Synthesis of solid arenediazonium nitrates under nonaqueous condition

Article abstract of DOI:10.1081/SCC-100104011

Amines react with DMF-NO₂ adduct under nonaqueous condition to give solid aryl diazonium nitrate in high purity and excellent yield.

Full text of DOI:10.1081/SCC-100104011

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SYNTHESIS OF SOLID
ARENEDIAZONIUM NITRATES
UNDER NONAQUEOUS
CONDITION
QingZhi Zhang a , Shensong Zhang a , Xinming Liu a
& Jinming Zhang a
a College of Chemical and Environmental Science,
Henan Normal University, Xinxiang, 453002, P. R.
China
Published online: 09 Nov 2006.
To cite this article: QingZhi Zhang , Shensong Zhang , Xinming Liu & Jinming Zhang
(2001): SYNTHESIS OF SOLID ARENEDIAZONIUM NITRATES UNDER NONAQUEOUS
CONDITION, Synthetic Communications: An International Journal for Rapid
Communication of Synthetic Organic Chemistry, 31:8, 1243-1247
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SYNTHETIC COMMUNICATIONS, 31(8), 1243–1247 (2001)
SYNTHESIS OF SOLID ARENEDIAZONIUM
NITRATES UNDER NONAQUEOUS
CONDITION
QingZhi Zhang,* Shensong Zhang, Xinming Liu,
and Jinming Zhang
College of Chemical and Environmental Science,
Henan Normal University, Xinxiang, 453002, P. R. China
ABSTRACT
Amines react with DMF-NO2 adduct under nonaqueous
condition to give solid aryl diazonium nitrate in high purity
and excellent yield.
Since diazonium salts are important synthetic intermediates that have
long been used in the dye and pharmaceutical industries,1–7 their synthesis
has received considerable attention. The normal method for synthesis of
diazonium salts was carried out in aqueous medium and usually yielded
the diazonium salts in solution8 but this method needs low temperature
and does not produce solid diazonium salts. Furthermore, the synthesis of
diazonium nitrate has seldom been studied because of the strong oxidization
of nitric acid. To avoid the oxidation of aromatic amines by nitric acid,
Kagiyama and Tsurushima9 recently reported a successful method using
alkyl nitrites to prepare diazonium nitrates, while Wagenblast10 reacted
NO2 in the gaseous or liquid phase with aromatic amines to obtain corres-
ponding diazonium nitrates.
* Corresponding author.
1243
Copyright & 2001 by Marcel Dekker, Inc.
www.dekker.com

1244
ZHANG ET AL.
In the course of our study on the treatment and utilization of the waste
gas NOx with organic compounds, DMF was used as an absorbent, which
absorbed NO2 gas to give a DMF-NO2 adduct. DMF-NO2 was found to be
a new and mild oxidizing agent.11 The structure of DMF-NO2 may be
similar to that of alkyl nitrate, which makes the oxidative power of NO2
mild. Using this oxidizing agent with aromatic amines in DMF produces
solid diazonium nitrates in excellent yield and high purity (see Table).
Table. Diazonium Nitrates from Aromatic Amines and DMF-NO2 Adduct
Microanalysis
(%)(found)
Product
Yield (%)
90a
1H NMR (ꢀ)
IR (cmꢀ1
)
8.46(d,2H,Ha)
8.20(s,1H,Hc)
7.87(s,2H,Hb)
2293(m,sharp) C, 43.11 (43.38)
1384(vs)
826(w)
H, 3.02(3.12)
N, 25.15 (25.09)
72a
78a
8.43(s,1H,Ha)
8.06(d,1H,Hc)
2267(w,sharp) C, 46.40 (46.79)
1385(vs)
H, 3.90 (4.01)
N, 23.20 (23.91)
7.67(m,2H,HbþHd) 844(w)
2.73(s,3H,CH3)
8.32(s,2H,HaþHd) 2279(m,sharp) C, 46.40 (46.69)
8.05(s,1H,Hc)
7.74(s,1H,Hb)
2.46(s,3H,CH3)
1384(vs)
825(w)
H, 3.90 (3.75)
N, 23.20 (23.55)
84a
86a
8.58(m,1H,Ha)
8.24(m,1H,Hd)
8.03 (m,1H,HC)
7.81(m,1H,Hb)
2271(m,sharp) C, 35.75 (34.90)
1384(vs)
825(w)
H, 2.00 (1.82)
N, 20.85 (20.45)
8.61(s,1H,Hd)
8.47(d,1H,Ha)
8.27(d,1H,Hc)
7.85(t,1H,Hb)
2277(w)
1384(vs)
826(w)
C, 35.75 (35.86)
H, 2.00 (1.89)
N, 20.85 (20.91)
81a
8.53(d,2H,Ha)
7.92(d,2H,Hb)
2279(w)
1384(vs)
826(w)
C, 35.75 (35.80)
H, 2.10 (1.93)
N, 20.85 (21.12)

