Thermolysis of hydrogen sulphate, nitrate and perchlorate salts of diphenylamine. Part LXVIII

Article abstract of DOI:10.1007/s10973-009-0230-1

Hydrogen sulphate, nitrate and perchlorate salts of diphenylamine have been prepared and characterized by elemental, spectral and gravimetric analyses. Thermal decomposition of these salts has been evaluated by TG (static air) and DSC (inert atmosphere). The proton transfer reaction plays a major role during thermolysis of these salts. The diphenylammonium hydrogen sulphate under thermal and microwave irradiation forms 4-(phenylamino) benzenesulphonic acid by sulphonation process, whereas nitrate and perchlorate salts do not form corresponding nitro and perchloro derivatives, rather they ignite and explode, respectively, to form gaseous products along with a residual carbon .

Full text of DOI:10.1007/s10973-009-0230-1

J Therm Anal Calorim (2010) 102:723–728
DOI 10.1007/s10973-009-0230-1
Thermolysis of hydrogen sulphate, nitrate and perchlorate salts
of diphenylamine. Part LXVIII
Inder Pal Singh Kapoor Æ Manisha Kapoor Æ
Gurdip Singh
Received: 19 March 2009 / Accepted: 16 June 2009 / Published online: 6 August 2009
´
´
Ó Akademiai Kiado, Budapest, Hungary 2009
Abstract Hydrogen sulphate, nitrate and perchlorate salts
of diphenylamine have been prepared and characterized
by elemental, spectral and gravimetric analyses. Thermal
decomposition of these salts has been evaluated by TG
(static air) and DSC (inert atmosphere). The proton transfer
reaction plays a major role during thermolysis of these
salts. The diphenylammonium hydrogen sulphate under
thermal and microwave irradiation forms 4-(phenylamino)
benzenesulphonic acid by sulphonation process, whereas
nitrate and perchlorate salts do not form corresponding
nitro and perchloro derivatives, rather they ignite and
explode, respectively, to form gaseous products along with
a residual carbon .
temperatures to give oxygen as one of the major products
[17–20]. Further, perchlorates are generally more violent in
their explosive behavior as compared to nitrate salts [21–
24]. The proton transfer process was considered as a pri-
mary and rate controlling step in the thermal decomposi-
tion of these salts.
Yet, a lot of work has been done on salts of mono and
disubstituted arylamines, whose thermal stability depends
upon the nature of substituted groups, but no work has so
far been done on diphenylamine (a weak secondary amine).
Based on our ongoing research programmes, we report
here the preparation, characterization and thermolysis of
hydrogen sulphate, nitrate and perchlorate salts of
diphenylamine.
Keywords Diphenylamine ꢀ Thermolysis ꢀ
Proton transfer ꢀ Ignition/explosion
Experimental
Introduction
Materials
Extensive studies have been made on preparation, charac-
terization and thermolysis of ring substituted arylammo-
nium sulphates [1–7], nitrates [8–11], perchlorates [12–15]
salts. It has been observed that sulphate salts when heated
under vacuum were found to form aminobenzenesulphonic
acids, which find applications [16] in organic synthesis,
dyestuffs, sulpha drugs and detergents.
Diphenylamine (s.d.fine) was purified by usual methods,
conc. H2SO4 (Merck) 70% HNO3 (Merck), 70% HClO4
(Merck), silica gel of TLC grade (Ranbaxy), Iodine
(s.d.fine) and Nitron (CDH) were used as received.
Preparation and characterization
The nitrate and perchlorate salts find applications in
explosive and propellant formulations. Nitrates are pow-
erful oxidizing agent and decompose at elevated
The diphenylammonium hydrogen sulphate (DPAHS) was
prepared by reacting diphenylamine with excess of conc.
H2SO4 at room temperature (Scheme 1). Readily formed
white leaflike crystals, after washing with diethylether to
remove amine and excess of sulphuric acid were recrys-
tallized under vacuum. The purity was checked by thin
layer chromatography (TLC) and further characterized by
elemental and spectral analyses.
