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Mechanism of reactions of unsaturated ethers and thioethers. XI: Acid-catalyzed addition of water to 1-alkynyl thioethers

✍ Scribed by H. Hogeveen; W. Drenth

Publisher
Elsevier Science
Year
2010
Tongue
English
Weight
767 KB
Volume
82
Category
Article
ISSN
0165-0513

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✦ Synopsis

Abstract

Infrared analysis has shown that acid‐catalyzed hydration of ethylthioethyne in heavy water does not involve the uptake of deuterium in the initial compound. This confirms earlier evidence that protonation of the triple bond is the rate‐determining step.

Values for the entropy of activation of five 1‐alkynyl thioethers were determined. They range between −1 and −6 e.u. The rate of hydration of 1‐tert.‐butylthio‐1‐propyne in 0–98.7 weight‐percent ethanol‐water mixtures has been analyzed by a theory of Grunwald. A plot of (log k~1~−log f~H⊕~) against Y~0~ gives a straight line. The triple bond of vinylthioethyne has been hydrated in moderately concentrated perchloric acid solutions. A Zucker‐Hammett plot of these data affords a straight line with a slope of 1.07 and a Bunnett plot a “straight” line with a slope of −0.9. These facts suggest that the addition of the water molecule takes place in a step subsequent to protonation.

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