Spectral investigations of amino acid picrates

Abstract

FTIR and laser Raman spectra of β-alanine β-alaninium picrate and dl-phenylalanine dl-phenylalaninium picrate crystals of space group P 1 ¯ ( C i ) have been me in the 4000–50 cm −1 range, at room temperature. The former crystal consists of β-alanine β-alaninium and the later dl-phenylalanine dl-phenylalaninium as cations. The presence of both carbonyl (C O) and carboxylate COO − groups in these crystals is the evidence for the existence of the zwitterion and the protonated forms. Factor group analysis has been made and the numbers of vibrational modes have been calculated. The tentative assignments of the observed bands are given. Fermi resonance has also been observed in one of the crystal β-alanine β-alaninium picrate. The picrate group forms the anion in both crystals and the characteristic bands ν asNO 2, ν sNO 2, and ν phenC–O stretching are observed in the spectra. These suggest that the picrate ion is unaffected by the presence of the cations.