ISSN:
0894-3230
Keywords:
Organic Chemistry
;
Physical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Equilibrium displacements within the enol-enthiolic tautomeric systems of β-thioxoketones caused by long-range isotope effects were monitored by 1H and 13C NMR spectroscopy. Thioacetylacetone and 1,3-diphenyl-3-thioxopropanone deuteriated at various positions were investigated. Both compounds are in fast (Z)-enol-(Z)-enethiol equilibrium on the NMR time scale. The investigations showed that CD3 and C6D5 groups changes the equilibrium so that the tautomer having a C = X bond next to the CD3 or C6D5 groups decreases. Deuteriation at the methine position pushes the equilibrium towards the (Z)-enol form. The study further showed that deuteriation at the phenyl ring next to the C = O group causes the largest effect if the deuterium is at the ortho position and the smallest if it is at the para position. Long-range effects on equilibrium are discussed in general in order to establish a common pattern. Deuterium scrambling is observed both during the coupling reaction of ethyl thionoacetate with hexadeuterioacetone and during preparation of specifically labelled acetophenone. The latter compounds are synthesized by acetylation of specifically labelled benzenes. The scrambling reaction is suggested to be a transdeuteriation of the deuteriated benzenes rather than involving the acetophenones.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/poc.610040405
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