Adventitious water

The nitric acid used in this work contained 10% of water, which introduced a considerable proportion of acetic acid into the medium. Further dilution of the solvent wnth acetic acid up to a concentration of 50 moles % had no effect on the rate, but the addition of yet more acetic acid decreased the rate, and in the absence of acetic anhydride there was no observed reaction. It was supposed from these results that the adventitious acetic acid would have no effect. The rate coefficients of the nitration diminished rapidly with time in one experiment the value of k was reduced by a factor of 2 in i h. Corrected values were obtained by extrapolation to zero time. The author ascribed the decrease to the conversion of acetyl nitrate into tetranitromethane, but this conversion cannot be the explanation because independent studies agree in concluding that it is too slow ( 5.3.1). 

The most direct test of the tensile strength hypothesis would be to compare the value of Tq calculated from the closure point of the isotherm by Equation (3.61) with the tensile strength of the bulk liquid determined directly. Unfortunately, experimental measurement of the tensile strength is extremely difficult because of the part played by adventitious factors such as the presence of solid particles and dissolved gases, so that the values in the literature vary widely (between 9 and 270 bar for water at 298 K, for example). 

Fig. 12. Photo-induced chemistry of a 4-sulfonyl DNQ. The intermediate species reacts with adventitious water in the resist film to produce a sulfonic acid...

Unless working with superdried systems or in the presence of proton traps, adventitious water is always present as a proton source. Polymeriza tion rates, monomer conversions, and to some extent polymer molecular weights are dependent on the amount of protic impurities therefore, weU-estabHshed drying methods should be followed to obtain reproducible results. The importance is not the elimination of the last trace of adventitious water, a heroic task, but to estabhsh a more or less constant level of dryness. 

No clear picture of the primary radical intermediate(s) in the HO2 photooxidation of water has appeared. The nature of the observed radical species depends on the origin and pretreatment of the HO2 sample, on the conditions and extent of its reduction, on the extent of surface hydroxylation, and on the presence of adventitious electron acceptors such as molecular oxygen (41). The hole is trapped on the terminal OH group (54). 

Environmentally Available Reactants. Under normal conditions ethyleneamines are considered to be thermally stable molecules. However, they are sufftciendy reactive that upon exposure to adventitious water, carbon dioxide, nitrogen oxides, and oxygen, trace levels of by-products can form and increased color usually results. 

The AE reaetion is general and effieient, thus few substantial improvements have been reported. The most signifieant improvement to the original eonditions is the addition of aetivated moleeular sieves. The addition of aetivated moleeular sieves allows for almost all AE reaetion to be performed under eatalytie eonditions (5-10 mol%). The role of the moleeular sieves is thought to sequester any adventitious water or water that may be generated during the eourse of the reaetion via side reaetions. 

Adventitious surfactants also have a marked effect on the mechanism of coalescence. In studying the coalescence of curved water surfaces, Lindblad (L8) used aged distilled water that was stored for about 30 h in a polyethylene bottle opened to the air through a narrow polyethylene tube inserted in the water. He found that if fresh distilled water (water exposed not longer than 1 h to the air) was used, the delay time in coalescence was approximately half as long. Consequently, he concluded that this difference is due to some form of contamination which settled into the water or onto the water surface. 

The authors concluded that the side reactions normally observed in amine-initiated NCA polymerizations are simply a consequence of impurities. Since the main side reactions in these polymerizations do not involve reaction with adventitious impurities such as water, but instead reactions with monomer, solvent, or polymer (i.e., termination by reaction of the amine-end with an ester side chain, attack of DMF by the amine-end, or chain transfer to monomer) [11, 12], this conclusion does not seem to be well justified. It is likely that the role of impurities (e.g., water) in these polymerizations is very complex. A possible explanation for the polymerization control observed under high vacuum is that the impurities act to catalyze side reactions with monomer, polymer, or solvent. In this scenario, it is reasonable to speculate that polar species such as water can bind to monomers or the propagating chain-end and thus influence their reactivity. 

Adventitious water is responsible for the formation of the dimeric hydroxo complex 31 obtained by reaction of AuCb with 1,4-dilithiotetraphenylbutadiene in ether solution [97[. The hydroxo-bridged complex [Au(C6H4N02-2)2( i-0H)[2 (32) was obtained either by reaction of Na[Au(C6H4N02-2)2(0Ph)2] with traces of water in CH2Cl2/n-hexane solution or by treatment of the dichloroaurated complex with NaOH [98[. The crystal structure of 32 2Et20 shows that it is a centrosymmetric... 

