The Vaporization Enthalpy and Vapor Pressure of (±) N-Ethyl Amphetamine by Correlation Gas Chromatography

Abstract

The vaporization enthalpy, and vapor pressure as a function of temperature of N-ethylamphetamine, a substance used in the 1950s as an appetite suppressant and more currently abused as a designer drug, is reported. Its physical properties are compared to those of S (+)-N-methamphetamine, a substance whose physiological properties it mimics. A vaporization enthalpy of (62.4 ± 4.4) kJ·mol−1 and vapor pressure of (19 ± 11) Pa at T = 298.15 K has been evaluated by correlation gas chromatography. Results are compared to estimated values and to the limited amount of experimental property data available.

Estimating Vapor Pressure Data from Gas–Liquid Chromatography Retention Times: Analysis of Multiple Reference Approaches, Review of Prior Applications, and Outlook

“…However, vapor pressures in this handbook are in fact taken from another two-volume handbook, published in 1979 and 1983 by Dykyj and co-workers. , The principal difference between the two handbooks lies in the fact that the latter , also contains references to original literature, which is Dreisbach in the case of dialkylamines. Thus, correlated values were at the same time rejected but indirectly accepted by Chickos and co-workers. , This exemplifies how dangerous is the utilization of anonymous (i.e., unreferenced) handbooks and databases.…”

“…This section starts with the analysis of papers − presenting p GLC for amine derivatives in order to show another source of uncertainty, namely, anonymous and/or obsolete literature data used as a source of reference pressures. The first paper by Thornton et al reporting vaporization enthalpy and p GLC for (D)-amphetamine differs from the other two papers; , vapor pressures p 0 for benzylamine, α-methyl-benzylamine 2-phenethylamine, and three primary aliphatic amines were measured by the transpiration method (Rostock laboratory) and published in the same paper, and no extrapolation was needed to obtain values at 298.15 K. Since “Work not previously described suggested that primary aliphatic amines do not correlate as well with aromatic amines such as aniline and its derivatives”, p 0 values for benzylamine, α-methyl-benzylamine 2-phenethylamine were used as reference standards (along with 1-decanamine, which appeared to follow the same trend; see Figure 3 in Thornton et al). Thus, the only additional source of uncertainty is therefore 100 K extrapolation of chromatographic data, measured from 399 to 429 K. A paper by Gobble et al (which was published only two months after Thornton et al) reported p GLC for several amines of pharmaceutical importance.…”

“…Those data sources significantly overlap with the ones used as reference standards for vaporization enthalpies; additional calorimetric values and (in the case of dibutylamine) a value from the industrially oriented handbook published in 1961 by Dreisbach are used. In fact, Dreisbach contains vapor pressures and vaporization enthalpies for all dialkylamines from dibutyl- to diheptylamine; however, those data originate from some kind of correlation and were therefore not used by Chickos and co-workers. , Data from the handbook of Stephenson and Malanowski were used instead. However, vapor pressures in this handbook are in fact taken from another two-volume handbook, published in 1979 and 1983 by Dykyj and co-workers. , The principal difference between the two handbooks lies in the fact that the latter , also contains references to original literature, which is Dreisbach in the case of dialkylamines.…”

“…Full circles are reference vapor pressures from direct measurements (Pětroš et al, Messerly et al, Steele et al), triangles are correlated data by Dreisbach, and the empty circle represents reference pressure obtained in a preceding paper by CGC methodology. Values were taken from Table 6 in Thornton et al and Table 6 in Chickos; note that linearity is not perfect. Though the reported r 2 values of 0.9968, 0.9921, and 0.9972 seem to be high, the resulting relative deviations of p 0 from the correlation equation span from −19% to +24%.…”

“…Values were taken from Table 6 in Thornton et al and Table 6 in Chickos; note that linearity is not perfect. Though the reported r 2 values of 0.9968, 0.9921, and 0.9972 seem to be high, the resulting relative deviations of p 0 from the correlation equation span from −19% to +24%. Relative deviations from the fitted line are shown in parentheses after compound names.…”