A vapor pressure equation for heavy compounds

Abstract

A vapor pressure calculation procedure based on a lattice equation is applied to several compounds. Originally, the method was used to predict low vapor pressures of heavy hydrocarbons. In this work, the method is used at low vapor pressure for nonhydrocarbons, and a modified version is employed at high vapor pressure for n-alkanes. As the procedures require the knowledge of one vapor pressure datum only, they work in a predictive mode. Prediction for hydrocarbons is good and for nonhydrocarbons is poor. Prediction of n-alkanes high vapor pressure is good with an overall average relative absolute deviation under 6 percent.

Vapor Pressure and Enthalpy of Vaporization of Fentanyl

“…(1.1 ( 0.0) ln(V ⁄ 10 -6 g 0.5 • mol 0.5 • K 0.5 • min -1 ) -(1.1 ( 0.1) (10) Equation 10 was a general equation which could be used for the estimation of vapor pressure of any compound at different temperatures provided its rates of vaporizations/sublimations have been determined from TGA analysis. However, before applying this method for fentanyl, the authenticity of eq 10 was checked by determining the vapor pressure of bis(2-ethylhexyl)phthalate and comparing the results with the published values.…”

“…9 These predictive schemes have been implemented in computer modeling software. 10,11 The vapor pressures obtained from predicative methods, however, can show significant deviations from experimental values and are often not reliable. 12 Thermogravimetry has been known for the estimation of vapor pressure of compounds having low volatility.…”

“…There also exist various predictive schemes for the calculation of vapor pressure based on the group contribution approach . These predictive schemes have been implemented in computer modeling software. , The vapor pressures obtained from predicative methods, however, can show significant deviations from experimental values and are often not reliable …”