I. P. S. Kapoor ꢀ M. Kapoor ꢀ G. Singh (&)
Department of Chemistry, DDU Gorakhpur University,
Gorakhpur 273009, India
e-mail: gsingh4us@yahoo.com
123

724
I. P. S. Kapoor et al.
_
H
data (Table 2). Moreover, this acid gave effervescences
with aq. NaHCO3.
HSO4
+
N
H2SO4
HNO
Conc.
DPAHS
H
H
_
NO3
H
Elemental and spectral analyses
+
+
N
N
cold20
%
3
..
DPAN
DPAP
H
H
The C, H, N analyses were done with elemental Vario EL
(II) Carlo Erba 1108 instrument. FT-IR spectra were taken
with Perkin–Elmer RXI spectrometer in the range of
4,000–450 cm-1. The FAB mass spectra were recorded on
a Jeol SX 102/DA. NMR spectra were taken in Brucker
500 avance (field-500 MHz).
_
ClO4
20
N
H
HClO
%
cold
4
Scheme 1 Preparation of DPAHS, DPAN and DPAP from
diphenylamine
Thermal studies
Diphenylammonium nitrate (DPAN) and diphenylam-
monium perchlorate (DPAP) were prepared by the reaction
of diphenylamine (in ether), with excess of cold 20%
HNO3 and 20% HClO4, respectively (Scheme 1). Both
nitrate and perchlorate salts were precipitated out after
keeping the reaction mixture at room temperature for about
2 h. After washing with absolute alcohol, crystal were
vacuum dried, Further their purity was checked by TLC
and characterized by a gravimetric method using nitron
reagent [25] (Table 1).
Non-isothermal TG
Non-isothermal TG of sulphate, nitrate and perchlorate
salts (wt. 20 mg, 100–200 mesh) were undertaken in a
static air at a heating rate of 5 °C min-1 using homemade
TG apparatus [27]. The accuracy of the furnace was
1 °C. A round bottom gold crucible was used as a sample
holder. The fraction decomposition (a) has been plotted
against temperature (°C) and thermograms are shown in
Fig. 1.
The sample of DPAHS was heated at 90 °C in a tube
furnace [26] (TF) for 17 min under reduce pressure
(400 mm Hg) and kept under 700 Watt for 3 min in a
commercial household microwave oven (MS 1921 HE LG
electronics private Ltd.,) gave a gray residue. The residue
obtained then washed with double distilled water and dried
under vacuum to get the gray amorphous solid and purity
was checked by TLC. The residue then identified as 4-
(phenylamino) benzenesulphonic acid [4-(PA) BSA] by
physical parameters, TLC, elemental (Table 1) and spectral
Dynamic TG analyses on the salts has also been done
by using Perkin Elmer instrument at a heating rate of
10 °C min-1 (wt. 10.5 mg, 100–200 mesh, under nitrogen
atmosphere) and the thermograms are shown in Fig. 2.
Ignition delay (Di)/explosion delay (DE) measurements
The ignition delay (Di) of DPAN and explosion delay (DE)
of DPAP were undertaken, in the temperature range
Table 1 Physical parameters, TLC, gravimetric analysis of hydrogen sulphate, nitrate and perchlorate salts of diphenylamine
Compound Molecular weight Structure
Colour
MP/°C TLC Spot colour Rf
Nitrate and perchlorate/%
Experimental Theoretical
H
_
DPAHS
267
White amorphous 120
a:b:c Yellow
a:b:c Yellow
0.84
0.93
–
–
HSO4
+
N
H
H
4(PA) BSA 250
Gray
80
–
–
N
..
