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Title: CASSCF and CASPT2 ab initio electronic structure calculations find singlet methylnitrene is an energy minimum

Abstract

(12/11)CASSCF and (12/11)CASPT2 ab initio electronic structure calculations with both the cc-pVDZ and cc-pVTZ basis sets find that there is a barrier to the very exothermic hydrogen shift that converts singlet methylnitrene, CH{sub 3}N, to methyleneimine, H{sub 2}C{double{underscore}bond}NH. These two energy minima are connected by a transition structure of C{sub s} symmetry, which is computed to lie 3.8 kcal/mol above the reactant at the (12/11)CASPT2/cc-pVTZ//(12/11)CASSCF/cc-pVTZ level of theory. The (12/11)CASSCF/cc-pVTZ value for the lowest frequency vibration in the transition structure is 854 cm{sup {minus}1}, and CASPT2 calculations concur that this a{double{underscore}prime} vibration does indeed have a positive force constant. Thus, there is no evidence that this geometry is actually a mountain top, rather than a transition structure, on the global potential energy surface or that a C{sub 1} pathway of lower energy connects the reactant to the product. Therefore, computational results indicate that the bands seen for singlet methylnitrene in the negative ion photoelectron spectrum of CH{sub 3}N{sup {minus}} are due to singlet methylnitrene being an energy minimum, rather than a transition state. These results also lead to the prediction that, at least in principle, singlet methylnitrene should be an observable intermediate in the formation of methyleneimine.

Authors:
; ; ;
Publication Date:
Research Org.:
California State Univ., Bakersfield, CA (US)
Sponsoring Org.:
National Science Foundation (NSF); USDOE
OSTI Identifier:
20017359
DOE Contract Number:  
FG02-87ER13695
Resource Type:
Journal Article
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 122; Journal Issue: 6; Other Information: PBD: 16 Feb 2000; Journal ID: ISSN 0002-7863
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ELECTRONIC STRUCTURE; MATHEMATICAL MODELS; REACTION INTERMEDIATES; IMINES; AMINES; WAVE FUNCTIONS

Citation Formats

Kemnitz, C R, Ellison, G B, Karney, W L, and Borden, W T. CASSCF and CASPT2 ab initio electronic structure calculations find singlet methylnitrene is an energy minimum. United States: N. p., 2000. Web. doi:10.1021/ja9907257.
Kemnitz, C R, Ellison, G B, Karney, W L, & Borden, W T. CASSCF and CASPT2 ab initio electronic structure calculations find singlet methylnitrene is an energy minimum. United States. https://doi.org/10.1021/ja9907257
Kemnitz, C R, Ellison, G B, Karney, W L, and Borden, W T. 2000. "CASSCF and CASPT2 ab initio electronic structure calculations find singlet methylnitrene is an energy minimum". United States. https://doi.org/10.1021/ja9907257.
@article{osti_20017359,
title = {CASSCF and CASPT2 ab initio electronic structure calculations find singlet methylnitrene is an energy minimum},
author = {Kemnitz, C R and Ellison, G B and Karney, W L and Borden, W T},
abstractNote = {(12/11)CASSCF and (12/11)CASPT2 ab initio electronic structure calculations with both the cc-pVDZ and cc-pVTZ basis sets find that there is a barrier to the very exothermic hydrogen shift that converts singlet methylnitrene, CH{sub 3}N, to methyleneimine, H{sub 2}C{double{underscore}bond}NH. These two energy minima are connected by a transition structure of C{sub s} symmetry, which is computed to lie 3.8 kcal/mol above the reactant at the (12/11)CASPT2/cc-pVTZ//(12/11)CASSCF/cc-pVTZ level of theory. The (12/11)CASSCF/cc-pVTZ value for the lowest frequency vibration in the transition structure is 854 cm{sup {minus}1}, and CASPT2 calculations concur that this a{double{underscore}prime} vibration does indeed have a positive force constant. Thus, there is no evidence that this geometry is actually a mountain top, rather than a transition structure, on the global potential energy surface or that a C{sub 1} pathway of lower energy connects the reactant to the product. Therefore, computational results indicate that the bands seen for singlet methylnitrene in the negative ion photoelectron spectrum of CH{sub 3}N{sup {minus}} are due to singlet methylnitrene being an energy minimum, rather than a transition state. These results also lead to the prediction that, at least in principle, singlet methylnitrene should be an observable intermediate in the formation of methyleneimine.},
doi = {10.1021/ja9907257},
url = {https://www.osti.gov/biblio/20017359}, journal = {Journal of the American Chemical Society},
issn = {0002-7863},
number = 6,
volume = 122,
place = {United States},
year = {Wed Feb 16 00:00:00 EST 2000},
month = {Wed Feb 16 00:00:00 EST 2000}
}