1.2.4- Triazolines spectra

Figure 2. IR spectrum of 5-isopropyl-l-phenyl-A2-l,2,3-triazoline and its change...

For UV spectra of parent and substituted 1,2,3-triazoles and benzotriazoles, see CHEC-I <84CHEC-1(5)684 >. The UV spectra of benzotriazole, 1-methyl- and 2-methyl-benzotriazole in the gas phase at 90°C have been recorded <94JOC2799>. 1-Alkyltriazolines show two A ax in acetonitrile, 239-242 and 263-266 nm, both with log e w 3.50 <93JOC2097>. The UV spectra of bicyclic triazolines (754) have been recorded <9lJOC4463>. The Si-So electronic absorption spectrum of 1/f-benzotriazole at 286 nm has been studied by computer simulation of the rotational contours. The result shows that the benzotriazole band is an almost pure type-5 band <93JSP(158)399>. 

Photoelectron spectroscopy has been used to study equilibria in the gas phase. Thus, the taut-omerism of triazoline-5-thione is studied by variable temperature photoelectron spectroscopy <83CJC1197). PhotoeleCtron spectra of 1,2-dimethyltriazoline-5-thione (67a) calibrated with the Pi/2 and Ps/2 lines of argon and xenon are recorded with a resolution of 30 meV. The spectra of freshly evaporated material obtained with a Pj probe indicate the presence of the unchanged thione even at 160 °C. A spectrum recorded with a P2 probe after heating the evaporated sample to 160 °C exhibits an additional minor band at 9.40 eV which is most likely due to 2-methyl-4-methylthiotriazole (67b). 

The regiochemistry of trimethylsilyl azide addition to dicyclopentadiene is not clearly indicated in the proton NMR spectrum 13C-NMR studies may provide a definite answer.104 The same is true of the triazoline adducts from phenyl azide and 7-oxa- and 7-azabenzonorbornadiene, respectively.145 ... 

The azide band in the IR spectrum of the vinyl azide in Scheme 43 disappears after 18 hours at room temperature and a crystalline triazoline is obtained.204... 

Most of the A2-triazolines undergo primary loss of a molecule of nitrogen in the mass spectrum and usually do not show a molecular ion peak. Initially, an M - 28 peak is observed at higher temperatures (250°C) for triazolinonor-bornanes, but at lower temperatures (150°C), by increasing the sample pressure, an M + 1 peak is obtained. The intensity ratio, M + 1/M - 28, is... 

The ultraviolet spectrum of AM,2,3-triazoline-4,5-dicarboxylate (II) has been recorded.23... 

The infrared spectrum has been employed mainly to establish the presence22 or absence23 of the NH function in the A3- and A4-triazolines in 10 the NH absorption appears at 3300 cm 1.22 Absence of imine-enamine tautomerization in 7 is also established by IR.6... 

Unlike the labile A2-l,2,3-triazolines, A3- and A4-triazolines do not suffer nitrogen loss in the mass spectrum, and molecular ion peaks have been reported for several related bicyclic A3-l,2,3-triazolines.6... 

The A4-triazoline II showed a single proton at higher field than for diethyl maleate, indicating that the ester groups might be cis, an arrangement which would reduce steric congestion.23 Other possible structures for II were excluded based on the absence of NH, as shown by the NMR spectrum which was unaltered by addition of deuterium oxide.23... 

The hydrazonothiazole in Scheme 13 undergoes nitrosation with formation of a triazoline. The open-chain tautomer is ruled out, based on the single methyl resonance in the NMR spectrum (Section III) and the fact that hydrolysis of the acetonylhydrazone does not occur in dilute hydrochloric acid (Scheme 13) (78JHC401). 

Fig. 2.4. Gas chromatography-electron-impact mass spectrum of the 4-methyl-l,2,4-triazoline-3,5-dione (MTAD) adduct of 10,12-18 2 methyl ester from a commercial conjugated linoleic acid (CLA) mixture.

---