Hydrolysis heating

Sulphonatnides. Sulphonamides are very resistant to the normal reagents for hydrolysis. Heating with 80 per cent, sulphuric acid at 160-170° results in rapid hydrolysis ... 

Hydrolysis. Heating 1,2-dichloroethane with excess water at 60°C in a nitrogen atmosphere produces some hydrogen chloride. The rate of evolution is dependent on the temperature and volume of the aqueous phase. Hydrolysis at 160—175°C and 1.5 MPa (15 atm) in the presence of an acid... 

Thus, errors in all the heats, apart from the precisely known water value, are decreased ra-fold in the required heat. The hydrolysis heat A//2 is always much less than At and can be measured less precisely. The reactions involved in reactions 2, 3, and 6 of Table II have been used in the CODATA evaluation of Aif,(F q)), although in theorv reactions 7 and 8 should lead to more accurate values. In practice this may not be true. Thus the fluorination of iodine produces some IF7, together with the bulk of IF5, and errors in estimating the mixture can cause uncertainty in the final value of AZf/IF ). The hydrolysis heat for the reaction... 

Hydrolysis of FCIO3 is very slow even at 250°-300°C 92). For quantitative hydrolysis, heating of FClOg with concentrated aqueous hydroxide solution to 300°C in a sealed tube is required ... 

Various protocols and modifications have been reported in the literature on how to perform the TBA test. In foodstuffs, malonalde-hyde can be bound to various constituents of the food (e.g., proteins), and therefore it must somehow be released prior to determination. It is difficult to determine the optimal conditions for release of malonaldehyde as they differ from one material to another and require different conditions for hydrolysis. Heat and/or strong acid are thought to be essential for the liberation of malonaldehyde from precursors or bound forms, for condensation with TBA, and for maximal color development. For edible oil samples or lipid extracts, the test is simplified in that samples are directly dissolved in butanol and then an aliquot is reacted with TBA. Alternatively, a food sample can be heated with TBA solution and the red pigment that is formed can be extracted from the reaction mixture with butanol or a butanol/pyridine solution (Turner etal., 1954 Sinnhuberand Yu, 1958 Placer et al., 1966 Uchiyama and Mihara, 1978 Ohk-awa et al., 1979 Pokorny and Dieffenbacher, 1989). 

Macromolecule therapeutic agents tend to be more reactive than small-molecule drags under various circumstances, from sample collection to analysis. Biological and chemical transformation may occur as a result of enzyme hydrolysis, heat or... 

The polymers with (meth)acrylic chain ends can be crosslinked with peroxides or by UV irradiation 175 176), a procedure used for adhesives. Flexibility, resistance to attack by hydrolysis, heat, and ozone, as well as improved modulus and strength of the plastic adhesives are the characteristic effects of this modification on properties. 

Earlier work of this school was concerned to establish heats of formation of halogen-containing organic compounds by measuring heats of hydrolysis. Heats of hydrolysis of acetyl fluoride, chloride, bromide, and iodide402 of the chloro-substituted acetyl chlorides oi of the benzoyl halides and of chloral and bromal 3 have also been made. Comparison with heats of formation derived from heats of combustion is not normally possible, but there is a large discrepancy between the two methods for benzoyl chloride, where an early combustion measurement is available, in the sense that the determined heat of combustion appears to be about 14 kcal low. 

A number of acylphosphonic acids are of interest for their biological activity, or as intermediates in syntheses of potentially bioactive phosphonic acids [7, 34, 48 - 50]. In many cases, they are most conveniently prepared by hydrolysis of the corresponding esters. Due to the presence of the keto function, acid hydrolysis (heating in aqueous HCl) is generally not a practical method to achieve this. Silyldealkylation of methyl-, ethyl- or isopropyl phosphonates with BTMS, followed by very mild hydrolysis is normally compatible with acyl and other sensitive functionalities [7,34,48]. 

Purposeful degradation studies of the drug substance include appropriate solution and solid-state stress conditions (e.g., acid/base hydrolysis, heat, humidity, oxidation, and light exposure, in accordance with ICH guidelines). Guidelines from the United States Pharmacopoeia (USP), ICH, and FDA provide a brief outline of drug substance conditions. The ICH guidelines specifically state ... 

There is no direct evidence on the form of the glycosyl-enzyme intermediate. Nonetheless, stabilization of a noncovalent oxocarbonium for the period between product fructose release and acceptor binding may not be realistic for slow reactions, given the extremely short lifetime of a glycosyl oxocarbonium ion (9). Levansucrase and particularly GTase-S are quite slow enzymes, with sucrose hydrolysis Heat of 48 sec 122) and 9.1 see" 213), respectively. Thus, the carbonium ion may well collapse to a more stable covalent complex or develop an equilibrium between the two forms. Nucleophilic catalysis is consistent with... 

Anthrylphosphonic add 167 Anthracene (53.6 g, 0.3 mole), diethyl phosphite (170 ml, 1.33 moles), and di-/er/-butyl peroxide (30.1 ml, 0.168 mole) are heated for 4 h at 150°, whereafter much (120 ml) of the diethyl phosphite is recovered by distillation in a vacuum. The residue is treated with water (200 ml), collected, washed with water, and, for hydrolysis, heated under reflux for 72 h with a mixture of ethanol (500 ml) and concentrated hydrochloric acid (150 ml). The resulting solution is evaporated and the solid residue is heated with 5% aqueous potassium hydroxide (500 ml). Filtration and acidification then precipitate a yellow crude product (38.6 g), m.p. 279-282°, which is washed with water. For purification this product (6.5 g) is stirred with charcoal in a solution of sodium acetate (10 g) in water (100 ml) for 0.5 h at 70°. Filtration and acidification precipitate the white acid which, after drying at 120° in a vacuum, has m.p. 282-283° (dec.) (6.2 g). 

Within certain limits it is possible to change these properties using chemical modification, enzymatic hydrolysis, heat denaturation, etc. 

In the case of PVA paint hydrolysis, heat ageing stability will need to be carefully checked. The use of alkaline extenders such as calcium carbonates as buffers will definitely improve... 

Shimoyamada, M. Yoshimura, H. Tomida, K. Watanabe, K. Stabilities of bovine P-lactoglobulin/reti-nol or retinoic acid complexes against tryptic hydrolysis, heating and light-induced oxidation. Lebensm. Wiss. u. Technol. 1996, 29 (8), 763-766. 

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