Linear free energy ortho-correlations in the thiophen series. Part II. Acid dissociation of some 3-substituted thiophen-2-carboxylic acids in water
- 1 January 1976
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 6,p. 747-751
- https://doi.org/10.1039/p29760000747
Abstract
The acid dissociation constants of some 3-substituted thiophen-2-carboxylic acids (I; X = OMe, Me, SMe, H, I, Br, SOMe, or SO2Me) in water, at 25 °, have been measured. The data obtained furnish a good linear free energy relationship of the Yukawa–Tsuno type (ρ+1.34, r+ 0.57, R 0.996) emphasizing the large difference, probably linked to the geometry of the five-membered ring, from the situation observed for ortho-substituted benzoic acids. A ρ2,3/ρ2,5 ratio higher than unity (1.37) has been observed.Keywords
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