Infinite dilution (29)Si and (13)C NMR chemical shifts were determined from concentration dependencies of the shifts in dilute chloroform and acetone solutions of para substituted O-silylated phenols, 4-R-C6 H4 -O-SiR'2 R″ (R = Me, MeO, H, F, Cl, NMe2, NH2, and CF3), where the silyl part included groups of different sizes: dimethylsilyl (R' = Me, R″ = H), trimethylsilyl (R' = R″ = Me), tert-butyldimethylsilyl (R' = Me, R″ = CMe3), and tert-butyldiphenylsilyl (R' = C6 H5, R″ = CMe3). Dependencies of silicon and C-1 carbon chemical shifts on Hammett substituent constants are discussed. It is shown that the substituent sensitivity of these chemical shifts is reduced by association with chloroform, the reduction being proportional to the solvent accessible surface of the oxygen atom in the Si-O-C link.

Institute of Chemical Process Fundamentals of the ASCR v v i 16502 Prague 6 Czech Republic

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