Application of Correlation-Gas Chromatography to
Problems in Thermochemistry
James S. Chickos
Department of Chemistry and Biochemistry
University of Missouri-St. Louis
Louis MO 63121
E-mail: jsc@umsl.edu
Spring 2016
My Collaborations with Tim
1R, 2R
[α]D20 = (-0.015 ± 0.011)°
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.
Berson, J. A.; Pedersen, L. D.; Carpenter , B. K.
J. Am. Chem. Soc. 1976, 86, 122
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.
250
Signal Intensity
200
150
100
ta = tanalyte – tnon-ret ref
50
0
0
100
200
300
Time (sec)
400
500
A plot of ln(to/ta) of each analyte versus 1/T
results in a straight line, the slope of which is an
enthalpy
Htrn(Tm) = lgHm (Tm) + Hintr(Tm)
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
lgHm (298.15 K) vs Htrn(Tm) is linear and the equation of the line together with Htrn(Tm)
of the targets can be used to calculate lgHm (Tm) of the targets.
Similarly plots of ln(p/po) vs ln(to/ta) are also linear and can be used to evaluate p of the
target in a similar manner.
Catnip
The essential oil from the plant, Nepeta cataria, has held the interest of many
because of the remarkable effect it has on various felids.
CH3
CH3
H
H
4
3
O
4a
7a
1
H
O
5
3
O
7
4
4a
7a
1
5
7
H
CH 3
O
CH 3
Structures of the major and minor
diasteriomers of (4aS,7S,7aR) and
(4aS,7S,7aS)-nepetalactone isolated from
Nepata catonia.
Catnip is very effect at
repelling Aedes aegypti
(yellow fever mosquito) and
other Afro-tropical pathogen
vector mosquitoes
Infrared Spectrum of commercial sample ofCatnip
ln(p/Pa) = {A – B/T(K) –Cln(T/K/298.15)}/R
ln(p/po) = A’ – B’/T
Figure. A plot of ln(to/ta) vs 1/T; from top to bottom: -hexanolactone,  octalactone, -octalactone, catnip (minor isomer), catnip (major isomer), decalactone, -undecalactone, -undecalactone, -dodecalactone, -dodecalactone,
90000
g
-1
l Hm(298.15 K) /kJ.mol
85000
80000
75000
70000
65000
60000
55000
50000
35000
40000
45000
50000
55000
60000
-1
trnHm(414 K) / kJ.mol
FIGURE. ΔlgHm(298.15 K) vs ΔtrnHm(414 K) ; ; minor isomer and major
isomer of catnip are the squares.
65000
10 9
8 7
6
5 4
3 2
1
Figure. A plot of ln(p/po) vs ln(to/ta); 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).
CH3
CH3
H
H
4
3
O
4a
7a
1
5
3
O
7
H
4a
7a
1
5
7
H
CH 3
O
O
Catnip (major isomer)
Catnip (minor isomer)
CH3
4
CH 3
vapor pressure (298.15 K) p/Pa = 0.9±0.3
p/Pa = 1.2±0.4
O
CH3
N
CH3
DEET vapor pressure (298.15 K) p/Pa = 0.75
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-82-87. NTIS AD-B070947 (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 C60. In addition, alkanes derived from oligomers
of polyethylene are available up to ~C100
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