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The effect of solvent accessible surface on Hammett‐type dependencies of infinite dilution 29 Si and 13 C NMR shifts in ring substituted silylated phenols dissolved in chloroform and acetone
Author(s) -
Blechta Vratislav,
Šabata Stanislav,
Sýkora Jan,
Hetflejš Jiří,
Soukupová Ludmila,
Schraml Jan
Publication year - 2012
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.2860
Subject(s) - chemistry , chloroform , acetone , phenols , ring (chemistry) , solvent , dilution , carbon 13 nmr , hammett equation , solvent effects , organic chemistry , computational chemistry , proton nmr , nuclear magnetic resonance spectroscopy , kinetics , thermodynamics , physics , quantum mechanics , reaction rate constant
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‐C 6 H 4 ‐O‐SiR′ 2 R″ (R = Me, MeO, H, F, Cl, NMe 2 , NH 2 , and CF 3 ), where the silyl part included groups of different sizes: dimethylsilyl (R′ = Me, R″ = H), trimethylsilyl (R′ = R″ = Me), tert ‐butyldimethylsilyl (R′ = Me, R″ = CMe 3 ), and tert ‐butyldiphenylsilyl (R′ = C 6 H 5 , R″ = CMe 3 ). 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. Copyright © 2012 John Wiley & Sons, Ltd.