Kinetics and possible mechanisms of alkaline hydrolysis of alkoxy-NNO-azoxy compounds

Article abstract of DOI:10.1134/S1070363210090124

Abstarct: Hydrolysis rate of alkoxy-NNO-azoxy compounds like di(methoxy-NNO-azoxy)methane I, di-(methyl-NON-azoxy)formal II, di(methoxy-NNO-azoxy)methane III, and 2,2-di(methoxy-NNO-azoxy)propane IV in 5 M KOH solution was measured by manometric method at 80°C; rates relation is 1:40:540:10. Reversible deprotonation to form C-anions followed by their rapid decomposition is a presumable mechanism for compounds I-III. Nucleophilic attack of OH-anion on the carbon atom of CH₃ON=N(O) group is the most probable first stage of hydrolysis in the case of compound IV.

Full text of DOI:10.1134/S1070363210090124

ISSN 1070-3632, Russian Journal of General Chemistry, 2010, Vol. 80, No. 9, pp. 1792–1794. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © I.N. Zyuzin, D.B. Lempert, 2010, published in Zhurnal Obshchei Khimii, 2010, Vol. 80, No. 9, pp. 1473–1475.
Kinetics and Possible Mechanisms of Alkaline Hydrolysis
of Alkoxy-NNO-azoxy Compounds
I. N. Zyuzin and D. B. Lempert
Institute of Chemical Physics Problems, Russian Academy of Sciences,
pr. Akademika Semenova 1, Moscow oblast’, Chernogolovka, 142432 Russia
e-mail: zyuzin@icp.ac.ru
Received November 23, 2009
Abstarct―Hydrolysis rate of alkoxy-NNO-azoxy compounds like di(methoxy-NNO-azoxy)methane I, di-
(methyl-NON-azoxy)formal II, di(methoxy-NNO-azoxy)methane III, and 2,2-di(methoxy-NNO-azoxy)propane
IV in 5 M KOH solution was measured by manometric method at 80°C; rates relation is 1:40:540:10.
Reversible deprotonation to form C-anions followed by their rapid decomposition is a presumable mechanism
for compounds I–III. Nucleophilic attack of OH– anion on the carbon atom of CH3ON=N(O) group is the most
probable first stage of hydrolysis in the case of compound IV.
DOI: 10.1134/S1070363210090124
Alkoxy-NNO-azoxy compounds (AAC) are known
since the end of the nineteenth century [1]. In the last
30 years some representatives of this insufficiently
explored class of compounds are considered as energety-
rich materials [2–4] and biologically active compounds
(NO-donors, antitumor drugs) [5, 6]. According to
literary data AAC are highly chemically stable, especially
to acids and oxidants [1, 5, 7]. Rare qualitative
estimates of AAC stability relative to bases are
contradictory [7, 8]. In order to clear this deficiency
we measured alkaline hydrolysis rate of di(methoxy-
NNO-azoxy)methane I, di(methyl-NON-azoxy)formal
II, di(methoxy-NNO-azoxy)methane III, and 2,2-di(me-
thoxy-NNO-azoxy)propane IV by manometric method.
O
O
O
O
MeO
O
OMe
OMe
O
O
N
N
N
N
N
N
N
N
N
N
Me
Me
Me
III
I
II
O
O
MeO
OMe
N
N
N
N
H3C
CH3
IV
Gas release rate in the hydrolysis in 5 М KOH
solution at 80°C for compounds I, II and IV is
described by the first-order equation, and for com-
pound III, using equations of first order consecutive
reactions. Rate constants and yields of gaseous
products are given in the table.
tion rate to give C-anion. Nitrogen is the main gaseous
product of hydrolysis of compounds I and II. The
probable transformation mechanism of compounds I
and II anions was suggested in [8] to explain the
formation of N2 and PhCH=O by the action of tert-
BuOK on PhCH2N(O)=NOCH3. It includes the
electron density redistribution in anion V, the loss of
anion RO–, and the rearrangement of the residue
followed by decomposition to CH2=O and N2.
The reaction rate of alkaline hydrolysis of com-
pounds I–III is apparently limited by the deprotona-
1792

