Nucleophile-electrophile interactions in the reaction of oxiranes with carboxylic acids in the presence of tertiary amines

Abstract

The nucleophile-electrophile interactions in the reaction system "N,Ndimethylanilineacetic acidepichlorohydrin" have been investigated using kinetic methods and computer modeling. The observed orders of reactions have been determined for the overall reaction as well as for individual stages. The kinetic equations have been proposed; the activation parameters of the reactions have been evaluated.The behavior of the initial (amine) and intermediate (carboxylate) nucleophiles has been detailed in reaction pathway. Amine reacts with oxirane activated by acidic reagent while carboxylate-anion-with both activated and nonactivated epichlorohydrin. The mechanism of oxirane ring opening by acid reagent in the presence of tertiary amine has been proposed, which comprise parallel-consecutive compensation stages of reaction product formation. It has been demonstrated that the observed reaction order with respect to acid reactant depends upon the nature of electrophilic reagent (activated/nonactivated oxirane) and the ratio of the rates of compensation stages.

Experimental and computational studies of the mechanism of base‐catalyzed ring opening of 2‐(chloromethyl)oxirane by benzoic acid

“…If amine catalysts are used, as opposed to the utilization of ammonium salts, then the amount of free benzoate anion (intermediate) decreases and this reduces the yield of the a‐P product yield. An additional advantage of the use of weak nucleophilic tertiary amines as catalysts is the low rate of undesired intermediate product formation 23 . Moreover, the ion pair of benzoate anion (in tetraalkylammonium benzoate formed in situ ) can attack C 1 atom of 2‐(chloromethyl)oxirane via A2 mechanism (S N 2 type) without the unwanted dissociation into free ions.…”

“…There are three accepted mechanisms that describe the catalytic action of tertiary amines and tetraalkylammonium halides: the base mechanism, 18 the nucleophilic mechanism, 19 and the mechanism of the nucleophilic reagent anion transfer by the ion pair 20–23 . All three mechanisms include an intermediate formation of tri‐ or tetraalkylammonium carboxylate, as depicted in Scheme 2.…”

“…However, the nucleophilic mechanism 19–21 involves trimolecular interaction of base, oxirane, and carboxylic acid, which results in the formation of tetraalkylammonium carboxylate. For the nucleophilic reagent anion transfer by the ion pair, 20–23 a set of consecutive parallel interactions leads to the formation of the intermediate product. In all cases, the carboxylate oxygen of the carboxylate then directly attacks the oxirane.…”

“…There are three accepted mechanisms that describe the catalytic action of tertiary amines and tetraalkylammonium halides: the base mechanism, 18 the nucleophilic mechanism, 19 and the mechanism of the nucleophilic reagent anion transfer by the ion pair. [20][21][22][23] All three mechanisms include an intermediate formation of tri-or tetraalkylammonium carboxylate, as depicted in Scheme 2. In the first case (Scheme 2a), the catalyst acts as a base that promotes partial or total ionization of the carboxylic acid by forming either a hydrogen bond complex or a trialkylammonium carboxylate complex.…”

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

“…[1,6,7,20] An investigation of special aspects of n-P ester formation includes consideration of the joint effect of electrophile and nucleophile. [21][22][23] The ring opening of oxiranes by nucleophilic reagents (SN2-like mechanism) may proceed without (A) and with (B) preliminary activation of oxirane ring by electrophile (without and with electrophilic activation) (Scheme 2), and the last one has an energetic benefit. [11,22] To consider the contribution of the electrophilic activation, it is important to model the ring-opening reaction by reagent containing both electrophilic and nucleophilic particles (E-Nu).…”