55526-39-1Relevant academic research and scientific papers
Rapid Scan UV Spectroscopic and Kinetic Studies of the Reaction of Methyl 4-Methoxy-3,5-dinitrobenzoate with Pyrrolidine in Dimethyl Sulfoxide
Hasegawa, Yoshinori
, p. 649 - 652 (1985)
An intermediate complex in the aromatic nucleophilic substitution reaction of methyl 4-methoxy-3,5-dinitrobenzoate with pyrrolidine in dimethyl sulfoxide has been observed by rapid scan UV spectroscopy, and kinetic and equilibrium constants have been obtained for its formation and decomposition.The observable intermediate is the conjugate base (I-) of the zwitterionic form (IH).The formation of I- is base catalyzed and the decomposition of I- is first order in pyrrolidine hydrochloride.The possible mechanism is that proton transfer between IH and I- is not more rapid than the k-1 step and that general acid catalyzed leaving group departure from I- is rate limiting.
Kinetic Studies of the Reactions of Some Phenyl Aryl Sulfides with Aliphatic Amines in Dimethyl Sulfoxide: the Mechanism of Base Catalysis
Chamberlin, Rachel A.,Crampton, Michael R.
, p. 425 - 432 (2007/10/02)
The reaction of n-butylamine, pyrrolidine and piperidine with 4'-R-phenyl 2,4,6-trinitrophenyl sulfides (R = H, Me, Br, NO2), 4a-d, result in the rapid formation of ?-adducts by attack at the unsubstituted 3-position; rate and equilibrium data are reported and substituent effects examined. Attack by amine at the 1-position of of 4a-d, phenyl 2,4-dinitronaphthyl sulfide 9, and phenyl 2,6-dinitro-4-trifluoromethyl sulfide 11, results in displacement of the phenylthio group.The substitutions by butylamine show a first order dependence on the amine concentration indicating that nucleophilic attack is rate determining.However the substitutions by pyrrolidine are subject to general base catalysis and it is argued that here the rate limiting step is deprotonation of the initially formed zwitterionic intermediate.
Kinetic and Equilibrium Studies of ?-Adduct Formation and Nucleophilic Substitution in the Reactions of Ethyl Thiopicrate with Aliphatic Amines in Dimethyl Sulfoxide
Chamberlin, Rachel,Crampton, Michael R.
, p. 75 - 82 (2007/10/02)
Kinetic and equilibrium results are reported for the reaction of ethyl thiopicrate with butylamine, pyrrolidine and piperidine in dimethyl sulfoxide.The most rapid reaction involves attack at the unsubstituted 3-position to give anionic ?-adducts.The rate-limiting step in this process changes from nucleophilic attack by amine with butylamine to proton transfer from the zwitterionic intermediate with piperidine; pyrrolidine shows intermediate behaviour.Attack by amine at the 1-position results in displacement of the ethylthio group, although intermediates are notobserved during this process.It is suggested that base catalysis observed in the reaction with pyrrolidine may result from rate-limiting proton transfer from the zwitterionic intermediate. 1H NMR measurements using 0.1 mol dm-3 solutions of substrate show that the displaced ethanethiolate ion may attack ring-carbon atoms of either unreacted substrate or substitution products.
Catalysis of Transimination by Rate-Limiting Proton Transfer to Buffer Bases
Fischer, Helene,DeCandis, Francis X.,Ogden, Sharon D.,Jencks, William P.
, p. 1340 - 1347 (2007/10/02)
General base catalysis of the hydroxylamonilysis of benzhydrylidenedimethylammonium ion gives a Broensted plot that follows the Eigen curve expected for rate-determining trapping of the initially formed addition intermediate by proton transfer to a buffer base or water.The solvent deuterium isotope effects for catalysis by oxy anions exhibit a maximum at the break point of the Eigen curve, close to the estimated pKa for the addition intermediate.This maximum can be accounted for by a partial change in rate-limiting step of the proton-transfer process near ΔpK = 0.Water shows a positive deviation from the Broensted plot and a solvent isotope effect of kH2O/kD2O = 4.7 that provide additional evidence for the trapping mechanism.The addition of glycerol increases the rate of the base-catalyzed reaction; much larger increases are observed with ethylene glycol and methanol.In contrast, the base-catalyzed hydrolysis of the cationic imine follows a linear Broensted plot (β = 0.24), with a negative deviation for catalysis by water, and gives a constant value of kH2O/kD2O = 1.9 +/- 0.2.A concerted mechanism of base-catalyzed attack by water is suggested for this reaction.