SO3H
H
N
H
_
DPAN
DPAP
169
232
White amorphous 52 (d) a:b:d Yellow
White amorphous 82 (d) a:b:d Gray
0.72 0.1610
0.62 0.1521
0.1616
NO3
+
+
_
H
N
H
0.1530
ClO4
Eluent: a = H2O, b = CHCl3, c = n BuOH, d = Et2O; locating reagent: iodine
123

Thermolysis of hydrogen sulphate, nitrate and perchlorate salts of diphenyl amine
725
Table 2 Elemental and spectral parameters for DPAHS and 4-(PA) BSA
Compound % Observed (calculated)
IR/cm-1
m/z
Chemical shift/d
C
H
N
1HNMR
DPAHS
53.9 (5.29) 4.86 (4.82) 5.24 (5.2) 3,433 mN–H str, 2,890 (m) C–H str,
1,322 C–H bend,
169.8, 335, 92.2 6.5–7.5, 2.5 (–NH2)
-
1,592 (C=C), 616 (s) HSO4
4-(PA) BSA 57.6 (56.8) 4.8 (5.5)
5.6 (4.9) 3,435 (s) mN–H str, 3,023 (m) C–H str,
1,522 (s) C–H bend, 750 (v,s) C–H,
1,300 (s) C–N, 1,196 (s) and 601.4 (s) SO3H
170.3, 128
6.5–7.2, 5.3, 2.5 (–NH2)
explosion delay (DE). Each run was repeated three times
and mean values are reported in Table 3. The Di or DE data
were found to fit separately in following equation [28–31]
D ¼ A expðEa=RTÞ
D ¼ Di for nitrate and DE for perchlorate
where Ea is the activation energy for thermal ignition/
explosion, A the preexponential factor and T the absolute
temperature. Ea assessed by above equation along with the
correlation coefficient (r) are given in Table 3. Plots of
D vs. 1/T are presented in Fig. 3.
Fig. 1 Nonisothermal TG of diphenylammonium salts
230–330 °C by taking the sample in an ignition tube
(4.5 cm length and 0.4 cm diameter) and the time interval
between the insertion of the ignition tube into the TF and
the moment of an ignition/explosion noted with the help of
a stopwatch, gave the value of ignition delay (Di) Similarly
moment of an audible explosion gave the value of
Results and discussion
The C, H, N data (Table 2) confirms beyond doubt the
formation of DPAHS. The IR data (Table 2) shows the
bands in the region 3433.97 cm-1 mN–H str, 2,890 (m) for
C–H str, 1,322 (w) C–H bending and 616 (s) m HSO4-; MS,
m/z 169.8 = 170, 333.5, and 92 are due to (C6H5)2 ?NH2,
(C6H5N)2, and ?NH-Ph species respectively; 1HNMR
(DMSO) d 6.8–7.6 is due to the three types of interacting H
nuclei. A peak at d 2.5 is due to some nondeuterated
DMSO molecules. The observed and experimental value
by nitron estimation for nitrate and perchlorate are char-
acterized within experimental error (Table 1). Non iso-
thermal TG of DPAHS in static and inert atmosphere
shows that mass loss occurs in two steps. Step I is the solid
state decomposition of salts to form corresponding sul-
phonic acid and step II is concerned with the decomposi-
tion of acid. In DPAHS, there is 13% weight loss due to
evolution of water of crystallization and a water molecule
during sulphonation. The plateau in region 200–250 °C
shows the stability of acid in that particular temperature
range. The DSC shows two endotherms at 149 °C (elimi-
nation of a molecule of water) and at 241 °C (due to sul-
phonation). It has been observed that heating DPAHS in air
at high temperature gave bluish black product which con-
tain 4-(PA) BSA. This is presumably due to formation of
quinonoid like material arising from hydroxylation,
Fig. 2 TG, DTG and DSC curves of DPAHS, DPAN and DPAP salts
123

726
I. P. S. Kapoor et al.
Table 3 Ignition delay (Di), explosion delay (DE) and activation energy (Ea) for thermal ignition/explosion for DPAN and DPAP (Di or DE/s at
temperature 1 °C)
Compound
230 °C
250 °C
270 °C
290 °C
310 °C
330 °C
Ea/kJ mol-1
r
DPAN
DPAP
DNI
92
78
52
57
35
45
29
36
24
31.8
36.7
0.9951
0.9922
DNE
DNE
DNI Did not ignite, DNE did not explode, r correlation coefficient
5
a water molecule (confirmed by Karl Fisher Reagent).
