CONFORMATIONAL AND STRUCTURAL STUDIES OF ISOPROPYLAMINE FROM TEMPERATURE

CONFORMATIONAL AND STRUCTURAL STUDIES OF ISOPROPYLAMINE FROM TEMPERATURE DEPENDENT RAMAN SPECTRA OF XENON SOLUTIONS AND AB INITIO CALCULATIONS JOSHUA J. KLAASSEN, IKHLAS D. DARKHALIL, JAMES R. DURIG

Isopropylamine, (CH 2)2 CHNH 2 • Two stable conformers • Microwave work shows trans conformer only • Trans form is predicted to be most stable conformer • energy predictions vary significantly with the addition of diffuse functions

(A) observed Raman spectrum in xenon (B) simulated Raman spectrum of the mixture at -100°C with ΔH = 113 cm-1 (C) simulated spectrum of pure trans (D) simulated spectrum of pure gauche

Raman spectra of the xenon solution (Top) Infrared spectra of the vapor phase (Bottom) (A) 1510 – 1310 cm-1 (B) 1300 – 1100 cm-1 (C) 900 – 700 cm-1

(A) Infrared spectra of the vapor phase (B) Raman spectra of the xenon solution

Variable temperature xenon

Conclusions The utilization of liquid rare gases as solvents for enthalpy determinations has many advantages as well as disadvantages. The advantages are: 1. Bands are very narrow 2. Very accurate measurement of the temperature 3. Fairly large temperature range 4. Little interaction of solvent with solute molecules 5. Small enthalpy changes can be measured 6. Band areas easily measured 7. Long paths for the liquids so very dilute solutions can be used 8. Solvent has no absorption bands 9. Usually several conformer pairs can be measured 10. Very low statistical uncertainty of determined values

Conclusions The disadvantages are: 1. Limited solubility of many polar molecules 2. Difficult to have very dry xenon so water can interfere 3. At low temperatures sample may deposit on the window

Acknowledgement J. R. D. acknowledges the University of Missouri-Kansas City for a Faculty Research Grant for partial financial support of this research.

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