Gas‐Phase Structure of N,N‐Dimethylglycine

Abstract

Three conformers of the neutral amino acid N,N-dimethylglycine [(CH3)2NCH2COOH] were detected in a supersonic expansion by a combination of laser ablation (LA) and molecular-beam Fourier transform microwave (MB-FTMW) spectroscopy. A bifurcated methyl-to-carbonyl (C--HO==C) weak intramolecular hydrogen bond might stabilise the most stable conformer of C(s) symmetry. The second most stable conformer of C1 symmetry has a hydrogen bond between the hydroxyl group and the lone pair at the nitrogen atom (NH--O). The r(s) and r0 structures were derived for this conformer from the rotational data for the parent and six minor 13C, 15N and OD isotopomers. A third conformer exhibits a cis-carboxyl functional group and C1 symmetry. Ab initio MP2/6-311++G(d,p) predictions of the spectroscopic parameters were useful in analysing the spectra. In particular, the agreement of the nuclear quadrupole coupling constants with those calculated was conclusive in identifying the different conformers.

Molecular Beam Rotational Spectrum of Cyclobutanone–Trifluoromethane: Nature of Weak CH⋅⋅⋅OC and CH⋅⋅⋅F Hydrogen Bonds

“…The C-H···O contacts most frequently observed in protein structures, [9] correspond to C-H···O=C interactions in which carbonyl peptide groups are involved. This interaction, which has recently been proposed to stabilize the most stable conformer of neutral N,N-dimethylglycine, [10] has been suggested to have a significant contribution in the determination of protein conformation. [11] However, little experimental information on the intrinsic properties of this weak hydrogen bond is known from studies of isolated molecular complexes.…”

Conformations of α‐Aminobutyric Acid in the Gas Phase

“…Our LA-MB-FTMW spectrometer was first applied to several organic solids [7,8] and then extended to different amino acids, including to date several coded aliphatic a-amino acids (alanine, [9] valine, [10] isoleucine [11] ) and derivatives (N,N-dimethylglycine, [12] phenylglycine [13] ), imino acids (proline, [14] 4-hydroxyproline [15] ), and a b-amino acid (b-alanine [16] ). Previous information on the rotational spectrum of coded a-amino acids using thermal heating was limited to studies of glycine [2,17] and alanine.…”

The Glycine–Water Complex

“…This technique has been applied successfully to analyze the shape of the neutral form of several amino acids [2][3][4][5][6][7] and identify their energetically accessible conformers under isolation conditions. The knowledge of the gas-phase structure has provided important insight into the intramolecular interactions that determine their conformation.…”

“…The hydration in amino acids is known to trigger the transformation from the neutral form observed in the gas phase [1][2][3][4][5][6][7] to the charged zwitterion (NH 3 + CH(R)COO À ) [8,9] present in condensed media. A detailed understanding of these effects requires the characterization of the isolated clusters formed between biomolecules and water in the gas phase.…”