Application of Correlation-Gas Chromatography to

1
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_at_umsl.edu October 3,
2011
2
Outline

• The Correlation-Gas Chromatographic Method
• Applications
• 1) Evaluation of the vaporization
  enthalpies of large molecules, the n-alkanes,
  C21 to C92.
• 2) Evaluation of the vaporization
  enthalpies of tautomeric mixtures.
• 3) Identifying unusual interactions in
  heterocyclic systems 4) Measurement of Vapor
  Pressure Isotope Effects

3
1.The Correlation-Gas Chromatographic Method
A typical series of isothermal gas chromatograms
as a function of temperature the compounds in
these chromatograms are hydrocarbons
4

• Fundamentals of Correlation Gas
  Chromatography
• tnrr time of a non-retained reference a measure
  of the time needed to travel through the column
  usually the solvent or methane
• ta adjusted retention time tanalyte tnrr a
  measure of the time the analyte spends on the
  column
• ta is inversely proportional to the vapor
  pressure of the analyte off the column
• A plot of ln(to/ta) versus 1/T (K-1) results in a
  linear relationship with a slope equal to the
  enthalpy of transfer from the column to the gas
  phase, -?gslnHm(Tm)/R to 1 min
• ?gslnHm(Tm) ?lgHm(Tm) ?slnHm(Tm)
• Enthalpies of transfer values measured at Tm are
  found empirically to correlate linearly with the
  vaporization enthalpies of standards evaluated at
  any temperature, including T 298.15 K
• Since solids do not crystallize on the column,
  the measurement provides the vaporization
  enthalpy of the solid
• Peacock, L. A. Fuchs, R Enthalpy of
  Vaporization Measurements by Gas Chromatography,
  J. Am. Chem. Soc. 1977, 99, 5524-5.
• Lipkind, D. Chickos, J. An Examination of
  the Factors Influencing the Thermodynamics of
  Correlation Gas Chromatography as Applied to
  Large Molecules and Chiral Separations, J. Chem.
  Eng. Data 2010, 55, 698-707.

5
A Determination of Vaporization Enthalpy

• Experimental retention times for n-C14 to C20

6
Enthalpy of Transfer Determination for Hexadecane

• ln(to/ta) -?gslnHm(Tm)/R1/T intercept
• ?gslnHm(Tm) 8.314 J mol-1 60.308 kJ mol-1

7

• Equations for the temperature dependence of
  ln(to/ta) for C14 to C20 where to 1 min

ln(to/ta) -?gslnHm(Tm)/R1/T intercept
8

• Vaporization enthalpies (in kJ mol-1) of the n-
• alkanes (C14 to C20)

82?1.1
?
81.4
unknown
9
Correlations between vaporization enthalpy at
T 298.15 K against the enthalpy of transfer
10
B Determination of Vapor Pressures

• literature vapor pressure evaluated using the Cox
  equationa
• ln (p/po) (1-Tb/T)exp(Ao A1T A2T 2)

po 101.325 kPa
aRuzicka, K. Majer, V. Simultaneous Treatment of
Vapor Pressures and Related Thermal data Between
the Triple Point and Normal Boiling Temperatures
for n-Alkanes C5-C20. J. Phys. Chem. Ref. Data
1994, 23, 1-39.
11

• Equations for the temperature dependence of
  ln(to/ta) for C14 to C20

ln(to/ta) -?gslnHm(Tm)/R intercept
12

• Vapor pressures of n-alkanes (C14 to C20) at T
  298.15 K

-13.3
-13.3
unknown
?
po 101.325 kPa
13
Correlation between ln(1/ta) calculated by
extrapolation to T 298.15 K versus ln(p/po)
calculated from the Cox equation for C14 to C20
(po 101.325 kPa)
ln(p/po) (1.27 ? 0.01) ln(to/ta) - (1.693 ?
0.048) r 2 0.9997
14
Vapor pressure -temperature dependence for
hexadecane line vapor pressure calculated from
the Cox equations for C14, circles vapor
pressures calculated by correlation treating
hexadecane as an unknown and correlating
ln(to/ta) with ln(p/po) for C14, C15,
C17-C20. normal boiling temperature 560.2
(expt) 559.9 (calcd)
15
Validation of the results

Compare with (?Hvap) lit
Vaporization. Enthalpy
Sublimation Enthalpy (for cryst. solids)
Compare with (?Hsub) lit
Fusion Enthalpy
c-GC
Liquid Vapor Pressure
Boiling Temperature
Compare with (BT) lit
Compare with (ln p/p0) lit
16
Some Advantages and Limitations of
Correlation-Gas Chromatography
1. The method works well on hydrocarbons and
hydrocarbon derivatives regardless of the
hydrocarbon structure
2. With hydrocarbon derivatives, standards need
to be chosen with the same number and type of
functional group as the compound(s) to be
evaluated unless demonstrated otherwise
3. Measurements can be made on small sample sizes
and purity is not generally an issue
4. Correlation of the standards needs to be
documented experimentally
5. The correlation equations can be used to
obtain vapor pressures as well provided vapor
pressures of the standards are available and to
estimate boiling temperatures.
6. The results are only as good as the quality
of the standard data
17

• What if suitable standards for the compounds of
  interest are not available?

