2182 J. Agric. Food Chem., Vol. 53, No. 6, 2005
Chandra et al.
Table 1. Reactions of O,O-Diethylchlorophosphate with Piperazine Dithiosemicarbazone
reactants taken (g)
found (calcd) %
substituted piperazine
dithiosemicarbazonea
molar
ratio
reflux
time (h)
product
color, yield (%)
(C2H5O)2POCl
1.8
C
H
N
S
BCPTH2 (2.3)
BPPTH2 (2.0)
BMPTH2 (2.3)
BNPTH2 (2.5)
BOCPTH2 (2.3)
2:1
2:1
2:1
2:1
2:1
10
10
10
16
16
[{
[{
[{
[{
[{
(C2H5O)2 PO
yellowish brown, 59
}
2 (BCPT)]
44.00
(44.74)
49.20
(49.26)
48.30
(48.38)
43.41
(43.51)
44.60
5.12
(5.09)
5.80
(5.90)
5.81
(5.94)
4.92
(4.95)
5.10
11.02
(11.18)
12.23
(12.30)
11.0
(11.28)
14.44
8.51
(8.53)
9.30
(9.39)
8.52
(8.60)
8.18
1.8
1.8
1.8
1.8
(C2H5O)2PO
}2(BPPTH)]
yellowish brown, 61
(C2H5O)2 PO
yellow, 52
(C2H5O)2 PO
yellow, 55
}
2 (BMPT)]
2 (BNPT)]
}
(14.50)
11.04
(8.29)
8.44
(C2H5O)2
O}2(BOCPT)]
yellow, 60
(44.74)
(5.09)
(11.18)
(8.53)
a BCPTH2, 1,4-bis(4-chlorobenzaldehyde)piperazine dithiosemicarbazone; BPPTH2, 1,4-bis(benzaldehyde)piperazine dithiosemicarbazone; BMPTH2, 1,4-bis(4-methoxy-
benzaldehyde)piperazine dithiosemicarbazone; BNPTH2, 1,4-bis(4-nitrobenzaldehyde)piperazine dithiosemicarbazone; BOCPTH2, 1,4-bis(2-chlorobenzaldehyde)piperazine
dithiosemicarbazone.
Table 2. 1H NMR Data (
Containing Piperazine Dithiosemicarbazones
δ Scale) of Organophosphorus Derivatives
MATERIALS AND METHODS
The reactions of O,O-diethylchlorophosphate were carried out under
inert atmosphere and anhydrous conditions. Special precautions were
taken to exclude moisture from the apparatus and chemicals as the
starting materials (O,O-diethylchlorophosphate) and reactions were
susceptible to hydrolysis. Glass apparatus with interchangeable joints
were used throughout the work. All of the organic solvents used were
of analytical reagent grade. The solvents were purified and dried using
the method described in the literature (8). O,O-Diethylchlorophosphate
was prepared (9) by adding a solution of pyridine, absolute ethanol,
and benzene dropwise to an ice-cooled solution of phosphorus
oxychloride in benzene at temperature below 20 °C. After 3 h of stirring,
the pyridine hydrochloride was filtered off. The product, after distil-
lation, was obtained as a colorless liquid (bp 60-63 °C/2.5 mmHg).
All reactions were carried out in the hood. A hood is a specially
constructed workplace that has, at the least, a powered vent to suck
noxious fumes outside. The details of analysis and physical measure-
ments were the same as reported earlier (6).
For antifungal activity, all compounds were tested against all test
fungi by the food poison technique (10) at three concentrations (10,
100, and 1000 ppm). For this, the desired amount of chemical was
dissolved in 0.5 cm3 of solvent and mixed with the culture medium on
the basis of the volume of medium in each Petri plate (80 mm diameter).
