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

Journal Article · Wed Oct 20 00:00:00 EDT 1993 · Journal of the American Chemical Society; (United States)

DOI:https://doi.org/10.1021/ja00074a035· OSTI ID:5114370

Schreiner, P R; Rague Schleyer, P von ^[1]; Schaefer, III, H F ^[2]

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1. Univ. of Georgia, Athens, GA (United States) Universitaet Erlangen-Nuernberg (Germany)
2. Univ. of Georgia, Athens, GA (United States)

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.

• DOE Contract Number: FG09-87ER13811
• OSTI ID: 5114370
• Journal Information: Journal of the American Chemical Society; (United States), Vol. 115:21; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

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-)