18
Functional Group Contributions to Vaporization
Enthalpies Functional Group Group
Value Functional Group Group Value
b b acid -C(O)OH
38.8 iodide -I 18.0 alcohol
-OH 29.4 ketone gtCO 10.5aldehyde
-CHO 12.9 nitrile -CN 16.7 amide
mono- nitro -NO2 22.8 subst.
-C(O)NH- 42.5 heterocyclic aromatic amine
pri. -NH2 14.8 nitrogen N- 12.2 amine
sec. -NH- 8.9 sulfide gtS 13.4 amine
tert. gtN- 6.6 disulfide -SS- 22.3 bromi
de -Br 14.4 sulfoxide gtSO 42.4 ch
loride -Cl 10.8 sulfone -SO2-
53.0 ester -C(O)O-
10.5 thiolester -C(O)S- 16.9 ether
gtO 5.0 thiol -SH 13.9
?lgHm(298.15 K)/(kJ.mol-1) 4.69.(n-nQ)
(1.3).nQ b (3.0) n number of
non-quaternary carbons nQ number of quaternary
carbons values in brackets are tentative
assignments Chickos, J. S. Acree, Jr. W.
Liebman, J. F. (Frurip, D. Irikura, K.,
Editors) Computational Thermochem., Prediction
and Estimation of Molecular Thermodynamics, ACS
Washington DC, 1998, pp 63-93
19
Applications

• The evaluation of vaporization enthalpies of
  large molecules

20
1. Applications of correlation gas chromatography
for the evaluation of the vaporization enthalpies
of large molecules, the n-alkanes, C21 to C92.

C60
A partial GC trace of a mixture of Polywax 1000
spiked with n-alkanes C42, C50 and C60 run at T
648 K
21

• Applications of correlation gas chromatography
  for the evaluation of the vaporization enthalpies
  of large molecules, the n-alkanes, C21 to C92.
• Reliable vaporization enthalpies and vapor
  pressures are available up to eicosane
• Using the available data from heptadecane to
  eicosane, vaporization enthalpies were evaluated
  for C21,C22, C23. These values in turn were used
  to evaluate the larger n-alkanes in a stepwise
  process up to C38, most of which are commercially
  available.
• Additionally, a few other larger n-alkanes, C40,
  C42, C48, C50, and C60 are likewise commercially
  available. These were used in conjunction with
  polywax to evaluate vaporization enthalpies and
  vapor pressures up to C92 (even series)
• Since very little experimental data was available
  for comparison, the results from correlation gas
  chromatography were compared with estimations by
  PERT2a and estimated Antoine Constantsb

aPERT2 is a FORTRAN program written by D.L.
Morgan in 1996 which includes parameters for
n-alkanes from C1 to C100 and heat of
vaporization and vapor pressure correlations.
Morgan, D. L. Kobayashi, R. Extension of Pitzer
CSP models for vapor pressures and heats of
vaporization to long chain hydrocarbons, Fluid
Phase Equilibrium 1994, 94, 51-87. bKudchadker,
A. P. Zwolinski, B. J. Vapor Pressures and
Boiling Points of Normal Alkanes, C21 to C100,
J. Chem. Eng. Data 1966, 11, 253-55.
22
curvature
The vaporization enthalpies at T 298.15 for C5
to C92. N represents the number of carbon atoms.
The solid line was derived using the recommended
vaporization enthalpies of C5 to C20 The empty
circles are values calculated values using the
program PERT2 The solid circles are values
evaluated from correlations of ?slngHm(Tm) with
?lgHm(298.15K).
Vapor pressures and Vaporization Enthalpies of
the n Alkanes from C78 to C92 at T 298.15 K by
CorrelationGas Chromatography, Chickos, J. S.
Lipkind, D. J. Chem.Eng. Data 2008, 53,
24322440.
23
The Vaporization Enthalpies of the n-Alkanes at
T 298.15 K As A Function of the Number of
Carbon Atoms, N
N ?lgHm(298.15 K) kJ mol-1 N ?lgHm(298.15 K) kJ mol-1 N ?lgHm(298.15 K) kJ mol-1 N ?lgHm(298.15 K) kJ mol-1
5 26.42 21 106.82.6 36 182.85.5 64 315.42.9
6 31.52 22 111.92.7 37 187.55.6 66 324.03.0
7 36.57 23 117.02.8 38 192.55.7 b 68 331.93.0
8 41.56 24 121.92.8 40 203.52.9 70 340.33.1
9 46.55 25 126.82.9 42 213.52.1 72 348.43.2
10 51.42 26 131.73.3 44 223.72.3 74 356.23.3
11 56.58 27 135.63.3 46 233.32.3 76 364.33.3
12 61.52 28 141.95.1 48 243.02.4 78 372.11.4
13 66.68 29 147.15.3 50 252.52.5 80 379.62.2
14 71.73 30 152.35.3 52 261.83.6 82 387.22.4
15 76.77 31 157.21.4 b 54 271.03.7 84 394.03.2
16 81.35 32 162.51.4 56 279.73.8 86 402.22.6
17 86.47 33 167.61.4 58 288.53.9 88 409.33.9
18 91.44 34 172.71.5 60 299.93.0 90 416.54.3
19 96.44 35 178.15.4 b 62 306.82.8 92 424.54.5

