Knowledge Bank

The conformational behaviour of N,N-dimethylglycine (m.p. 180 C) and sarcosine (m.p. 208 C) has been studied for the first time in gas phase as an extension of our recent work on natural amino acids}, 41 (2002) 4673; A. Lesarri, E. J. Cocinero, J. C. Lopez, J. L. Alonso, \emph{Angew. Chem. Int. Ed.}, 43 (2004) 605; S. Blanco, A. Lesarri, J. C. Lopez, J. L. Alonso, \emph{J. Am. Chem. Soc.}, 126 ( 2004) 11675; A. Lesarri, E. J. Cocinero, J. C. Lopez, J. L. Alonso, \emph{J. Am. Chem. Soc.}, 127 (2005) 2572. }. The solid amino acids were vaporized using laser ablation (LA) from a Q-switched Nd:YAG laser, and probed spectroscopically in a supersonic jet using molecular beam Fourier transform microwave spectroscopy (MB-FTMW)}, 74 (2003) 4799.}. The rotational spectrum revealed the presence of three conformers of neutral N,N-dimethylglycine in the jet. A bifurcated methyl-to-carbonyl (C--H$\cdots$O=C) weak intramolecular hydrogen bond has been proposed to stabilize the most stable conformer of C symmetry. The second conformer of C$1$ symmetry presents an intramolecular hydrogen bond N$\cdots$O--H analogue to glycine II. Substitution and effective structures have been derived for this conformer from the rotational data of seven isotopomers. A third conformer presents a cis-carboxylic functional group and C$1$ symmetry. Two conformers were observed for neutral sarcosine. The most stable conformer is stabilized by an intramolecular hydrogen bond N--H$\cdots$O=C, analogue to the interaction observed in the most stable conformer of glycine I. The second stable conformer exhibits an intramolecular hydrogen bond N$\cdots$O--H similar to glycine II. The observed conformers in both molecules are consistent with previous experiments using matrix-isolation FT-IR} 5 (2003) 41; A. Gomez-Zavaglia, R. Fausto, \emph{Vib. Spectr.}, 33 (2003) 105.}.