Substituent Effect in the Ionization of cis -2-Substituted 1-Cyclopropanecarboxylic Acids
1979; Oxford University Press; Volume: 52; Issue: 7 Linguagem: Inglês
10.1246/bcsj.52.1944
ISSN1348-0634
Autores Tópico(s)Free Radicals and Antioxidants
ResumoAbstract Ten cis-2-substituted 1-cyclopropanecarboxylic acids (substituents: H, CH3, C6H5, CH3O, C2H5O, Cl, Br, CH3CO, CH3OCO, and C2H5OCO) were prepared, and their pKa values were determined in water at 25 °C, along with those of the trans-2-chloro and 2-methoxy derivatives. The pKa values for cis isomers are somewhat larger than those for the corresponding trans isomers, except for the chloro and bromo derivatives. The substituent effects obtained were in the usual order in the sense of the electronic effects, except for the phenyl group, which produced a decrease in acidity relative to the unsubstituted acid. It was shown that the carbon-13 chemical shifts for the methylene carbon of the ethyl group in the ethyl cis-2-substituted 1-cyclopropanecarboxylate obtained in deuteriochloroform gave a reasonable linear relation with the pKa(cis) values.
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