Blechta Vratislav, Sabata Stanislav, Sýkora Jan, Hetflejš Jiří, Soukupová Ludmila, Schraml Jan
Institute of Chemical Process Fundamentals of the ASCR, v. v. i., 16502, Prague, 6, Czech Republic.
Magn Reson Chem. 2012 Feb;50(2):128-34. doi: 10.1002/mrc.2860. Epub 2012 Feb 15.
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.
通过对对位取代的 O-硅烷基化苯酚 4-R-C6H4-O-SiR'2R″（R = Me、MeO、H、F、Cl、NMe2、NH2 和 CF3）在稀氯仿和丙酮溶液中化学位移的浓度依赖性，测定了无限稀释下的 (29)Si 和 (13)C NMR 化学位移，其中硅烷基部分包括不同大小的基团：二甲基硅烷基（R' = Me，R″ = H）、三甲基硅烷基（R' = R″ = Me）、叔丁基二甲基硅烷基（R' = Me，R″ = CMe3）和叔丁基二苯基硅烷基（R' = C6H5，R″ = CMe3）。讨论了硅和 C-1 碳化学位移对哈米特取代基常数的依赖性。结果表明，这些化学位移的取代基敏感性因与氯仿缔合而降低，降低程度与 Si-O-C 键中氧原子的溶剂可及表面积成正比。
