Hydrolysis temperature requirements

The carboxylation of ketones is carried out essentially as in the preceding experiment, but at slightly higher temperatures (requiring an oil bath or mantle). Thus, acetophenone (6 g, 0.05 mole) in 100 ml of approx. 2 M MMC is stirred and heated at 110-120° for 1 hour. After cooling, hydrolysis in the acid-ice mixture, and isolation from ether, benzoylacetic acid, mp 99-100°, is obtained in 68% yield. Similarly, 1-indanone gives l-indanone-2-carboxylic acid, mp 100-101°, in 91 % yield. 

The highly ordered cyclic TS of the D-A reaction permits design of diastereo-or enantioselective reactions. (See Section 2.4 of Part A to review the principles of diastereoselectivity and enantioselectivity.) One way to achieve this is to install a chiral auxiliary.80 The cycloaddition proceeds to give two diastereomeric products that can be separated and purified. Because of the lower temperature required and the greater stereoselectivity observed in Lewis acid-catalyzed reactions, the best diastereoselectivity is observed in catalyzed reactions. Several chiral auxiliaries that are capable of high levels of diastereoselectivity have been developed. Chiral esters and amides of acrylic acid are particularly useful because the auxiliary can be recovered by hydrolysis of the purified adduct to give the enantiomerically pure carboxylic acid. Early examples involved acryloyl esters of chiral alcohols, including lactates and mandelates. Esters of the lactone of 2,4-dihydroxy-3,3-dimethylbutanoic acid (pantolactone) have also proven useful. 

Standard hydrolysis is performed with 6M HC1 at 110°C for 24 hJ2 But the method can be varied in terms of acids used, temperature, and time, as well as in the mode of gas- or liquid-phase hydrolysis (Table 1). Time-dependent hydrolysis is required to determine the exact stoichiometry for unstable amino acids as well as for particular sequences difficult to hydrolyze. Tryptophan, methionine, cystine, tyrosine, serine, and threonine are known to be degraded at an extent of >50, >50, >30, >20, >10, and >5%, respectively.141 Therefore, performing standard hydrolysis for 24, 48, and 72 h, and extrapolation to zero time of hydrolysis allows for better quantitation of these unstable amino acids, whereas extrapolation... 

Lithium niobate is a ferroelectric material used as an optical switch. Preparation by the simple ceramic method leads to problems in obtaining the correct stoichiometry, and a mixture of phases often results. Several sol-gel preparations have been described, their advantage being the lower temperature required for the preparation and the greater homogeneity of the product. One such preparation starts with lithium ethoxide (LiOC2H5 (or LiOEt)) and niobium ethoxide Nb2(OEt)io. Each ethoxide was dissolved in absolute ethanol and the two solutions mixed. The addition of water leads to partial hydrolysis giving hydroxy-alkoxides, for example ... 

The hydrolysis reaction however, requires higher temperatures (650°F) than the optimum for the Claus redox. Nonetheless it has been clearly demonstrated in plant studies during the 1970 s that running the first converter bed at this higher COS hydrolysis temperature and sacrificing some Claus redox efficiency that can be recovered in later beds does result in an improved overall sulfur recovery efficiency especially in four stage Claus converter systems. 

Different labile crosslinkers have different rates of bond cleavage at different temperatures. The temperature required and the mechanism of bond dissociation depend on the chemical structure of the crosslinker. For example, when the labile crosslinker is a diacrylate ester, hydrolysis of the ester linkage becomes the most likely mechanism of de-crosslinking. Proper selection of crosslinker can give particles with different activation temperature. The product... 

In an attempt to produce sugars directly from barley seeds, these were extracted with superheated water in our laboratory. Unfortunately, at the temperature required for hydrolysis, a dark brown extract was obtained, which smelled of burning. At lower temperature, however, a pleasant cooking aroma was obtained, due to the Maillard reaction. Similar results were obtained with other vegetable material, and superheated water could be used to manufacture food flavors [6]. The most inter-... 

Amide bonds are among fhe most fundamental and important chemical bonds in nature because of their existence in peptide and protein structures. Amide bonds are stable because of delocalization of the lone pair electrons on the nitrogen atom over the amide functionality (Fig. 1). The half-life of amide bonds in spontaneous hydrolysis is estimated to be 350-600 years in a neutral pH solution at room temperature [1]. Traditional methods for amide hydrolysis generally require harsh reaction conditirais, such as strong acids or bases at high temperatures [2]. 

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