Moreover, DPAHS under microwave irradiation for 3 min
yields too 4-(PA) BSA. The acid was confirmed by TLC,
elemental, chemical and spectral analyses (Table 2) and C,
H, N data are within experimental error; IR (cm-1) peaks at
3,433 (s) mN–H str, 3,023 (m) C–H str, 1,522 (s) C–H
bending, 750 (v, s) C–H, 1,300 (s) C–N, 1,196 (s) and 601.4
(s) for SO3H; m/z at 170 and 128 are due to respectively
diphenylammonium ion and a dimer (5-cyclopentadienyl-
4
DPAN
DPAP
3
0.0016
0.0017
0.0018
0.0019 0.002
1
1/ T
1,3-cyclopentadiene); HNMR (DMSO); d 2.5 is may be
due to two aromatic protons ortho with the –CSO3H moiety
and 6.6–7.2 ppm is due to another four interacting H nuclei.
The TG data taken in inert and static air (Figs. 1, 2)
reveals that nitrate and perchlorate both show incomplete
mass loss as they are highly fuel rich and a black residue
remains in the crucible after completion of decomposition
followed by ignition or explosion. During TG the DPAN
were found to ignite while DPAP explodes; DSC of nitrate
Fig. 3 Graph of ln Di vs. 1/T (DPAN) and ln DE vs. 1/T (DPAP)
oxidation and polymerization of amino compounds. In
order to prepare the 4-(PA) BSA in pure form, it was
thought best to heat the DPAHS under low pressure. Thus,
the sample of DPAHS heated at 90 °C for 17 min at
400 mm Hg pressure, was found to contain 4-(PA) BSA and
H
H
N
OC
N
..
90
Sulphonation
Sulphonation
H O
+
..
H2SO4
H2SO4
,
2
PT
min.
+
17
_
H
HSO4
+
SO3H
N
H
Condensed phase
H
H
N
..
N
H O
+
DPAHS
..
2
+
Watt
700
3
,
min.
PT
SO3H
Condensed phase
H
H
_
NO3
+
N
PT
ORR
N
H
..
Ignition
+
HNO3
Gaseous product
+
Carbon
Condensed phase
H
DPAN
_
H
ClO4
+
N
..
N
PT
ORR
Gaseous product
+ Carbon
Explosion
HClO4
+
H
DPAP
Condensed phase
Scheme 2 Thermolytic pathways of diphenylammonium hydrogen sulphate, nitrate and perchlorate salts. PT Proton transfer, ORR oxidation–
reduction reactions
123

Thermolysis of hydrogen sulphate, nitrate and perchlorate salts of diphenyl amine
727
Acknowledgements Thanks are due to Head, Chemistry Depart-
ment for laboratory facilities, to CDRI Lucknow, for elemental and
spectral analyses, IIT Roorke, for TG and DSC analyses. Authors are
also thankful to UGC for financial assistance to Manisha Kapoor and
CSIR for Emeritus Scientist to Dr. Gurdip Singh.
show one endotherm at 98 °C (phase transition) and one
exotherm at 225 °C; while perchlorate show two endo-
therm at 75 °C (melting) and 120 °C (phase transition) and
one exotherm at 200 °C. The exotherms may be due to
-
oxidation reduction reactions between oxidizer part (NO3
-
or ClO4 and fuel part (diphenylamine) leading to igni-
)
tion/explosion to produce gaseous products along with a
residual carbon.
References
The thermolysis of diphenylammonium hydrogen sul-
phate, nitrate and perchlorate may be illustrated in
Scheme 2. The overall decomposition process of these salts
seems to commence by the transfer of a proton from diph-
enylammonium ion to SO4-, NO3- and ClO4- ions forming
diphenylamine and respectively, H2SO4, HNO3 and HClO4
molecule in the condensed phase prior to sulphonation
(DPAHS), ignition (DPAN) and explosion (DPAP). A
molecule of water will be given off as vapour at higher
temperature in the case of sulphates along with the forma-
tion of solid 4-(PA) BSA, whereas nitrate and perchlorate,
respectively get ignite and explode at higher temperatures.
