Boiling points and critical temperatures

We have computed the surface areas, IT, halogenated derivatives, some of which also bear other functional groups. These data are listed in Table 4, along with experimentally determined boiling points and critical temperatures. 

Earlier, for a more diverse group of one-hundred molecules, containing heteroatoms and most typical functional groups, e.g. OH, NH2, OCH3, CN, N02, F, Cl etc., we have shown that their normal boiling points and critical temperatures (and other critical constants) can be related in dual-parameter relationships to some of our computed molecular surface properties66,72,73. Our best relationships for TbP and Tc are of the forms given in equations 18 and 19 the linear correlation coefficients are 0.949 and 0.914, respectively ... 

Nineteen of the sixty-eight molecules in Table 4 contain fluorine. It is noteworthy that the intermolecular effect within these and other halogenated and nonhalogenated systems, as measured by their boiling points and critical temperatures, can be well represented by our calculated measures of size and electrostatic interaction tendency (i.e. surface area and v<720t). 

Egolf, L.M., Wessel, M.D. and Jurs, P.C. (1994). Prediction of Boiling Points and Critical Temperatures of Industrially Important Organic Compounds from Molecular Structure. J.Chem. Inf.Comput.Sci., 34,947-956. 

Hall, L.H. and Story, C.T. (1996). Boiling Point and Critical Temperature of a Heterogeneous Data Set QSAR with Atom Type Electrotopological State Indices Using Artificial Neural Networks. J.Chem.lnf.Comput.ScL, 36,1004-1014. 

What is the relationship between intermolecular forces in a liquid and the liquid s boiling point and critical temperature Why is the critical temperature of water greater than that of most other substances ... 

Table 1. Boiling points and critical temperatures of four gases. 

What is the relationship between intermolecular forces in a liquid and the liquid s boiling point and critical temperature Why is the critical temperature of water greater than that of most other substances How do the boiling points and melting points of water and carbon tetrachloride vary with pressure Explain any difference in behavior of these two substances. Why is solid carbon dioxide called dry ice ... 

In the studies cited to date, SC-CO2 has been the predominant critical fluid media that has been used, in deference to its benign environmental impact and compatibility with the processing of food-related agricultural products. Another medium that meets these criteria is subcritical water that is hot compressed water held between 1-218 atmospheres and its normal boiling point and critical temperature of 374°C. Several studies [55,56] have shown that water under these conditions can be utilized as a reaction medium, both for non-degradative/degradative reactions as well as hydrolysis. Research conducted in our laboratory has utilized subcritical water for the hydrolysis of vegetable oils to synthesize fatty acid mixtures [56]. The results in Table 7 demonstrate how complete this conversion... 

These tables show saturated vapor properties at 8 pressures. The saturation temperatures were determined from the vapor pressure equation of neon, As this equation did not give the observed boiling point and critical temperatures precisely, a linear correction was used to adjust these and the intermediate temperatures. The saturated vapgr volumes tabulated agree well with experimental values,... 

This table summarizes the significant points on the phase diagrams for the elements. When reliable date are available, vtilues are given for the solid-liquid-gas triple-point temperature and pressure normal melting point at 101.325 kPa pressure normal boiling point and critical temperature and pressurep. All temperatures are on the lTS-90 scale. 

The difficulty in removing carbon monoxide from the air is due to its physical and chemical properties. It has a low boiling point and critical temperature, and hence is not readily adsorbed. It is almost total insoluble in most solvents and consequently cannot be easily removed by absorption. The main practical method for the effective removal of carbon monoxide at most temperatures utilizes catalytic oxidation (to carbon dioxide). Catalysis is the process in which a chemical reaction is initiated or accelerated by the presence of a catalyst, which is a material that induces a chemical reaction but which itself is unaltered during the reaction. The type of catalyst that has proved most useful for the removal or elimination of carbon monoxide, by the oxidation to carbon dioxide, is generally known as a hopcolite. 

---