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Steric effects induced by solvent association. 29 Si NMR chemical shifts in trimethylsiloxysteroids controlled by solvent accessible surface
Author(s) -
Kasal A.,
Schraml J.,
Čermák J.
Publication year - 1994
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.1260320704
Subject(s) - steric effects , chemistry , chemical shift , solvent , hydrogen bond , solvent effects , molecule , silicon , computational chemistry , nuclear magnetic resonance spectroscopy , silylation , hydrogen , organic chemistry , catalysis
Chemical shifts of silicon‐29 in 39 trimethylsiloxy derivatives of 5α‐ and 5β‐androstanes reported here satisfy an empirical linear correlation with terms describing molecular geometry. The steric 29 Si chemical shifts are controlled by association of the silyl ethers with the hydrogen bonding solvent. The chemical shifts measured in dilute solutions show a dependence on the surface of the oxygen atom accessible to the solvent for hydrogen bonding. The steric upfield shifts are due to steric hindrance to hydrogen bonding which itself produces downfield shifts.