Abstract
Our simple Meisenheimer model for predicting the principal site for nucleophilic substitution in aromatic perfluorocarbons is further tested on a series of recently published reactions in liquid ammonia primarily from Malykhin and coworkers. The model accurately predicts the experimental results for all of the reactions reported further confirming its general applicability.
Highlights
In earlier work we introduced a simple calculational model for predicting the primary substitution site for nucleophilic substitution involving the replacement of fluorine, initially in aromatic perfluorocarbons [1] and subsequently in fluorinated aromatic systems containing both ring heteroatoms and non-fluorine substituents [2]
On the other hand it is known that most substituents to an aromatic ring direct para as far as replacement of fluorine is concerned, with any preferable ortho substitution nearly always resulting from direct interaction between the attacking nucleophile and the substituent, an interaction that cannot be modeled using fluorine
We have found that the following tactics when constructing the initial starting geometry of a Meisenheimer complex increases the likelihood of optimizing to the global or a near-global minimum: (1) Methyl or similar substituents are added to the aromatic ring such that one of the C-H bonds is perpendicular to the ring
Summary
In earlier work we introduced a simple calculational model for predicting the primary substitution site for nucleophilic substitution involving the replacement of fluorine, initially in aromatic perfluorocarbons [1] and subsequently in fluorinated aromatic systems containing both ring heteroatoms (principally nitrogen, and oxygen, phosphorus and sulphur) and non-fluorine substituents [2]. This simple model has been remarkably successful in predicting the primary site in aromatic nucleophilic substitution reactions, and secondary sites.
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