Activation energy hydrolysis

Keywords Service life prediction Activation energy Hydrolysis Kinetics PET Polycarbonate Solar... 

Nitrocellulose is among the least stable of common explosives. At 125°C it decomposes autocatalyticaHy to CO, CO2, H2O, N2, and NO, primarily as a result of hydrolysis of the ester and intermolecular oxidation of the anhydroglucose rings. At 50°C the rate of decomposition of purified nitrocellulose is about 4.5 x 10 %/h, increasing by a factor of about 3.5 for each 10°C rise in temperature. Many values have been reported for the activation energy, E, and Arrhenius frequency factor, Z, of nitrocellulose. Typical values foiE and Z are 205 kj/mol (49 kcal/mol) and 10.21, respectively. The addition of... 

FIGURE 3.8 The activation energies for phosphoryl group-transfer reactions (200 to 400 kj/mol) are substantially larger than the free energy of hydrolysis of ATP ( — 30.5 kj/mol). 

The calculated activation energy for the hydrolysis of sarin [43] on Amberlite-IRIOO is relatively low (22,000... 

J mol ). This is additional evidence in favor of rate limitation by inner diffusion. However, the same reaction in the presence of Dowex-50, which has a more open three-dimensional network, gave an activation energy of 44800 J mol , and closely similar values were obtained for the hydrolysis of ethyl acetate [29] and dimethyl seb-acate [30]. The activation energy for the hydrolysis of ethyl acetate on a macroreticular sulphonated cationic exchanger [93] is 3566 J mol . For the hydrolysis of ethyl formate in a binary system, the isocomposition activation energy (Ec) [28,92] tends to decrease as the solvent content increases, while for solutions of the same dielectric constant, the iso-dielectric activation energy (Ed) increases as the dielectric constant of the solvent increases (Table 6). 

Table 6 Iso-Dielectric Activation Energy Ed) for the Hydrolysis of Ethyl Formate in Acetone-Water Systems [28]...

The calculated activation energy is now 96 kJ mol-1 for die uncatalyzed second-order reaction and 88 kJ mol-1 for the third-order reaction. From hydrolysis data using very low water concentrations (0.005 -0.1 mol-kg-1), the reaction was found to be second order but exhibited a dependence on water concentration in the rate constants (Fig. 3.14). With 1.1 mol - kg 1 water, a combination of second- and third-order reactions was observed with activation energies of 109 and 63 kJ mol-1, respectively.8... 

Oligosaccharide hydrolysis, 153-154 activation energy in enzyme active site vs. 

The hydrolysis of sucrose is a part of the digestive process. To investigate how strongly the rate depends on our body temperature, calculate the rate constant for the hydrolysis of sucrose at 35.0°C, given that k = 1.0 mL-mol -s 1 at 37.0°C (normal body temperature) and that the activation energy of the reaction is 108 kj-mol. ... 

The hydrolytic depolymerisation of PETP in stirred potassium hydroxide solution was investigated. It was found that the depolymerisation reaction rate in a KOH solution was much more rapid than that in a neutral water solution. The correlation between the yield of product and the conversion of PETP showed that the main alkaline hydrolysis of PETP linkages was through a mechanism of chain-end scission. The result of kinetic analysis showed that the reaction rate was first order with respect to the concentration of KOH and to the concentration of PETP solids, respectively. This indicated that the ester linkages in PETP were hydrolysed sequentially. The activation energy for the depolymerisation of solid PETP in a KOH solution was 69 kJ/mol and the Arrhenius constant was 419 L/min/sq cm. 21 refs. 

Decomposition kinetics of five compounds by alkaline hydrolysis were measured. For three compounds, second-order reaction rate constants and activation energies were given. These five compounds andd be divided two groups with high and low decomposition rates. 

The reaction shows a rather high activation energy of 32.0 kcal.mole . Speculation about the mechanism is worthless until more controlled experiments are performed, taking account of hydrolysis, the role of the reaction Fe(lI)+NH20H, etc. 

Chemically dextrans are similar to one another. The activation energy for acid hydrolysis is about 30-35 Kcal/mol (5j. The C-2 hydroxyls appear to be the most reactive in most Lewis base and acid-type reactions. A wide variety of esters and ethers have been described as well as carbonates and xanthates ( 7,8j. In alkaline solution, dextran forms a varying complex with a number of metal ions (9). 

Amino Acid Dating Techniques depend on the "rates of hydrolysis reactions of proteins and racemization, epimerization, and decomposition reactions of amino acids [they have] been applied to the age-dating of fossil bone, teeth, and shell. Activation energies range from near 20 kcal per mole for hydrolysis reactions to around 30 kcal per mole for racemization... 

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