The effects of solvents, including polymeric substrates, and substituentson the absorption spectra of 4,4'-donor acceptorsubstituted azo dyes were studied. The position of the intense, visible charge-transfer band was dependent on the dielectric properties of the solvent ; a linear relationship was found between observed and calculated frequency shifts. Spectral behavior obtained for the dyes in polymeric solvents was consistent with that obtained for the dyes in nonpolymeric solvents. The relationship between dye structure and solvent effects was also determined. Shifts in absorption maxima with substitution in positions insulated from the conjugated chromophoric system were consistent with Taft polar-substituent constants; the effects of such substituents were, therefore, primarily inductive in nature.
írans-Di-tert-butylcyclopropanone (1) has been prepared by reaction of potassium iert-butoxide with a-bromodineopentyl ketone. Partial resolution has been effected by reaction with d-amphetamine and with diisopinylcampheylborane. Reaction of 1 with water affords the hydrate (rates and equilibrium constants are reported in Table I). Reaction of 1 with alcohols affords the hemiketals, isolable for primary alcohols (relative rates of formation of hemiketals in alcohol solution at 25°follow: methanol, 90; ethanol, 20; isopropyl alcohol, 1; tert-butyl alcohol, 0). The rate of reversion of the methanol hemiketal to 1 in methanol has been determined by use of deuterium-labeled hemiketal. Under basic conditions the hemiketals are converted to the ring-opened Favorskii ester 2, under acidic conditions to -alkoxy ketone 3. Reaction of 1 with potassium iert-butoxide in terf-butyl alcohol-O-d affords ester 3 of deuterium content da 3%, di 50%, d2 31%, d3 16%, pointing to some attack at a hydrogen. The cyclopropanone is stable to oxygen; the hydrate and hemiketals are not.
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