Organic Chemistry

Organic Chemistry and Hydrocarbons“Organic” originally referred to any

chemicals that came from organisms

1828 - German chemist Friedrich Wohler synthesized urea in a lab

Today, organic chemistry is the chemistry of virtually all compounds containing the element carbon

Allotropes of carbonCarbon exists naturally in three

forms: Graphite

Diamonds

Fullerenes

Organic Chemistry and HydrocarbonsOver a million organic compounds, with a dazzling array of properties

Why so many? Carbon’s unique bonding ability!Can form 4 covalent bondsForm double or triple bondsBonds with other carbon atoms.

AlkanesOnly have single bonds between them

(saturated)Formula CnH2n+2

Naming hydrocarbonsPrefixes used

# Carbon atoms

1 2 3 4 5 6 7 8 9 10

Prefix Meth- Eth-

Prop-

But- Pent- Hex-

Hept- Oct- Non- Dec-

Naming alkanesEnd in –anePrefix used corresponds to number of

carbons in chain.Ex.

Occur when a carbon atoms bonds with three or four carbon atoms.

Branched chain alkanes:

Substituents: take place of a hydrogen atom on a parent chain hydrocarbon (longest continuous chain).

Branched chain alkanes:

c c c c c c c c c c c c c

Parent alkane (propane)

Parent alkane (hexane)

substituent

Hydrocarbon substituentsAre called alkyl groupName ending with –ylMethyl group (CH3-)Ethyl group (CH3CH2-)Propyl group (CH3CH2CH2-)

Rules for naming branched alkanes p753 in textbook1. Find the longest chain of carbons in the molecule or

parent chain. (not necessarily a straight line)

2. Number the carbons in parent chain. Start at the end that will give the groups attached to the chain the smallest numbers.

3. Identify with numbers the positions of the substituents on the chain.

4. Use prefixes to indicate the appearance of the same group more than once: di- (twice), tri- (three times)5. List the names of the substituents groups in alphabetical order.

6. Commas separate numbers, hyphens separate numbers and words. Name is written without spaces

Ex. 1 Name the following alkane:

CH3 CH2 CH CH3

CH3

1. Choose parent chain and name it

butane

1 2 3 4

4 3 2 12. Number parent chain in a way that substituents have smallest numbers.

3. Identify position of substituent group and name it.

2- methyl (located in carbon 2)

4. Not applicable

5. List substituent groups in alphabetical order. 2-methyl

6. Separate letters and numbers with hyphen

Ex.2 CH3 CH CH2 CH2 CH3

CH2

CH3

Ex.2 CH3 CH CH2 CH2 CH3

CH2

CH3

Parent alkane

Does not have to be a straight line, only longest chain.

Name of parent alkane: hexane

Ex.2 CH3 CH CH2 CH2 CH3

CH2

CH3

Number Parent alkane

Number in way that substituent group has smallest number.

Name and position of substituent group: 3-methyl

1

3 5 6

2

4

Ex.2 CH3 CH CH2 CH2 CH3

CH2

CH3

Name of organic compound

3-methylhexane

1

3 5 6

2

4

Writing structural formulas:1. Write the complete structural formula for 2,2-dimethylpropane

Writing structural formulas:1. Write the complete structural formula for 2,2-dimethylpropane Write only the carbons first. Start with the

parent alkane.2,2-dimethylpropane

C C C

Writing structural formulas:1. Write the complete structural formula for 2,2-dimethylpropane

Number the parent alkane from left to right.

C C C 1 2 3

Writing structural formulas:

Identify the substituent groups and their position:

CH3

C C C

CH3

1 2 3

1. Write the complete structural formula for 2,2-dimethylpropane

2,2-dimethylpropane There are two (di) methyl groups (CH3-) in

carbon #2

Writing structural formulas:

Add the necessary hydrogen bonds so that each carbon has a maximum of 4 bonds.

H CH3 H H C C C H H H CH3

1. Write the complete structural formula for 2,2-dimethylpropane

CycloalkanesA hydrocarbon ring (has 3 C or more) is

called a cyclic hydrocarbonCycloalkanes: cyclic hydrocarbon with

single bonds onlyEx. Cyclohexane: used in paint and varnish

removersRepresenting cycloalkanes

Structural formula

Line structure

Naming cycloalkanes:Ring structure is considered parent chain.

Count # C in the ring, name ring; use prefix cyclo-

Numbering is started in the carbon that is bonded to the substituent group: If there is only 1 substituent group, no numbering is

necessary If there are 2 or more substituent groups, C are

numbered in way that gives lowest possible set of numbers for substituents.

Ex. Name the following cycloalkanes

Ex. 2

Write the structure for: Ex. 3 1,2-dimethylcyclopropane

Ex. 4 1-ethyl-2-methylcyclobutane

Properties of alkanesAlkanes are nonpolar

Good solvents for other nonpolar substancesNot miscible in waterHave low reactivity

CW: p757 #10-11, p758 #13,14,16