Ultraviolet absorption spectra: Some substituted coumarins

Abstract

The U.V. absorption spectra of forty-one substituted coumarins have been studied in methanol and aqueous methanol over a pH range. The effect of the nature and position of the substituent in the coumarin nucleus is discussed. 7-OH-3-isopropyld-Me coumarin was prepared by the method of Chakravarti, * m.p. 230 "C. (Chakravarti reported 224 'C.) 7-OH-4,8-diMe coumarin was obtaincd from Professor Sethna's laboratory and the methyl ether was prepared by refluxing it (1 g) in acetone (75 ml) with nahydrous potassium carbonate (2 g) and dimcthyl sulphate (I ml) for 6 h. Thc acetone was removed by distillation and potassium carbonate dissolved in water. The residue crystallised from aqueous alcohol, m.p. 156 "C. AnalysisFound C = 70.50; H = 5.46 C,,H,,03 Requires C = 70.60; H = 5.88%. 331C 332

Efficiency of perturbation-selection and its orbital dependence in the SAC-CI calculations for valence excitations of medium-size molecules

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Dereplication of natural products from complex extracts by regression analysis and molecular networking: case study of redox-active compounds from Viola alba subsp. dehnhardtii

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