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The Vaporization Enthalpies and Vapor Pressures of Two
Insecticide Components, Muscalure and Empenthrin By
Correlation Gas Chromatography
Jessica Spencer and James Chickos
Department of Chemistry and Biochemistry
University of Missouri-St. Louis
Louis MO 63121
E-mail: [email protected]
A portion of the Science
Complex at UMSL
Outline of the Presentation
Properties of the targets
Introduction to the fundamentals of correlation gas chromatography
Demonstration of the method as applied to: Muscalure
Application to evaluate the vaporization enthalpy and vapor pressure of empenthrin
Comparison of the results on empenthrin with those obtained by another gas
chromatographic retention time method that has been criticized recently 1
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. Data 2011, 57, 1349-68.
Information on the Compounds Investigated
Muscalure: Z 9-Tricosene, is a sex pheromone
produce by female house flies (Musca domestica).
Muscalure in combination with other fecal odors
provides maximum attraction for male flies. It is
used as a pesticide is in combination with fly paper
or other traps. Z 9-Tricosene also serves as a
communication pheromone in the waggle dance of
bees. The synthetic sample also contains a small
amount of E 9-Tricosene.
Empenthrin: (E)-(RS)-1-ethynyl-2-methylpent-2-enyl
(1RS)-cis-trans-2,2-dimethyl-3-(2-methylprop-1-enyl)cyclopropane-carboxylate is a synthetic pyrethrin used as a
pesticide. It has a broad spectrum of activity on various
flying insects but relatively low mammalian toxicity. It
consists of a racemic mixture of up to 4 possible
diasteriomers. At least three of the diasteriomers were
detected in the commercial product.
40000
5500
5000
30000
Intensity
Intensity/arbitrary units
4500
FIGURE 1 Gas
chromatograph. From left to
right: hexane, nonadecane,
eicosane, henicosane,
docosane, Z-9-tricosene
(muscalure), E-9-tricosene,
tetracosene
Z
4000
E
3500
3000
20000
2500
2000
12.0
10000
13.0
13.5
14.0
T/min
0
5
10
T/min
13C
12.5
NMR
15
20
40000
5500
5000
30000
4500
Intensity
Intensity/arbitrary units
FIGURE 2. Gas chromatograph.
From Left to right: CH2Cl2, methyl
dodecanoate, empenthrin 1 and 2,
methyl tetradecanoate, methyl
hexadecanoate, methyl
octadecanoate, ethyl octadecanoate,
methyl nonadecanoate on a 5%
phenylmethyl silicone column.
4000
3500
3000
20000
2500
2000
4.2
4.4
4.6
4.8
5.0
5.2
T/min
10000
0
5
10
15
T/min
1H
NMR
2.45 ppm
20
25
Fundamentals of Correlation Gas Chromatography- Vaporization Enthalpy
1. The residence time of a compound on the column, ta, is inversely proportional
the compounds vapor pressure (ta = retention time of a solute – retention time of
a non-retained reference , ta = t – tnrr (often the solvent)
2. A plot of ln(to/ta), where to is the reference time, 1 min, versus 1/T over a 30 K
temperature range results in a straight line
3. The slope of the line, -∆Htrn(Tm)/R, is the enthalpy of transfer of the analyte from
the column to the gas phase
4. The enthalpy of transfer is related to the vaporization enthalpy (∆lgH(T) by the
following equation where ∆Hsln represents the enthalpy of interaction of the
solute with the column: ∆Htrn(Tm) = ∆lgH (Tm) + ∆Hsln (Tm)
5. If a series of standards are properly selected, a second plot of ∆lgH(298.15 K)
versus ∆Htrn(Tm) of the standards is also linear and the equation of the line can
be used to evaluate the vaporization enthalpy of any additional targets included
in the mixture
6. Appropriate standards with known vaporization enthalpies generally include
compounds with the same number and type of functionality as the targets. The
structure of the hydrocabon portion of the molecule may vary
Fundamentals of Correlation Gas Chromatography - Vapor Pressure
Use of appropriate standards with known vapor pressures also results in linear plots
between ln(p/po) and ln(to/ta)
The equation of the line plus values of ln(to/ta) of the targets results in their vapor
pressures
Performed over a range of temperatures can provide the vapor pressure temperature
profile of the targets
Vaporization Enthalpies and Vapor Pressure Equations of the Standards (po = 101325 Pa)
ln (p/po) = (1-Tnb/T)exp(Ao +A1T + A2T2)
Cox equation
ln(p/po) = AT -3 + BT -2 + C T -1 + D
Third order polynomial
Rln(p/po) = - cdgG°()/ + lgH°()[1/ - 1/T] + cdgCp,m()[/T -1 + ln(T/)]
Equation of Clark and Glew
2
TABLE 2.Experimental
Retention Times of Muscalure and Various Alkanes
-0.5
-1.0
FIGURE 3. A plot of ln(to/ta)
where to = 1 min and ta is equal
to the difference in retention
time between each analyte and
a non-retained reference (the
solvent) against 1/T.
