Molecular model studies based on ab initio calculations of nucleophilic and electrophilic addition‐substitution reactions focused on carbon–halogen compounds

Buck, HM Henk

doi:10.1002/qua.22937

Cited by 2 publications

(1 citation statement)

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“…The ab initio value is 3.14 Å. For this specific case, we refer to our original papers based on the vtH model because in the latter case the C ··· C distance passes the critical value of 2.57 Å 14, 25–27. Generally, the ratio numbers ( R ( n ,θ)) and corresponding distances ( d XY ) connected with this model description are expressed as: in which d XY is the conventional bonding distance.…”

Section: Resultsmentioning

confidence: 99%

Mechanistic models for the intramolecular hydroxycarbene–formaldehyde conversion and their intermolecular interactions: Theory and chemistry of radicals, mono‐, and dications of hydroxycarbene and related configurations

Buck¹

2012

Int J of Quantum Chemistry

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We have studied with theoretical and mechanistic models the intramolecular 1,2-hydrogen shift in trans-hydroxycarbeneformaldehyde and trans-methylhydroxycarbene-acetaldehyde/ vinyl alcohol, and the corresponding intermolecular complexation between hydroxycarbene (cis and trans) with formaldehyde. The purpose of our work is making an analysis of the proposed intramolecular hydrogen shifts mainly based on thermodynamic principles and the product selectivity on monochromatic irradiation of trans-hydroxycarbene in carbon monoxide and molecular hydrogen, and formaldehyde. A geometric visualization of the various intermolecular complexes between hydroxycarbene and formaldehyde, based on ab initio results, is demonstrated and discussed with a concept abstracted from the van't Hoff dynamics for a regular tetrahedron in which the interstitial carbon changes its position from tetrahedral into a trigonal-bipyramidal configuration. This concept has been also used for interactions via proton transfer, concretized as hydrogen-bonded complexation in hydroxycarbene-formaldehyde. With the introduced definitions for various van't Hoff ratio numbers, it was possible to judge the ab initio results of the intermolecular complexes between the hydroxycarbenes and formaldehyde. To make an eye-opener, we discuss the role of the carbene lone pair in hydroxycarbene extended to the formation of mono-and dications demonstrating intermediates or transition states with an exclusive mechanistic behavior. Especially, substituted diaryl methylene dications are of interest for nucleophilic substitution reactions, which occur via an in-plane tetracoordinate carbon intermediate, showing coherence with the orbital organization of methylene dications. A reaction of this type differs fundamentally from the classical S 2 N reaction.

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