Functional Group Review

They are alcohols, ethers, carboxylic acids, esters, amines, and aromatics. There are, believe it or not, other functional groups called aldehydes and ketones, but I'll not hold you responsible for those. So I need you to recognize the functional group in a Lewis structure or draw a Lewis structure containing the functional group given it name. So lets look at some examples of each type.

Functional Group

Condensed Formula

Name

Structure

Lewis Structure

Comments

alcohol

CH3OH

methyl alcohol

In methyl alcohol, or methanol the red atom is an oxygen. It has a hydrogen attached to it as well as the methyl group. Methanol is similar to water, HOH, where one of the hydrogens is replaced with the methyl group. The geometry is 'bent' around the oxygen atom in methanol. Notice the condensed structural formula and the arrangement of the atoms in the Lewis structure.

alcohol

CH3CH2OH

ethyl alcohol

Ethanol is the second alcohol. Both of these two alcohols are very important and you must be able to draw their Lewis structures and name them. Notice the condensed formula CH3CH2OH and the Lewis structure so you see oxygen atom is bonded to a carbon and a hydrogen.

ether

H3COCH3

dimethyl ether

Ethers are slightly differnet compared to an alcohol. Notice in an alcohol the oxygen atom has one hydrogen atom and the other group is a hydrocarbon. In ethers both groups attached to the oxygen atom are hydrocarbon groups. In this case both are methyl groups.

ether

CH3CH2OCH2CH3

diethyl ether

Here the hydrocarbons are both ethyl groups.

carboxylic acid

HCOOH

formic acid

In carboxylic acids there are two oxygen atoms. One of the oxygen atoms has a hydrogen bonded to it like in the alcohols. The other oxygen atom is double bonded to the carbon. Look at the Lewis structure. The carboxyl group is sometime written as -COOH group in the compound.

carboxylic acid

CH3COOH

acetic acid

Acetic acid, a component of vinegar is the first carboxylic acid with an R- group bonded to the carbon atom of the carboxyl group. I want you to know this structure.

ester

CH3COOCH3

methyl methyl ester

In esters the hydrogen atom bonded to the oxygen atom in the carboxylic acid is replaced with an R- group.

amine

CH3NH2

methylamine

The blue atom is the nitrogen atom. Notice in methylamine the carbon atom of the methyl group is bonded to the nitrogen. In amines the nitrogen atom alway has three bonding groups and one lone-pair.

amine

(CH3)2NH

dimethylamine

In this example of an amine two R- groups are bonded to the nitrogen.

amine

(CH3)3N

trimethylamine

In this example of an amine three R- groups are bonded to the nitrogen.

aromatic

C6H6

benzene

Aromatics are rings with carbon atoms with alternating single and double bonds.

Are you ready for some examples of some interesting organic componds where you identify the functional groups attached?

Return to man functional group page.