Oyumi and Brill et al. [32] have also reported that salts
with O/H \ 1 release NH3 (g) while those with O/H [ 1
do not release NH3 (g). Nambier et al. [33] have also
reported the evaluation of NH3 as a dissociation product of
methylammonium perchlorates. Since for DPAHS, DPAN
and DPAP O/H \ 1 hence ammonia may be one of the
decomposition products.
1. Singh G, Kapoor IPS. Kinetics of thermal decomposition of
dianilinium sulphate. J Chem Soc Perkin Trans II. 1989;2155–58.
2. Singh G, Kapoor IPS, Jain M. Kinetics of thermal decomposition
of aryl-ammonium sulphate. Part 2: m-ditoluidinium sulphate. J
Chem Soc Perkin Trans II. 1993;1521–24.
3. Singh G, Kapoor IPS, Jain M. Sulphonation of arylamines. Part
III: solid state synthesis of 2-amino-5-methyl benzene sulphonic
acid. Indian J Chem. 1996;35B:369–72.
4. Singh G, Kapoor IPS, Jain M. Sulphonation of arylamines. Part 6:
thermal decomposition of ring substituted aryl ammonium sul-
phates. Thermochim Acta. 1997;292:135–43.
5. Singh G, Kapoor IPS, Singh J. Sulphonation of arylamines. Part
VII: kinetics of thermal decomposition of tetramethyldianilinium
sulphates. Indian J Chem. 1997;36B:590–5.
6. Singh G, Kapoor IPS, Singh J. Sulphonation of aryl amines. Part
5: preparation and thermal decomposition of di-m-chloroanilini-
um sulphate. Indian J Eng Mater Sci. 1998;5:334–8.
7. Kapoor IPS, Srivastava P, Singh G. Preparation, characterization
and thermal decomposition of phenylene diammonium sulphate
salts. J Therm Anal Calorim. 2008;92(2):553–8.
8. Singh G, Kapoor IPS. Kinetics of thermolysis of ring-substituted
aryl ammonium nitrates. Combust Flame. 1993;92:283–91.
9. Singh G, Kapoor IPS, Mannan SM, Agarwal JP. Kinetics of
thermolysis of ring-substituted arylammonium nitrates. Part II:
TG, DTA, impact and friction sensitivity studies. Combust Flam.
1994;97:355–71.
10. Kapoor IPS, Srivastava P, Singh G. Preparation, characterization
and thermolysis of phenylenediammonium dinitrate salts. J
Hazard Mater. 2008;150:687–94.
11. Singh G, Baranwal BP, Kapoor IPS, Kumar D, Singh CP,
Frohlich R. Some transition metal nitrate complex with hexa-
methylenetetramine. Part LX: preparation, X-ray crystallization
and thermal decomposition. J Therm Anal Calorim. 2008;91(3):
971–7.
It is inferred that proton transfer is the rate determining
step and thermal stability of diphenylammonium salts
depends upon the tendency of diphenylammonium cation
to release a proton to corresponding anion. In the case of
-
NO3 and ClO4-, further, weak bonds are broken, and
groups of atoms are produced. These charged and
uncharged groups of various stabilities have different
lifetimes and thus can be considered as intermediates
possessing enhanced reactivity. Because of this, they
propagate solid-phase interactions to chain-like or even
branching chain-like process having strongly exothermic
reactions which may cause an ignition/explosion.
12. Singh G, Kapoor IPS. Kinetics of thermolysis of ring substituted
arylammonium perchlorate. J Phys Chem. 1992;96:1215–20.
13. Kapoor IPS, Srivastava P, Singh G, Singh UP, Frohlich R.
Preparation, crystal structure and thermolysis of diperchlorate
salts. J Phys Chem A. 2008;112(4):652–9.
14. Singh G, Kapoor IPS, Mannan SM. Studies on energetic com-
pounds. Part 4: dimethylanilinium perchlorates. J Energ Mater.
1995;13:141–5.
Conclusions
15. Singh G, Kapoor IPS, Mannan SM. Studies on energetic com-
pounds. Part 4: thermal explosion of ring substituted arylammo-
nium perchlorates. J Therm Anal. 1996;46:1751–60.
