The key difference between tert butyl and isobutyl is that the tert butyl group contains a double branched carbon chain whereas the isobutyl contains a single branched carbon chain.
The two terms tert butyl and isobutyl refer to two different functional groups in organic chemistry. However, these two groups have the same number of carbon atoms and hydrogen atoms but have different spatial arrangement of these atoms. The chemical formula of both is −C4H9. Moreover, these groups may exist as radicals or functional groups.
CONTENTS
1. Overview and Key Difference
2. What is Tert Butyl
3. What is Isobutyl
4. Side by Side Comparison – Tert Butyl vs Isobutyl in Tabular Form
5. Summary
What is Tert Butyl?
Tert butyl is a four carbon alkyl radical or functional group in which a carbon centre attaches with three methyl groups. Therefore, this group contains a double branched alkane structure. There, the central carbon atom that is attached with three methyl groups has a vacant point to which a separate moiety of a molecule may attach to.
Figure 01: Tert Butyl Acetate
Since the functional group has three methyl groups, we name it as tertiary-butyl, tert-butyl or t-butyl. The systematic name for this group is “1,1-dimethyl ethyl”, and the chemical formula is (CH3)3C−.
Ex: tert-butyl acetate contains a tert-butyl functional group attached with an acetate group.
What is Isobutyl?
Isobutyl is a four carbon alkyl radical or functional group in which a three-membered carbon chain attached with one methyl group at its second carbon atom. Therefore, this functional group contains a single methyl branch. The three-membered carbon chain contains a methyl group at the second carbon atom while the third carbon atom has a vacant point to which a separate moiety of a molecule may attach with.
Figure 02: Isobutyl Acetate
The chemical formula for this group is (CH3)2CH−CH2−, and the systematic name is “2-methyl propyl”.
Ex: isobutyl acetate contains an isobutyl functional group attached with an acetate group.
What is the Difference Between Tert Butyl and Isobutyl?
Tert butyl is a four carbon alkyl radical or functional group in which a carbon centre attaches with three methyl groups whereas isobutyl is a four carbon alkyl radical or functional group in which a three-membered carbon chain attached with one methyl group at its second carbon atom. Hence, this is the fundamental difference between tert butyl and isobutyl. Moreover, the above difference gives rise to another significant difference between tert butyl and isobutyl. That is, the tert butyl group contains a double branched structure while the isobutyl group contains a single branched structure. Also, the systematic name of tert butyl is 1,1-dimethyl ethyl while that of isobutyl is 2-methyl propyl.
The below infographic tabulates the difference between tert butyl and isobutyl as a side by side comparison.
Summary – Tert Butyl vs Isobutyl
The term butyl and isobutyl are functional groups that are isomers of each other. Therefore, they have the same atomic composition, but a different atomic arrangement. The key difference between tert butyl and isobutyl is that the tert butyl group contains a double branched carbon chain whereas isobutyl contains a single branched carbon chain.
Reference:
1. “Butyl Group.” Wikipedia, Wikimedia Foundation, 25 May 2018. Available here
2. “Don’t Be Futyl, Learn The Butyls.” Master Organic Chemistry RSS. Available here
Image Courtesy:
1.”T-butyl acetate”By Edgar181 – Own work, (Public Domain) via Commons Wikimedia
2.”Isobutyl-acetate”By Benrr101 – Own work, (Public Domain) via Commons Wikimedia