Parachor Studies at Various Temperatures

Abstract

The parachor, P, as derived by Sugden, has been stated in the form d My\ D-d' where M is the molecular weight, 7 the surface tension, and D and d are the densities of the liquid and vapor respectively at the same temperature.The CHt group.*-By applying the above formula to hundreds of organic compounds and fixing, as a standard for comparison, the covalent bond at zero, Sugden1 arrived at an average value of 39.0 for the CH2 group. This value has been the subject of much discussion ever since. Mumford and Phillips2, from a study of high-molecular-weight compounds, concluded that the CH2 group should be given a value of 40.0, Vogel3, from parachor determinations on the methyl and ethyl esters of n-dibasic acids, obtained 40.3, and Desreux4, from the higher members of the paraffin and normal alkyl fluoride and chloride series, found values which varied but slightly from 39.9. More recently Sugden6 has been inclined to accept the value of 39.6 for the CH2 group.These variations at once detract from the usefulness of the parachor in any quantitative approach to the determination of structure. Although the differences were at first thought to be due to impurities or inaccurate measurements, it now appears that they are of a more fundamental nature. As Desreux pointed out, they doubtless indicate that the atomic parachors are not strictly additive. In fact the CH2 values of Desreux for the paraffins and alkyl fluorides and chlorides are unique in their constancy.* Shortly after the submission of this manuscript Bayliss, J. Am. Chem. Soc., 69, 444 (1937), by the method of least squares, found the CHi value to be 39.92.

Surface properties of nine liquids

“…For the toluene-air system, 58 acceptable data points were collected from refs. 1,3,4,8,11,14,18,23,26,36,42,46,47,48,50,58,59,67,68,73, 81, 86-88 plus ref. 89 recalculated by Sugden (78).…”

Properties of Alkylbenzenes.

“…For many alkylbenzenes an assumption of an average value of 0.86 for density and 1. 49 for refractive index wrould be less in error than to use the published observations. For example, the lowest of the fifteen observations on the density of isobutylbenzene included in Egloff's compilation (95) is 0.8628, although the value now accepted (8) and supported by three recent excellent observations (50,121,142) is only 0.8532.…”

The Surface Tension of Pure Liquid Compounds

“…55°Methyl pentadecanoate ______________________________________________ 29.3828.56 27.75 25.93 Ethyl myristate ____________________________________________________ 29 27. 28.26 27.24 26.23 Propyl tridecanoate _________________________________________________ 28.84 27.92 27.00 26.08 Butyl dodecanoate" _________________________________________________ 28.33 27.54 26.76 25.98 Pentyl undecanoate _________________________________________________ 28.20 27.37 26.54 25.72 Hexyl decanoate _________________________________________________ c __ 28.29 27.36 26.43 25.50 Heptyl nonanoate __________________________________________________ 28.14 27.29 26.44 25.59 Octyl octanoate ____________________________________________________ 29.99 27.12 26.29 25.47 Nonyl heptanoate __________________________________________________ 28.24 27.46 26.68 25.90 Decyl hexanoate ____________________________________________________ 28.59 27.66 26.72 25.79 Undecyl valerate ___________________________________________________ 28.45 27.64 26.83 26.03 Dodecyl hutyrate ______________ .…”