Benchmark Study on the Smallest Bimolecular Nucleophilic  Substitution Reaction: H−+CH4 →CH4+H−

The reaction potential energy surface (PES), and thus the mechanism of bimolecular nucleophilic substitution (SN2), depends profoundly on the nature of the nucleophile and leaving group, but also on the central, electrophilic atom, its substituents, as well as on the medium in which the reaction takes place. Here, we provide an overview of recent studies and demonstrate how changes in any one of the aforementioned factors affect the SN2 mechanism. One of the most striking effects is the transition from a double‐well to a single‐well PES when the central atom is changed from a second‐period (e. g. carbon) to a higher‐period element (e.g, silicon, germanium). Variations in nucleophilicity, leaving group ability, and bulky substituents around a second‐row element central atom can then be exploited to change the single‐well PES back into a double‐well. Reversely, these variations can also be used to produce a single‐well PES for second‐period elements, for example, a stable pentavalent carbon species.

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Nucleophilic Substitution (S_N2): Dependence on Nucleophile, Leaving Group, Central Atom, Substituents, and Solvent

Hamlin

2018

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DFT study of the hydrolysis reaction in atranes and ocanes: the influence of transannular bonding

et al. 2015

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Thermochemical kinetics of hydrolysis reactions of compounds with transannular intramolecular M…N bonds, i.e., atranes RM(OCH2CH2)3N and ocanes R2M(OCH2CH2)2NH (M = Si, Ge; R = F, Cl, Me), is studied at the B3LYP/aug-cc-pVDZ theoretical level. Several DFT methods are assessed for the reproduction of the experimental activation barrier for the Si-O bond cleavage of 1-methylsilatrane. Activation barriers for atranes and ocanes show the tendency for their growth with the decrease of the electronegativity of a substituent R on going from F to Me and their decrease from Si to Ge. Hydrolysis activation barriers of atranes and ocanes are compared with those of their acyclic analogs RM(OCH3)3 and R2M(OCH2)2NH in order to study the role of transannular M…N bonds in the stability of these molecules to hydrolysis. Substantially larger barriers for atranes support the opinion that stability of atranes may be explained by the formation of intramolecular bonds; however, the strengthening of transannular M…N bonds results in lower M-O cleavage barriers. It was proposed that the M-O cleavage barrier height is determined not by a weak M…N bonding itself, but rather by the contribution of a nitrogen lone pair to the antibonding orbitals of M-O bonds. The NBO analysis show that this interaction increases with the decrease of the electronegativity of a substituent R and decreases on going from atranes to ocanes. In ocanes, the presence of M…N bonds does not kinetically hinder the hydrolytic process; M-O cleavage activation barriers for acyclic analogs are higher. M-Hal cleavage barriers are substantially higher than those for M-O cleavage for R = F, but lower for R = Cl. Graphical Abstract The experimental barrier height of the Si-O bond cleavage in 1-methylsilatrane is well reproduced when three explicit water molecules are included in the B3LYP/aug-cc-pVDZ theoretical model.

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Benchmark Study on the Smallest Bimolecular Nucleophilic Substitution Reaction: H−+CH4 →CH4+H−

Cited by 2 publications

References 82 publications

Nucleophilic Substitution (S_N2): Dependence on Nucleophile, Leaving Group, Central Atom, Substituents, and Solvent

Nucleophilic Substitution (S_N2): Dependence on Nucleophile, Leaving Group, Central Atom, Substituents, and Solvent

DFT study of the hydrolysis reaction in atranes and ocanes: the influence of transannular bonding

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Benchmark Study on the Smallest Bimolecular Nucleophilic Substitution Reaction: H−+CH4 →CH4+H−

Cited by 2 publications

References 82 publications

Nucleophilic Substitution (SN2): Dependence on Nucleophile, Leaving Group, Central Atom, Substituents, and Solvent

Nucleophilic Substitution (SN2): Dependence on Nucleophile, Leaving Group, Central Atom, Substituents, and Solvent

DFT study of the hydrolysis reaction in atranes and ocanes: the influence of transannular bonding

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Nucleophilic Substitution (S_N2): Dependence on Nucleophile, Leaving Group, Central Atom, Substituents, and Solvent

Nucleophilic Substitution (S_N2): Dependence on Nucleophile, Leaving Group, Central Atom, Substituents, and Solvent