How is it possible to measure a vaporization
enthalpy greater that a C-C bond strength (335
kJmol-1)?
24
Vapor pressures and vaporization enthalpies for
C14 to C20 are known over a large temperature
range. ?glHm(Tm) and ?slngHm(Tm) correlate at any
temperature

• Values of at ?slngHm(449 K) and ?lgHm(449 K) on
  an SPB-5 Column
• Tm 449 K -slope/T
  intercept ?slngHm(449 K) ?lgHm(449 K)
• kJ?mol-1 kJ?mol-1
• lit1 calcd (eq 1)
• tetradecane 6393.895 14.1610.01
  53.20.8 56.92 57.00.8
• pentadecane 6787.973 14.5970.01
  56.40.6 60.71 60.60.8
• hexadecane 7251.562 15.1900.01
  60.30.5 64.50 64.80.9
• heptadecane 7612.665 15.5870.01
  63.30.5 68.19 68.10.9
• octadecane 8014.871 16.0700.01
  66.60.6 72.11 71.81.0
• nonadecane 8457.474 16.6400.01
  70.30.6 76.01 75.81.0
• eicosane 8919.685 17.2570.01
  74.20.7 79.81 80.11.1

?glHm(449 K)/kJ?mol-1 (1.098?0.0133)
?slngHm(449 K) - (1.39?0.25) r2 0.9993
(1)


?slngHm(Tm) ?lgHm(Tm) ?slnHm(Tm)
?slnHm(Tm) must be of opposite sign to ?lgHm(Tm)
1Ruzicka, K. Majer, V. Simultaneous Treatment of
Vapor Pressures and Related Thermal data Between
the Triple Point and Normal Boiling Temperatures
for n-Alkanes C5-C20. J. Phys. Chem. Ref. Data
1994, 23, 1-39.
25
Values of at ?slngHm(509K) and ?lgHm(509 K) on an
SPB-5 Column -slope T intercept
?slngHm(509 K) ?lgHm(509 K)
kJmol-1 kJmol-1
lit1,2 calcd heptadecane
6108.278.2 12.1480.008 50.80.7
62.831 62.90.3 octadecane 6489.963.8
12.5840.006 54.00.5 66.341 66.20.3
nonadecane 6901.058.7 13.0770.006 57.40.5
69.741 69.80.3 eicosane 7270.060.5
13.4960.006 60.40.5 73.071 73.10.3 heneicos
ane 7670.965.3 13.9740.006 63.80.5
76.662 76.60.3 docosane 8064.571.6
14.4390.007 67.10.6 80.132 80.10.4
tricosane 8451.173.9 14.8970.008 70.30.7
83.542 83.50.4
?lgHm(509 K)/kJ?mol-1 (1.062?0.004)
?slngHm(509 K) (8.94.02?0.07) r2 0.9999
1Ruzicka, K. Majer, V. Simultaneous Treatment of
Vapor Pressures and Related Thermal data Between
the Triple Point and Normal Boiling Temperatures
for n-Alkanes C5-C20. J. Phys. Chem. Ref. Data
1994, 23, 1-39. 2Chickos, J. S. Hanshaw, W.
Vapor pressures and vaporization enthalpies of
the n-alkanes from C21-C30 at T 298.15 K by
correlationgas chromatography, J. Chem. Eng Data
2004, 49, 77-85.
26
Enthalpies of Condensation -?slngHm(T), -
?lgHm(T) and ?slnHm(T) as a Function of
Temperature
-?slngHm(449 K) -?lgHm(449 K) (lit)
?slnHm(449 K) kJmol-1 tetradecane
-53.20.8 -56.92 3.70.8 pentadecane
-56.40.6 -60.71 4.30.6 hexadecane
-60.30.5 -64.5 4.20.5 heptadecane
-63.30.5 -68.19 4.90.5 octadecane
-66.60.6 -72.11 5.50.6 nonadecane
-70.30.6 -76.01 5.70.6 eicosane
-74.20.7 -79.81 5.60.7
-?slngHm(509 K) -?lgHm(509 K) (lit)
?slnHm(509 K) kJmol-1 heptadecane
-50.80.7 -62.83 12.00.7 octadecane
-54.00.5 -66.34 12.30.5 nonadecane
-57.40.5 -69.82 12.40.5 eicosane
-60.40.5 -73.07 12.70.5 heneicosane
-63.80.5 -76.66 12.90.5 docosane
-67.10.6 -80.13 13.00.6 tricosane
-70.30.7 -83.54 13.20.7
?gslnHm(Tm) ?lgHm(Tm) ?slnHm(Tm)


