Investigation Of Solvent Effects On Carbonyl Stretching Vibrational Frequency Of Camphor

Solvent effects on the carbonyl stretching vibrational frequency of Camphor wererninvestigated. The solvents were chosen to cover wide polarity range and include carbonrntetrachloride,2-propanol, methanol, and acetonitrile. For protonic and aprotonic solventsrntwo distinct behaviors were observed. In non-protonic or aprotonic solvent there seems littlernor negligible polarity dependent shift was observed. The situation is different for protonicrnsolvent where strong blue shift was obtained. These facts could be attributed to the lowrndipole moment of the chromophore (in aprotonic solvents) and hydrogen bonding withrnsolvent molecules. The broadness in protonic solvents compared to that in aprotonicrnsolvents support the suggestion made earlier and indicate the Band I is due to mainlyrnhydrogen bonding. Similarly, the solvent dependence of Band II analyzed. Generally, arnbathochromic shift was observed though the peak in acetonitrile appears at higherrnfrequency than both protonic solvents. Additional shoulder peak of absorption was observedrnin methanol and propanol solvents. What is striking was that the shoulder is approximatelyrnsame as that found in CCl4 solution. This may be due to complex (hydrogen bonding)rnbetween the carbon of carbonyl and oxygen of the alcohols.

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