The Effect of Medium on Rate and Mechanism:  Aminolysis of O-4-Nitrophenyl Thionobenzoate in MeCN and H2O

Pseudo-first-order rate constants (k obs) have been measured spectrophotometrically for reactions of O-4-nitrophenyl thionobenzoate (1) with a series of alicyclic secondary amines in MeCN and H2O at 25.0 ± 0.1 °C. The plot of k obs vs amine concentration exhibits an upward curvature in all cases, in...

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Bibliographic Details
Published inJournal of organic chemistry Vol. 68; no. 20; pp. 7742 - 7746
Main Authors Um, Ik-Hwan, Seok, Jin-A, Kim, Han-Tae, Bae, Sun-Kun
Format Journal Article
LanguageEnglish
Published Washington, DC American Chemical Society 03.10.2003
Subjects
Chemistry
Exact sciences and technology
Kinetics and mechanisms
Organic chemistry
Reactivity and mechanisms
Water
Reaction intermediate
Nitro compound
Zwitterion
Chemical reaction kinetics
Anions
Thione
Aminolysis
Medium effect
Acetonitrile
Reaction mechanism
Benzenic compound
Alkalinity
Rate constant
Spectrophotometry
Secondary amine
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Summary:Pseudo-first-order rate constants (k obs) have been measured spectrophotometrically for reactions of O-4-nitrophenyl thionobenzoate (1) with a series of alicyclic secondary amines in MeCN and H2O at 25.0 ± 0.1 °C. The plot of k obs vs amine concentration exhibits an upward curvature in all cases, indicating that the reactions proceed through two tetrahedral intermediates (a zwitterionic T± and its deprotonated anionic T-) regardless of the amine basicity and the nature of the reaction medium. However, all the amines investigated have been found to be much less reactive in MeCN than in H2O, although the amines are more basic in the former medium by 7−9 pK a units.
Bibliography:ark:/67375/TPS-3CZDTL6C-4
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ObjectType-Article-1
SourceType-Scholarly Journals-1
ObjectType-Feature-2
content type line 23
ISSN:0022-3263
1520-6904
DOI:10.1021/jo034637n