Organic Chemistry

Nomenclature:

Alkanes

Alkanes

• Hydrocarbon chains where all the bonds

between carbons are SINGLE bonds

• Name uses the ending –ane

• Examples: Methane, Propane, Butane,

Octane, 2-methylpentane

• For straight chain hydrocarbons. The prefix indicates

the number of carbon atoms.

• The suffix -ane is added to designate that the

compound is an alkane

• General Formula: CnH2n+2

Naming Alkanes

Prefixes for # of Carbons

1 Meth 6 Hex

2 Eth 7 Hept

3 Prop 8 Oct

4 But 9 Non

5 Pent 10 Dec

• Alkenes have one (or more) carbon to carbon double bonds

• When there are 4 or more carbon atoms in a chain, the location of the double bond is indicated by a number.

• Numbering the location of the double bond(s) takes precedence over the location of side chains

• General Formula: CnH2n

Alkenes

1 butene 2-butene methylpropene

• Alkenes have one (or more) carbon to carbon triple bonds

• When there are 4 or more carbon atoms in a chain, the location of the double bond is indicated by a number.

• Numbering the location of the triple bond(s) takes precedence over the location of side chains

• General Formula: CnH2n-2

Alkynes

1 butene 2-butene methylpropene

• For branched chain hydrocarbons, identify the longest

consecutive (straight) chain first. Then name the side

chains or branches.

• The name of the branches end in “yl” and go before

the name of the straight chain

Naming Alkanes with

branched chains

-methylpropane

methyl butane

dimethyl propane

Summary: IUPAC Rules for Branched

Alkane Nomenclature

1. Find and name the longest continuous carbon chain. This is called the parent chain. (Ex: methane, propane, etc.)

2. Number the chain consecutively, starting at the end nearest an attached group (alkyl or substituent).

3. Identify and name groups attached to this chain. (Examples: methyl-, bromo-, etc.)

4. Designate the location of each substituent group with the number of the carbon parent chain on which the group is attached. Place a dash between numbers and letters. (Example: 3-chloropentane)

5. Assemble the name, listing groups in alphabetical order. The prefixes di, tri, tetra etc., used to designate several groups of the same kind, are not considered when alphabetizing. Place a comma between multiple numbers. (Example: 2,3-dichloropropane)

Step 1. Find the parent chain.

• Where is the longest continuous chain of

carbons?

Step 2. Number the parent chain.

• Number the parent chain so that the

attached groups are on the lowest

numbers

1 2 3 4 5

Methyl is on carbon #2 of the parent chain

5 4 3 2 1

Methyl is on carbon #4 of the parent chain

GREEN is the right

way for this one!

1 2

3 7 8

4 5 6

8 7

6 2 1

5 4 3

Groups on 2, 3, and 5

Groups on 4, 6, and 7

1 2 3 4 5 6

7

Groups on 2 and 5

7 6 5 4 3 2

1

Groups on 3 and 6

Step 3. Name the attached groups.

• Carbon (alkyl) groups: – Methyl CH3 -

– Ethyl CH3CH2-

– Propyl CH3CH2CH2 – (if connected by center carbon, it is ISOPROPYL)

• Substituents: (we’ll discuss later) – Halogens

• Fluoro (F-)

• Chloro (Cl-)

• Bromo (Br-)

• Iodo (I-)

– Functional Groups

Step 4. Designate where the group

is attached to the parent chain.

• Use the numbers of the parent chain from

step 2 to designate the location of the

attached groups to the parent chain.

1 2 3 4 5

2-methyl

Step 5. Alphabetize the groups, combine like

groups, and assemble.

• The prefixes di, tri, tetra etc., used to designate several

groups of the same kind. ***Prefixes are not considered

when alphabetizing (Example: dimethyl = m for

alphabetizing)

• Parent chain goes LAST

2-methyl pentane

5-ethyl, 2,3-dimethyl octane

5-isopropyl-2-methyl heptane

Structural Formulas

• “Lazy” way to write the Hydrogens

• Instead of drawing the bonds, just state

how many hydrogens are attached

• NOTE: The bonds are between

CARBONS in a parent chain, and not

hydrogens!

