Hydrolysis products, effect temperature

The temperature resistance of the polysiloxane on the samples was tested by stepwise heating up to 500°C. Whereas the pure hydrolysis product undergoes a complete thermal degradation via oxidative conversion of the CH3-Si groups into HO-Si groups, the polysiloxane persists on the silica sample. This stabilization effect most likely results from the covalent attachment of the methyl-polysiloxane. 

Benzylideneamino)-phenols (49) can be oxidatively cyclized to form 2-phenyloxa-zols (50) (Eq. (13)) by direct anodic oxidation 2, by Pb(OAc)4AgjO " and nickel peroxide The oxidation of 49 proceeded disappointingly in t-butanoT. water at the nickel hydroxide electrode. 50 was isolated only in traces, benzaldehyde was the major product, which indicated that 49 hydrolysed under the reaction conditions. The hydrolysis could effectively be suppressed by electrolysis in an emulsion of water and cyclohexane, where the portion of water was kept low. The temperature was around 70 °C to secure a fast oxidation. With these reaction conditions good yields of 50 were obtained (Table 16). 

Related compound (A) has the systematic name (+)-(S)-(o-chlorophe-nyl)-6,7-dihydrothieno[3,2-c]pyridine-5-(4H)-acetic acid [2], and is a hydrolysis product of the ester group of clopidogrel. This impurity is formed as a result of the combined effects of moisture and temperature [2, 6, 7],... 

The m.elted glass is transparent, but a whitish coating of hydrolysis products is formed on the surface by the effect of atmospheric humidity. The rate of dissolution in water at room temperature is low. The dissolution is therefore carried out at elevated temperature and pressure in an autoclave. The insoluble residue should not exceed 1%. The effects of the individual parameters on the rate of dissolution are dealt with in detail by Matveyev (1957). 

Increase in temperature favours the formation of the hydrolysis product, as does an excessively high pH. The dye-fibre linkage can be split by the action of alkalis at high temperatures. This means that there will be loss of depth if laundered at the boil in alkaline wash liquors, or should the goods subsequently be scoured with strong alkalis when Remazol dyes are used for effect threads. 

It should increase delivery of the bioactive moiety and decrease toxicity. In aqueous solutions, cisplatin hydrolyzes with a reaction half-life of nine hours at room temperature or 2.4 hours at 37 °C. Cisplatin hydrolyzes in the body forming a wide variety of platinum-containing agents, none of which is as active as cisplatin itself and most of which exhibit increased toxicity to the body. Formation of these hydrolysis products increases the amount of platinum complex that must be added to effect desired tumor reduction. Consequently, this increases the amount of platinum complexes that must be processed by the body. The polymeric structure should also shield the platinum moiety from unwanted hydrolysis increasing the concentration of platinum in the beneficial form that is retained in the body thus permitting lower effective doses of the drug to be used. The nature of the more hydrophobic polymer chain should also act to protect the platinum moiety from ready attack by water. 

Some crystalline short-chain polyphosphates can be hydrolysed by their own water of crystallisation if it is present. The hydrolysis of NasPjOjo 6H2O is complex and has been represented by various reactions but if the crystals are stored in a sealed chamber at room temperature, the reaction is mainly (5.152). On the other hand, dehydration at 100°C is said to follow the path (5.153), but rapid heating of the hexahydrate at 220°C results in recondensation of the hydrolysis products and the equation is effectively (5.154). As already stated above, neither of the anhydrous forms can be obtained by dehydration of the hexahydrate at lower temperature or by recrystallisation from aqueous solution. 

The final partitioning of fission product iodine between the sump water and the atmosphere of the containment is determined by the equilibrium partition coefficient as will be discussed in more detail in Section 7.4.3.1., this figure depends on several parameters, such as iodine concentration and sump water pH and, to a lesser extent, temperature. As can be seen from Fig. 4.13., the iodine partition coefficient increases with decreasing iodine concentration in the solution this behavior is the consequence of the shift in the h hydrolysis reaction towards a lower I2 equilibrium fraction at lower total iodine concentration. Below a concentration of about 10" g/1, however, the partition coefficient remains virtually constant, an effect which has been attributed to the volatility of the hydrolysis product HOI (Lin, 1981). This constant value is about l(f at pH 7 and 25 °C it applies as well for the concentration range to be expected in a loss-of-coolant accident. Concerning the HOI partition coefficient at 100 °C, several measurements yielding quite different values have been reported. The lowest one is 240 given by Lin (1981) Lemire et al. (1981) reported values between 100 and 1(1, while Wren and Sanipelli (1984) measured values between 7 10 and 3 10. Since the HOI compound was... 

Phthalic and isophthalic resins are hydrolyzed by 60 °C hot water here, the rate of hydrolysis noticeably increases with temperature. The water washes the hydrolysis products out of the resin. Because this process superposes absorption, weight change in glass fiber-reinforced polyester resins caused by exposure to warm water is lower than caused by water at 20 °C. At 100 °C, however, the effect of water on glass fiber-reinforced phthalic and isophthalic resins results in severe weight loss and the formation of deposits in water, a clear indication of degradation. Bisphenol-based resins are more resistant to water. Table 5.116 [32]. 

Results of experiments on the effects of temperature and HD concentration on the rate and products of the hydrolysis reaction have been described previously [4]. Briefly, the reaction proceeds relatively slowly at 30° C and is accelerated approximately 28-fold by an increase in temperature to 70° C (rates are described in relative terms due to the mass-transfer-limited nature of the reaction, which makes the rate dependent on agitation). Thiodiglycol is the main hydrolysis product various sulfonium ions are intermediates in the reaction[9]. 

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