Knowledge Bank

Vibrational circular dichroism spectra of $(S-(+)-1-amino-2-propanol$ and (S)-(+)-2-amino-1-propanol in tetrachloroethylene solvent have been obtained in the OH- and NH-stretching regions. In dilute solution, absorption bands corresponding to free OH and NH and to both OH--N and NH--O hydrogen-bonded species are observed. No VCD intensity is observed for the ``free'' OH or NH stretches. Negative VCD bands for $v(NH2)$asym and $v(NH2)$sym are observed for NH--O conformations in both compounds. Only (S)-(+)-1-amino-2-propanol exhibits an intense negative OH-stretching VCD band for the OH--N species; no VCD corresponding to v(OH) is observed for (S)-(+)-2-amino-1-propanol. An interpretation of the VCD spectra based on the ring current mechanism will be presented that identifies the most abundant solution conformations in these amino alcohols.