27
Figure. The effect of temperature, 450, 509, 539
K, on the magnitude of ?slnHm(T/ K). ,
eicosane ?, nonadecane.
28

• Conclusions
• The enthalpy of interaction of analyte with the
  column is endothermic and a function of
  temperature this allows access to the
  measurement of large vaporization enthalpies
• This may also help focus GC peaks and oppose
  diffusion broadening
• The overall enthalpy of condensation on the
  column is still highly exothermic, just less so
  then might have been imagined

29
2. An Application of Correlation-Gas
Chromatography to a Tautomeric Mixture

0.186
0.814 The enthalpy
of formation of the equilibrium mixture of the
pure liquid, (-425.51.0)kJmol-1, has been
reported by Hacking and Pilcher. Acetylacetone
forms a number of metal complexes whose
enthalpies of formation have been used to
determine metal oxygen bond strengths.

• Hacking, J.M. Pilcher, G. J. Chem. Thermodyn.
  1979, 11, 1015-1017. Irving, R.J. Wadso, I. Acta
  Chem.Scand. 1970, 24, 589-592

30
Table. Summary of all enthalpy differences
between 2,4-pentanedione and (Z)-4-hydroxy-3-pente
n-2-one in the liquid and gas phase available to
Hacking and Pilcher, and Irving and Wadso.
Enthalpy differences measured by the temperature
dependence of the equilibrium constant.
?Hdiketo/enol(Tm)liq kJ mol1 Tm/K ?Hdiketo/enol(Tm)gas kJ mol1 Tm/K Method Year




    18.0 388 UV 1977
    7.51.5 373 Photoelectron Spectroscopy 1974
11.90.8 306     NMR 1966
    16.3     1959
11.30.4       NMR 1957
    7.8 273 Bromination 1952
    10.00.8 386 IR 1951
31
Vaporization Enthalpy of the Pure Enol at T
298.15 K
?Hk/e 0.67 kJ mol-1
C5H8O2(gas, 93.3enol)
C5H8O2(gas, 100enol)
?lgHm(298.15K) (41.8 0.2) kJmol-1 measured
calorimetrically
?lgHm(298.15K) (43.2 0.2) kJ mol-1
C5H8O2(liquid, 81.4enol)
C5H8O2(liquid, 100enol)
?Hk/e -2.1 kJ mol-1

• A trace of concentrated sulfuric acid was used by
  Irving and Wadso to rapidly equilibrate the
  diketo and enol forms. Since the enol is more
  volatile, it was assumed that tautomerization of
  the diketo form to the enol contributed 2.1 kJ
  mol-1during vaporization.. It was also assumed
  that the composition in the gas phase was the
  equilibrium concentration.

?lgHm(298.15K) (41.8 0.2) ( -2.1 - 0.67)
(43.2 0.2) kJmol-1
32
The thermochemical scheme to calculate the
enthalpy of formation of (Z)-4-hydroxy-3-pentene-2
-one and 2,4-pentanedione scheme used by Hacking
and Pilcher in 1979
33
The enthalpy difference of the two tautomers in
the gas phase was measured by infrared
spectroscopy in 1951
Gas Phase FT-IR spectrum of 2,4-pentanedione,
Aldrich Chemical Co.
34
The enthalpy difference of the two tautomers in
the gas phase was re-measured by gas phase 1H NMR
spectroscopy in 1985.
5.3 ppm enol vinyl 1H 3.3 ppm keto methylene 1H
1.9 ppm enol methyl 1H 2.0 ppm keto methyl 1H
Folkendt, M.M.J.et.al. Phys. Chem. 1985, 89,
3347-3352
35
Table. A summary of all the enthalpy differences
measured between 2,4-pentanedione and
(Z)-4-hydroxy-3-penten-2-one in the liquid and
gas phase. Enthalpy differences measured by the
temperature dependence of the equilibrium
constant.
?Hdiketo/enol(Tm)liq kJ mol1 Tm/K ?Hdiketo/enol(Tm)gas kJ mol1 Tm/K Method Year
11.7 303     NMR 1996
  - 17.0 422 Photoelectron Spectroscopy 1987
11.8 394.5 19.5 409 NMR 1985
11.71.3 311     NMR 1982
    18.0 388 UV 1977
    7.51.5 373 Photoelectron Spectroscopy 1974
11.90.8 306     NMR 1966
    16.3     1959
11.3       NMR 1957
    7.8 273 Bromination 1952
    10.00.8 386 IR 1951
The gas phase and condensed phase enthalpies are
different, suggesting tautomer interaction
36
If the pure enol form( 0.814 mol) is mixed with
the pure keto form (0.186 mol) at the equilibrium
concentrations, will ?H 0 ?
Is ?Hmix 0 ?
If ?Hmix ? 0

