Collect. Czech. Chem. Commun. 1980, 45, 1589-1594

The ortho effect in ortho-substituted 2-(X-benzal)-1,3-indanediones, 3-(2-X-benzal)phthalides and 3-(2-X-benzal)-5,6-dihydro-4,7-dithiaphthalides: A 1H-NMR study

Ľudovít Krasnec, Jr.a, Eva Solčániováb and Pavol Hrnčiara

a Department of Organic Chemistry
b Institute of Chemistry, Comenius University, 816 31 Bratislava


The 1H-NMR spectra of ortho-substituted 2-(X-benzal)-1,3-indanediones, 3-(2-X-benzal)-phthalides and 3-(2-X-benzal)-5,6-dihydro-4,7-dithiaphthalides have been studied. The chemical shifts observed for the methine proton were correlated with various constants of the substituents. In addition to simple correlations, two- and three-parameter correlations were also made. Statistically most important one-parameter correlations were observed for σp-constants. Apart from the common electronic effects, in the transfer of effects of the substituents from the ortho-position upon the chemical shift of the methine proton the field effect plays also an important role. The deviations observed in the case of substances substituted in both ortho-positions confirm the assumed considerable distortion of the coplanarity of the studied systems.