INFRARED-SPECTRA AND THEORETICAL-STUDY OF METHYL, FORMYL AND ACETYL DERIVATIVES OF CHROMONES

The C=O stretching frequencies of substituted 2-methylchromones (3a-3j ). 2-formylchromones (4a-4j), 3-formylchromones (5a-5j) and 3-acetyl-2 -methylchromones (6a-6i) were measured in CCl4 and CHCl3 and correlate d with sigma+ substituent constants. Using the results of the infrared spectral investigation and the theoretical calculations by the semiem pirical AM1 method, the conformation and the transmission of electroni c effects in compounds 4-6 were studied. For the 2-substituted chromon e system the transmission factory gamma according to the definition of Charton was determined. The preparation of some new 2-methylchromones (3e-3j) and 3-(2,2-diformyl-chlorovinyl)-6-methylchromone (7) is also described.