Enthalpy of hydrolysis

The enthalpies of hydrolysis of glycoside cyclic phosphodiesters have been measured42 by flow microcalorimetry, using a phosphohydrolase from Enterobacter aerogenesiz as catalyst. This phosphohydrolase can hydrolyse a wide variety of phosphodiesters, which enables the enthalpies of hydrolysis of glycoside cyclic phosphodiesters to be compared with those of acyclic and monocyclic phosphodiesters. It was found42 that the phosphohydrolase cleaves the 3 - and 5 -ester bonds with similar enthalpies, which are less negative (—11.1 0.2 kcal mol-1) than the value (-13.2 0.4 kcal mol-1) that had been reported previously.44... 

There is one additional study on the enthalpy of hydrolysis of solid butylmagnesium chloride. Additional calculations result in a solid phase enthalpy of formation of -455.7 2.0 kJmol-. ... 

A variety of other olefins were studied 1,6-diphenylhexatriene, anthracene and cyclooc-tatetraene also displace butadiene from its polymeric magnesium complex. Now should these olefin-magnesium species be viewed as magnesacycles Or as contact ion pairs with olefin dianions In any case, no enthalpies of hydrolysis are available, nor quantitation of stabilities by even equilibrium constants. We welcome this information. 

In the course of calorimetry study of hydrolysis ofTi(OR)4, at different concentrations and h ratios the values of enthalpies of hydrolysis reaction were measured (-AHJ at 298.15K as 14.2, 64.9, 19.3 kJ/mol for R = Et, Pr, Bun respectively [660], These values grow linearly at the first stage when h increases from 0 to 1 and practically do not undergo any changes with further introduction of water. Therefore, the first step of hydrolysis should be regarded as reaction with stoichiometry of h = 1 ... 

Given the tendency of acyl halides of any composition to hydrolyze, how does their enthalpy of hydrolysis depend on the substituent R ... 

Chromium enolate chemistry exhibits diverse thermochemical facets. For example, contrast the energetics of enolate addition reactions to benzaldehyde and to benzaldehyde JT-bonded to Cr(CO)3 and of the enolate addition reactions to acetophenone and to acetophenone 71-bonded to Cr(CO)3. Thermochemical analysis is still unreported, although the reactions are synthetically usefuP . It is clear that the organic ligands are electronically coupled to the metallic center—PhCHO Cr(CO)3 is red, PhCH(OEt)2 Cr(CO)3 is yellow but benzaldehyde and its diethyl acetal are both colorless. It is well established that acetophenone, and presumably other acylated benzenes such as benzaldehyde, binds Cr(CO)3 rather more weakly than does toluene, and presumably other alkylated benzenes such as the aforementioned benzaldehyde acetal. The enthalpy of hydrolysis of the metallated acetal remains unknown other than it is therefore smaller than that of the unmetallated species . ... 

Wartenberg and Riteris (4) measured the enthalpy of hydrolysis of CPgO, the reaction... 

The enthalpy of formation was calculated from the enthalpy of hydrolysis of K(cr), the enthalpies of solution of HCl(g) and KCl(cr), and the standard enthalpy of neutralization of a strong acid and strong base. Extensive measurements are available for all these quantities. Values used in the calculation, in addition to the enthalpy of formation for HCl(g), are summarized below. 

The enthalpy of formation of CsOH(cr) is obtained from the enthalpy of hydrolysis of metallic cesii solution of the hydroxide in water, and appropriate auxiliary data. 

The enthalpy of hydrolysis of metallic sodium has been determined by various investigators ( -6 ). For the reaction Na(cr) (n+l)H20 Na0H n HgO + 0.5 HgCg) data are summarized below. 

The enthalpy of hydrolysis of MgHgCcr) was measured by Sinke and Stull (1). The value of a H (298.15 K) was calculated to be -19.1 2 kcal tnol". From the decomposition pressure measurements for MgHgCcr) reported by Ellinger (2) and Stampfer et al. (3),... 

Confirmation of the enthalpy of formation was obtained by combination of the enthalpies of hydrolysis and sublimation of N20g(cr). The results are summarized below. 2nd law values are given for the enthalpies of sublimation, but 3rd law analyses suggest that the value from Russ and Pokorny (4) is more reliable. Most of the uncertainty in this path, however, arises from the enthalpy of hydrolysis. 

However, much more reliable data were obtained from the calorimetric measurement of the enthalpy of hydrolysis of COF [2131] ... 

E14.9 The enthalpy of hydrolysis of a compound can be calculated as the difference in energy between the bonds broken and the bonds formed in the hydrolysis reaction. The relevant equations for the hydrolysis of CCI4 and CBr4 are ... 

Using a phosphodiesterase, it has been possible to measure directly the enthalpies of hydrolysis of ethylene phosphate, trimethylene phosphate, and diethyl phosphate (all as their sodium salts). As expected, that of the first was found to be appreciably more negative than the latter two. 

Table 5 Activation energy and enthalpy of hydrolysis (kcal mol ) of cyclic and ...

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