Conformational instability upon dimerization: Prolinol

Prolinol monomers are shown to exist in two stable conformations with internal O-H⋯N hydrogen bonds, leading to distinct OH-stretching bands in the infrared spectrum. Prolinol dimers mostly adopt different monomer conformations. There is experimental and quantum chemical evidence for two particularly stable and spectrally separated homodimers, whereas heterodimers built from enantiomeric monomer units are structurally more diverse and therefore spectrally broader. The underlying types of hydrogen-bonded networks are analyzed.