1) Alkyl with five carbon atoms 1) Amyl 
In organic chemistry, pentyl is a five-carbon alkyl functional group (substituent) with chemical formula -C5H11. It is the substituent form of the alkane pentane. In older literature, the common non-systematic name `amyl` was often used for the pentyl group. Conversely, the name pentyl was used for several five-carbon branched alkyl groups, dist.....
• (n.) The hypothetical radical, C5H11, of pentane and certain of its derivatives. Same as Amyl.
Pen'tyl noun [ Pent a + - yl .] (Chemistry) The hypothetical radical, C 5 H 11 , of pentane and certain of its derivatives. Same as Amyl . 
Type: Term Pronunciation: pen′til Definitions: 1. The CH3(CH2)3CH2— moiety. Synonyms: amyl