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Title: Isomers and conformational barriers of gas phase nicotine, nornicotine and their protonated forms

Abstract

We report extensive conformational searches of the neutral nicotine, nornicotine and their protonated analogs that are based on ab-initio second order Møller-Plesset perturbation (MP2) electronic structure calculations. Initial searches were performed with the 6-31G(d,p) and the energetics of the most important structures were further refined from geometry optimizations with the aug-cc-pVTZ basis set. Based on the calculated free energies at T=298 K for the gas phase molecules, neutral nicotine has two dominant trans conformers, whereas neutral nornicotine is a mixture of several conformers. For nicotine, the protonation on both the pyridine and the pyrrolidine sites is energetically competitive, whereas nornicotine prefers protonation on the pyridine nitrogen. The protonated form of nicotine is mainly a mixture of two pyridine-protonated trans conformers and two pyrrolidine-protonated trans conformers, whereas the protonated form of nornicotine is a mixture of four pyridine-protonated trans conformers. Nornicotine is conformationally more flexible than nicotine, however it is less protonated at the biologically important pyrrolidine nitrogen site. The lowest energy isomers for each case were found to interconvert via low (< 6 kcal/mol) rotational barriers around the pyridine-pyrrolidine bond.

Authors:
; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1163818
Report Number(s):
PNNL-SA-95198
KC0301020
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physical Chemistry B, 118(28):8273-8285
Country of Publication:
United States
Language:
English

Citation Formats

Yoshida, Tomoki, Farone, William A., and Xantheas, Sotiris S. Isomers and conformational barriers of gas phase nicotine, nornicotine and their protonated forms. United States: N. p., 2014. Web. doi:10.1021/jp501646p.
Yoshida, Tomoki, Farone, William A., & Xantheas, Sotiris S. Isomers and conformational barriers of gas phase nicotine, nornicotine and their protonated forms. United States. doi:10.1021/jp501646p.
Yoshida, Tomoki, Farone, William A., and Xantheas, Sotiris S. Thu . "Isomers and conformational barriers of gas phase nicotine, nornicotine and their protonated forms". United States. doi:10.1021/jp501646p.
@article{osti_1163818,
title = {Isomers and conformational barriers of gas phase nicotine, nornicotine and their protonated forms},
author = {Yoshida, Tomoki and Farone, William A. and Xantheas, Sotiris S.},
abstractNote = {We report extensive conformational searches of the neutral nicotine, nornicotine and their protonated analogs that are based on ab-initio second order Møller-Plesset perturbation (MP2) electronic structure calculations. Initial searches were performed with the 6-31G(d,p) and the energetics of the most important structures were further refined from geometry optimizations with the aug-cc-pVTZ basis set. Based on the calculated free energies at T=298 K for the gas phase molecules, neutral nicotine has two dominant trans conformers, whereas neutral nornicotine is a mixture of several conformers. For nicotine, the protonation on both the pyridine and the pyrrolidine sites is energetically competitive, whereas nornicotine prefers protonation on the pyridine nitrogen. The protonated form of nicotine is mainly a mixture of two pyridine-protonated trans conformers and two pyrrolidine-protonated trans conformers, whereas the protonated form of nornicotine is a mixture of four pyridine-protonated trans conformers. Nornicotine is conformationally more flexible than nicotine, however it is less protonated at the biologically important pyrrolidine nitrogen site. The lowest energy isomers for each case were found to interconvert via low (< 6 kcal/mol) rotational barriers around the pyridine-pyrrolidine bond.},
doi = {10.1021/jp501646p},
journal = {Journal of Physical Chemistry B, 118(28):8273-8285},
number = ,
volume = ,
place = {United States},
year = {Thu Jul 17 00:00:00 EDT 2014},
month = {Thu Jul 17 00:00:00 EDT 2014}
}