RESUMO
Ab initio calculations are reported for three of four possible conformers of 1,3-dichloropropane. The fourth conformer, with Cs symmetry, has a predicted enthalpy difference of more than 1500 cm(-1) from the most stable conformer from each calculation regardless of the basis set used, so there is little chance of observing it. Thus, there is no evidence in the infrared or Raman spectrum of the presence of a fourth conformer. The order of stability given by the ab initio calculations is C2(GG)>C1(AG)>C2v(AA)>Cs(GG'), where A indicates the anti form for one of the CH2Cl groups and G indicates the gauche conformation for the other CH2Cl group relative to the plane of the carbon atoms. Almost every band observed can be confidently assigned to one or another of the conformers. Many observed bands proved to be of a composite nature, with several nearly coincident vibrations of different conformers contributing to the band contour. Nonetheless, a complete assignment of fundamentals is possible for the most stable C2 conformer, and 5 of the fundamentals of the C2v conformer and 13 those of the C1 conformer can be confidently assigned.
Assuntos
Propano/análogos & derivados , Propano/química , Conformação Molecular , Espectrofotometria Infravermelho , Análise Espectral Raman , TemperaturaRESUMO
A model system for the characterization of molecular recognition events in molecularly imprinted polymers (MIPs) is presented. The use of a biologically inspired, three-point hydrogen-bonding motif and a thin film polymeric matrix allows for pre- and post-polymerization binding properties to be characterized by infrared spectroscopy. A method to determine binding constants was developed and utilized before and after cross-linking. These values showed a 10-fold decrease in binding after polymerization, which was attributed to an increase in molecular confinement after polymerization and a change in the local structural environment of the binding cavity. Transport of the guest molecule was shown to be reversible.
