct­9 non­10 dec­

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Step 2 Next, use the ending “-ane” to indicate single bonded carbon atoms

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Therefore: CH4

• Since 1 Carbon, we use “Meth”• Since alkane, we use the ending “ane”• Therefore, we have CH4, which is

Methane!!!

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Ex2: Name the compounds

A. C3H8

propane

H

HH

H

HH

H

H

CC C

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B. C4H10 answer: butane

HH

HHH

CC

H H

H

H

CH

C

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C. C5H12

answer: pentane

HHHH

HHHHH

H

CCC

H

CH

C

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D. C7H16

answer:Heptane

H

HHHH

HHHHH

H

C C C

H

CC

H

C

H

HHHH

H

HHHHH

C C C

H

CC

H

C

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Ex3: Name the compoundsa)

b)

c) C8H18

hexane

decane

octane

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Homologous Series• a group of compounds that change by a constant increment in molecular structure from one compound in the series to the next

• compounds within a homologous series are known as homologs

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• Continuous chain alkanes are an example of a homologous series

• the constant increment in alkanes is the –CH2– group

The methane, ethane, propane and butane are an example of a homologous series.

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Drawing Alkane Structures• Each carbon will have 4 bonds • Three types of structural diagrams 1. Complete – all atoms and bonds in a molecule are shown

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2. Condensed – C-H bonds are omitted but C-C bonds are shownFor example, the chemical formula of C4H10 can be represented as:

(dashes are optional) or

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• Line – each end of a line segment represents a carbon atom; hydrogen atoms are not shown

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Ex 4:Draw all the structure diagrams for the following alkanes:A) C7H16

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B) C5H12

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Structural formulas show the bonds in a molecule, but they cannot represent molecules three­dimensionally.

Notice that a carbon "skeleton" is not perfectly straight, but zigzagged. Each carbon atom is bonded to four other atoms. VSEPR theory predicts that each of the single bonds involving carbon points to a corner of a tetrahedron to give bond angles of about 109.5°.

A really compact way of representing this structure is to use a line structural diagram.

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• branch ­ an atom or group of atoms that can take the place of a hydrogen atom on the main carbon chain of a hydrocarbon molecule• alkyl group ­ a hydrocarbon branch that can be one or more carbons long• It has one less hydrogen atom than a corresponding alkane• named by removing –ane ending and adding ­yl • General Formula: CnH2n+1 .

Naming Branched Chain Alkanes

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• Branched chain alkane ­ alkane with one or more alkyl groups. Like the highway has roads branching off!

Examples of branches:methyl: ­CH3

ethyl: ­C2H5 or ­CH2CH3

propyl: ­C3H7 or ­CH2CH2CH3

butyl: ­C4H9 or ­CH2CH2CH2CH3

pentyl: ­C5H11 or ­CH2CH2CH2CH2CH3

Alkyl groups are examples of substituents: atoms or groups of atoms that replace a hydrogen atom on a chain or ring of carbon atoms.

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• Ex 5: Write a IUPAC name to represent this structural formula

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Solution:• 1. Begin by locating the longest continuous chain of carbon atoms.

The longest chain is seven carbon atoms long, so the parent chain is heptane

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• 2. Assign number "1" to the carbon at the end to which branching is closest.

Since, branching is closest to the right side, the parent chain is numbered sequentially from right

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• 3. Identify the alkyl groups.

There are two: a methyl at carbon #3, and an ethyl at carbon #4.

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4. If an alkyl group occurs more than once, use a Latin prefix to indicate the number present. The Latin prefixes are di = 2, tri = 3, tetra = 4, penta = 5, and so on. - e.g. two methyl groups would be represented as dimethyl5. Use a number to indicate the location of each alkyl group on the parent chain.

6. Build the name of the branched alkane.

• 4-ethyl-3-methylheptane

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Ex 6: Give the name for the following:

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Drawing Structural Formulas for Branched Alkanes1. Draw the parent chain.2. Add the alkyl groups (substituents).3. Make sure each carbon atom has an octet (e.g. four single covalent bonds).

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Ex 7: Draw the structural formula for 3­ethyl­2,4­dimethylhexane. Answer The parent chain is hexane.

Add methyl groups to carbon atoms 2 and 4 in the parent chain.

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Add the ethyl group to carbon 3Final Answer:

Or

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• Draw structures to represent the following:• (a) 2,2,4-trimethylpentane

• (b) 3-methylheptane

Ex 8: use notebook

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• (c) 3-ethylhexane

• (d) 3-ethyl-2-methyl-4-propylnonane

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• (e) 2,3-dimethylhexane

• (f) 4-methylheptane

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Condensed Structural Formulas for Branched AlkanesMethod 1: Draw a condensed parent chain and draw lines to the alkyl substituents.

Method 2: Draw a condensed parent chain and write the formulas for the alkyl substituents in parentheses

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Cycloalkanes (CnH2n)• hydrocarbons which are arranged in a closed ring• all c-c bonds are single bonds

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Ex 9: Draw the full structural formula, condensed structural formula, and line drawing for cyclobutane.

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Naming Cycloalkanes1. Count the number of carbon atoms in the ring.2. Name the structure the same as naming alkane but add the prefix cyclo to the alkane name.

Ex 10: Name this compound.

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cyclopropane cyclobutane

cyclopentane

cyclohexane

Ex11: Name these compounds.

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Physical Properties of Alkanes1. Boiling Point• relatively low melting and boiling points compared to inorganic compounds of similar size. (why? They have weak intermolecular force (LDF) holds them together ­ hydrocarbons are nonpolar)• generally, as the number of carbons atoms in a pure hydrocarbon increases, there is an increase in boiling and melting points

ALKANES BOILING POINT number of electrons

ethane, C 2H6 ­88.5 18

propane,C3H8 ­42.0 26

butane,C4H10 ­ 0.5 34

pentane, C 5H12 36.0 42

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2. Solubility: refers to the ability of a substance to dissolve in a particular solvent.Alkanes are non­polar and are soluble in non­polar solvents only.

Q1.Why does alcohol dissolve in water? Water is polar. It will dissolve polar compounds. Alcohol is polar. ie:methanol, CH3OH

Q2. Why does oil not dissolve in water? Oil is a pure hydrocarbon and like other pure hydrocarbons it is nonpolar. It will not dissolve in polar water. A common nonpolar solvent used to dissolve some hydrocarbons is carbon tetrachloride (CCl4 ).

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3. Rotation occurs around the single C-C bonds

4. The term saturated refers to organic compounds, which contain single carbon-to-carbon bonds

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• - compounds that have the same molecular formula but different structures

•Ex11: Draw the structural isomers of C4H10.

Structural Isomerism

butanemethylpropane

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Ex 12: Draw the structural isomers ofC6H14 (5 structural isomers)

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