Linked Life Data

16526777

Source:http://linkedlifedata.com/resource/pubmed/id/16526777

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
6
pubmed:dateCreated
2006-3-10
pubmed:abstractText
A kinetic study is reported for nucleophilic substitution reactions of 4-nitrophenyl phenyl carbonate (5) and 4-nitrophenyl phenyl thionocarbonate (6) with a series of primary amines. The thiono compound 6 is less reactive than its oxygen analogue 5 toward strongly basic amines but is more reactive toward weakly basic CF3CH2NH2. The Brønsted-type plots obtained from the aminolyses of 5 and 6 are curved downwardly. The reactions are proposed to proceed through a stepwise mechanism with a change in the RDS on the basis of the curved Brønsted-type plots. The microscopic rate constants (k(1) and k(2)/k(-1) ratio) associated with the current aminolyses are consistent with the proposed reaction mechanism. The replacement of the C=O bond in 5 by a polarizable C=S group results in a decrease in the k(1) value but an increase in the k(2)/k(-1) ratio. Besides, such a modification of the electrophilic center causes a decrease in pKa degrees , defined as the pK(a) at the curvature center of curved Brønsted-type plots, but does not alter the reaction mechanism. The larger k(2)/k(-1) ratio for the reactions of 6 compared to those of 5 is proposed to be responsible for the decreased pK(a) degrees value.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Mar
pubmed:issn
0022-3263
pubmed:author
pubmed:issnType
Print
pubmed:day
17
pubmed:volume
71
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
2302-6
pubmed:meshHeading
pubmed:year
2006
pubmed:articleTitle
Aminolyses of 4-nitrophenyl phenyl carbonate and thionocarbonate: effect of modification of electrophilic center from C=O to C=S on reactivity and mechanism.
pubmed:affiliation
Department of Chemistry, Ewha Womans University, Seoul 120-750, Korea. ihum@mm.ewha.ac.kr
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't