1. Microwave and Ab Initio Investigations of CHCl 2 F-OCS and Related Hydrochlorofluorocarbon Complexes Rebecca A. Peebles and Amanda L. Steber Department of Chemistry Eastern Illinois University Charleston, IL 61920

2. CHCl 2 F and CHClF 2 are hydrochloro- fluorocarbons (HCFCs) Commonly used as coolants before introduction of limits on HCFC use Interested in interactions with other small molecules (H 2 O, CO 2, etc.) Introduction

3. Background Ab initio calculations on CHCl 2 F-H 2 O indicated a weak C-H … O interaction Further calculations on CHClF 2 -H 2 O and on CO 2 complexes also showed C-H … O interactions

4. Ab initio Calculations (MP2/6-311++G(2d,2p)) 3.60 Å 58.7° 62.3° 2.49 Å 3.59 Å 60.6° 63.6° 2.53 Å 3.47 Å 61.5° 73.7° 2.61 Å 3.41 Å 64.4° 77.3° 2.67 Å

5. Experimental Initial search for CHCl 2 F-OCS Fourier-transform microwave spectroscopy ~1% of each component in first run He/Ne Total pressure 1.5 – 2.5 bar Spectrum ~100 MHz from predictions Very weak lines, extensively split by two equivalent chlorine nuclei

6. Spectroscopic Constants (MHz) a root-mean-squared deviation of the fit b number of transitions in fit c fixed at value from rigid rotor fit (59) (66)

7. Structural Comparison Complexes also compare nicely to fluorinated methane complexes (previous talk – RG04) Lowering of symmetry removes chance of internal motions

8. 2.62 Å 3.48 Å 60.8  74.8  3.45 Å 2.65 Å 74.9  63.8  3.60 Å 58.7° 62.3° 2.49 Å CHF 3 -OCS CH 2 F 2 -OCS 3.47 Å 61.5° 73.7° 2.61 Å CHClF 2 -OCS CHCl 2 F-OCS Ab Initio Structures

9. Conclusions CHCl 2 F and CHClF 2 form complexes with weak C-H … O interactions CHClF 2 complexes are structurally similar to dimers of fluorinated methanes Substitution of F by Cl breaks the symmetry of CHF 3, providing a means to simplify spectra (such as HCCH-HCF 3 [2006 talk MH13]) that are complicated by internal motions

10. Acknowledgements Dreyfus Faculty Start Up Grant SU-04-048 Petroleum Research Fund Type G Grant 43130-GB6 Eastern Illinois University Council for Faculty Research Eastern Illinois University Honors College Michael Foellmer, Michal Serafin Dr. Sean Peebles

11. Ab initio Calculations 3.60 Å 58.7° O C S F H C Cl 62.3° C F Cl H 3.59 Å O C O 60.6° 63.6° S C O Cl C F H 3.47 Å 61.5° 73.7° O C O C H Cl F 3.41 Å 64.4° 77.3°