Abstract
| - The barriers for three internal motions (i.e., phenyl and tert-butyl rotation as well as N-inversion)have been determined by dynamic NMR spectroscopy in the two diastereoisomeric forms of a typicalamino alcohol [dimethylamino-2,4,4-trimethyl-3-phenyl-3-pentanol, Me2NCH2CHMeC(OH)PhBut].The two structures were assigned by connection with those of the corresponding amide precursorsdetermined by single-crystal X-ray diffraction. These amides (CO in place of CH2) too were foundto undertake internal motions amenable to NMR observation, i.e., phenyl, tert-butyl, and NCOrotations: the corresponding barriers were also measured. Ab initio computations indicate thatH-bonding makes all these molecules adopt six-membered cyclic conformations, a conclusion whichagrees well with the X-ray crystal structure determined for the amide precursors.
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