1976
Russ.Chem.Bull., Int.Ed., Vol. 49, No. 12, December, 2000
Andreev et al.
+
of the NH4 cation in such a way that one N atom
ing effect can be related to the reduction ability of the
amino groups rather than their basicity. Indeed, the
experimental results show that when ðÊà of amines
changes by 5 units from urotropine (4.9) to dicyanodi-
amide (0.4), the initial decomposition rate remains
unchanged and amounts to ∼2.0 cm3 g1 h1 at 120 °C.
Thus, the stabilization of the ADNA melt due to the
oxidation of additives makes it possible to explain the
influence of both amines and other readily oxidized
compounds on the decomposition of the liquid oxidant.
The stabilizing effect of some readily oxidized com-
pounds on the decomposition of the ADNA melt does
not ensure their chemical compatibility with a solid
oxidant. This is due to the fact that the decomposition
rate of the solid ADNA sample is lower by two orders of
magnitude than that of the liquid sample.
Therefore, the interaction of an additive with ADNA,
which is imperceptible against the background of fast gas
evolution from the melt, can become significant as
compared to the low decomposition rate of the solid salt.
The stability of solid ADNA can be worsened due to
the existence of low-melting eutectics with some com-
pounds5 because of the indicated difference between the
rates of the solid and melted oxidant along with direct
chemical interaction.
+
originates from the NH4 cation, and the N(NO2)2
anion produces the second N atom.
In the decomposition of ADNA with a labeled cen-
tral N atom, the 15N label was found in N2O, which
evolved only in the form of 15N14NÎ, and partially in
N2 and NO. The content of labeled N2 and NO was only
∼10% of the total content of these gases. These results
can be explained within the framework of a scheme that
agrees with the published data6,7 on the mechanism of
ADNA decomposition
15
NH4N(NO2)2
15NN + NO + N2O,
N2 + 15NNO + NO.
NH415N(NO2)2
The ratio between N2O and N2 changes during de-
composition. In the initial step their amounts are ap-
proximately the same. Then the rate of N2O decomposi-
tion increases, and that of N2 evolution remains un-
changed for some time (see Fig. 1). The data on the
kinetics of accumulation of the main decomposition
products (see Table 1 and Fig. 1) and the results of
isotope analysis suggest that the oxidation of the ammo-
nium cation is responsible for the formation of N2 and
an autocatalyst, whereas N2O and NH4NO3 are the
The results of the study of the interaction of some of
the most efficient stabilizers with the solid oxidant at low
temperatures will be published elsewhere.
products of the acid decomposition of the N(NO2)2
anion. Autocatalysis can also be eliminated by the intro-
duction of readily oxidized compounds, which prevent
+
the oxidation of the NH4 cation. Based on these pre-
References
requisites, we tested different readily oxidized com-
pounds: amines (both in the free state and in the com-
position of complex and onium DNA salts), amides,
ammonium salts, iodides, and others (see Table 2). At
the same molar content, compounds containing amino
groups and iodides are the most efficient stabilizers.
They decrease the initial decomposition rate 23-fold
rather than increase considerably the induction period.
The solubility of an assumed stabilizer in the ADNA
melt plays an important role. For example, dipheny-
lamine is insoluble in the melted oxidants and does not
inhibit autocatalysis.
At the same weight content, semicarbazide, oxalyldi-
hydrazide, aminotriazole, and urea are the most efficient
stabilizers. According to the published data,4,6,7 t he
stabilizing effect of amines is due to the suppression of
ADNA decomposition via a dissociative mechanism. In
our opinion, the stabilizing effect of amines and other
additives is based on their ability to be oxidized by
intermediate products of ADNA decomposition. Since
amines can be oxidized by nitrogen oxides, their stabiliz-
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1999, 50 [Russ. Chem. Bull., 1999, 48, 50 (Engl. Transl.)].
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379 (Engl. Transl.)].
Received January 20, 2000;
in revised form May 31, 2000