Thermodynamic properties of organic compounds. Note III

Abstract

Calorimetric and cryometric methods are employed to measure the enthalpies of fusion and prefusion of some organic acids.

Thermodynamic properties of organic compounds

“…The agreement between the cryoscopic and calorimetric values of AHf is satisfactory (Table 1) In Table 2 ~'f, as defined previously [2], is reported for the paraffins, monocarboxylic acids and amides (even series); it is evident that the melting entropy per Cnumber decreases in the order paraff• monocarboxylic acids, amides. The agreement between the cryoscopic and calorimetric values of AHf is satisfactory (Table 1) In Table 2 ~'f, as defined previously [2], is reported for the paraffins, monocarboxylic acids and amides (even series); it is evident that the melting entropy per Cnumber decreases in the order paraff• monocarboxylic acids, amides.…”

“…Recently the thermodynamic properties of fusion of some aliphatic acids [1,2] have been discussed and related [2,3] to their structural properties. The results of similar research on two amides are reported in this note.…”

Dependence of the viscosities of some organic aliphatic acids on temperature and molar volume

“…ofC-R which, as demonstrated \OH... in preceding papers [1,2] is the structural entity of the fusion. The length [6] 12 is calculated in the following way: where N is Avogadro's number and 7 represents the number of cylinders contained in each hexagonal prism.…”

“…The fusion entropies of these acids [1,2] are a linear function of the parameter (b -Vp,r,l. ), i.e.…”

“…The dependence of the viscosity on the molar volume permitted calculation of the covolume, which is compared to that obtained from structural data.The thermodynamic properties of fusion of organic aliphatic acids from C10 to Cas were dealt with in two preceding notes [1,2], in which two stages were distinguished in the fusion process: prefusion and actual fusion. The prefusion enthalpy for stearic acid represents a value of about 10 70 of the fusion enthalpy; this value decreases from stearic acid to the acids with lower molecular weights.…”