The Thermodynamics of Chromatography - The Thermodynamic Analysis of the Dispersive Interactions that Can Take Place between Different Solutes and High Molecular Weigh > Page 21

  

 

The behavior of the alkanes tends to be ideal in their general physical chemical behavior. As a consequence, it is important to examine other homologous series to ensure the validity of the argument. Data from the same source is available for a homologous series of aliphatic amines, alcohols, halogenated hydrocarbons etc. that can all be treated in the same way. The chlorinated hydrocarbons can be taken as another example.

Retention data for the n-chloroalkanes taken over a temperature range of 76˚C to 88˚C on a n-C30 alkane stationary phase can also be examined thermodynamically. Employing the same procedure Log(V'r(T)) for the solutes n-chlorobutane, n-chloropentane, n-chlorohexane and n-chloroheptane were plotted against the number of methylene groups at each temperature. The slope (representing the methylene contribution (), the intercept for the methyl group () (taken from data for the n-alkane series which was also available on the same stationary phase and temperature range), and the intercept due to the interaction with the chlorine atom,  (taken as the difference between the actual intercept and that of the methyl group) were each plotted against the reciprocal of the absolute temperature.and the results are shown in figure 10.