Application of Correlation-Gas Chromatography to Problems in Thermochemistry James S. Chickos Department of Chemistry and Biochemistry University of Missouri-St. Louis Louis MO Spring 2016

My Collaborations with Tim 1R, 2R [α] D 20 = ( ± 0.011)° Berson, J. A.; Pedersen, L. D.; Carpenter, B. K. J. Am. Chem. Soc. 1976, 86, 122 Thermolysis of 1R,2R-1,2-Cyclobutane-d2. An Application of VCD to Kinetic Analysis. Chickos, J. S.; Annamalai,A.; Keiderling, T. A. J. Am. Chem. Soc. 1986, 108, 4398.

Evolution of Research

Vaporization enthalpies and vapor pressures have been measured for over 200 years. Numerous methods have been developed to measure them. Vaporization enthalpies are very useful thermodynamic properties. They find applications in chemical engineering, in evaluating gas phase enthalpies of formation of liquids, solubility and are one of the few methods of quantitatively evaluating intermolecular interactions in liquids. Vapor pressures are very useful for evaluating the rate of mass transport in the environment Our lab has been interested in developing a new method of measuring both vaporization enthalpies and vapor pressures. Why develop a new method when numerous method are currently available? All existing methods require pure materials, near gram quantities, have a limited dynamic range of measurement and are very time consuming if measured carefully. Our lab has been developing a technique we refer to as correlation gas chromatography

If one takes a series of compounds and subtracts the retention time of an a non-retained reference from the retention time of each analyte, the difference in time is the time each analyte spends on the column; this in turn is inversely propotional to the analyte’s vapor pressure off the column. t a = t analyte – t non-ret ref A plot of ln(t o /t a ) of each analyte versus 1/T results in a straight line, the slope of which is an enthalpy  H trn (T m ) =  l g H m (T m ) +  H intr (T m ) Enthalpy of transfer = vaporization enthalpy + enthalpy of interaction on the column. If the compounds chosen are have the same functionality as the targets moleules, a plot of  l g H m ( K) vs  H trn (T m ) is linear and the equation of the line together with  H trn (T m ) of the targets can be used to calculate  l g H m (T m ) of the targets. Similarly plots of ln(p/p o ) vs ln(t o /t a ) are also linear and can be used to evaluate p of the target in a similar manner.

The essential oil from the plant, Nepeta cataria, has held the interest of many because of the remarkable effect it has on various felids. Structures of the major and minor diasteriomers of (4aS,7S,7aR) and (4aS,7S,7aS)-nepetalactone isolated from Nepata catonia. Catnip Catnip is very effect at repelling Aedes aegypti (yellow fever mosquito) and other Afro-tropical pathogen vector mosquitoes

Infrared Spectrum of commercial sample ofCatnip

l n(p/Pa) = {A – B/T(K) –C  ln(T/K/298.15)}/R ln(p/p o ) = A’ – B’/T

Figure. A plot of ln(t o /t a ) vs 1/T; from top to bottom:  -hexanolactone,  - octalactone,  -octalactone, catnip (minor isomer), catnip (major isomer),  - decalactone,  -undecalactone,  -undecalactone,  -dodecalactone,  -dodecalactone,

FIGURE. Δ l g H m ( K) vs Δ trn H m (414 K) ; ; minor isomer and major isomer of catnip are the squares.

Figure. A plot of ln(p/p o ) vs ln(t o /t a ); from right to left:  -hexanolactone (1),  - octalactone (2),  -octalactone (3), catnip (minor isomer, 4), catnip (major isomer, 5),  - decalactone (6),  -undecalactone (7),  -undecalactone(8),  -dodecalactone (9),  - dodecalactone (10)

DEET vapor pressure ( K) p/Pa = 0.75 Catnip (major isomer) vapor pressure ( K) p/Pa = 0.9±0.3 Catnip (minor isomer) p/Pa = 1.2±0.4 Arthur D Little, Inc; Development of Candidate Chemical Simulant List: The Evaluation of Candidate Chemical Simulants Which May Be Used in Chemically Hazardous Operations. Air Force Aero Med Res Lab, Wright-Patterson AFB, OH, AFAMRL-TR NTIS AD-B (1982)]; accessed 6/9/15. Vapor pressure and enthalpy of vaporization of oil of catnip by correlation gas chromatography D Simmons, C. Gobble, J. Chickos. J. Chem. Thermodyn. 92 (2016) 126–131.

Advantages of Correlation gas Chromatography Vapor pressure and vaporization enthalpy of mixture evaluated on a mg or less of sample in a couple of hours. Limitations: Requires reliable standards with similar functionality Other systems previously examined: Amphetamine Methamphetamine Angel Dust (PCP) Various legitimate drugs

Leasa Keating Dan Simmons Carissa Nelson Chase Gobble Dick Heinze

Individual n- alkanes are available commercially for most even n-alkanes up to C 60. In addition, alkanes derived from oligomers of polyethylene are available up to ~C 100

Correlation Gas Chromatography Advantages: Mixtures can be analyzed directly Mg quantities are sufficient Limitations: Standards with the same functional group are required

Acknowledgements Dan Simmons Chase Gobble Dr. Barry Walker Melissa Thornton