Communication
A Convenient and Safer Synthesis of Diaminoglyoxime
†
,†
,‡
Eric C. Johnson, Jesse J. Sabatini,* and Nathaniel B. Zuckerman*
†U.S. Army Research Laboratory, Energetics Technology Branch, Aberdeen Proving Ground, Maryland 21005, United States
‡Lawrence Livermore National Laboratory, Material Science Division, Livermore, California 94550, United States
*
S Supporting Information
equiv of hydroxylammonium chloride, and 4 equiv of sodium
hydroxide for several hours. After isolation of the yellow,
crystalline material, the crude product is redissolved in hot
water, treated with decolorizing carbon, and filtered hot to
obtain pure DAG as a white, crystalline solid. While convenient
as a one-step procedure that provides pure material in a matter
of a few hours, this method is prone to thermal runaway, and
the yields are typically a maximum of ca. 40%.
Given the aforementioned yield and lengthy processing
issues, the development of a simpler process that yields DAG in
a higher yield would provide a significant benefit to the
energetic materials community. Such a high yielding and simple
process to obtain DAG from glyoxal is given in Scheme 3. In
this procedure, an excess of 50% aqueous hydroxylamine is
heated to 95 °C with stirring, and a 40% aqueous solution of
glyoxal is then added dropwise over an hour. Following
addition, the flask is fitted with a reflux condenser, and the
reaction mixture is stirred for 72−96 h. Following this time, the
reaction mixture is slowly cooled to room temperature with
stirring and is then further cooled to 0−5 °C with stirring.
Filtration of the resulting white crystalline solid affords the
product in a greatly improved yield of 77−80%. Treatment with
decolorizing carbon and further recrystallizations are not
necessary to obtain a pure product.
ABSTRACT: A new procedure for the synthesis and
isolation of diaminoglyoxime (DAG) is described. A
previous procedure involved treating glyoxal with 2 equiv
each of hydroxylammonium chloride and sodium hydrox-
ide to form glyoxime, followed by further treatment of this
intermediate with two additional equivalents of hydrox-
ylammonium chloride and sodium hydroxide at 95 °C to
form DAG. Two recrystallizations were needed to obtain
the desired product in pure form. Another previous
procedure employed glyoxal in the presence of 4 equiv
each of hydroxylammonium chloride and sodium hydrox-
ide at 95 °C to form DAG. Though this latter procedure
gives product after a few hours, yields do not exceed 40%,
and the reaction is prone to thermal runaway.
Furthermore, the use of decolorizing carbon and
recrystallization of the crude solid are necessary to obtain
a pure product. The new disclosed procedure involves
treating a preheated aqueous hydroxylamine solution (50
wt %, 10 equiv) with aqueous glyoxal (40 wt %), followed
by heating at 95 °C for 72−96 h. The reaction is cooled to
room temperature and then to 0−5 °C to obtain DAG in
pure form, without recrystallization or decolorizing carbon
in 77−80% yield. The exothermic nature of the reaction is
also minimized by this updated process.
Optimization of the new, all aqueous procedure focused
initially on the protocols of previous reports using hydrox-
ylammonium salts in the one-pot formation of DAG from
INTRODUCTION
6
■
glyoxal. The glyoxal solution was added to aqueous hydroxyl-
Diaminoglyoxime (DAG) is a popular intermediate for the
synthesis of a multitude of energetic materials. This includes
not only materials stemming from the bis-1,2,4-oxadiazole ring
amine (5 molar equiv) in such a manner to keep the reaction
below 5 °C. Halfway through the addition, glyoxime
precipitated, and following the addition, the mixture was
warmed to 20 °C. The thick white precipitate was then heated
in one of two manners: heating rate controlled by the
1
system but also the many compounds derived from
diaminofurazan (DAF). Some representative molecules that
fall into these two classes of materials are summarized in Figure
2
,3
temperature of the reaction (T
temperature of the heating jacket (T
°C. During the initial temperature ramp, the reaction was
heterogeneous and the slope of T vs time steadily climbed at
∼5 °C/min, but at approximately 75 °C, the solids went into
solution and the rate of T increase doubled. In trials where T
r
) over 10 min, or ramping the
r
1.
) immediately to 95−100
j
Though DAG has been synthesized by numerous methods4,
the most popular methods to-date are via a two-step synthesis
r
5
or a one-step synthesis. In the two-step procedure, as
summarized in Scheme 1, glyoxal is first converted to glyoxime
r
was used to ramp temperature, the heating rate of the jacket
was immediately reduced by the control software to limit the
reaction temperature rate during this event. The reaction
(
1) upon exposure to 2 equiv of hydroxylammonium chloride
and 2 equiv of aqueous sodium hydroxide. Following
recrystallization, 1 is then treated with these same reaction
conditions, plus exposure to heating for several hours to
provide crude DAG (2). Crude DAG is recrystallized from
boiling water to afford DAG as a yellow crystalline solid. The
overall yield for the two-step procedure is 44%.
temperature would plateau just around the input temperature
7
and no thermal runaway would occur. When T was used to
j
control the reaction heating, the same pattern of dissolution
In the one-step procedure (Scheme 2), DAG is obtained as a
Received: October 13, 2017
crude material by heating an aqueous solution of glyoxal, 4
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XXXX American Chemical Society
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Org. Process Res. Dev. XXXX, XXX, XXX−XXX