Temperature decomposition, spectra

The VEEL spectrum of a surface vinyl group derived from low-temperature decomposition of vinyl iodide on Pt(lll) has been reported with features at 2920 cm 1 (s), eCH 1600 cm 1 (w), vCC 1380 cm-1 (m), 8= CH2 scissors 1255 cm1 (mw), <5C=CH 955 cm 1 (s), -y=CH2 and 690 cm 1 (mw), y=CH2 twist (208). The strength of the out-of-plane y = CH2 mode shows that the plane of the vinyl group is more nearly parallel than perpendicular to the surface, probably o--bonded to one metal atom and 77-bonded to another. This inference is confirmed by the relatively low wavenumbers of the eCH modes. However, in such a situation, the vCC wavenumber... 

When sublimed, anthraquinone forms a pale yellow, crystalline material, needle-like in shape. Unlike anthracene, it exhibits no fluorescence. It melts at 286 0 and boils at 379 —38UC. At much higher temperatures, decomposition occurs. Anthraquinone has only a slight solubility in alcohol or benzene and is best recrystaUized from glacial acetic acid or high boiling solvents such as nitrobenzene or dichlorobenzene. It is very soluble in concentrated sulfuric acid. In methanol, uv absorptions of anthraquinone are at 250 nm (e = 4.98), 270 nm (4.5), and 325 nm (4.02) (4). In the ir spectrum, the double alljdic ketone absorbs at 5.95 am (1681 cm ), and the aromatic double bond absorbs at 6.25 im (1600 cm ) and 6.30 Jm (1587 cm ). 

Heath and Majer (H3) have recently used a mass spectrometer to study the decomposition of ammonium perchlorate. Decomposition was detected in the range from 110° to 120°C. At this temperature, there were ions in the mass spectrum caused by NH3, HC104, Cl2, HC1, nitrogen oxides, and 02. The appearance of the species NO, N02,02, and Cl2 in the decomposition products under very low pressure (i.e., in the absence of gas-phase molecular collisions) indicates that the principal decomposition reactions take place in the crystal and not in the gas phase. 

On exposure to air, the initially clear orange crystals of the adduct turn cloudy within 1 min as a result of the loss of CS2, and ultimately form a yellow oil. In CS2 solution the adduct decomposes fairly rapidly at room temperature the decomposition products SOCI2, SO2, Sg, and SbCls are already detectable after 10 min. The SO stretching vibrations of Si202-2SbCl5 occur at 940 cm in the infrared spectrum (in CS2) [61]. Free S12O2 has not been prepared yet. 

Figure 2. A decomposition example for a spectrum taken during an XAS/TPS experiment on Co20 /Si02-923 in 1 atmosphere of flowing 2% H2S/H2. The temperature ramp was 5 C/minute.

Catalyst Activation Gas phase activation of supported DENs was examined using in-situ FTIR spectroscopy and FTIR spectroscopy of adsorbed CO. For in-situ dendrimer decomposition studies, the spectra were collected under a gas flow composed of 20% 02/He or 20% H2/He. The supported DEN sample was pressed into a self-supporting wafer, loaded into a controlled atmosphere IR cell, and collected as the sample background. The temperature was raised stepwise and spectra were collected at each temperature until little or no change was observed. After oxidation, the sample was reduced in 20% H2/He flow with various time/temperature combinations. The sample was then flushed with He for lhr at the reduction temperature. After cooling under He flow, a background spectrum was collected at room temperature. A 5% CO/He mixture was flowed over the sample for 15 minutes, followed by pure He. IR spectra of CO adsorbed on the catalyst surface were collected after the gas phase CO had been purged from the cell. 

In the case of allylpotassium, the metal complex exists as a symmetric n structure. No temperature dependence was shown by either 13C NMR for A5[C(i) —C(3)] or by 1H NMR for substitution with deuterium at Cp). Thompson and Ford measured experimentally a variety of allylalkali metal compounds using variable-temperature NMR in THF-dx45. Addends such as TMEDA, hexamethylphosphoric triamide (HMPA), 15-crown-5-ether, [2.1.1]cryptand and n-butyllithium showed either no change in the spectrum or rapid decomposition of the complexing agent. Measurement of the populations of E (17) and Z (18) isomers of 1-isopropylallylpotassium showed the Z isomer to be more stable (Table 11). 

Neomycin is insufficiently volatile for direct mass spectrometric analysis. To overcome this problem Inouye- - prepared the volatile N-salicylidene Schiff s base, the M.S. of which, however, did not exhibit a peak for the molecular ion. To observe the molecular ion it was necessary to use the o-trimethylsilyl ether of the N-salicylidene Schiff s base. The spectrum of N-salicylidene neomycin was found to be dependant on the ion-chamber temperature indicating that thermal decomposition plays a significant part in the fragmentation process. 

B) Spectrum recorded at room temperature (R.T.) following decomposition at 373 K, (C) Spectrum recorded at R.T. following decomposition at 673 K, (D) Spectrum recorded at R.T. following exposure to ambient atmosphere, (E) Spectrum recorded at R.T. following reduction in a flowing 90%C0/... 

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