Vibrational Intensities in Halogenated Methanes. III. The Interpretation of Solution Data

Abstract

Using solution samples, the absolute infrared absorption intensities of five fundamental bands of CH2Cl2 were measured by an extrapolation technique and by approximate methods suggested by Ramsay. These determinations were used to test a classical relationship, proposed by Polo and Wilson, between corresponding liquid and vapor absorption band intensities. Qualitative agreement with published vapor intensity measurements was obtained.

Towards an accurate description of anharmonic infrared spectra in solution within the polarizable continuum model: Reaction field, cavity field and nonequilibrium effects

“…Various examples exist in this context, especially in the field of nonlinear optical properties 1 and vibrational spectroscopies. [2][3][4][5][6][7][8] As a result, experimental data reported in the literature require careful analysis, i.e., any approximation and treatment of the data has to be taken into account if a direct comparison with absolute values is to be achieved. Second, from the purely theoretical and computational point of view, in order to obtain calculated values directly comparable to experiments, the models to be used should reliably represent the experimental sample, i.e., the physical model should be as realistic as possible, which in practice means that all the physical interactions in the sample and between the sample and the probing field have to be taken into account in the model.…”

On the Calculation of Infrared Intensities in Solution within the Polarizable Continuum Model

“…For this reason we will use in the following the simplified formula shown in Table 3. It is worth noticing the analogy between the Mallard-Straley, Person (MSP) equation 9,10 for solutions and the Polo-Wilson 6 for pure liquids, which reads…”

“…Mallard-Straley, 9 Person 10 We report in Table 4 the calculated results for the f factor. For the sake of comparison we also report what we obtain by exploiting the above-mentioned semiclassical approaches (see Table 3).…”

“…Different formulations for the calculation of IR intensities in solution have been proposed in the past, both regarding pure liquids − and systems in solution. − The common point of all these approaches is the derivation of relations between absorption integrated intensities in liquid and in gas phase.…”

Intermolecular forces and solvent effects I. Frequency shifts

“…The variations of band intensity also indicate such interactions. Relationships have been set up to express the change of intensity between the vapour and the liquid or solution by Chako (1934), Polo & Wilson (1955), van Kranendonk (1957, Hirota (1954), Mallard & Straley (1957), Person (1958) and Brown (1957. These involve essentially the refractive index and dielectric constants, but the experi mental results are not interpreted satisfactorily by any of them (Mander & Thompson 1957;Bayliss et al 1959;Krueger & Th theoretical considerations by Pullin (1958, i960) are again based upon the dielectric medium approximation, and Buckingham (1958), although providing a more thorough treatment of the perturbing effect of the non-polar or polar solvent upon the energy levels of the solute, still ignores more specific interactions.…”