Thermodynamic properties of piperidine and cyclic alkanone mixtures

The excess molar enthalpies, HE, of piperidine (1) ? cyclopentanone or cyclohexanone or cycloheptanone (2) at 308.15 K and densities, q, speeds of sound, u, and molar heat capacities, CP, of the same set of the mixtures
have been measured as a function of composition at temperatures from 293.15 to 308.15 K. The measured q, u & CP data have been employed to determine excess molar volumes, VE, excess isentropic compressibilities, jES , and excess heat capacities, CE P . The thermodynamic properties
have been fitted to Redlich–Kister equation to compute
binary adjustable parameters and their standard deviations.
The results have been analyzed in terms of Graph theory
(which deals with the topology of the molecule) to correctly
predict (1) state of the components in pure and mixed
states, (2) to understand the nature and extent of molecular
interactions existing in their mixtures, (3) VE, jES
, HE, and CE P values. The analysis of VE data in terms of Graph theory suggests that while piperidine is characterized by hydrogen bonding and exists as associated molecular
entity, cyclopentanone, cyclohexanone, and cycloheptanone
exist as mixture of open and cyclic dimers. The estimated inter-nuclear distances among the interacting atoms using quantum mechanical calculations also support the existence of proposed molecular entities in pure and mixed states. It has been found that VE, jES, HE and CE P data predicted by Graph theory compare well with the their experimental data. The IR studies also support this view point.