that is bonded to one other group in the molecule through a single covalent bond from one of its carbon atoms alkyl groups can be cyclic or acyclic branched or unbranched and saturated or unsaturated typically an alkyl group has one to about 24 carbons atoms or one to about 12 carbon atoms lower alkyl groups have one to four carbon atoms and include methyl ethyl n propyl iso propyl n butyl sec butyl and tert butyl aromatic or aryl groups include carbocyclic aromatic groups such as phenyl p tolyl 1 naphthyl 2 naphthyl 1 anthracyl and 2 anthracyl aromatic groups also include heteroaromatic groups such as n imidazolyl 2 imidazole 2 thienyl 3 thienyl 2 furanyl 3 furanyl 2 pyridyl 3 pyridyl 4 pyridyl 2 pyrimidyl 4 pyrimidyl 2 pyranyl 3 pyranyl 3 pyrazolyl 4 pyrazolyl 5 pyrazolyl 2 pyrazinyl 2 thiazolyl 4 thiazolyl 5 thiazolyl 2 oxazolyl 4 oxazolyl and 5 oxazolyl aromatic groups also include fused polycyclic aromatic ring systems in which a carbocyclic alicyclic or aromatic ring or heteroaryl ring is fused to one or more other heteroaryl or aryl rings examples include 2 benzothienyl 3 benzothienyl 2 benzofuranyl 3 benzofuranyl 2 indolyl 3 indolyl 2 quinolinyl 3 quinolinyl 2 benzothiazole 2 benzooxazole 2 benzimidazole 2 quinolinyl 3 quinolinyl 1 isoquinolinyl 3 quinolinyl 1 isoindolyl and 3 isoindolyl suitable substituents for alkyl groups include u2014 oh halogen u2014 br u2014 cl u2014 i and.