A Computational Study of 2-(chloromethyl)oxirane Ring Opening by Bromide and Acetate Anions Considering Electrophilic Activation with Cations of Alkali Metals

Kseniia Yutilova,Yuliia Bespal’Ko,Elena Shved

doi:10.5562/cca3505

Kseniia Yutilova, Yuliia Bespal’Ko + Show 1 more

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https://doi.org/10.5562/cca3505

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Abstract

Ring opening of 2-(chloromethyl)oxirane via the nucleophilic substitution with bromide and acetate anions was investigated using density functional theory (DFT) calculations. It was shown that the geometry of the transition states and the activation parameters of the reactions correspond to those of SN2-like mechanism. The nature of localized transition states was analyzed using More O’Ferrall – Jencks plots. The quantum chemical simulations of the potential energy surface for the ring-opening reaction of oxirane by nucleophiles confirmed the theoretical assumptions about the favored path of interactions, which is a backside α-attack of nucleophile. The effect of alkali metal cation (Li+, Na+, K+) on that path was estimated. It was found that the electrophilic activation with alkali metal cation is more pronounced in the reaction of 2-(chloromethyl)oxirane with dissociated ions, than with ionic pairs.

Highlights

R ING-OPENING reaction of oxiranes by nucleophilic reagents (H-Nu) is a well-known chemical process widely used in organic synthesis.[1,2,3]
The aim of this work is to study the selectivity of the ring opening of an asymmetric oxirane in the system “ECH – electrophilic and nucleophilic particles (E-Nu)”, where E is cation of an alkali metal and Nu is the bromide or acetate anion, by the method of quantum chemical modelling
Optimization of the geometry of TS, reactants, products of nucleophilic ring opening of ECH, bond orders calculations, and frequency analysis were performed by density functional theory (DFT) method with B3LYP exchange correlation functional and 6-31+G** basis set for the gas phase

Summary

Introduction

R ING-OPENING reaction of oxiranes by nucleophilic reagents (H-Nu) is a well-known chemical process widely used in organic synthesis.[1,2,3] The ring opening of the substituted oxiranes leads to a parallel formation of normal (n-P) and abnormal (a-P) products (Scheme 1), which are versatile intermediates in organic synthesis due to three reaction centers at contiguous carbon atoms.[4,5,6,7,8] Only normal product transformations allow obtaining the glycidyl esters, which are important compounds for polymer industry.[4,5,6,8,9,10] According to the Krasusky rule,[11] the formation of the n-P esters is favored[12,13,14] and is in good agreement with nucleophilic attack through SN2 mechanism with some contribution of “borderline” SN2-like mechanism.[15]. Scheme 1 exhibits the possible directions of attack by a nucleophilic reagent on both carbon atoms of the oxirane ring of 2-(chloromethyl)oxirane Possible paths of nucleophilic attack (H-Nu) on 2(chloromethyl)oxirane: formation of n-P and a-P products of ring-opening reaction and possible TS leading to these products

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