16. Lumbs HA. The chemistry of synthetic dyes and pigments.
Malabar, Florida: R. E. Kriger Publishers; 1982.
17. Savara A, Li M, Sachtler MH, Weitz E. Catalytic reduction of
NH4NO3 by NO: effect of solid acids and implications for low
temperature DeNOx process. J Indian Chem Soc. 2008;10:
251–7.
18. Kummer JT. Thermal decomposition of ammonium nitrate. J Am
Chem Soc. 1947;69:2559–62.
19. Singh G, Pandey DK. Thermal studies on energetic compounds.
Part 30: kinetics and mechanism of bis(diethylenetriamine) metal
nitrate. J Therm Anal Cal. 2004;76:507–19.
The proton transfer seems to be a primary and rate con-
trolling step in the thermolysis of hydrogen sulphate,
nitrate and perchlorate salts of diphenylamine. These salts
have been found to dissociate by proton transfer to form
diphenylamine and acid molecule (H2SO4, HNO3, HClO4)
in the condensed phase. Sulphate in solid state under
thermal and microwave irradiation, forms aminobenzene-
sulphonic acid, whereas nitrate and perchlorate oxidize the
fuel (diphenylamine) leading to ignition/explosion to form
various gaseous products and a residual carbon.
123

728
I. P. S. Kapoor et al.
20. Wood BJ, Wise H. Acid catalysis in the thermal decomposition of
ammonium nitrate. J Chem Phys. 1955;23:693–6.
26. Singh G, Vasudeva SK, Kapoor IPS. Thermolysis of AP-PS
additive mixtures. Indian J Technol. 1991;29:589–94.
27. Singh G, Singh RR. Indigenously fabricated apparatus for ther-
mogravimetric analysis. Res Ind. 1978;23:92–3.
28. Semenov N. Chemical kinetics and chain reactions. Oxford:
Clarendon Press; 1935.
29. Freeman ES, Gorden S. The application of the absolute rate
theory of the ignition of propagatively reacting systems. The
thermal ignition of the system lithium nitrate–magnesium,
sodium nitrate–magnesium. J Phys Chem. 1956;60:867–71.
30. Zinn J, Rogers RN. Thermal initiation of explosives. J Phys
Chem. 1962;66:2646–9.
31. Singh G, Singh RR, Rai AP, Kapoor IPS. Thermal analysis
of ammonium perchlorate?polystyrene?additive mixtures 1. J
Them Anal. 1990;36:2539–46.
21. Chem R, Russell TP, Rheingold AL, Brill TB. Thermal decom-
position of energetic materials, 44. Rapid thermal decomposition
of the propyl-1,3-diammonium salts of NO-3 and ClO4-, and the
crystal structure of the ClO-4 salt. J Crystallogr Spectrosc Res.
1991;21:167–71.
22. Russel TP, Brill TB.Thermal decomposition of energetic mate-
rials, 42. Fast thermal decomposition of five N-Methyl substituted
ethanediammonium dinitrate salts. Propellant Explos Pyrotech.
1990;15:123–6.
23. Russel TP, Brill TB. Thermal decomposition of energetic mate-
rials. 40. Fast thrmolysis patterns of alkanediammonium dinitrate
salts. Propellants Explos Pyrotech. 1990;15:77–80.
24. Russel TP, Brill TB. Thermal decomposition of energetic mate-
rials 31. Fast thermolysis of ammonium nitrate, ethylenediam-
monium dinitro dinitrate and hydrazinium nitrate and relationship
to the burning rate. Combust Flame. 1989;76:393.
32. Oyumi Y, Brill TB. Thermal decomposition of energetic mate-
rials, 25. Shifting of the dominant decomposition site by back-
bone substitution of alkylammonium nitrate salts. J Phys Chem.
1987;91:3657–61.
33. Nambiar PR, Pai Vernekar VR, Jain RS. Thermal decomposition
of methyl ammonium perchlorate. J Therm Anal. 1975;7:587–92.
25. Basset J, Denny RC, Jaffery GH, Manehan J. Vogel’s text book
of quantitative inorganic analysis. 4th ed. London: Longman.
p. 497.
123