ELECTRON-DIFFRACTION STUDY OF THERMAL-DECOMPOSITION PRODUCTS OF TRIMETHYLAMINE - MOLECULAR-STRUCTURE OF CH3-N=CH2

Structural studies of thermal decomposition products of trimethylamine have been performed by gas electron diffraction aided by mass spectrometry. Trimethylamine vapor is heated in a quartz tube shortly before the nozzle tip which is kept at room temperature. When the temperature inside the quartz tube is 515 degrees C, N(CH3)3 simply decomposes into CH4 and short-lived CH3-N=CH2. However, more complicated reactions, which include CH3-N=CH2-->CH4 + HCN, take place at the reaction temperature of 535 degrees C. The zero-point average structure of N-methylmethyleneimine (CH3-N=CH2) has been determined by a joint analysis of electron diffraction data and rotational constants, and then compared with ab initio calculations. Principal structural parameters are as follows: r(z)(N=C) = 1.279(6) Angstrom, r(z)(N-C) = 1.458(8) Angstrom and theta(z)(CNC) = 116.62(12)degrees. The molecular structure of trimethylamine has been determined much more precisely than that given in the literature.