83502-55-0Relevant articles and documents
Reaction Mechanism in Ionic Liquids: Kinetics and Mechanism of the Aminolysis of 4-Nitrophenyl Acetate
Pavez, Paulina,Millán, Daniela,Rojas, Mabel,Morales, Javiera I.,Santos, José G.
, p. 337 - 343 (2016/05/02)
In this work, we report a kinetic study of the reactions of the title compound with secondary alicyclic amines at different temperatures in acetonitrile and several ionic liquids (ILs). From this study, we have described that the reactions in MeCN and in
Structure-Reactivity Correlations in the Aminolysis of Phenyl and p-Nitrophenyl Thiolacetates
Castro, Enrique A.,Ureta, Carmen
, p. 2153 - 2159 (2007/10/02)
Second-order rate constants (kN) for the nucleophilic reactions of piperidine, morpholine, piperazine, and N-substituted piperazines with the title substrates are reported in water, at 25 deg C, ionic strength 0.2 M (maintained with KCl).The Broensted-type plot obtained for the aminolysis of phenyl thiolacetate is linear while that for the p-nitrophenyl derivative (NPTA) is curved, with the center of curvature at pKa=10.5 (pKa0).According to these results the most likely mechanism involves a zwitterionic tetrahedral intermediate (T+/-), for which decomposition to products is the rate-limiting step for all the reactions, except that of NPTA with piperidine.For this reaction the formation of T+/- is rate determining.A semiempirical equation based on the above hypothesis accounts for the Broensted-type curve obtained in the aminolysis of NPTA.Estimation of the microscopic rate constants involved, in a possible more general reaction scheme and evaluation of the pKa's of T+/- indicate that expulsion of the leaving group of the substrate from T+/- is faster than deprotonation of T+/- by a base, precluding therefore the formation of an anionic tetrahedral intermediate.The fact that pKa0=10.5 for the NPTA reactions means that an (hypothetical) amine of pKa=10.5 leaves T+/- as readily as p-nitrothiophenoxide ion (pKa=4.6).From these and other data it is calculated that the nucleofugality from T+/- of an amine of pKa=4.6 is ca. 3*104 times larger than that of p-nitrothiophenoxide ion.The estimated pKa0 values for the aminolysis of (hipothetical) aryl acetates with leaving groups of pKa=4.6 and 6.5 (the same pKa as thiophenol) are pKa0=8.0 and 9.0, respectively, which gives nucleofugality ratios (a given amine/aryl oxide ion) from the oxy T+/- smaller than those from the corresponding sulfur T+/-.It is claimed that expulsion of ArS- from T+/- is only slightly slower than that of an isobasic ArO- from the oxy T+/-.Therefore, the above results indicate that the "push" provided by ArS in T+/- to expel a given amine is much stronger than that exerted by an isobasic ArO in the oxy T+/-.Activation parameters are reported for the reactions of the title substrates with piperidine, piperazine, and N-formylpiperazine.