(140a) Analysis of Vapor Pressures Using Family Variations: A Case Study of Hexadecanol Isomers

Vapor pressure is one of the most critical properties needed when designing chemical processes. Experimental data are preferred; however, predictive methods must be used when data are not available. Even when experimental data are available, they are often sparse, and the quality is unknown. In this work, we have used the isomers of hexadecanol (C16H34O) for a vapor-pressure case study, and a database of 33 isomers has been collected. All the isomers are saturated alcohols, and the variation in vapor pressure arises from the placement of the alcohol (-OH) group and the extent of branching. The recently published modified Trouton method has been used to analyze the available data, and a database of boiling points at the representative vapor pressure of 2 kPa has been developed for the 33 compounds in the study; further, the uncertainty in the 2 kPa boiling points has been estimated. The database has used to been evaluated to gain insight into the trends of the vapor pressures. Next, three representative approaches have been used to test the ability of estimation methods to predict and correlate the data: (1) the Nannoolal group-contribution method; (2) the COSMO-RS quantum-chemistry method; and (3) an empirical method based upon structural factors. The study has revealed the nature and extent of vapor-pressure variation with this family of isomers and the ability of estimation methods to develop reliable and accurate correlations. The database developed here may also be helpful for related studies, for example, the use of molecular simulation to predict the vapor pressures.