Carbonyl compounds are known to form aggregates by intermolecular forces, such as hydrogen bonding and dipole-dipole interaction, etc. in a solution. Therefore, 13C NMR spectroscopic studies were performed for carbonyl compounds having an ester group and a carboxyl group such as half-esters in various solvents for observation of their behaviors of carbonyl carbons in solutions. In a half-ester, the chemical shifts of the carbonyl carbon of the ester group were observed at lower magnetic field than those of the carboxyl group due to intramolecular hydrogen bonding in five kinds of solvents. They were almost constant regardless of the polarity of the solvent except for one case. On the other hand, the chemical shifts of the carbonyl carbon of the carboxyl group moved downfield as polarity of the solvent increased. These results indicate that polar solvents interact primarily with the carbonyl group of the carboxyl group when these two groups have intramolecular hydrogen bonding. For the behaviors of the 13C NMR chemical shifts of the corresponding sodium salt of the half ester, the chemical shifts of the carbonyl carbon of the carboxylate group were observed at lower magnetic field than that of the ester group. These results indicate that both the carbonyl carbons were affected by polarity of the solvent due to lack of the intramolecular hydrogen bonding in the sodium salt. The behaviors of other carbonyl compounds having a hydroxy group and a carboxyl group (e.g. hydroxybenzoic acids) in different polar solvents will also be presented.

NMR spectroscopic studies for the behaviors of carbonyl compounds in various solvents

254th National Meeting (2017)

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