SOLID ARENEDIAZONIUM NITRATES
Table. Continued
1245
Microanalysis
(%)(found)
Product
Yield (%)
80a
1H NMR (ꢀ)
IR (cmꢀ1
)
8.63(d,1H,Ha)
8.15 (m,2H,HcþHd)
7.83(t,1H,Hb)
2273(m,sharp) C, 29.29 (28.83)
1384(vs)
826(m)
H, 1.64 (1.78)
N, 17.08 (17.30)
82a
8.72(s,1H,Hd)
8.54(d,1H,Ha)
8.41(d,1H,Hc)
7.78(t,1H,Hb)
2278(m,sharp) C, 29.29 (29.45)
1384(vs)
826(w)
H, 1.64 (1.49)
N, 17.08 (17.18)
87a
91a
8.42(d,2H,Ha)
8.17(d,2H,Hb)
2276(s)
1384(vs)
826(m)
C, 29.29 (29.49)
H, 1.64 (1.75)
N, 17.08 (17.23)
8.59(d,1H,Ha)
8.30(d,1H,Hd)
8.22(t,1H,Hc)
7.95(t,1H,Hb)
2286(m)
1384(vs)
825(w)
C, 39.82 (39.89)
H, 2.39 (2.27)
N, 19.90 (19.78)
93a
9.07(s,1H,Hd)
8.73(m,2H,HaþHc)
8.00(t,1H,Hb)
2291(m)
1385(m)
825(w)
C, 39.82 (39.90)
H, 2.39 (2.26)
N, 19.90 (19.72)
92a
90b
8.65(d,2H,Ha)
8.35(d,1H,Hb)
2290(s)
1384(vs)
826(w)
C, 39.82 (39.92)
H, 2.39 (2.18)
N, 19.90 (19.79)
8.97(d,1H,Ha)
8.81(d,1H,Hd)
8.53(t, 1H, Hc)
8.34(t, 1H,Hb)
2276(m)
1384(s)
826(w)
C, 33.97 (33.95)
H, 1.90 (1.81)
N, 26.42 (26.61)
92b
9.43(t,1H,Hd)
8.96(m,1H,Ha)
8.90(m,1H,Hc)
8.17(t,1H,Hb)
2289(m)
1384(vs)
826(w)
C, 33.97 (34.10)
H, 1.90 (1.49)
N, 26.42 (26.45)
91b
8.87 (d,2H,Ha)
8.71 (d,2H,Hb)
2290(w)
138(s)
826(w)
C, 33.97 (33.82)
H, 1.90 (1.69)
N, 26.42 (26.50)
b
aCrystallized as colorless needle; light yellow needle.

1246
ZHANG ET AL.
When aromatic amines in DMF were reacted with 8 equiv. of DMF-
NO2, a lot of gas evolved off. Adding ether to the solution, the diazonium
nitrates precipitated through a liquid phase. The arenediazonium nitrates
with electron-withdrawing substituents were very pure without recrystalliza-
tion, but the diazonium nitrates without electron-withdrawing substituents
should be recrystallized with DMF-Et2O. The IR peaks at 2252–2293 cmꢀ1
confirmed the existence of ArN2þ, while the peaks at 1384 cmꢀ1 and 825–
1
826 cmꢀ1 belong to the nitrate ions. The IR, microanalysis, and H NMR
data all confirmed that the products were diazonium nitrates.
The arenediazonium nitrates with electron-withdrawing substituents
prove to be very stable and could be stored at room temperature for a
half year without any change. These salts were prepared at 10ꢁ–40ꢁC in
excellent yield. While the diazonium nitrates without electron-withdrawing
substituents should be stored at 10ꢁ–15ꢁC, after two months (or storage at
room temperature) these salts gradually darken. These salts were obtained
at lower reaction temperatures (10ꢁ–15ꢁC) in good yield. Higher reaction
temperature leads to the formation of tar. Furthermore, when heated to
about 65ꢁC, struck, or ignited, all these diazonium salts explode. Maybe
these diazonium nitrates can be considered as useful synthetic intermediates
as other diazonium salts.
EXPERIMENTAL
Starting materials were reagent grade and used without further purifi-
cation. IR spectra were obtained on a FTS-40 infrared spectrophotometer.
1H NMR spectra were recorded on a Bruker DPX-400 spectrometer using
TMS as an internal standard. Elemental analyses were carried out on a
PE-2400 microelemental analyzer.
DMF-NO2 Adduct
In a typical procedure, 21.1 g (0.3 mol) of sodium nitrite (98%) in a
three-neck round-bottom flask was added dropwise to 18 g (0.18 mol) of
conc. sulfuric acid (98%). The resulting NOx was oxidized and blew by
O2 into the bottom of a drying tower (packed with the mixture of phos-
phorus pentaoxide and quartz sand), an oxidizing tower (packed with the
quartz sand carrying chromium trioxide to guarantee all NO oxidized into
NO2), an absorption tower (packed with glass ring) successively. At the top
of the absorption tower, 21.93 g (0.3 mol) of DMF was dropped downwards

SOLID ARENEDIAZONIUM NITRATES
1247
through a dropping funnel. The counter-face absorption of NO2 by DMF
gave the adduct DMF-NO2.
Arenediazonium Nitrates
Three mmol of aromatic amines dissolved in 6 mL DMF was added to
1.86 mL (24 mmol) of DMF-NO2 immediately with vigorous stirring. Gases
evolved. About 5 m later, to the solution was added 20 mL ether, then
it became two layers. The solution was stirred until the diazonium salts
precipitated completely. The diazonium nitrates were filtered and washed
with Et2O, then dissolved in DMF, and added Et2O to the DMF solu-
tion. Collection, washing with Et2O, and vacuum drying obtained the
pure diazonium nitrates.
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Accepted July 7, 2000