Volume 14, Issue 34, July - December, 2020

The proton affinities of a sequence of β-substituted acrylamide in the ground state: A DFT based computational approach

Biswarup Mandal¹, Umasankar Senapati², Bhudeb Ranjan De^1♦

¹Department of Chemistry and Chemical Technology, Vidyasagar University, Midnapore, W.B., India, Pin – 721102, E-mail: biswarupmandal75@gmail.com
²Department of Chemistry, Belda College, Belda, Paschim Medinipur, Pin- 721424, W.B., India, E-mail: Senapatiumasankar@gmail.com

^♦Corresponding author
Prof. Bhudeb Ranjan De, E-mail: biswarupmandal75@gmail.com

ABSTRACT

A detailed study of the proton affinities of a series of β-substituted acrylamides and their O-protonated counterparts has been performed by B3LYP (DFT) method using 6-311G (d,p) basis sets with complete geometry optimization both before and after protonation. The gas phase O-protonation is observed to be exothermic and the local stereochemical disposition of the proton is found to be almost the same in each case. The presence of β-substituent is seen to cause very little change of the proton affinities, relative to the unsubstituted acrylamides. Computed proton affinities are sought to be correlated with a number of computed system parameters such as the Mulliken net charge on the carbonyl oxygen of the unprotonated bases, Mulliken net charge on the carbonyl oxygen and Mulliken net charge on the proton of the protonated bases. The overall basicity is explained by the distant atom contribution in addition to the contribution from the carbonyl group. The electron-releasing substituents are seen to increase the computed proton affinities (PAs) while the electron-withdrawing groups have an opposite effect as expected.

Keywords: B3LYP DFT; GAUSSIAN; Acrylamides; Charge distribution; Gas phase

Drug Discovery, 2020, 14(34), 238-245

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