Formation from the Oxides

A convention in common use as an alternative to energies and enthalpies of formation from the elements is energies and enthalpies of formation from the oxides. Thus instead of having 

This convention is somewhat more limited in its application than is formation from the elements. For example, it could not be used for many reactions involving non-oxides such as 

For oxides such as the silicate minerals, the RHF tables list thermodynamic properties twice first as formation from the elements, and second as formation from the oxides. Table 7.3 is an example for the mineral jadeite showing properties on the right-hand side calculated for formation from the oxides these are marked with an asterisk as a reminder not to confuse them v/ith formation from the elements. 

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Literature articles, which report the formation and evaluation of difunctional cyanoacrylate monomers, have been published. The preparation of the difunctional monomers required an alternative synthetic method than the standard Knoevenagel reaction for the monofunctional monomers, because the crosslinked polymer thermally decomposes before it can revert back to the free monomer. The earliest report for the preparation of a difunctional cyanoacrylate monomer involved a reverse Diels-Alder reaction of a dicyanoacrylate precursor [16,17]. Later reports described a transesterification with a dicyanoacrylic acid [18] or their formation from the oxidation of a diphenylselenide precursor, seen in Eq. 3 for the dicyanoacrylate ester of butanediol, 7 [6]. 

Fig. 10.5 NO formation from the oxidation of N-al kyl-N -hyd roxyguan id ines in the presence of NOS. The reaction rates were assessed by a hemoglobin assay and are expressed as a percentage of those of NHA.

The lactam formation from the oxidation of cyclic amines (353, for example) probably proceeds via intermediate 364. The nitrogen-iodine bond dissociates to give imine 365, which reacts again with a second equivalent of iodosobenzene to give another intermediate 366. Finally, 366 on reductive... 

The heat of formation of sodium orthoarsenate in aqueous solution from the elements is 381,500 calories,1 and that of the solid 360,800 calories.2 The heat of neutralisation (3Na0H.H3As04.aq.) is 35,920 calories,8 and the heat of formation from the oxides is 2... 

Iron monosulfides comprise about 20% of the iron sulfide minerals in the noneuxinic sediment and about 50% in the euxinic sediment. Their greater preservation in the euxinic sediment, as in sediment from Walker Lake, is probably a result of insufficient elemental sulfur formation in this extremely reducing environment. Seasonally aerobic conditions at the sediment-water interface of the noneuxinic sediment would promote elemental sulfur formation from the oxidation of H2S that accumulates in pore water. 

Holm and Kleppa (2) combined their Aj,H" for formation from the oxides with the corresponding a G from Young (3) in order to calculate A. Based on the present functions and Young s result at 1800 K, we calculate an entropy which is 1.2 cal K mol... 

The enthalpies of formation from the oxides of thirty-two 2-3 and 2-4 spinels, among others Ni2Ge04, have been determined by solution calorimetry in molten oxide solvents at 970 K. Regularities in the thermodynamics of spinel formation and the olivine -spinel transition for orthosilicates of Mg, Fe, Mn, Co, and Ni have been discussed. 

The enthalpy of formation from the oxides of Mg2Sn04 and Co2Sn04 were found by oxide solution calorimetry. Using thermochemical data for the formation of olivine, for olivine - spinel transitions and for the transformation of quartz to stishovite, pressures for the disproportionation of silicate spinels were calculated to be in the range 150 - 200 kbar. 

Table 7.3. Thermodynamic properties of jadeite as tabulated by Robie et al. (1978). The three right-hand columns represent formation from the oxides (not the elements) NaiO-i-2Si02 + IAI2O3 = NaAl(Si03)2... 

Enthalpies of formation (from the oxides) of MgAl204 and AlgSiOs (kyanite and sillimanite) have been determined by oxide melt solution calorimetry at 965 and 1173... 

A formalism defining the enthalpies of formation from the oxides of anhydrous zeohtes was proposed by [lOMlj. The formalism was based on (1) a relationship between the measured enthalpies of formation of zeosils and a parameter characterizing the natnre of the zeolite framework represented by the ntrmber of tetrahedral atoms per 1000 (FD) (2) electronegativity difference. For a constant framework (or same structrrral zeolite... 

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