Solvent effect on 13C chemical shifts of 6-methylquinoline and 8-Methylquinoline has been studied in eight different solvents. 13C chemical shifts of these compounds have been measured in 30% (v/v) solution using DMSO-~ as an internal locking agent and Hexamethyldisiloxane (HMDSO) as an external reference. Carbon tetrachloride (CCL,) has been taken as a reference compound for comparison of these shifts because this is non polar. The purpose of the present study is to see the solvent effects of various solvents in the light of Buckingham, Schaefer and Schneider (BSS) theory. Present study has shown that polar solvents like chloroform, dimethylsulphoxide, acetone, methanol and ethanol, show positive deviation from CCL" while benzene show negative deviation. More negative shifts behavior at C8, C9 and CIO carbon atoms in these compounds is due to neighboring nitrogen atom whose lone pair of electron causes this change. C2 carbon atom shifts are also affected by nitrogen atom. Benzene shows negative shifts and entirely different behavior because of 1t-bonding and ring current phenomenon. Cyclohexane is a non-polar compound and it shows negative behaviour, because it has low dielectric constant compared to carbon tetrachloride.The present study on solvent dependent I3C chemical shifts has been done at a frequency of 22.50 MHz using JEOL FX-90Q IT NMR.
M H PHULPOTO ,A R SOLANGI ,A W K KHANZADA ,S A PATHAN ,
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