A lot of drugs in the market are small organic molecules and as a student of medicinal chemistry, biochemistry, pharmacy, pharmacology or medicine, knowledge of the different functional groups is crucial. Functional groups are specific substituents or moieties, composed of an atom or a group of atoms, within molecules that possess similar chemical properties whenever it occurs in different compounds. Functional groups determine the characteristic physical, chemical and biological properties of a molecule.
When hydrogens attached to carbons are shown in the skeletal formulas of organic compounds, the hydrogens are said to be explicitly shown. However, the hydrogens bonded to carbons are often not shown as it is tedious to do so and the omission makes structures look neater. A shorthand notation, where the hydrogens bonded to carbons aren’t shown in drawings but are assumed to be present, is preferred. In such cases, the hydrogens are said to be implicit. In a similar fashion, the symbol “C” for carbon is often not drawn in skeletal formulas of organic compounds (i.e. implicit carbons).Non-carbon and non-hydrogen atoms are shown in the shorthand notation. Examples:
Note that in organic chemistry, the R group is a generic placeholder for other groups such as aliphatic groups.
Chemical Class | Group | Prefix | Suffix | Example | Example of Functionality Found in a Drug Molecule |
---|---|---|---|---|---|
Alkane R(CH2)nH | Alkyl | Alkyl- | -ane | ![]() | ![]() |
Alkene R2C=CR2 | Alkenyl | Alkenyl- | -ene | ![]() | ![]() |
Alkyne RC≡CR’ | Alkynyl | Alkynyl- | -yne | ![]() | ![]() |
Benzene RC6H5RPh | Phenyl | Phenyl- | -benzene | ![]() | ![]() |
Alkyl halides, which contain carbon-halogen bonds, are sometimes referred to as haloalkanes or halogenoalkanes.
Chemical Class | Group | Prefix | Suffix | Example | Example of Functionality Found in a Drug Molecule |
---|---|---|---|---|---|
Fluoroalkane RF | Fluoro | Fluoro- | Alkyl fluoride | ![]() | ![]() |
Chloroalkane RCl | Chloro | Chloro- | Alkylchloride | ![]() | ![]() |
Bromoalkane RBr | Bromo | Bromo- | Alkylbromide | ![]() | ![]() |
Iodoalkane RI | Iodo | Iodo- | Alkyliodide | ![]() | ![]() |
Chemical Class | Group | Prefix | Suffix | Example | Example of Functionality Found in a Drug Molecule |
---|---|---|---|---|---|
Alcohol ROH | Hydroxyl | Hydroxyl- | -ol | ![]() | ![]() |
Ether ROR’ | Ether | Alkoxy- | Alkyl ether | ![]() | ![]() |
Aldehyde RCHO | Aldehyde | Formyl- or oxo- | -al | ![]() | ![]() |
Ketone RCOR’ | Carbonyl | Oxo- or –oyl- | -one | ![]() | ![]() |
Carboxylic Acid RCOOH | Carboxyl | Carboxy- | -oic acid | ![]() | ![]() |
Ester RCOOR’ | Carboalkoxy | alkanoyloxy- or alkoxycarbonyl | Alkyl alkanoate | ![]() | ![]() |
Notes:
Chemical Class | Group | Prefix | Suffix | Example | Example of Functionality Found in a Drug Molecule |
---|---|---|---|---|---|
Amine RNH2; R2NH; R3N; R4N+ | Amine | Amino- | -amine | ![]() | ![]() |
Imine RC(=NH)R’; RC(=NR’’)R’; RC(=NH)H; RC(=NR’)H | Imine | Imino- | -imine | ![]() | ![]() |
Nitrile RCN | Nitrile | Cyano- | -nitrile or alkyl cyanide | ![]() | ![]() |
Chemical Class | Group | Prefix | Suffix | Example | Example of Functionality Found in a Drug Molecule |
---|---|---|---|---|---|
Amide RCONR2 | Carboxamide | carboxamido- or carbamoyl- | -amide | ![]() | ![]() |
Nitro RNO2 | Nitro | Nitro- | ![]() | ![]() | |
Carbamate RO(C=O)NR2 | Carbamate | (-carbamoyl)oxy- | -carbamate | ![]() | ![]() |
Urea R2N(C=O)NR2 | Urea | ![]() | ![]() |
Chemical Class | Group | Prefix | Suffix | Example | Example of Functionality Found in a Drug Molecule |
---|---|---|---|---|---|
Thiol RSH | Sulfhydryl | sulfanyl- | -thiol | ![]() | ![]() |
Thioether (sulfide) RSR’ | Sulfide | substituent sulfanyl- | (substituent) sulfide | ![]() | ![]() |
Sulfoxide RSOR’ | Sulfinyl | -sulfinyl- | (substituent) sulfoxide | ![]() | ![]() |
Sulfone RSO2R’ | Sulfonyl | -sulfonyl- | (substituent) sulfone | ![]() | ![]() |
The number of names functional groups and moieties is far greater than what is listed here. A more comprehensive list can be found in this article.