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Reduction of 1‐benzyl‐3‐cyanoquinolinium ion by phosphonate: Solvent effects in propan‐2‐ol–water mixed solvents
Author(s) -
Lee InSook Han,
Kim Sun Hee,
Kreevoy Maurice M.,
Lee Chang Kiu,
Lee Chang Hee
Publication year - 1992
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.610050508
Subject(s) - chemistry , solvent , benzyl alcohol , phosphonate , solvent effects , inorganic chemistry , ion , organic chemistry , catalysis
Rate constants ( k 2 ) were determined for the reduction of 1‐benzyl‐3‐cyanoquinolinium ion by phosphonate dianion in mixed solvents consisting of propan‐2‐ol and water. The reduction product was mostly 1‐benzyl‐3‐cyano‐1,4‐dihydroquinoline with a trace of the 1,2‐isomer. The solvent properties were varied by increasing the fraction of water in the mixed solvent, which increases the polarity of the solvent. Increasing the proportion of alcohol makes the solvent a better electron pair donor. The higher fraction of propan‐2‐ol in the mixed solvent gives rise to a substantial increase in k 2 . A quantitative comparison of the solvent effect on this reaction with the solvent effects on related reactions suggests a solvent Brønsted α value of 0·45. This suggests that the PO 3 − unit of the transition state interacts only weakly with the solvent although the final oxidized product is phosphate.