KINETICS AND POSSIBLE MECHANISMS OF ALKALINE HYDROLYSIS
1793
Effective rate constants and yields of gaseous products of
alkoxy-NNO-azoxy compounds hydrolysis in 5 М KOH
solutions at 80°C
OR
O
N
N
Me
I, II
OR
Yields, mol/mol of AAC
Comp.
keff, s–1
Relative keff
O
OR
O
no.
OH−
H2O
_
N
N2
N2O
0.03
0.03
1.37
N
O
N
N
O
_
2.09×10–7
9×10–6
1
40
0.97
1.12
0.25
I
H2C
H2C
V
II
_
N
+
k
1,eff 1.12×10–4
k2,eff 3.03×10–4
540
III
N
N
N
−RO−
H2C
H2C
2.0×10–6
10
0.07
1.17
IV
CH2=O + N2
R = Me (I), CH2ON=N(O)Me (II).
differs from that of I and II, as shows the predominant
formation of N2O. One of the possible transformation
mechanisms of compound IV anion is similar to the
protocol of hydrolysis of nitro-compounds (Nef
reaction) and involves addition of anion OH– to aci-
form VII formed by the N-protonation of starting
anion IV.
Compound III is less stable than I and II. This fact
can be explained by the more acidic character of
central protons, which is caused by electron–acceptor
effect of two geminal groups CH3ON=N(O). The
transformation procedure of C-anion of compound III
OMe
O
H
OMe
NH
O
N
N
N
OH−
X
X
H2O
OH−
_
CH
III
N
O
NH
OMe
X
CH
_
O
VII
VI
H2O
_CH2=O
O
H
OMe
N2O + N2 + MeOH
+ HO
N
N
N
N
_
OMe
O
X = N(O)=OMe.
The addition of C-anion VI to aci-form VII
followed by rapid reaction series is also possible. The
form of the kinetic curve, which is characteristic of
consecutive reactions, can be ascribed to the
comparable rates of deprotonation and anion VI
transformation.
due to the absence of C–H acidic protons in its molecule.
In comparison with the molecule III they are substi-
tuted by methyl groups. Therefore alkaline hydrolysis
protocol of compound IV is principally another. The
most probable key stage is the nucleo-philic attack on
the carbon atom of CH3ON=N(O) by OH– anion
followed by rapid decomposition of nitrosohydroxyl-
amine anion VIII and conjugate to it acid to give N2O.
The deprotonation of compound IV is impossible
_
O
O
O
MeO
OH−
_MeOH
H2O
IV
N2O + MeOH
N
N
N
N
H3C
CH3
VIII
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 9 2010

1794
ZYUZIN, LEMPERT
sistemy Energetic Condense Systems, Moscow: Yanus-K,
EXPERIMENTAL
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Compounds I–IV were synthesized using the
known procedures [9–12]. Compound I was twice
distilled in a vacuum. Compounds II–IV were twice
recrystallyzed and carefully dried. The kinetics of
alkaline hydrolysis was measured manometrically in
sealed vials (140–170 ml) using crescent-shaped zero-
manometer (Burdon’s vials), the substance charge
100–200 mg and 10 ml of 5 М KOH aqueous solution.
Temperature was maintained with the accuracy of
±0.1°C by means of water thermostate. Gaseous
hydrolysis products were analyzed on a chromatograph
LKhM-8MD (detector katharometer, gas-carrier helium
(100 ml min–1), copper column, l 6 m, d 5 mm,
Polysorb-1 (0.2–0.3 mm), columns tempera-tures –60°
C and 35°C.
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SSSR, Ser. Khim., 1997, no. 8, p. 1486.
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RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 9 2010