• If the solution heats up when the pure diketo
  and enol are mixed at their equilibrium
  concentration, it will take more energy to
  vaporize the two liquids as a mixture at T
  298.15 K
• If the solution cools down, it will take less
  heat to vaporize the two liquids as a mixture at
  T 298.15 K.
• Since ?Hdiketo/enol(liq) ? ?Hdiketo/enol(gas),we
  decided to measure ?lgHm(298.15K)

37
Correlation Gas Chromatography an ideal method
for determining the vaporization enthalpy of a
pure material even though the material of
interest may be present in the mixture provided
all components can be separated
Gas Chromatograph of acetylacetone
38
Table. Enthalpy of transfer and vaporization
enthalpy obtained for (Z)-4-hydroxy-3-penten-2-one
.
Compound Slope Intercept ?slngHm(387 K) /kJ mol-1 ?lgHm(298.15 K) /kJ mol-1(lit) ?lgHm(298.15 K) /kJ mol-1(calcd)
3-hydroxybutanone -3358.8 10.092 27.92 48.7 48.7
(Z)-4-hydroxy-3-penten-2-one -3703.9 10.520 30.79 50.80.6
ethyl 2-hydroxypropanoate -3942.7 10.977 32.78 52.5 52.3
4-hydroxy-4-methyl-2-pentanone -3998.0 10.914 33.24 52.3 52.6
ethyl 3-hydroxybutanoate -4516.7 11.712 37.55 55.9 55.8
ethyl 3-hydroxyhexanoate -5476.8 13.020 45.53 61.9 61.6
o-hydroxyacetophenone -5213.3 12.053 43.34 59.6 60.0
?lgHm(298.15 K)/kJ mol1 (0.7340.021)
?slngHm(359 K) (28.210.32) r2 0.997
39
Table. Enthalpy of Transfer and Vaporization
Enthalpies obtained for 2,4-pentanedione
Compound Slope Intercept ?slngHm(328 K) /kJ mol-1 ?lgH (298.15 K) /kJ mol-1(lit) ?lgHm(298.15K) /kJ mol-1(calcd)
2,3-butanedione -3153.8 1.493 26.22 39.0 38.9
2,4-pentanedione -4305.8 12.034 35.80 51.22.2
2,2,4,4-tetramethyl-cyclobutanedione -4603.4 12.285 38.27 54.2 54.3
benzoquinone -4614.4 12.111 38.36 53.4 54.4
2,5-hexanedione -4800.5 12.592 39.91 57.5 56.4
?lgHm(298.15 K)/kJ mol1 (1.2830.1)
?slngHm(328 K) (5.211.1) r2 0.989
40
(Z)-4-hydroxy-3-penten-2-one ?lgHm(298.15K)/kJ.mo
l-1(corr- gas chromatography)(50.80.6) kJ mol-1
?lgHm(298.15K)/kJ mol-1(measured as a mixture)
(43.2 ?0.2) kJ.mol1a a Measured as a mixture but
calculated for the pure material
?Hmix (50.80.6) - (43.2 0.2) 7.60.6
kJ.mol-1
?Hketo-enol tautomerism observed ?Hketo-enol
tautomerism real ?Hmix ?Hketo-enol tautomerism
real (-11.3)-(7.60.6) -18.90.6 kJ mol-1
Since the vaporization enthalpy at T 298.15 K
is approximately the same for 2,4-pentanedione
and (Z)-4-hydroxy-3-penten-2-one, the difference
in the gas phase between the two tautomers is
also -18.9 kJ mol-1
41
The enthalpies of formation of the tautomers of
acetylacetone in the liquid phase and in the gas
phase
42
Table. Summary of Standard Molar Enthalpies at T
298.15 K of the Two Acetylacetone Tautomers
Compound ?fHºm(l) / kJ mol1 ? lgHm / kJ mol1 ?fHºm(g) / kJ mol1
2,4-pentanedione 410.1 ? 1.2 416.3 ? 1.1 51.2 ? 2.2 358.9 ? 2.5 374.4 ? 1.3
Z 4-hydroxy-3-penten-2-one 429.0 ? 1.0 427.6 ? 1.1 50.8 ? 0.6 43.2 ? 0.1 378.2 ? 1.2 384.4 ? 1.3
?fHm (T 298.15 K, liquid, 81.4 enol and 18.6
diketo) -425.51.0 kJ mol-1. values in the
brackets are the previous accepted values.
Temprado, M. Roux, M. V. Umnahanant, P. Zhao,
H. Chickos, J. S. J. Phys. Chem. B. 2005 109,
12590-12595.
43
Application 3 Identifying unusual interactions
in heterocyclic systems
1,2-Diazines

