The azinyl–azinylidene tautomerism of azinylmethanes and general problems of the tautomerism of azines

Abstract

In this paper, the dependence of negative bias temperature instability (NBTI) and low-frequency noise characteristics on the various nitrided gate oxides is reported. The threshold voltage shift (ÁV T ) under NBTI stress for thermally nitrided oxide (TNO) was greater than that of plasma nitrided oxide (PNO), whereas the slopes of ÁV T versus stress time for PNO were similar to those for TNO. The flicker noise (1=f noise) characteristic of PNO was better than that of TNO by about 1 order of magnitude, although the 1=f noise of PNO showed almost the same dependence on the frequency as that of TNO. The carrier number fluctuation model due to the trapping and detrapping of electrons in oxide traps was found to be a dominant mechanism of flicker noise. The probability of the generation of drain current random telegraph signal (I D -RTS) noise shows similar values (70-78%) for all nitrided oxides, which shows that the generation of RTS noise is not greatly affected by the nitridation method or nitrogen concentration. #

The structure of 2,4,6-tris[di(tert-butoxycarbonyl)methylidene]-hexahydro-1,3,5-triazine

“…26, 27 2,4,6 Tris[di(tert butoxycarbonyl)methylidene]hexahydro 1,3,5 triazine (1c). 1 Quantum chemical calculations were carried out using the MOPAC 17 and GAUSSIAN 98 28 program packages at the Com putation Center of the N. D. Zelinsky Institute of Organic Chemistry. …”

“…10 The data on the structure of 2,4 dimethoxy 6 (cyanoethoxycarbonylmethyl) 1,3,5 triazine presented in various sources are contradictory. 1 between the aromatic and ylidene forms have been re ported. The corresponding methyl, ethyl, and tert butyl derivatives 1a-c are described; however, no data on their structures in the solid phase are available.…”

“…This result is inconsis tent with the known view on the higher polarity of the ylidene forms. 1 The results of DFT calculations with the 6 31G**/3 21G basis set distinguish the hexahydrotriazine tautomer as the most stable one (the total energy of this form is 23.82 kcal mol -1 lower than that for the aromatic structure).…”

“…1, 3 The energy range corresponding to a comparable tautomer contents is 0-5 kcal mol -1 ; according to spectroscopy, only one tautomer exists in many cases, which means that tautom erism is practically missing. 1 In the 1,3,5 triazine series, compounds containing one di(alkoxycarbonyl)methyl group are believed to be aro matic. 4,5 According to available data, 6-8 bis[di(alkoxy carbonyl)methyl] 1,3,5 triazines exist in the ylidene form; however, their structure was estimated only on the basis of 1 H NMR spectra without taking into account the pos sibility of existence of the enol form 9 and detailed investi gation.…”