2434 Journal of Chemical and Engineering Data, Vol. 52, No. 6, 2007
Table 4. Structural Contributions to Calculate ∆T in Equation 1510
Figure 4. Integral plot of 2-amino-3-methylpyridine against the standard
compound: line 1, 3-methylpyridine; line 2, benzene.
∆
vapH(Tb) into eq 13, the enthalpy of vaporization of 2-amino-
3-methylpyridine can be calculated at any selected temperature.
Finally, taking T ) 298.15 K to eq 13, ∆vapH(298.15 K) was
calculated to be 63.66 kJ‚mol-1, which is well in agreement
with the values obtained from Othmer’s method. The deviations
were 1.72 % and -0.48 % for 3-methylpyridine and benzene
as standard substances, respectively.
To validate the value of ∆vapH(298.15 K), another substance,
benzene, was also chosen as the standard substance, whose
∆
vapH′(298.15 K) was reported to be 33.92 kJ‚mol-1 15
, and its
Antoine constants are also reported in the literature.16 The plot
of log p against log p′ was shown in Figure 4 (line 2), and the
regressive equation was as follows
Conclusion
log p ) 1.886 log p′ - 4.1116
(12)
The vapor pressures of 2-amino-3-methylpyridine were
determined in the temperature range from (328.70 to 499.88)
K using the boiling point method. The data were represented
by the Antoine equation with an absolute average deviation of
0.30 %. On the basis of the values of Antoine constants, the
So the enthalpy of vaporization ∆vapH(298.15 K) for 2-amino-
3-methylpyridine derived using benzene is 63.97 kJ‚mol-1
,
which is close to that obtained with 3-methylpyridine (62.58
kJ‚mol-1).
∆
vapH(Tb) for 2-amino-3-methylpyridine was calculated by the
Verification of ∆vapH(298.15 K) for 2-Amino-3-methylpy-
ridine. The enthalpy of vaporization at the normal boiling point
Clausius-Clapeyron equation. The ∆vapH(298.15 K) for 2-amino-
3-methylpyridine was also estimated by Othmer’s method using
3-methylpyridine and benzene as the standard substance,
respectively. The results showed that there was a small deviation
between the estimated values and those values derived from
different standard substances.
∆
vapH(Tb) can be extended to a desired temperature, using the
well-known relation reported by Watson.17 To further verify
the reliability of Othmer’s method, the value of ∆vapH(298.15
K) for 2-amino-3-methylpyridine can be estimated independently
according to the value of ∆vapH(Tb).
The Watson relation used to estimate ∆vapH(T) at any
temperature for a pure substance is as follows
Literature Cited
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of ibuprofen heterocyclic amides and investigation of their analgesic
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(3) Barreca, M. L.; Balzarini, J.; Chimirri, A. Design, sythesis, structure-
activity relationships, and molecular modeling studies of 2,3-diaryl-
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45, 5410-5413.
n
1 - T/Tc
1 - Tb/Tc
∆
vapH(T) ) ∆vapH(Tb)
(13)
(
)
where Tc is the critical temperature; Tb is the normal boiling
point; and ∆vapH(Tb) is the enthalpy of vaporization at Tb.
Viswanath and Kuloor18 recommended that n in eq 13 can
be obtained by the expression
(4) Abramovitch, R. A.; Helmer, F.; Saha, J. G. On the mechanism of
the amination of pyridine. Chem. Ind. 1964, 659-660.
(5) Abramovitch, R. A.; Helmer, F.; Saha, J. G. Aromatic substitution
part VIII. Some aspects of the mechanism of the tschitschibabin
reaction. Can. J. Chem. 1965, 43, 725-731.
10
∆
vapH(Tb)
n ) 0.00264
+ 0.8794
(14)
(
)
RTb
(6) Buckingham, J.; Donaghy, S. M. Dictionary of Organic Compounds,
5th ed.; Chapman and Hall: New York, 1982.
The boiling point of 2-amino-3-methylpyridine is 496.06 K.
Taking Tb and ∆vapH(Tb) to eq 14, n is calculated to be 0.3967.
To estimate the ∆vapH(298.15 K) of 2-amino-3-methylpyri-
dine, the critical temperature of 2-amino-3-methylpyridine must
be known. However, no data on this compound are available.
Tc can be estimated by the equation proposed by Riedel et al.:
10 Tc ) Tb/θ. In this study, the Lydersen method19 was used to
estimate θ
(7) Hala, E.; Pick, J.; Fried, V.; Vilim, O. Vapor-Liquid Equilibrium;
Pergamon Press: New York, 1958; pp 148-149.
(8) Bridgeman, O. C.; Aldrich, E. W. Vapor pressure tables for water. J.
Heat Transfer 1964, 279-286.
(9) Jack, M. C. Correlation and prediction of the vapor pressure of pure
liquids over large pressure range. Ind. Eng. Chem. Process Des. DeV.
1983, 22, 313-322.
(10) Reid, R. C.; Prausnitz, J. M.; Poling, B. E. The Properties of Gases
and Liquids, 4th ed.; McGraw-Hill: New York, 1987.
(11) Boublik, T.; Fried, V.; Hala, E. The Vapor Pressures of Pure
Substances: Selected Values of the Temperature Dependence of the
Vapor Pressures of Some Pure Substances in the Normal and Low-
Pressure Region, 2nd ed.; Elsevier: Amsterdam ,1984.
(12) Fang, W.-J.; Lei, Q.-F.; Lin, R.-S. Enthalpies of vaporization of
petroleum fractions from vapor pressures measurements and their
correlation along with pure hydrocarbons. Fluid Phase Equilib. 2003,
205, 149-161.
θ ) 0.567 +
∆T - ( ∆T)2
(15)
∑
∑
where ∑ ∆T was obtained by adding the contributions listed in
Table 4.
Taking ∑ ∆T to eq 15, θ could be estimated to be 0.667.
Finally, Tc was calculated to be 743.72 K. Taking Tb, Tc, and