• Unknowns
• s-triazine
• Pyrimidines
• Pyridazines
• Standards
• Pyrazines
• Pyridines

44
A Comparison of calculated vaporization
enthalpies and normal boiling temperatures with
literature values

s-triazine
50.00.3
?lgHm (298.15 K)/kJ.mol-1 (0.941?0.07)
?slngHm(358 K) - (13.1?0.59), (r2 0.9865)
a Literature boiling temperatures from SciFinder
Scholar
A Examination of the Vaporization Enthalpies and
Vapor Pressures of Pyrazine, Pyrimidine,
Pyridazine and 1,3,5-Triazine. Lipkind D.,
Chickos J. S. Structural Chemistry 2009, 20, 49-58
45
Unknowns Standards
Top, from left to right phthalazine,
benzoccinnoline, quinazoline, quinoxaline.
Standards phenazine, 2,6-dimethylquinoline,
acridine, 4,7-phenanthroline, 7,8-benzoquinoline,
Lipkind, D. Chickos, J. S. Study of the
Anomalous Thermochemical Behavior of 1,2-Diazines
by Correlation-Gas Chromatography J. Chem. Eng.
Data 2010, 55, 698-707
46
Since all of the compounds studied are
crystalline solids, the following equations were
used to adjust sublimation and fusion enthalpies
to T 298.15 K and evaluate the vaporization
enthalpy
Sublimation ?crgHm(298.15 K)/(kJ?mol-1)?crgHm(T
m)0.750.15Cp(cr)/(J?mol-1?K-1)Tm/K-298.15
K/1000 Fusion ?crlHm(298.15 K)/(kJ?mol-1)?crlH
m(Tfus)(0.15Cp(cr)-0.26 Cp(l))/(J?mol-1?K-1)-9.8
3)Tfus/K-298.15/1000 Vaporization ?lgHm(298.
15 K) ?crgHm(298.15 K) - ?crlHm(298.15 K)
where Cp(cr), Cp(l) refer to the heat capacity
of the crystal and liquid, respectively
Acree, Jr. W. Chickos, J. S. Phase Transition
Enthalpy Measurements of Organic and
Organometallic Compounds. Sublimation,
Vaporization and Fusion Enthalpies From 1880 to
2009, J. Phys. Chem. Ref Data 2010, 39, 1-942.
47
A summary of the vaporization enthalpies for
diazines at T 298 K
58.7?1.456.5?2.0-2.2?2.4
59.6?1.4 61.1?1.1 1.5?1.8
67.3?1.6 71?1.9 3.7?2.5
Vap. Enth. Calc, kJ?mol-1 Vap. Enth. Lit,
kJ?mol-1 Difference, kJ?mol-1
46.4?2.0 53.5?0.4 7.1?2.0
79.71.3
78.42.0 -1.0?2.4
Vap. Enth. Calc, kJ?mol-1 Vap. Enth. Lit,
kJ?mol-1 Difference, kJ?mol-1
76.7?0.7 78.8?2.2 2.1?2.3
81.9?0.8 89.2?2.3 7.3?2.4
Difference in the strength of intermolecular
interactions between 1,2-diazines and their
isomeric counterparts is approximately 6-7
kJ?mol-1
Lipkind, D. Chickos, J. S. Study of the
Anomalous Thermochemical Behavior of 1,2-Diazines
by Correlation-Gas Chromatography J. Chem. Eng.
Data 2010, 55, 698-707
48
Vaporization Enthalpies Using Pyridine
Derivatives as Standards
  ?lgHm (298 K) (kJ?mol-1) ?lgHm (298 K) (kJ?mol-1) Lit ??lgHm (298 K) (kJ?mol-1)
1-MeIMI   48.6?2.2 55.61.3 6.8?3.6
1-EtIMI   51.4?2.3 66.03.9 14.6?3.7
1-Phpyrazole    63.5?2.0 70.23.4 6.73.9
1-BzIMI    72.3?3.8 83.01.0 10.83.9
1-EthylIMI
What structural factors influence this behavior ?
A Study of the Vaporization Enthalpies of Some
1-Substituted Imidazoles and Pyrazoles by
Correlation-Gas Chromatography, Lipkind, D.
Plienrasri, C. Chickos, J. S. J. Phys. Chem. B
2010, 114, 1695916967
49
Unknowns
Standards Set 1

