Rate of acid hydrolysis

It is well known that the 1-phosphates of the ketoses, L-fuculose (51) and L-rhamnulose (52) have considerable biochemical interest. Their chemical synthesis has not been described as far as is known to the writer, but the rate of acid hydrolysis of L-fuculose 1-phosphate, obtained by enzymatic synthesis, has been determined by Heath and Ghalambor (20) and that of L-rhamnulose 1-phosphate by H. Sawada (48) and by Chiu and Feingold (II). They found that the rate of... 

RATES OF ACID HYDROLYSIS OF SOME Co(IlI) COMPLEXES AT 250 °C The labile ligand is italicized. 

Electron-withdrawing substituents at C(7) in cephalosporins decrease the rate of acid hydrolysis just as substituents at C(6) in penicillins do. However, in terms of acid-catalyzed hydrolysis cephalosporins are much less reactive than penicillins, even when the substituents on the side chains are similar [76], because cephalosporins do not show neighboring-group participation. The absence of neighboring-group participation in cephalosporins can be explained by the lower basicity of the N-atom of the dihydrothiazine ring compared to that of the thiazolidine ring of penicillins. 

H. H. Jensen, L. Lyngbye, and M. Bols, A free-energy relationship between the rate of acidic hydrolysis of glycosides and the pKa of isofagomines, Angew. Chem. Int. Ed., 40 (2001) 3447-3449. 

It remains unclear whether or not the rate of cleavage of the gly-cosyl bond in sugar nucleotides depends upon the structure of the nucleotide residue, and the same uncertainty is true for other reactions that affect the glycosyl group no systematic kinetic studies have been reported. However, it may be noted that there appears to be no essential difference between the rates of acidic hydrolysis of the 5 -(a-D-glucopyranosyl pyrophosphates) of uridine and N3-methyluridine, 331... 

Feather and Harris64 demonstrated that the relative rates of acid hydrolysis of the glycosidic linkages in cellotriose (21) are k kb =... 

In a similar study,95 the rates of acid hydrolysis of 26, 27, and 28 in 125 mM sulfuric acid were determined (see Table II). These structures are typical for D-glucose residues that are unsubstituted (26),... 

Kinetic investigations of amide hydrolysis showed that the rate of hydrolysis in basic media is proportional to the concentration of amide and hydroxide ion. Similarly, early work180-183 on the acid-catalysed hydrolysis of amides showed that the rate of acidic hydrolysis is, in general, proportional to the concentration of amide and hydroxonium ion. In several acidic hydrolyses, however, a maximum is observed in the pH-rate profile at 3-6 pH units, a phenomenon first reported by Benrath184 and since supported by other workers185"190. This behaviour of amides is in contrast to the hydrolysis of nitriles whose rate constant increases continuously with the hydrogen ion concentration191. 

Figure 7. Effect of ball milling on rate of acid hydrolysis...

Garton, Robinson and Williams66 have studied the rate of acid hydrolysis of phenyl D-glucosiduronic acid as compared with phenyl acid sulfate. The ester acid sulfate was hydrolyzed completely by N hydrochloric acid at 93-95° in 10 minutes, 50 times as rapidly as the D-glucosiduronic acid. After 20 minutes, only 40% of the latter was hydrolyzed. On refluxing... 

Barley starches exhibit a relatively high rate of acid hydrolysis during the first 10 days, followed by a slower rate thereafter.28,39 The extent of degradation follows the order waxy > normal > high-amylose (Table 16.6). This order is similar to that... 

IV, Effect of the 1,6-Anhydro Ring on the Rate of Acid Hydrolysis of the Furan-... 

It is noteworthy that, in distinction from aldosides, there is little difference in the rates of acid hydrolysis of D-fructofuranosides and D-fructopyranosides.101... 

Carboxyl groups bound to the polysaccharide chains have a considerable influence on the rate of acid hydrolysis probably mainly because of steric interaction even if inductive effects should also be considered. For example,... 

The effect of the neutralization reaction on the rate of metal-catalyzed degradation can be assessed in isolation from its effect on the acidic hydrolysis component by a comparison of the relative stability values before and after the sodium bicarbonate treatment. In the iron-catalyzed system, the relative stability values observed after the bicarbonate treatment are appreciably higher, especially at higher metal concentrations. The catalytic effect of iron for the autoxidative process may be reduced. However, the iron species adsorbed from the sulfate solution may itself be acidic. In such a case, neutralization of this acidic moiety would reduce the rate of acidic hydrolysis. Some metal salts, such as alum, are known to increase the acidic content of paper and accelerate its hydrolytic degradation (36). 

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