Organic Chemistry
Functional Groups
Organic chemical compounds are historically those found in living organisms or in materials derived from such sources. Advances in synthesis have enabled the creation of new compounds that are considered organic as they are typically made with organic ingredients, which must include carbon. The backbone of all organic molecules is composed primarily of carbon atoms to which are attached mostly hydrogen, oxygen and nitrogen. The simplest organic molecules that contain chemical elements only carbon and hydrogen are called hydrocarbons. A chemical derivative of a hydrocarbon is formed on substituting for one or more hydrogen atoms a functional group. A functional group, which might comprise a single atom such as chlorine, is a reactive portion of a molecule that is responsible for its characteristic chemical properties. Organic molecules are classified according to functional groups; some common groups are listed as follows.
Halohydrocarbons are characterized by the presence of a halogen in place of a hydrogen atom. Halohydrocarbons are generally named by replacing the -ine in the halogen with -o- and prepending it to the parent hydrocarbon name. Some common halohydrocarbons are: fluoromethane, chloromethane and iodomethane.
Alcohols are characterized by the presence of a hydroxyl group (-OH) attached to a carbon atom. In general, alcohols are named by replacing the final -e on the parent hydrocarbon name with -ol. Some common alcohols are: methanol, ethanol, 1-propanol, and 2-propanol (where 1 and 2 denotes the position of the carbon atom the hydroxyl group is attached to. So, essentially, 1-propanol is the same as propanol, and 1-ethanol is the same as ethanol).
Ethers are characterized by a single-bonded oxygen (-O-) within a parent hydrocarbon chain. Ethers are generally named by replacing the final -ane on the shorter hydrocarbon chain with the suffix -oxy. Some common ethers are: methoxyethane and phenoxybenzene.
Aldehydes are characterized by the presence of the formyl group (-CHO) where the hydrogen atom is attached to a carbon atom double-bonded with oxygen. The double-bonded carbon and oxygen forms the carbonyl (-C(O)-) group. The formyl group is always observed at the end of a hydrocarbon chain. Aldehydes are named by replacing the final -e on the parent hydrocarbon name with -al. Some common aldehydes are: methanal, ethanal, and propanal.
Ketones are characterized by the presence of a carbonyl group within the parent hydrocarbon chain. Ketones are named after the longest chain containing the carbonyl group. The ketone suffix, -one, is added after the hydrocarbon suffix by replacing the final -e. Some common ketones are: propanone and butanone.
Carboxylic acids are characterized by the presence of the carboxyl group (-C(O)OH), where a carbonyl and hydroxyl groups are joined by single bond. This functional group normally appears at the end of a hydrocarbon chain. Carboxylic acids are named after the longest hydrocarbon chain including the carboxyl group, where the final -e in the parent hydrocarbon name is replaced with -oic acid. Some common carboxylic acids are: methanoic acid, ethanoic acid, and pentanoic acid.
Esters can be derived from carboxylic acids and are characterized by the -C(O)O functional group. In contrast to a carboxylic acid, this oxygen structure appears within the hydrocarbon chain instead of at the end. Esters are generally named by replacing the -ane in the part of the hydrocarbon name connected to the single-bonded oxygen with -yl and by replacing the -e in the part of the hydrocarbon chain with -oate. Some common esters are: ethyl propanoate, propyl methanoate and methyl butanoate.
Amines are characterized by the presence of a nitrogen atom bonded to a maximum of two hydrogen atoms. This structure appears within or at the end of a hydrocarbon chain. Amines are named after the longest chain the functional group is attached to, where the final -ane at the end of the parent hydrocarbon name is replaced with -yl amine. Some common amines are: methylamine and propylamine
The following colors are used to denote hydrogen, carbon, nitrogen, oxygen and iodine atoms in the molecular structures illustrated below.
Use the radio buttons to view the three-dimensional structure of example molecules from various classes of organic chemicals. Note that dragging in the plot window allows you to rotate the view.
Class
General Formula
Examples
View Structure
Halohydrocarbons
−X(F, Cl, Br, I)
R−X
CH3I
Alcohols
−OH
R−O−H
CH3OH
Ethers
−O−
R−O−R'
CH3−O−CH3
Aldehydes
O
∥
−C−H
R−C−H
H−C−H
Ketones
−C−
R−C−R'
CH3−C−CH3
Carboxylic Acids
−C−OH
R−C−OH
CH3−C−OH
Esters
−C−O−
R−C−O−R'
CH3−C−OCH2CH3
Amines
−NH2
R−NH2
CH3NH2
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