Matching Pairs Nomenclature (O. Chem)Online version Have a hard time remembering what an isopropyl is and whether or not to use "but" or "hept" when there are four carbons? Me too! Hopefully this will help us both memorize the rules of nomenclature. (This is specifically based on Indiana University's Organic Chemistry 1 class, but it may apply to others learning college-level organic chemistry, as well.) by Candace Nunn 1 Ethyl (Et) 2 Isopropyl (iPr) 3 Pentyl 4 sec-Butyl (s-Bu) 5 2-Methylbutyl 6 Butyl (Bu) 7 Neopentyl (2,2, Dimethylpropyl) 8 Methyl (Me) 9 Isopentyl 10 Isobutyl (iBu) 11 tert-Butyl (t-Bu) 12 Propyl (Pr)