Oatmeal agar medium was used for all test fungi. In controls, the same
amount of medium containing the requisite amount of solvent was
poured in place of test chemicals. A mycelial disk (5 mm diameter)
obtained from the periphery of 2-week-old cultures was taken and
transferred to the center of each Petri plate. Plates were incubated for
7 days at 28 ( 2 °C. Each treatment was repeated three times, and the
inhibition was recorded relative to percent mycelial inhibition calculated
using the formula
compound
C4H4N2 phenyl group
3.45 (s) 7.30 (s)
C2H5
CH3
[
[
[
[
[
{
{
{
{
{
(C2H5O)2 PO
}
}
}
}
}
2 (BPPT)]
2 (BOCPT)] 3.48 (s) 7.60
2 (BCPT)]
2 (BMPT)]
2 (BNPT)]
2.50 (t), 4.15 (q)
(C2H5O)2 PO
(C2H5O)2 PO
(C2H5O)2 PO
(C2H5O)2 PO
−
−
−
−
7.75 (m) 2.65 (t), 4.00 (q)
7.72 (m) 2.55 (t), 4.25 (q)
7.85 (m) 2.60 (t), 4.20 (q) 3.40 (s)
7.82 (m) 2.58 (t), 4.25 (q)
3.47 (s) 7.62
3.45 (s) 7.72
3.46 (s) 7.70
according to Figure 1. The methods used for the preparation
and isolation of these compounds gave materials of good purity
as supported by their analyses and TLC. The elemental analyses
and physical properties of the organophosphorus derivatives are
given in (Table 1). The organophosphorus derivatives are found
to be soluble in chloroform, dimethylformamide, tetrahydrofu-
ran, and dimethyl sulfoxide. All of these compounds are yellow
or brown in color. The compounds melt in the temperature range
of 145-205 °C.
Infrared Spectra. These thiosemicarbazones can exist either
as a thione or the thiol tautomeric forms or as an equilib-
rium mixture of both forms, because they have a thioamide,
-NHsC(dS) function. The IR spectra in the solid state do not
show any ν(S-H) band but exhibit a medium ν(N-H) band at
∼3150 cm-1, indicating that in the solid state they remain
mainly in the thione form. However, in solution they readily
convert to the thiol tautomeric form with the concomitant
formation of phosphorus complex by the protonated mercapto
form of the ligands. This is indicated by the the absence of a
-NH band in the organophosphorus derivatives. The IR spectra
of the organophosphorus derivatives also show a new medium-
intensity band at ∼700 cm-1 owing to conversion (11) of CdS
to CsS-. The formation of a bond between the thiol sulfur and
phosphorus is supported (6) by the appearance of band at ∼620
cm-1, assigned to ν(P-S-C).
The spectra of dithiosemicarbazones show bands at ∼1570-
1560 cm-1 due to (11) ν(CdN), which remain almost at the
same position in the corresponding organophosphorus deriva-
tives, suggesting noninvolvement of the azomethine nitrogen
atom in bond formation with phosphorus. However, the loss
of N(2)H’s from the two dithiosemicarbazone moieties, by
thione-thiol tautomerism, produces an additional carbon-
nitrogen double bond N(2)dC(S), which is indicated by the
appearance of a band at ∼1590 cm-1 in the organophosphorus
derivatives. In addition, all organophosphorus derivatives show
bands at ∼1015-1030 and ∼1280-1295 cm-1 assignable (6)
to ν(PsOsC) (alkyl) and ν(PdO) vibrations, respectively.
[(dc - dt)/dc] × 100
where dc is the average diameter of the mycelial colony of the control
and dt is the average diameter of the mycelial colony of the treatment.
Reactions of O,O-Diethylchlorophosphate with Piperazine Dithio-
semicarbazones. O,O-Diethylchlorophosphate was added to a solution
of the appropriate piperazine dithiosemicarbazone in 2:1 molar ratio,
respectively, in methanol (∼40 cm3) in the presence of pyridine (5 cm3),
and the reaction mixture was refluxed for 10-18 h. The solid product
was separated out and filtered and crystallized from acetone.
RESULTS AND DISCUSSION
Reactions of O,O-diethylchlorophosphate with thiosemicar-
bazones derived by the condensation of piperazine dithiosemi-
carbazide with benzaldehyde, 2-chlorobenzaldehyde, 4-chlo-
robenzaldehyde, 4-nitrobenzaldehyde, or 4-methoxybenzaldehyde
have been carried out in methanol in the presence of pyridine,
and a variety of organophosphorus derivatives have been isolated