Standards Set 2


50
Vaporization Enthalpies as a Function of
Standards Used
/kJ?mol-1 /kJ?mol-1 ??H
Standards Set 1 Transpiration Correlation gas chromatography
2-(N,N-dimethylamino)pyridine (1) 55.2?0.10 54.6?2.3 0.6?2.3
1,5-diazabicyclo4.3.0non-5-ene (3) 61.9?0.21 61.1?2.4 0.8?2.4
4-(N,N-dimethylamino)pyridine (2) 68.4?0.9a 61.3?2.5 7.1?2.7
1,8-diazabicyclo5.4.0undec-7-ene (4) 70.7?0.15 67.8?2.6 2.9?2.6
imidazo1,2-apyridine (6) 67.4?0.2 60.5?2.6 6.9?2.6
triazolo1,5-apyrimidine (5) 74.23.8b 63.7?2.7 10.5?4.7

Standards Set 2
imidazo1,2-apyridine (6) 67.4?0.23 67.1?4.6 0.3?4.6
triazolo1,5-apyrimidine (5) 74.23.8b 70.7?4.5 3.5?5.9
4-(N,N-dimethylamino)pyridine (2) 68.4?0.9a 69.6?3.8 1.2?3.9
All the compounds whose vaporization enthalpy is
in red are planar in the solid state all are
reproduced using various pyridazines and
imidazole derivatives as standards
The Vaporization Enthalpies of 2- and
4-(N,N-Dimethylamino)pyridine, 1,5-Diazabicyclo4.
3.0non-5-ene, 1,8-Diazabicyclo5.4.0undec-7-ene,
Imidazo1,2-apyridine and 1,2,4-Triazolo1,5-ap
yrimidine by Correlation Gas Chromatography,
Lipkind, D. Rath, N. Chickos, J.S. Pozdeev, V.
A. Verevkin, S. J. Phys. Chem. 2010, 55, 1628-35.
51
Table A (kJ?mol-1) Lit CGC Refa (kJ?mol-1) Lit CGC Refa (kJ?mol-1) Lit CGC Refa (kJ?mol-1) (D)b B benzene
C5H5N pyridine 40.20.1 40.02.3 1,25 0.22.3 2.19 B
C5H7N N-methylpyrrole 40.60.8 40.32.5 3,26 0.32.6 1.96 B
C5H11N N-methylpyrrolidine 34.20.7 36.62.4 3,27 -2.42.5 1.1 B
C6H7N 3-methylpyridine 44.50.2 44.52.0 1,14 0 2.0 2.4 B
C7H10N2 2-N,N-dimethylamino-pyridine 55.20.1 54.62.3 tw 0.62.3 1.92 B
C8H6N2 quinoxaline 56.52.0 58.71.9 2,30 -2.22.8 0.51 B
C8H11N 2,4,6-trimethylpyridine 51.01.0 50.42.9 1,19 -0.63.0 2.26 C
C9H7N quinoline 59.30.2 59.51.3 7,18 -0.21.3 2.24 B
C9H7N isoquinoline 60.30.12 60.11.3 7,18 -0.21.3 2.53 B
C10H8N2 2-2-bipyridyl 67.0?2.3 63.53.2 7 3.53.9 0.69 B
C10H9N 2-methylquinoline 62.60.1 62.81.3 7,17 -0.21.3 2.07 B
C12H10N2 trans azobenzene 74.71.6 74.9?0.7 3,28 -0.21.7 0 B
C13H9N phenanthridine 80.14 79.3?5.5 7,29 0.85.5 2.39 B
C13H9N acridine 78.63 78.21.3 7,29 0.41.3 2.29 B
Table B
C4H4N2 pyridazine 53.5?0.4 46.5?2.2 1,4 7.0?2.2 4.1 B
C4H6N2 N-methylimidazole 55.60.6 48.8?3.5 3,5,6 6.8?3.6 3.7d B
C4H6N2 N-methylpyrazole 48.01.3 41.62.9 twe,6 6.43.2 2.29 B
C7H10N2 4-N,N-dimethylaminopyridine 68.4?0.9 61.3?2.5 tw 7.12.7 4.33 B
C9H8N2 N-phenylpyrazole 70.23.4 63.5?2.9 3,25 6.74.5 2.0 B
C9H8N2 N-phenylimidazole 84.63.7 67.7?2.1 3,25 16.94.3 3.5 B
C12H8N2 benzoccinnoline 89.2?2.3 81.9?1.1 2,28 7.3?2.5 4.1 B
52
Summary Polarity seems to play a role Extensive
conjugation seems to be an important property All
compounds exhibiting enhanced intermolecular
interactions are planar the crystal structure
of 1,2,4-triazolo1,5-apyrimidine suggests the
presence of p- p stacking in the solid state