Condensed

Structural Formula Lewis Structure

Draw Some Simple Alkanes

• 2-methylpentane

• 3-ethylhexane

• 2,2-dimethylbutane

• 2,3-dimethylbutane

Types of Carbon Atoms

• Primary carbon (1o)

– a carbon bonded to

one other carbon

• Secondary carbon (2o)

– a carbon bonded to

two other carbons

• Tertiary carbon (3o)

– a carbon bonded to

three other carbons

C

C

C

C

H

H

H

C C

H

H

C

C

C

H

C

C

C

C

H

H

H

C C

H

H

C

C

C

H

C

C

C

C

H

H

H

C C

H

H

C

C

C

H

C

C

C

C

H

H

H

C C

H

H

C

C

C

H

Isomers

• Straight chain alkanes: An alkane that has all its carbons connected in a row.

• Branched chain alkanes: An alkane that has a branching connection of carbons.

• Isomers: Compounds with same molecular formula but different structures.

• There is only one possible way that the

carbons in methane (CH4), ethane (C2H6),

and propane (C3H8) can be arranged.

• However, carbons in butane (C4H10) can be arranged in two ways; four carbons in a row (linear alkane) or a branching (branched alkane). These two structures are two isomers for butane.

•Different isomers are completely different

compounds. They have different structures,

different physical properties such as melting point

and boiling point, and may have different

physiological properties.

Learning Check

• Draw all possible structural isomers of C5H12

Alkanes

Example: Name the following compounds:

CH3

CH3CH(CH

3)2CH

2CH

2Br

CH3

CH CH CH2

CH CH3

CH2CH

3C

CH

CH3

CH3

CH3

CH3

CH3

C CH2

CH2Br

CHCH3

CH2CH

3

CH3

CH3

CH CH CH2

CH CH3

CH2CH

3C

CH

CH3

CH3

CH3

CH3

CH3

Alkanes

Example: Write the condensed

structure for the following compounds:

3,3-dimethylpentane

4-sec-butyl-2-methyloctane

1,2-dichloro-3-methylheptane

Naming Compounds With

Functional Groups • Various functional groups have unique suffixes that

designate the functional group.

• The functional group takes precedence in

numbering the carbon chain.

• Branches to the carbon chain are named in the

usual manner.

alcohols “ol” Amides “amide”

Aldehydes “al” Amines “amine” or amino as a prefix

Ketones “one” Ethers Ethoxy as prefix

Acids “oic” halohydrocarbons Fluoro, bromo, chloro or

iodo

Esters “oate” 27

Alcohols

Suffix = “ol” 1- Propanol

2- Propanol

2-methyl-2-propanol

28

Suffix = “al”

Propanal

Note that the

aldeyhde group is

always on an end

carbon or carbon 1

Aldehydes

29

Suffix = “one”

Propanone

(also known as acetone)

Butanone

(also known as methyl ethyl ketone)

2-Pentanone

(note the number is necessary

Because the C=O could be on carbon

2 or carbon 3)

Ketones

30

Suffix = “oic”

Butanoic acid

Note that the acid group

(called a “carboxyl”) is

always on an end carbon

or carbon 1

Carboxylic Acids

31

Suffix = “oate”

Ethyl butanoate

Butyl ethanoate

There are two branches. The

branch with the carbonyl gets

the suffix

Esters

32

Suffix = “amide”

butanamide

Note that the amide group is

always on an end carbon or

carbon 1

Amides

33

Suffix = “amine”

Or prefix = “amino”

Propylamine or 1-aminopropane

2-propylamine or 2-aminopropane

2-methyl-2-propylamine or

2-methyl -2- aminopropane

Amines

34

prefixes = “fluoro,

chloro, bromo,

iodo”

1-bromopropane

2 chlorobutane

1,2 diiodoethane

Cis 1,2difluroethene

Trans 1,2 difluoroethene

1,1,2 trifluorothene

Halohydrocarbons

35

Suffix = “oxy”on first branch

Ethoxyethane

(diethylether)

Ethoxybutane

(ethylbutyl ether)

Ethers

36

Aromatic Compounds With

Functional Groups

Benzoic acid

2 hydroxybenzoic acid

3 bromobenzoic acid

37

Nitriles

38

Nitriles have a cyanide group. The

name is based on the longest carbon

chain that includes the carbon atom in

the nitrile group.

Order of Priority

• IN A TIE, halogens get the lower number

before alkyl groups

4-chloro-2-methylpentane or

2-chloro-4-methylpentane?

Order of Priority

• IN A TIE between SIMILAR GROUPS, the

group lower ALPHABETICALLY gets the

lower number

4-bromo-2-chloropentane or

2-bromo-4-chloropentane ?