Alkaline hydrolysis advantages

Last but not least of the liquid calorimetric media are aqueous solutions used in the hydrolysis of simple and complex fluorides. Stepwise replacement of F by OH occurs, and mixed products are not unusual. Thus the BFj ion hydrolyzes to species BF (OH)l and one has to ensure that the same product composition is formed in the auxiliary heat experiments (99). The problem is accentuated when polynuclear species form, as the equilibration can be slow. The inconsistencies in the heats of alkaline hydrolysis of MoF6 and WFe found by various authors and of the enthalpy of SbF5—derived by assuming SbF5 and Sb205 dissolved in 10 M HF produced the same species in solution—illustrate the difficulties. It is as well to confirm enthalpies of higher valent fluorides obtained by hydrolysis by alternative nonaqueous methods, especially since uncertainty in the Afl (Fderived enthalpy. The advantage of hydrolysis methods, apart from the simplicity of technique, is that the heats are small and one can tolerate... 

Alkaline hydrolysis with barium, sodium, or lithium hydroxides (0.2-4 M) at 110°C for 18-70 h126-291 requires special reaction vessels and handling. Reaction mixtures are neutralized after hydrolysis and barium ions have to be removed by precipitation as their carbonate or sulfate salts prior to analysis which leads to loss of hydrolysate. Correspondingly, peptide contents are difficult to perform by this procedure. Preferred conditions for alkaline hydrolysis are 4M LiOH at 145 °C for 4-8 h where >95% of tryptophan is recovered 291 An additional inconvenience of the alkaline hydrolysis procedure is the dilution effect in the neutralization step and thus the difficult application to the analyzer if micro-scale analysis is to be performed. The main advantage is the good recovery of tryptophan and of acid-labile amino acid derivatives such as tyrosine-0-sulfate1261 (Section 6.6) as well as partial recovery of phosphoamino acids, particularly of threonine- and tyrosine-O-phosphate (Section 6.5). 

Alkaline hydrolysis, as compared to other methods of lignin degradation, has certain advantages. The catalytic reagents are inexpensive and available commercially, and require no elaborate method of preparation. 

Rushizky and Sober (82) first described the use of RNase T2 for the base analysis of RNA as it hydrolyzes RNA practically completely to 3 -nucleotides. Ribonuclease T2 digestion is certainly more advantageous for the base analysis of RNA than alkaline hydrolysis which gives... 

Although the specific cleavage of RNA has to be further confirmed in different conditions, it is suggested that the enzyme will hydrolyze polyribonucleotides as shown below in appropriate experimental conditions. This degradation has the advantage that 3 and 5 terminals in the digests may be easily distinguished by alkaline hydrolysis as nucleosides and nucleoside diphosphates, respectively. 

The isocyanates (9) were transformed into amino derivatives by standard reactions. Acid-sensitive aminocyclopropanes were obtained preferentially from benzyr ) -naphthyl or trifluorethyl-urethanes which were cleaved by hydrogen, EtSNa/DMF or alkaline hydrolysis. The hydrazinolysis of phthalimido compounds obtained from the urethane and phthalic anhydride also was useful Trimethylsilylethanol proved to be advantageous for the isocyanate-amine conversion the resulting urethanes gave amines upon addition of Bu4N p- 161 (e.g. synthesis of amine (21) from truns-crysanthemic acid via isocyanate (20) S equation 3). Contrarily to... 

In the iV,iV -dicyclohexylcarbodiimide-alkyl phosphate reaction described here, 2-cyanoethyl phosphate (64) offers an additional advantage, as the 2-cyanoethyl protecting group is readily eliminated by mild, alkaline hydrolysis, as shown in the conversion of (77) (see Scheme 3, R == nucleoside residue) into... 

The rate of hydrolysis of carboxylic esters can be increased by raising the temperature. It is also advantageous to remove the alcohol produced by continuous distillation. Acid hydrolysis is dependent on the hydrogen ion concentration it is usually considerably slower than alkaline hydrolysis of esters. 

Lower dialkyl sulfides and vinyl sulfides293 are advantageously prepared by alkaline hydrolysis of S-alkylthiouronium salts, the resulting thiolate being alkylated, without isolation, by an alkyl halide or dialkyl sulfate.294... 

Alkaline hydrolysis offers a possible advantage for the investigation of tryptophan peptides since tryptophan itself is more stable in alkali than in acid (Lugg, 1938 Brand and Kassell, 1939). 

In spite of the advantage represented by its low cost, chemical hydrolysis has several negative aspects that impair the final quality of the product. A first drawback, common to acidic and alkaline hydrolysis, is the very low specificity of the cleavage hydrogen and hydroxyl ions do not distinguish one peptide bond from another, or do so minimally. 

The colorimetric reineckate method of Beattie (12) is probably the most generally used method for routine analysis because of its simplicity and speed. This procedure has been improved by Engel (27) and by Glick (36), but the principles are still the basis of reports dealing with this method. Glick (35) observed that the specificity of the method depended on the nature of the hydrolysis and the subsequent neutralization of the sample to be analyzed. Alkaline hydrolysis with barium hydroxide did not destroy choline but had the advantage of eliminating certain other contaminants, such as aminoethanol, thiamine, and nicotinic acid. 

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