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N. AL-AWADI ET AL.
temperatures comparable to those used in the kinetic
investigations. The products of pyrolysis were swept
through the column using a stream of nitrogen and the
effluents were trapped in a glass coil surrounded by a
jacket of dry-ice. The material collected on the walls of
the trap (glass coil) was crystallized and analysed by
NMR spectroscopy.
Synthesis. Preparation of 4-arylideneimino-1,2,4 tria-
zol-3.2H)-ones. To a stirred and heated solution of
aminotriazole11 (1 g, 10 mmol) in ethanol (10 ml) and a
few millilitres of water was added a solution of
benzaldehyde or substituted benzaldehyde (10 mmol) in
ethanol (5 ml). The resulting solution was refluxed for 1–
2 h and the precipitated product was filtered hot and
recrystallized from ethanol or dioxane in 80–85% yield.
The following compounds were thus prepared.
Scheme 3
formation of 2-hydroxytriazoles, a product of the same
reaction of the latter compounds.9,10
4-Benzylideneimino-1,2,4-triazol-3(2H)-one
(1),
white powder (m.p. 189–190°C (EtOH), lit.11 m.p.
1
182°C. H NMR (DMSO): ꢀ 7.49–7.57 (m, 3H, Ar H),
7.78–7.83 (m, 2H, Ar H), 8.43 (s, 1H, triazole H), 9.44 (s,
1H, CH=
N), 12.10 (s, 1H, NH). 13C NMR: ꢀ 128.6,
EXPERIMENTAL
130.0, 132.4, 134.0, 136.6, 151.6, 155.1. Anal. Calcd for
C9H8N4O (188): C 57.45, H 4.25, N 29.78. Found: C
Kinetic studies. Reaction set-up. Preliminary kinetic
results were obtained on a system featuring a Eurotherm
093 pyrolysis unit coupled to a Perkin-Elmer Sigma 115
gas chromatograph. The kinetic data reported are from a
reactor set-up including an HPLC system (Bio-Rad
Model 2700) fitted with a UV–VIS detector (Bio-Rad
Model 1740) and an LC-8 column (25 cm  4.6 mm i.d.,
5 mm film thickness) (Supelco) and a CDS custom-made
pyrolysis unit for the thermolysis reactions. The pyrolysis
tube was jacketed by an insulating aluminium block fitted
with a platinum resistance thermometer and a thermo-
couple connected to a Comark microprocessor thermo-
meter.
57.90, H 4.36, N 29.39%. MS: m/z 188 (M ). IR (cmÀ1):
3215, 3126, 1720, 1700.
4-p-Chlorobenzylideneimino-1,2,4-triazol-3(2H)-one
1
(2), white crystals, m.p. 225–226°C (EtOH). H NMR
(DMSO): ꢀ 7.58 (dd, 2H, Ar H), 7.84 (dd, 2H, Ar H), 8.40
(s, 1H, triazole H), 9.45 (s, 1H, CH=N), 12.10 (s, 1H,
NH). 13C NMR: ꢀ 130.0, 130.3, 132.6, 135.9, 137.1,
151.6, 154.0. Anal. Calcd for C9H7ClN4O (222.5): C
48.54, H 3.15, N 25.16. Found: C 48.82, H 3.44, N
24.62%. MS: m/z 222, 224 (M ). IR (cmÀ1): 3144, 1717,
1700.
4-p-Methylbenzylideneimino-1,2,4-triazol-3(2H)-one
1
(3), pale white powder, m.p. 222–223°C (EtOH). H
Kinetic runs and data analysis. Aliquots (0.2 ml) of very
dilute solutions (ppm) of neat substrates in acetonitrile as
solvent and chlorobenzene as internal standard were
pipetted into the reaction tube, which was then sealed
under vacuum (0.28 mbar), and the tube was placed
inside the pyrolyser for 600 s at a temperature where 10–
20% pyrolysis was deemed to occur. The contents of the
tube were analysed using the HPLC probe.
At least three kinetic runs were repeated for each 5–
10°C rise in temperature of the pyrolyser and for the
same time interval until 90–95% pyrolysis was achieved.
The rates were followed over a temperature range not less
than 50 K, and the rate coefficients were calculated using
the expression for a first-order reaction: kt = lna0/a. The
Arrhenius parameters were obtained from a plot of log k
vs 1/T (K).
NMR (DMSO): ꢀ 2.37 (s, 3H, CH3), 7.31 (d, 2H, Ar H),
7.68 (d, 2H, Ar H), 8.38 (s, 1H, triazole H), 9.38 (s, 1H,
CH=
N), 12.07 (s, 1H, NH). 13C NMR: ꢀ 22.0, 128.6,
130.1, 131.3, 136.7, 142.5, 151.7, 155.1. Anal. Calcd for
C10H10N4O (202): C 59.41, H 4.95, N 27.72. Found: C
59.82, H 4.99, N 27.38%. MS: m/z 202 (M ). IR (cmÀ1):
3374, 3150, 1707.
4-p-Methoxybenzylideneimino-1,2,4-triazol-3(2H)-
one (4), creamy white flakes, m.p. 221–222°C (EtOH).
1H NMR (DMSO): ꢀ 3.83 (s, 3H, CH3), 7.07 (d, 2H, Ar
H), 7.76 (d, 2H, Ar H), 8.35 (s, 1H, triazole H), 9.34 (s,
1H, CH=
N), 12.03 (s, 1H, NH). 13C NMR: ꢀ 56.3, 115.4,
126.4, 130.4, 136.6, 151.8, 155.2, 162.8. Anal. Calcd for
C10H10N4O2 (218): C 55.05, H 4.59, N 25.68. Found: C
55.29, H 4.74, N 25.15%. MS: m/z 218 (M ). IR (cmÀ1):
3149, 3139, 1707, 1607.
Product analysis. Flow technique. Solutions of sub-
strates in chlorobenzene were passed down a 1 m reactor
column packed with helices. The column was heated to
Preparation of 4-arylideneimino-3-mercapto-1,2,4-
triazoles. A mixture of the 4-amino-3-mercapto-1,2,4-
triazole12 (10 mmol) and benzaldehyde or its substituted
Copyright 2001 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2001; 14: 521–525