Low Temperature Dependence in 1H CRAMPS & 13C CP/MAS ssNMR Spectra of Alanine Enantiomers

Abstract

1H RAMPS solid state NMR and 13C CP/MAS spectra of D- and L- alanine crystals were measured at temperature ranging from 220K to 295K. Some major points are as follows: (1)alpha-H and protons in the methyl group showed a spin-spin coupling effect as temperature went down in the 1H- MAS spectra of D-alanine. (2) In the 1H CRAMPS spectra, peak widths of alpha-H and beta-H showed a different trend between alanine enantiomers when temperature varied.(3) The dynamic behavior of 13C spectra showed an obvious change around 250K, which was supposed as a phase transition in alanine crystal. In the discussion section, we give these experimental phenomena a possible explanation related to chirality.