Module 3 Need to Know

organic chemistry

An organic compound normally contains chains or rings of carbon atoms

Carbon is unusual Bonds strongly to itself (exceptions: Oxides of carbon and carbonates)

Forms long chains and rings

When carbon has four bonds to it, it adopts a tetrahedral geometry

Carbon can bond to fewer than 4 elements by forming one or more multiple bonds

Alkanes

Alkanes - are hydrocarbons that contain single bonds to four other atoms. Alkanes are said to be saturated

Hydrocarbons that form chains or ‘strings’ are regarded as normal (straight-chained) or branched

General formula: C_nH_2n+2 where n = number of C atoms

Normal alkanes can be represented as the following (where m is an integer:) CH₃ – (CH₂)_m—CH₃

steps for naming alkanes

1. Use Greek root as prefix and ‘ane’ as the suffix. The following Greek roots apply to alkanes following n = 4 (butane):

2. For a branched hydrocarbon, the longest continual chain gives the root name for the hydrocarbon. Replacing a hydrogen atom on a straight-chained alkane with another group gives rise to substituents The substituent is named by using the parent alkane and replacing ‘ane’ with ‘yl’

3. To specify the positions of the substituent groups, start at the end closest to the branching

4. When a given type of substituent occursmore than once, we indicate this by using a prefix. The prefix di- indicates two identical substituents, tri- for three, tetra- for four, etc.

names of straight chain alkanes

alkenes and alkynes

Double- and triple-bonded hydrocarbons

Alkenes: hydrocarbons that possess a carbon-carbon double bond

• Formula: C_nH_2n

• Suffix ‘-ene’

Alkynes: hydrocarbons that possess a carbon-carbon triple bond

• Formula: C_nH_2n-2

• Suffix ‘-yne’

alkenes and alkynes naming rules

1. The longest continuous chain of carbon atoms that contains the double/triple bond is selected

2. Root name of the carbon chain ends in ‘–ene’ or ‘-yne’

3. With more than 3 carbons, double/triple bond is indicated by the lowest-numbered carbon atom in the bond

4. Substituents on the parent chain are treated the same way as in naming alkanes

Benzene as a substituent

called a phenyl substituent

• ortho- (1,2) for 2 ajacent substiuents

• meta- (1,3) for 2 substiuents with 1 carbon between them

• para- (1,4) for 2 substiuents oppposite each other

Functional Groups

Alcohols

Alcohols are functional groups with a hydroxyl group (–OH) attached to a carbon atom via a single bond.

Alcohol classification

• Primary = 1 R group

• Secondary = 2 R groups

• Tertiary = 3 R groups

Ketones

contain a C=O (carbonyl) group, 2 carbon-based groups

Aldehydes

contain a C=O (carbonyl) group, 1 hydrogen atom and 1 carbon based group

Carboxylic acids

Compounds that contain a carboxyl functional group (–COOH or –CO₂H)

Esters

formed from the reversible condensation (loss of water) of a carboxylic acid and an alcohol molecule.