Base catalysis of .sigma.-complex formation between 1,3,5-trinitrobenzene and aniline in dimethyl sulfoxide. Rate limiting proton transfer

1977 ◽  
Vol 99 (18) ◽  
pp. 5958-5964 ◽  
Author(s):  
Erwin Buncel ◽  
Walter Eggimann
Keyword(s):  
Complex Formation ◽  
Proton Transfer ◽  
Dimethyl Sulfoxide ◽  
Base Catalysis ◽  
Sigma Complex ◽  
Rate Limiting

Kinetic studies of bold σ -adduct formation and nucleophilic substitution in the reactions of ethyl 2,4,6-trinitrophenyl ether, some phenyl 2,4,6-trinitrophenyl ethers, and phenyl 2,4-dinitronaphthyl ether with aniline in dimethyl sulfoxide

1998 ◽  
Vol 76 (6) ◽  
pp. 627-634
Author(s):  
Michael R Crampton ◽  
Ian A Robotham
Keyword(s):  
Proton Transfer ◽  
Dimethyl Sulfoxide ◽  
Nucleophilic Substitution ◽  
Kinetic Studies ◽  
Adduct Formation ◽  
Base Catalysis ◽  
Substitution Product ◽  
Equilibrium Data ◽  
Two Stages ◽  
Phenyl Ethers

The reaction of ethyl 2,4,6-trinitrophenyl ether with aniline in dimethyl sulfoxide containing Dabco occurs in two stages. The first gives 5, the σ -adduct intermediate on the substitution pathway, which has been identified spectroscopically. The second yields 2,4,6-trinitrodiphenylamine, the substitution product. Kinetic studies show that proton transfer is rate limiting both in the formation of the intermediate and in its subsequent acid-catalysed decomposition. Phenoxide is a considerably better leaving group than ethoxide and the substitution reactions of phenyl 2,4,6-trinitrophenyl ethers and phenyl 2,4-dinitronaphthyl ether with aniline in DMSO occur without the accumulation of intermediates. The kinetics indicate both uncatalysed and base-catalysed pathways. The kinetic and equilibrium data for reaction of the ethyl and phenyl ethers are compared with data for σ -adduct formation from 1,3,5-trinitrobenzene and aniline.Key words: nucleophilic substitution, proton transfer, base catalysis, σ -adducts

Kinetics of cyclization of S-ethoxycarbonylmethylisothiouronium chloride to 2-imino-4-thiazolidone

1979 ◽  
Vol 44 (3) ◽  
pp. 912-917 ◽  
Author(s):  
Vladimír Macháček ◽  
Said A. El-bahai ◽  
Vojeslav Štěrba
Keyword(s):  
Hydrochloric Acid ◽  
Dilute Hydrochloric Acid ◽  
Base Catalysis ◽  
General Base ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Kinetics Of Formation ◽  
Acid Catalyzed ◽  
Rate Limiting ◽  
Kinetics Of

Kinetics of formation of 2-imino-4-thiazolidone from S-ethoxycarbonylmethylisothiouronium chloride has been studied in aqueous buffers and dilute hydrochloric acid. The reaction is subject to general base catalysis, the β value being 0.65. Its rate limiting step consists in acid-catalyzed splitting off of ethoxide ion from dipolar tetrahedral intermediate. At pH < 2 formation of this intermediate becomes rate-limiting; rate constant of its formation is 2 . 104 s-1.

Proton transfer is not rate-limiting in buffer-induced non-enzymic glucation of hemoglobin

1988 ◽  
Vol 110 (24) ◽  
pp. 8265-8266 ◽  
Author(s):  
Herminia. Gil ◽  
Julio F. Mata-Segreda ◽  
Richard L. Schowen
Keyword(s):  
Proton Transfer ◽  
Rate Limiting
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