Science, Tech, Math › Science Butyl Functional Group Names Share Flipboard Email Print chain45154 / Getty Images Science Chemistry Molecules Basics Chemical Laws Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated January 02, 2020 The butyl functional group consists of four carbon atoms. These four atoms can be arranged in four different bond configurations when attached to a molecule. Each arrangement has its own name to distinguish the different molecules they form. These names are: n-butyl, s-butyl, t-butyl, and isobutyl. 01 of 04 n-Butyl Functional Group Todd Helmenstine The first form is the n-butyl group. It consists of all four carbon atoms forming a chain and the rest of the molecule attaches at the first carbon. The n- stands for 'normal'. In common names, the molecule would have n-butyl added to the molecule name. In systematic names, n-butyl would have butyl added to the molecule name. 02 of 04 s-Butyl Functional Group Todd Helmenstine The second form is the same chain arrangement of carbon atoms, but the rest of the molecule attaches at the second carbon in the chain. The s- stands for secondary since it attaches to the secondary carbon in the chain. It is also often labeled as sec-butyl in common names. For systematic names, s-butyl is slightly more complicated. The longest chain at the point of connection is a propyl formed by carbons 2,3 and 4. Carbon 1 forms a methyl group, so the systematic name for s-butyl would be methylpropyl. 03 of 04 t-Butyl Functional Group Todd Helmenstine The third form has three of the carbons single bonded to a center fourth carbon and the rest of the molecule is attached to the center carbon. This configuration is called t-butyl or tert-butyl in common names. For systematic names, the longest chain is formed by carbons 2 and 1. Two carbon chains form an ethyl group. The other two carbons are both methyl groups attached at the beginning point of the ethyl group. Two methyls equal one dimethyl. Therefore, t-butyl is 1,1-dimethylethyl in systematic names. 04 of 04 Isobutyl Functional Group Todd Helmenstine The final form has the same carbon arrangement as t-butyl but the attachment point is at one of the ends instead of the center, common carbon. This arrangement is known as isobutyl in common names. In systematic names, the longest chain is a propyl group formed by carbons 1, 2 and 3. Carbon 4 is a methyl group attached to the second carbon in the propyl group. This means isobutyl would be 2-methylpropyl in systematic names.