ln(to/ta)
-1.5
-2.0
-2.5
-3.0
-3.5
0.00192 0.00194 0.00196 0.00198 0.00200 0.00202 0.00204 0.00206 0.00208
1/(T/K)
TABLE 3. Correlation of Enthalpies of Transfer With Vaporization Enthalpies: Muscalure
lgHm(298.15 K)/kJmol-1 = (1.640.01)Htrn(500 K) - (3.460.7)
r 2 = 0.9999
125
120
g
-1
l H(298 K) / kJ.mol
FIGURE 4. Vaporization enthalpy of
muscalure and standards. From left to
right: eicosane, heneicosane, docosane,
Z 9-tricosene, E 9-tricosene,
tetracosane.
115
110
105
100
62
64
66
68
70
72
Htrn(Tm)/ kJ.mole-1
74
76
78
TABLE 4. A Summary of the Vaporization Enthalpies of Muscalure
2
Values in italics are estimated using the following
equation for hydrocarbons:
∆lgH(298.15 K) = 4.69(n-nQ) + 1.3 nQ +3.0 + b + C
n = number of carbon atoms: 23
nQ = number of quaternary sp3 carbon atoms: 0
b = contribution of a functional group: 0
branching correction: 0
TABLE 5. Correlation Between ln(to/ta) and Literature ln(p/po) for Muscalure at T = 298.15 K
ln(p/po) = (1.37  0.003) ln(to/ta) - (1.608  0.044)
r 2 = 0.9999
-17
p/Pa(298,15) = 1.2·10-4 (Z)
-18
p/Pa(298,15) =
1.1·10-4
(E)
FIGURE 5. A plot of
ln(p/po) vs ln(to/ta) where po =
101325 Pa for muscalure at T
= 298.15 K. From left to
right: tetracosane, Z-9tricosene, E 9-tricosene,
docosane, heneicosane, and
eicosane.
ln(p/po)
-19
-20
-21
-22
-23
-15.5
-15.0
-14.5
-14.0
-13.5
ln(to/ta)
-13.0
-12.5
-12.0
-11.5
The correlation between ln(to/ta) and literature values of ln(p/po) for
Muscalure and the standards was repeated from T = (298.15 to 500) K at
10 K intervals resulting in the following (r 2 for all correlations >0.99):
ln(p/po) = AT -3 + BT -2 + C T -1 + D
Third order polynomial
TABLE 7. A Summary of Liquid/Subcooled Liquid Vapor Pressures and Normal
Boiling Temperatures and Comparison with Experimental or Estimated Values (in
italics)
a
Estimation from US EPA; Estimation Program Interface EPI Suite Version 4.11
b
SciFinder Scholar: Estimated using Advanced Chemistry Development (ACD/Labs) Software V11.02
c
Khanal, O.; Schooter, D. Chemical analysis of organics in atmospheric particulates by headspace
analysis. Atmos. Environ. 2004, 38(40), 6917-6925.
d
Boiling temperature at p = 133 Pa. Yadav, J. S.; Ready, P. S.; Joshi, B.V. A convenient reduction of
alkylated tosylmethyl isocyanides. Applications for the synthesis of natural products. Tetrahedron 1988,
44, 7243-54.
Evaluation of Empenthrin
The vapor pressure of numerous substances have been measured by the gas
chromatography - retention time method 1 which differs from the method just
discussed.
Vapor pressure: Gas Chromatography - Retention Time Method
The vapor pressure - retention time method consists in ploting ln[(tr)tar/(tr)ref ]T against
ln(pref,,T) at different temperatures resulting in the following linear relationship:
ln[(tr)tar/(tr)ref ]T = [1- (lgH)tar/(lgH)ref] ln(p ref, T) - C
(tr)tar and lgH)tar are the relative retention time and vaporization enthalpy of the target
(tr)ref and lgH)ref refer to the corresponding properties of the reference materials.
The slope and intercept of the line obtained is given by [1- (lgH)tar/(lgH)ref] and - C
The vapor pressure of the target at T = 298.15 K is obtained from:
ln(ptar, 298.15 K/Pa) = [(lgH)tar/(lgH)ref] ln(p ref, 298.15 K/Pa) + C
1
Hamilton, D. J. Gas Chromatographic Measurement of Volatility of Herbicide Esters. J. Chromatography
1980, 195, 75-83.
