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Adventures in Thermochemistry. James S. Chickos * Department of Chemistry and Biochemistry University of Missouri-St. Louis Louis MO 63121. E-mail: jsc@umsl.edu 12 Jewel Box Forest Park 13. Applications of the The Correlation-Gas Chromatographic Method
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Adventures in Thermochemistry James S. Chickos* Department of Chemistry and Biochemistry University of Missouri-St. Louis Louis MO 63121 E-mail: jsc@umsl.edu 12 Jewel Box Forest Park 13
Applications of the The Correlation-Gas Chromatographic Method Objectives: To go where no one else has gone 1. Evaluation of the vaporization enthalpies of large molecules 2. Application of Correlation-Gas Chromatography to a Tautomeric Mixture - Acetylacetone 3. The Vaporization Enthalpies of Drugs and Related Substances 4. Evaluation of the Vaporization Enthalpies and Vapor Pressures of Plasticizers 5. Identifying unusual interactions in heterocyclic systems 6. Other retention time gas chromatographic methods
Recently Ruzicka, et al. have questioned the accuracy of results from the GC retention time measurements. From the Clausius Clapeyron Eq where L = ∆lgHm 1/L1 dln(p1) = 1/(RT2)dT 1/L2 dln(p2) = 1/(RT2)dT 1/L1dln(p1) = 1/L2 dln(p2) ln(p1) = L1/L2 ln(p2) + C eq 1 Also p1/p2= ta2/ta1 therefore ln(p1) = ln(p2) - ln(ta1/ta2); from eq 1, substituting for ln(p1): L1/L2 ln(p2) + C = ln(p2) - ln(ta1/ta2) and rearranging ln(ta1/ta2) = (1 – L1/L2)ln(p2) - C A plot of ln(ta1/ta2) vs ln(p2) should result in a straight line with slope (1-L1/L2) and intercept – C. If the vapor pressure of p2 is known, then p1 can be calculated from eq 1 Ruzicka, K.; Koutek, B.; Fulem, M.; Hoskovec, M. Indirect Determination of Vapor Pressures by Capillary Gas- Liquid Chromatography: Analysis of the Reference Vapor –Pressure Data and Their Treatment. J. Chem. Eng. Data2011, 57, 1349-68.
Using dibutyl phthalate as a standard, the vapor pressures (Pa) a variety of herbicide esters at T = 298.15 K were evaluated including: Pa ethyl 2,4-dichlorophenoxyacetate 3.3·10-2 butoxyethyl 2,4-dichlorophenoxyacetate 6.1·10-4 n-butyl 2,4,5 trichlorophenoxyacetate 2.0·10-3 butoxyethyl 2,4,5 trichlorophenoxyacetate 2.0·10-4 n-butyl fenoprop 3.1·10-3 Measurements were made at T = (345 to 455) K and extrapolated to T = 298.15 K fenoprop Hamilton, D. J. Chromatographic Measurements of Volatility of Herbicide Esters J. Chrom.1980, 195, 75-83
Commercial empenthrin is marketed as a mixture of several stereoisomers, two of which could be clearly resolved by the chromatography. A vapor pressureof p/Pa = 230·10−4 at T = 298.15 K, evaluated using a variant of the GC retention time method as reported by Hamilton has been reported by Tsuzuki,using dibutyl phthalate and 2-ethylhexyl phthalate as standards using a modified variant of the method reported by Hamilton. Tsuzuki, M. Vapor pressures of carboxylic esters including pyrethroids: measurement and estimation from molecular structure. Chemosphere2001, 45, 729−36.
Empentrin This Work Vapor pressures of p/Pa = (594 ± 380)·10−4 and (601 ±383)·10−4 at T = 298.15 K ∆lgHm (298.15 K) = (87.2 ± 4.8) and (87.0 ± 4.8) kJ·mol−1 Tnb/K = (567.9 and 569.2) Tsuzuki p/Pa = 230·10−4 at T = 298.15 K , Vaporization Enthalpies and Vapor Pressures of Two Insecticide Components, Muscalure and Empenthrin, by Correlation Gas Chromatography. Spencer, J.; Chickos, J. Chem. Eng. Data 2013, 59, 3513-20.
