Thermochemistry of Heteroatomic Compounds: the Heats of Combustion and Formation of Glycoside and Adenosine Phosphates
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Abstract
The heats of combustion of 4th glycoside in the condensed state with the use of the equation Δ<i><sub>comb</sub>H</i>＝15.7-117.2(<i>N</i>-<i>g</i>) , in which <i>N</i> is a number bond-forming (valence) electrons less the number (<i>g</i>) of lone electron pairs of nitrogen (<i>g</i> = 1) and oxygen (<i>g</i> = 2), have been determined. Such dependence is deduced previously joint for the description of the combustion enthalpies of 17 simple ethers of a cyclic structure and different sugars. The heats of formation ( Δ<i><sub>f</sub>H<sup>o</sup></i> ) of the mentioned above glycosides were calculated according to the Hess law via two ways: 1) through the use their heats of hydrolysis ( Δ<i><sub>hydr</sub>H</i> ), which have been investigated earlier experimentally, 2) with the use the calculated the heats of combustion. The last procedure has been used also for the calculation of the heats of formation of the adenosine tri(ATP)-, di(ADP)- and mono(AMP)phosphates because of such thermochemical parameter is often hard achieved experimentally. The heats of hydrolysis ( Δ<i><sub>f</sub>H<sup>°</sup><sub>hydr</sub></i> ) of ATP into ADP and ADP into AMP were calculated on the basis of their heats of formation in water ( Δ<i><sub>f</sub>H<sup>°</sup><sub>aq</sub></i> ). The free energies of the same process ( Δ<i><sub>hydr</sub>G</i> ) were known in literature. Last circumstance give us a possibility to calculate the hydrolysis entropies ( Δ<i><sub>hydr</sub>S</i> ) using the Gibbs equation. The entropy values are a large negative, that pointed on the preliminary complex formation between adenosine phosphates and water before the breaking of P-O bonds or P-O-C fragments in its.
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