From left to right: the two isomeric groups propyl and 1-methylethyl (or isopropyl), and the non-isomeric cyclopropyl group.
In organic chemistry, propyl is a linear three-carbon alkyl substituent with chemical formula -C3H7. It is the substituent form obtained by removing one hydrogen atom attached to the terminal carbon of propane. A propyl substituent is often represented in organic chemistry with the symbol Pr (not to be confused with the element praseodymium).
There is an isomeric form of propyl named 1-methylethyl or isopropyl obtained by removing a hydrogen ion (proton) attached to the middle carbon of propane.
Linear propyl is sometimes termed normal and written with a prefix n- (i.e., n-propyl). However, n- is redundant because the absence of any prefix implies an unbranched propyl.
In addition there is a third, cyclic, form called cyclopropyl, or c-propyl. It is not isomeric with the other two forms, having the chemical formula -C3H5.
Propyl ethanoate, also called propyl acetate
This is propyl ethanoate, an ester. The propyl group is attached to the molecule after the middle oxygen.