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Title: Mechanisms of electrophilic substitutions of aliphatic hydrocarbons. CH[sub 4] + NO[sup +]

Abstract

The substitution reaction of methane with the nitrosonium cation, a model electrophile, was investigated computationally at the Hartree-Fock and correlated MP2, MP4SDTQ, and CISD levels of theory, using standard basis sets (6-31G(d), 6-31G(dp), and 6-31+G(dp) for geometry optimizations and TZ2P for energy single points on the most critical structures). The energetically favored reaction course leads to N-protonated nitrosomethane. H[sub 3]/CHNO[sup 4] (6). The initial complex of CH[sub 4] and NO[sup +] in C[sub s] symmetry is bound by -3.7 kcal mol[sup 1] MP4SDTQ/6-31+G(dp)/MP2/6-31+G(dp) + ZPVE/MP2/6-31+G(dp). In the critical step, electrophile NO[sup +] attacks carbon directly, rather than a C-H bond, to yield a pentacoordinate intermediate (3) with a hydrogen unit attached to a H[sub 2]CNO[sup +] cation moiety [[Delta]H[sub O](CISD+Q/TZ2P/MP2/6-31G(dp)+ZPVE//MP 2/6-31G(d p)) = 57.3 kcal mol[sup [minus]1]]. This unusual mode of attack, proceeding through a transition structure which also has three-center two-electron (3c-2e) CHH bonding, can be visualized in two ways. During the reaction, tetrachedral methane distorts to lower symmetry (C[sub s]) and binding between the electrophile and the developing lone pair occurs. The energy required for the methane distortion is partly recovered from the new bonding interaction to the electrophile. An alternative pathway involving the insertion of NO[sup +]more » into a CH bond is less favorable by 14.4 kcal mol[sup [minus]1]. 27 refs., 9 figs., 3 tabs.« less

Authors:
;  [1];  [2]
  1. Univ. of Georgia, Athens, GA (United States) Universitaet Erlangen-Nuernberg (Germany)
  2. Univ. of Georgia, Athens, GA (United States)
Publication Date:
OSTI Identifier:
5114370
DOE Contract Number:  
FG09-87ER13811
Resource Type:
Journal Article
Journal Name:
Journal of the American Chemical Society; (United States)
Additional Journal Information:
Journal Volume: 115:21; Journal ID: ISSN 0002-7863
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE; 10 SYNTHETIC FUELS; CATIONS; CHEMICAL REACTIONS; REACTION KINETICS; METHANE; ENTHALPY; HARTREE-FOCK METHOD; ISOMERS; NITROSO COMPOUNDS; REACTION INTERMEDIATES; THEORETICAL DATA; ALKANES; CALCULATION METHODS; CHARGED PARTICLES; DATA; HYDROCARBONS; INFORMATION; IONS; KINETICS; NUMERICAL DATA; ORGANIC COMPOUNDS; ORGANIC NITROGEN COMPOUNDS; PHYSICAL PROPERTIES; THERMODYNAMIC PROPERTIES; 400201* - Chemical & Physicochemical Properties; 990200 - Mathematics & Computers; 100200 - Synthetic Fuels- Production- (1990-)

Citation Formats

Schreiner, P R, Rague Schleyer, P von, and Schaefer, III, H F. Mechanisms of electrophilic substitutions of aliphatic hydrocarbons. CH[sub 4] + NO[sup +]. United States: N. p., 1993. Web. doi:10.1021/ja00074a035.
Schreiner, P R, Rague Schleyer, P von, & Schaefer, III, H F. Mechanisms of electrophilic substitutions of aliphatic hydrocarbons. CH[sub 4] + NO[sup +]. United States. https://doi.org/10.1021/ja00074a035
Schreiner, P R, Rague Schleyer, P von, and Schaefer, III, H F. 1993. "Mechanisms of electrophilic substitutions of aliphatic hydrocarbons. CH[sub 4] + NO[sup +]". United States. https://doi.org/10.1021/ja00074a035.
@article{osti_5114370,
title = {Mechanisms of electrophilic substitutions of aliphatic hydrocarbons. CH[sub 4] + NO[sup +]},
author = {Schreiner, P R and Rague Schleyer, P von and Schaefer, III, H F},
abstractNote = {The substitution reaction of methane with the nitrosonium cation, a model electrophile, was investigated computationally at the Hartree-Fock and correlated MP2, MP4SDTQ, and CISD levels of theory, using standard basis sets (6-31G(d), 6-31G(dp), and 6-31+G(dp) for geometry optimizations and TZ2P for energy single points on the most critical structures). The energetically favored reaction course leads to N-protonated nitrosomethane. H[sub 3]/CHNO[sup 4] (6). The initial complex of CH[sub 4] and NO[sup +] in C[sub s] symmetry is bound by -3.7 kcal mol[sup 1] MP4SDTQ/6-31+G(dp)/MP2/6-31+G(dp) + ZPVE/MP2/6-31+G(dp). In the critical step, electrophile NO[sup +] attacks carbon directly, rather than a C-H bond, to yield a pentacoordinate intermediate (3) with a hydrogen unit attached to a H[sub 2]CNO[sup +] cation moiety [[Delta]H[sub O](CISD+Q/TZ2P/MP2/6-31G(dp)+ZPVE//MP 2/6-31G(d p)) = 57.3 kcal mol[sup [minus]1]]. This unusual mode of attack, proceeding through a transition structure which also has three-center two-electron (3c-2e) CHH bonding, can be visualized in two ways. During the reaction, tetrachedral methane distorts to lower symmetry (C[sub s]) and binding between the electrophile and the developing lone pair occurs. The energy required for the methane distortion is partly recovered from the new bonding interaction to the electrophile. An alternative pathway involving the insertion of NO[sup +] into a CH bond is less favorable by 14.4 kcal mol[sup [minus]1]. 27 refs., 9 figs., 3 tabs.},
doi = {10.1021/ja00074a035},
url = {https://www.osti.gov/biblio/5114370}, journal = {Journal of the American Chemical Society; (United States)},
issn = {0002-7863},
number = ,
volume = 115:21,
place = {United States},
year = {Wed Oct 20 00:00:00 EDT 1993},
month = {Wed Oct 20 00:00:00 EDT 1993}
}