A real-time analysis of the flash-vacuum pyrolysis products of 1-acetylbenzotriazole (1) and I-benzoylbenzotriazole (2) was performed by tandem mass spectrometry. In the temperature range 50(MOO0C, these compounds lose nitrogen, yielding N-acetyl-and N-benzoylcyclopenta-2,4-dienylidenemethaneimines (10 and 17, respectively). At higher pyrolysis temperatures, 1 gives 2-methylbenzoxazole, cyanocyclopentadiene, methylcyanocyclopentadiene(s), benzonitrile and ketene, which were identified by collision-activated dissociation mass spectrometry. Lowtemperature infrared experiments confirmed the pyrolytic transformation l(2) -+ lO(17) at mediated temperatures.

A real-time analysis of the flash-vacuum pyrolysis products of 1 -vinyl-, 1 -(2-methylprop-I -enyl)-, and 1 -styryl-benzotriazole (3), (16), and (18) has been performed by tandem mass spectrometry. In the

ChemInform Abstract (II) (real-time MS product analysis).

C4H90" ions have been produced in the high pressure ion source of a triple sector mass spectrometer either by protonation of C4Hs0 isomers using methane as the reagent gas, or by methylation of C&O isomers using iodomethane or chioromethane as reagent gas. The collisional activation spectra of these mass selected C4H90+ ions (miz 73) allow the identification of several stable isomers in the gas phase.

Unusual behaviour has been noted for allyl methyl ether (1) chemically ionized in a high-pressure ion source. Tandem mass spectrometry indicates the formation of methylcyclopentadienyl and methoxy-1-propenylcarbenium ions (d, m/z 81 and e, m/z 85). The origin of these unexpected ions has been elucidated using conventional and Fourier transform ion cyclotron resonance experiments: primary fragment ions derived from protonated 1 (allyl ions a and methoxymethyl cations b) generate collision complexes with neutral 1, giving rise to the ions d and e. respectively, after methanol elimination.