Strong effect of methyl group on the strength of ionic hydrogen bond between C₂H₂ and H₃O⁺

Abstract

ABSTRACT:The effect of methyl group on the strength of the ionic hydrogen bond between C 2 H 2 and H 3 O ϩ has been studied with quantum chemical calculations at the UMP2/6-311ϩϩG(d,p) level. The presence of a methyl group in the proton acceptor results in an energetic increase of 6.02 kcal/mol, increased by about 39%, whereas that in the proton donor leads to an energetic decrease of 2.18 kcal/mol, decreased by 14%. The charge analyses indicate that the methyl group in the proton acceptor is electrondonating and that in the proton donor is electron-withdrawing. The former plays a positive contribution to the formation of ionic hydrogen bond and the latter plays a negative contribution to the formation of ionic hydrogen bond. The weakening effect of solvent on the role of methyl group in the ionic hydrogen bond has also been studied at the UB3LYP/6-311ϩϩG(d,p) level.

A new unconventional halogen bond CX···HM between HCCX (X = Cl and Br) and HMH (M = Be and Mg): An ab initio study

“…The main aims of this paper are (1) to observe how the metal hydrides and halogen donors respond to each other, (2) to explore the bonding nature of the CX···HM complex, (3) to compare the bond energies of CX···HM bonds with those of dihydrogen bonds and conventional halogen bonds. Considering the regulating role of methyl group in intermolecular interactions,37–40 we also studied the role of methyl group in this type of halogen bond. This work should be interesting for future theoretical investigations and experimental works.…”