Since most of the compounds exhibiting stronger
intermolecular interactions examined so far
(pyridazines, imidazoles) seem to correlate with
each other, this suggests a common interaction
responsible for the enhanced intermolecular
interactions observed the origin of this
interaction has yet to be identified.
53

• 4) Measurement of Vapor Pressure Isotope Effects

54
Typical GC Plot of Deuterated and Undeuterated
Hydrocarbons
n-C7H16 n-C7D16 CH3C6H5 CD3C6D5 n-C8H18
n-C8D18 p-CH3C6H4CH3 o-CH3C6H4CH3
A typical gas chromatogram of a series of
labeled/unlabeled hydrocarbons run on an RTX-1
column at T 300 K in order of elution,
heptane-d16/heptane, toluene-d8/toluene,
octane-d18/octane, p-xylene-d10/p-xylene,
o-xylene-d10/o-xylene. The small peak with the
shortest retention time is methane.
55
Table. Deuterium Isotope Effects on Vaporization
Enthalpy
slope intercept
?slngHm(293 K) ?lgHm(298)/kJ.mol-1

kJ.mol-1 lit calc

hexane-d14 -3439.9 10.286 28.60
31.471.6 hexane -3472.3
10.308 28.87 31.52
31.741.6 cyclohexane-d12-3576.4 10.111
29.73 32.611.7 cyclohexane
-3601.7 10.127 29.94 33.12
32.831.7 heptane-d16 -4018.6 11.215
33.41 36.321.9 heptane -4058.5
11.252 33.74 36.57 36.661.9
toluene-d8 -4209.2 11.184 34.99
37.922.0 toluene -4215.1 11.169
35.04 37.99 37.972.0
?lgHm (298.15 K)/kJ.mol-1(1.009?0.056)?slngHm(293
K) (2.615?0.27), (r2 0.9946)
56
Measurement of Vapor Pressure Isotope Effects
A/T 3 BT 2
C/T 1 D Tb/K(calc)
Tb/K(exp) pH/pD
298.15 K hexane-d14 -17917619 -45199
-2909.62 9.429 339.3
341.9 0.909 heptane-d16
-5444070 -218518 -2758.60
9.220 368 371.4
0.892 p-xylene-d10 -71657137 282831
-4622.31 10.628 410.1
411.5 0.945 o-xylene-d10
-89591864 419760 -5088.30 11.06
415.7 417.6
0.937 toluene-d8 -42775261 88847
-3696.58 9.806 383.1
383.8 0.926
ln(p/po) A(T/K)-3 B(T/K)-2 C(T/K)-1 D
Zhao, H. Unhannanant, P. Hanshaw, W. Chickos,
J. S. The Enthalpies of Vaporization and Vapor
Pressures of Some Deuterated Hydrocarbons. Liquid
Vapor Pressure Isotope Effects J. Chem. Eng. Data
2008, 53, 15451556.
57
Graduate Students William Hanshaw Patamaporn
Umnahanant Hui Zhao Dmitry Lipkind Visiting
Graduate Students Manuel Temprado, Instituto de
Química Física Rocasolano, Madrid 28006,
Spain Visiting Faculty and Collaborators Maria
Victoria Roux, On leave from the Instituto de
Química Física Rocasolano, Madrid 28006,
Spain Sergey Verevkin, University of Rostock,
Rostock Germany
58
From Left to right Bill Hanshaw, Maria Victoria
Roux, Jim Chickos, Patanaporn Unmahanant (T),
Richard Heinz, and Hui Zhao
59
From left to right Rachel Maxwell, her friend,
Richard Heinz, Jim Chickos, Dmitry Lipkind, and
Darrell Hasty
60
separation between stacks 3.24 Å
61
Does a ring size play a role?

• All compounds used as standards were six-membered
  ring heterocycles.

  ?lgHm(298 K) (kJ?mol-1) ?lgHm(298 K) (kJ?mol-1) Lit
1-methylpyrrolidine   36.6?2.4 34.20.7
1-methylpyrrole   40.3?2.5 40.60.8
4-methylpyrimidine  43.8?2.6 44.2
2,5-dimethylpyrazine 47.6?2.7 47.0
2,4,6-trimethylpyridine  51.4?2.8 51.5
quinoline 59.2?3.0 59.31
1-methylindole  61.1?3.1 62.21.6