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Solvent effects on internal rotation about the BN bond in aminoboranes as studied by proton magnetic resonance spectroscopy
Author(s) -
Totani Tetsushi,
Tori Kazuo,
Murakami Junko,
Watanabe Haruyuki
Publication year - 1971
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270030519
Subject(s) - chemistry , steric effects , substituent , alkyl , adduct , solvent , proton , molecule , resonance (particle physics) , crystallography , benzene , proton magnetic resonance , solvent effects , nuclear magnetic resonance spectroscopy , spectroscopy , photochemistry , medicinal chemistry , stereochemistry , nuclear magnetic resonance , organic chemistry , physics , particle physics , quantum mechanics
Proton magnetic resonance spectra of two series of aminoboranes, Me 2 N BRPh (R = Cl, Me, Et, i ‐Pr, i ‐Bu, t ‐Bu and CCMe) and PhRN BMe 2 (R = Me, Et and i ‐Pr), have been examined in various solvents to show that the potential barrier to internal rotation about their BN bond is lowered in some electron‐pair donor solvents. The barrier in an aminoborane decreases with increasing electron‐donating power of the solvent. The barrier in alkylaminoboranes in an electronpair donor solvent was found to increase with increasing size of the substituent alkyl group, owing to the steric repulsion between the alkyl and the solvent molecule. The solvent effects of benzene resulted in downfield shifts of the proton signals due to B ‐substituents and in upfield shifts of the signals due to N ‐substituents, as expected. The formation of a 1:1 adduct of Me 2 N BPh( t ‐Bu) with carbon disulphide was found.