Original scientific paper

Neutral Intramolecular Hydrogen-Bonded Bases

Zhixin Tian ; Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA
Alireza Fattahi ; Department of Chemistry, Sharif University of Technology, Tehran, Iran
Lev Lis ; Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA
Steven R. Kass ; Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA

Abstract

B3LYP/aug-cc-pVDZ computations were carried out on polyamines with up to seven amino groups. The gas-phase proton affinities of these compounds are 219.6 (1-BuNH₂), 238.6 (H₂NCH₂CH₂CH₂CH₂NH₂), 252.8 [(H₂NCH₂CH₂CH₂)₂CHNH₂], 261.3 [(H₂NCH₂CH₂CH₂)₂CNH₂ (1)], and 288.5 kcal mol−1 [(H₂NCH₂CH₂CH(NH₂)CH₂CH₂)₂CNH₂]. These results indicate that the tetraamine is near the top of the basicity scale and the heptaamine is more basic than any neutral organic compound which has been measured to date. A gas-phase equilibrium acidity determination between 1 and DBU also was carried out, and PA(1) = 256.2 ± 2.1 kcal mol−1 was obtained. This demonstrates that multiple intramolecular hydrogen bonds can greatly increase basicities, and represents a new motif for designing super bases.

Keywords

super bases; gas-phase basicity; hydrogen-bonding; computations

Hrčak ID:

37977

URI

https://hrcak.srce.hr/37977

Publication date:

30.6.2009.

Visits: 1.799 *