Tsuzuki1 using an modification of the gas chromatographic method just described,
used dibutyl phthalate and bis 2-ethylhexyl phthalate as standards and measured a
number of other esters including empenthrin and the following:
CO2CH2CHCH2(CH)2CH3
CO2CH2(CH2)2CH3
CH2CH3
CH2CH3
CO2CH2CH(CH2(CH2)CH
CO2CH2(CH2)2CH3
N
CF3
Cl
O
O
Cl
O
O
O
CF3
fluvalinate
permethrin
O
Cl
O
Cl
O
CF3
N
fenvalerate
O
bifenthrin
It is not clear well phthalate diesters can serve as standards to these pyrethrinoids
which in addition to being single esters have a variety of other functional groups..
1
Tsuzuki, M. Vapor pressures of carboxylic esters including pyrethroids:
measurement and estimation from molecular structure. Chemosphere 2001, 45, 729-36.
FIGURE 6. Vaporization enthalpy
at T = 298.15 K versus the enthalpy
of transfer of fatty acid methyl esters
(FAMES) and dialkyl phthalates
evaluated simultaneously
TABLE 8. ∆trnH(Tm) versus ∆lgH(298.15 K)
FAMES
Diesters
Evaluation of the Vapor Pressure and Vaporization Enthalpy of Empenthrin Using FAMES
O
CH3(CH2)nCH 2
C
OCH3
n = 9, 12, 13, 15, 16
TABLE 9. Experimental Retention Times of Empenthrin with Various Esters
0.5
0.0
-0.5
-1.0
ln(to/ta)
FIGURE 7. A plot of ln(to/ta)
where to = 60 s and ta is equal to
the difference in retention time
between each analyte and a nonretained reference (the solvent)
against 1/T.
-1.5
-2.0
-2.5
-3.0
-3.5
0.00200 0.00202 0.00204 0.00206 0.00208 0.00210 0.00212 0.00214 0.00216 0.00218
1/(T/K)
TABLE 10. Correlation of Enthalpies of Transfer With Vaporization Enthalpies: Empenthrin
lgHm(298.15 K)/kJmol-1 = (1.480.055)Htrn(480 K) - (2.593.6), r2 = 0.9944
120
FIGURE 8. Vaporization enthalpy
of empenthrin and standards. From
left to right: methyl dodecanoate,
empenthrin I, empenthrin 2, methyl
hexadecanoate, methyl
octadecanoate, ethyl octadecanoate
methyl nonadecanoate.
g
-1
l H (298.15) / kJ.mol
110
100
90
80
70
45
50
55
60
Htrn(Tm) / kJ.mol-1
65
70
75
TABLE 11. A Comparison of Vaporization Enthalpies at T/K = 298.15 of
Empenthrin and Standards With Literature and Estimated Values (in italics)
aValues
in italics are estimated using the following equation for hydrocarbons:
∆lgH(298.15 K) = 4.69(n-nQ) + 1.3 nQ +3.0 + b + C
n = number of carbon atoms: 18
nQ = number of quaternary sp3 carbon atoms: 1
b = contribution of a functional group: 10.5
branching correction: -2
TABLE 12. Correlation Between ln(to/ta) and Literature ln(p/po) for Empenthrin at T =298.15 K
ln(p/po) = (1.25  0.032) ln(to/ta) avg - (2.24  0.38 )
r 2 = 0.9979
-10
-12
-14
ln(p/po)
FIGURE 9. A plot of ln(p/po) vs
ln(to/ta) where po = 101325 Pa at T =
298.15 K for empenthrin. From left
to right: methyl nonadecanoate, ethyl
octadecanoate, methyl octadecanoate,
methyl hexadecanoate, methyl
pentadecanoate, empenthrin 2,
empenthrin 1, methyl dodecanoate.
-16
-18
-20
-22
-15
-14
-13
-12
-11
ln(to/ta)
-10
-9
-8
-7
Repeating this process at 10 K intervals from T = (298.15 to 480) K resulted in the
following vapor pressure – temperature profile; the data were fit to the following
equation: ln(p/po) = AT -3 + BT -2 + C T -1 + D. All r 2 > 0.99.
TABLE 13. A Summary of Liquid/Subcooled Liquid Vapor Pressures and Normal Boiling
Temperatures and Comparison with Experimental Values
1Tsuzuki,
M. Vapor pressures of carboxylic esters including pyrethroids: measurement and estimation
from molecular structure. Chemosphere 2001, 45, 729-36.
2 SciFinder Scholar; obtained from Syracuse Research Corporation of Syracuse, New York.
3 SciFinder Scholar, estimate.
TABLE 14. Application of the Gas Chromatographic – Retention Time Method Using Fatty
Acid Methyl Esters as Standards
lgHm(298.15 K)/(kJ·mol-1) = lgHm(Tm) +
[(10.58 + 0.26·Cp(l)/(J·mol-1·K-1))( Tm/K 298.15 K)]/1000
Acknowledgements: Jessica Spencer and FKS Inc for financial support
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.
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. Data 2011, 57, 1349-68.