The investigation of the sensiririry of the product distribution to the presence of particular reactants such as adventitious water in non-aqueous media. 

This system was subsequently investigated by Christensen et at. (1990) also using in situ FTIR, who observed identical product features (see Figure 3.48). In order first to compare directly the IR spectrum of oxalate generated in situ, the authors took advantage of the surface reactivity of Pt and the poor diffusion of species to and from the thin layer. Thus, a solution of oxalic acid in the electrolyte was placed in the spectroelectrochemical cell, the potential of the platinum working electrode stepped to successively lower values and spectra taken at each step. The spectra were all normalised to the reference spectrum collected at the base potential of 0 V vs. SCE. As a result of the deprotonation of adventitious water ... 

The cation stabilization of the persulfoxide extends its lifetime sufficiently to allow trapping with adventitious water and with sulfide substrate46 (Fig. 27). These reactions provide a satisfying explanation for the enhanced intrazeolite sulfone yields... 

The advantage of this catalyst, as compared to classical Lewis acids such as A1C13, is the low catalyst loading required. Also, solvents and reactants do not need spetial drying, as the catalyst is not notably deactivated by adventitious water. 

The anomalous features are observed on well-ordered (111) surfaces in a variety of electrolytes over a wide range of pH (0-11), but the potentials at which the features appear and the detailed shapes of the I-V curves vary considerably. Specifically, the potential region (versus RHE) in which the features appear changes with anion concentration in sulphate and chloride electrolytes, but not in fluoride, perchlorate, bicarbonate or hydroxide electrolyte. In sulfate electrolyte, at constant anion concentration the region shifts (versus RHE) with varying pH, while in fluoride, perchlorate, bicarbonate and hydroxide electrolyte it does not. The use of UHV surface analytical techniques has established to a reasonable (but not definitive) extent that adventitious impurities are not involved in the anomalous process, i.e., the only species participating in the chemistry are protons/hydroxyIs, water and the anions of the solute. On the basis of the pH and anion concentration dependencies, I agree with the... 

Feeney, Holliday, and Marsden reported that when diboron tetrachloride and isobutene were mixed in a molar ratio of approximately 1 2, without solvent at -78°, the isobutene was polymerised to a rubbery polymer. It is likely that adventitious water, or a reaction product of water and the B2C14, was the co-catalyst in this reaction [39]. 

Catalysts In systems 1-19 the catalyst was AlCl in number 20 it was SnCl4 in numbers 21 and 22 it was TiCl4 Co-catalysts In systems 1-19 and 21 the co-catalyst is unknown. It may have been adventitious water, solvent (not in numbers 5 and 8), or the additive or an impurity contained therein in systems 21 and 22 it was water Temperature For systems 6 and 7 the temperature range was - 55 °C to - 125 °C for system 22 the temperature was -13 °C for all other systems it was - 78 °C to — 80 °C f In this paper another 18 compounds are mentioned which as additives gave type (A) curves d These curves are unlike the normal type (A) curves in that the maximum is flanked closely by a minimum on each side Biddulph, Plescb, and Rutherford, Symposium on Macromolecules, Wiesbaden, 1959, Paper III A 10. See no [54] in Publication List ... 

The catalyst in systems 30-36 was BF3,Et20 the co-catalyst is unknown, but was probably adventitious water the temperature was -78 °C a Okamura, Higashimura, and Sakurada, J. Polymer Sci., 1959, 39, 507 b Okamura, Higashimura, and Yamamoto, J. Chem. Soc. Japan, Ind. Chem. Section, 1958, 61, 1636... 

The catalyst in systems 30-36 was BP3,Et20 the co-catalyst is unknown, but probably adventitious water the temperature was -78 °C was... 

Evidence for ionic reactions has been derived by the use of specific scavengers (also applicable to radicals) and by inference from ion-molecule reactions observed in the mass spectrometer. Radical and ionic mechanisms can be written for many chemical changes and the preferred pathway is likely to depend on the irradiation conditions, e.g. temperature, and on the presence of adventitious impurities, such as water, which scavenge ions. 

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