A Study of the Interaction between Halomethanes and Water-Ice

Abstract

The infrared spectra of a series of twenty-three halogenocarbon compounds co-deposited onto water-ice held at 12 K have been investigated. Perturbations to the water (D2O) sites which are not saturated in the absence of guests show distinct trends depending on the type and extent of halogen substitution in the occluded molecules. The data are quantified in terms of the IR spectral positions of the so-called “dangling bond” of water; interaction also leads to changes in the halogenocarbon compound IR spectra. It is clear from the results that the halomethanes interact through lone pair donation from a halogen atom to a deuterium atom of the water molecule. A high level of correlation is found between the shift in the dangling bond and both the charge density and the molecular polarizability within each separate series for compounds of the formula CF n H4 - n , CCl n H4 - n , and CBrnH4 - n (where n = 1−4). It is demonstrated that profiles correlating either ionization potentials or molecular polarizabilities for Cl- and Br-containing halogenocarbons with dangling bond shift provide an accurate method for predicting the respective physicochemical parameters. When a combined polarizability/charge interaction parameter is plotted against the dangling bond shift a straight line, also with predictive capabilities, results.

Proton transfer reactions of halogenated compounds: Using gas chromatography/Fourier transform ion cyclotron resonance mass spectrometry (GC/FT-ICR MS) and ab initio calculations

“…We used the standard G3 procedure [45] with the zero point energy corrected by using the HF frequency scaled by 0.8929, while Ma apparently used the MP2 frequencies scaled by 0.9661. However, our calculations (also Ma et al [39] and He and Wang's [49]) of the PAs of the chloromethanes at 298 K are significantly higher than the numbers quoted by Hunt and Andrews [57] and Holmes and Sodeau [58] who assumed a linear relationship between the frequency shift of the IR absorption (HF or D 2 O) bands for the entire chloromethane series (cold trapped in solid argon matrices with either HF, DF [57] or D 2 O [58] guest proton donor molecules) and the proton affinity (151.1 kcal mol −1 vs. 143 kcal mol −1 [57] for CH 2 Cl 2 and 157.8 kcal mol −1 vs. 133 kcal mol −1 [57] for CHCl 3 ). Hunt and Andrews' estimate of the PA of CCl 4 as 130 kcal mol −1 is significantly lower than the G3 value of 167.2 kcal mol −1 calculated by Ma et al and also our PA estimate based on Hess law principles.…”

“…Hunt and Andrews' estimate of the PA of CCl 4 as 130 kcal mol −1 is significantly lower than the G3 value of 167.2 kcal mol −1 calculated by Ma et al and also our PA estimate based on Hess law principles. The examination by us of the frequencies of the 5 and IR absorption bands of HF [57] and reported frequency shifts of the D 2 O absorption band [58] vs. the available G3 calculated PA values (from this work and Refs. [39,49]) for CH 2 Cl 2 , CHCl 3 , and CCl 4 (i.e., excluding the CH 3 Cl) showed excellent linear coefficient of > 0.9 for the frequency shift as a function of PA (the linear coefficient is drastically reduced by including CH 3 Cl).…”

“…Using linear regression on the IR data ( and 5 bands) reported by Hunt and Andrews and the Ma et al 298 G3 PA results for CH 2 Cl 2 , CHCl 3 , and CCl 4 yielded the approximate relationship of PA ≈ 0.197 − 596 kcal mol −1 with a reduced linear coefficient of ∼0.85, where is IR frequency in cm −1 ; when applied to CH 3 Cl this equations yields a very low PA value for CH 3 Cl of ∼135 kcal mol −1 compared to the G3 value of 155 kcal mol −1 by Ma et al The formation of the bidentate H bond induces a ∼100 cm −1 decrease in the IR frequency compared to a more modest ∼5 cm −1 increase per 1 kcal mol −1 increase in PA which shows that IR frequency shifts due to the formation of a dipoledipole bifurcated H bond is a very significant factor if the variation in PAs is relatively small as in the case of the chloromethanes (150-170 kcal mol −1 ). We suggest that chloromethanes with two or more chlorine substituents can better solvate the donor HF or D 2 O compared to methylchloride by the formation of a bi/trifurcated hydrogen bonding between the two chlorine substituents of polychloromethanes and the donor D of D 2 O [58] or H (or D) of HF (or DF) [57]. We observed that the protonation of dichloromethanol by a bare proton occurs preferentially on the hydroxyl oxygen.…”

An overview of snow photochemistry: evidence, mechanisms and impacts

“…Adsorption of various organic molecules on ice surfaces can be described well with a multi-parameter linear free energy relationship, based on the van der Waals and the electron donor/acceptor interactions (such as H-bonding) (Roth et al, 2004 (Devlin, 1992;Devlin and Buch, 1995). Many organic halocarbon compounds have also been shown to adsorb on water-ices by interactions with the ice surface dangling bonds (Holmes and Sodeau, 1999). Studies of the adsorbed states of some organic molecules, such as acetonitrile, chloroform Roberts, 1999a, 1999b), acetone (Schaff and Roberts, 1998), or benzene derivatives (Borodin et al, 2004) have revealed the scope of hydrogen-bonding or dipolar interactions.…”

FTIR Spectroscopy Evidence for the Basicity Induced by Adsorption

“…siloxane bridges for silica or unsaturated surface oxygen atoms of ice. Dangling hydroxyl groups of water ice reveal slightly weaker frequency shifts on adsorption of weak bases, such as CO [13] or halogenated methanes [14]. In our case ethylene was tried as a base that could be put in contact with ice surface at 77 K, while the same CHF 3 and CO 2 were used as acids.…”