Argon compounds spectroscopy

The buildup of soluble corrosion products can be used to monitor corrosion kinetics. This method has been used extensively in oil field corrosion inhibitor testing, particularly in sweet (CO2) systems with only small amounts of HjS present [29]. Iron analysis in the laboratory is most rapidly done on the bench with the Hach method (Phenantridine) [.30], although a host of other wet chemical methods are applicable. Instrumental methods include Atomic Absorption Spectroscopy (AAS) and Inductively Coupled Argon Plasma Spectroscopy (ICAP). While both these methods are well suited for high volume routine analysis, care must be taken that the samples are not contaminated by even traces of hydrocarbons. This includes soluble hydrocarbons such as methanol, chelating compounds such as EDTA, or scale inhibition products. Also used in the laboratory is Ion Chromatography (IC). This latter method is even more sensitive to sample composition and not recommended on a routine basis. 

Kinetic measurements were performed employii UV-vis spectroscopy (Perkin Elmer "K2, X5 or 12 spectrophotometer) using quartz cuvettes of 1 cm pathlength at 25 0.1 C. Second-order rate constants of the reaction of methyl vinyl ketone (4.8) with cyclopentadiene (4.6) were determined from the pseudo-first-order rate constants obtained by followirg the absorption of 4.6 at 253-260 nm in the presence of an excess of 4.8. Typical concentrations were [4.8] = 18 mM and [4.6] = 0.1 mM. In order to ensure rapid dissolution of 4.6, this compound was added from a stock solution of 5.0 )j1 in 2.00 g of 1-propanol. In order to prevent evaporation of the extremely volatile 4.6, the cuvettes were filled almost completely and sealed carefully. The water used for the experiments with MeReOj was degassed by purging with argon for 0.5 hours prior to the measurements. All rate constants were reproducible to within 3%. 

The compounds benzonitrile, p-methylbenzonitrile, /)-methoxybenzonitrile, p-trifluoromethyl-benzonitrile, /)-methoxycarbonylbenzonitrile, and triethoxysilane are commercial products and are degassed and stored under argon before use. Trimethylsilane was prepared according to a literature report [38]. The nitrile (9.8 mmol) and the hydrosilane (49 mmol) are added to the rhodium catalyst (0.1 mmol) contained in a Carius tube. When using trimethylsilane, the operation is performed at —20°C. The tube is closed and the mixture stirred at 100 °C for 15h. The liquid is separated by filtration and the excess of hydrosilane removed under vacuum to leave the N, Wdisilylamine derivative. If necessary, a bulb to bulb distillation is performed to obtain a completely colorless liquid. The yields obtained in the different runs are reported in Table 6. The product have been characterized by elemental analysis, NMR spectroscopy, and GC-MS analysis. 

SDMA in toluene for 20 min at 0° under an argon atmosphere gave the 5-C-(phenylphosphinyl) compound 124, which, on acid hydrolysis, afforded the 5-C-(phosphinyl)hexopyranose 125. This was treated with acetic anhydride-pyridine, to give the peracetates (126), from which crystalline l,2,4-tri-0-acetyl-3,6-di-0-benzyl-5-deoxy-5-C-[(S)-phenyl-phosphinyl]-/ -D-glucopyranose-4C1 (127) was isolated in 2% overall yield from 123 none of the other diastereoisomers of 127 were obtained. Structure 127 was established by 400-MHz, -n.m.r. spectroscopy (see Section 11,5). 

Even reactive carbenes can be observed, however, if they are formed by irradiating precursors (often diazo compounds like diazomethane, which we have just been discussing) trapped in frozen argon at very low temperatures (less than 77 K). 1R and ESR spectroscopy can then be used to determine their structure. 

An Arrhenius plot of the deposition rate vs reciprocal absolute temperature is shown in Fig. 2. Depositions were made by indicated pressures with or without carrier gas. One notices in all cases that above 190 °C the deposition rate of several A/s was found with an activation energy of about 50-60 kJ mol". Below this temperature a strong decrease of the deposition rate was found. It did not matter whether the gas phase consisted of pure precursor or of a mixture of organometallic compound and argon carrier gas. Only the value of the deposition rate was varying with the different pressures which can be explained by the amount of precursor in the gas phase. Similar results (Fig. 3) were also obtained with in situ X-ray photoelectron spectroscopy (ESCA) studies, which indicate a sharp shift of the binding energy as an onset of the start of decomposition of the precusor at around 190 °C. 

Figure 2.17. Electron spectroscopy for chemical analysis ESCA) spectra of organometallic polymer films before and after exposure to oxygen plasma. The silicon 2p transition page 99) is shifted from 99.7 to 102.4 eV. The magnitude of the shift is consistent uMh conversion to SiO, where x is between 1.5 and 2. The Sn 3d transitions of the organotin compound above) undergo a similar shift 1.7 eV), consistent with generation of a SnOx surface, where x is again between 1.5 and 2. Argon sputter etching followed by ESCA analysis indicates that these oxide films are less than 100 A thick.

During the past eight years, we have studied the reactions of thermally generated silicon atoms with a variety of low-molecular-weight reactants in an argon matrix. The reaction products were identified by means of IR and UV/Vis spectroscopy aided by comparison with calculated spectra. The method turned out to be very versatile and successful [1]. The selected substrates were mainly molecules with isolated, conjugated or aromatic n bonds, and compounds containing a bonds and at the same time free electron pairs. 

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