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The Double tert ‐Butyl Rotation in Solid cis ‐2‐ tert ‐Butyl‐5‐( tert ‐butylsulphonyl)‐1,3‐dioxane
Author(s) -
Riddell Frank G.,
Rogerson Martin
Publication year - 1997
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/(sici)1097-458x(199705)35:5<333::aid-omr83>3.0.co;2-i
Subject(s) - chemistry , coalescence (physics) , rotation (mathematics) , medicinal chemistry , crystallography , stereochemistry , physics , geometry , mathematics , astrobiology
cis ‐2‐ tert ‐Butyl‐5‐( tert ‐butylsulphonyl)‐1,3‐dioxane displays a double tert ‐butyl coalescence at low temperatures in its 13 C CP/MAS NMR spectrum associated with slowing down of the rotation of both tert ‐butyl groups. The overlap of the resonances precluded the measurement of rates of rotation from lineshape analyses. However, 13 C T 1ρ measurements above coalescence allowed rates of rotation and activation parameters for the rotations of both groups to be derived. The C ‐ tert ‐butyl group has Δ H ‡ =26.3±3.6 kJ mol ‐1 and Δ S ‡ ‐13±14 J K ‐1 mol ‐1 . The S ‐ tert ‐butyl group has Δ H ‡ =31.8±2.2 kJ mol ‐1 and Δ S ‡ ‐9 J K ‐1 mol ‐1 . © 1997 by John Wiley & Sons, Ltd.