Interaction of N,N-dimethylperfluoroarylamines with nitric and nitrous acids

Article abstract of DOI:10.1016/S0022-1139(02)00066-0

N,N-Dimethylpentafluoroaniline enters easily into reactions with a mixture of nitric and sulphuric acids or nitric acid with conversion of the side chain. In the reactions with mixtures of HNO₃ and H₂SO₄, the formation of N-nitroso-N-methyl and N-nitro-N-methylpentafluoroanilines is observed. The ratio of these products was found to depend on the ratio of the acids: the formation of N-nitro-N-methylpentafluoroaniline increases with the quantity of sulphuric acid; N-nitroso-N-methylpentafluoroaniline is obtained when only nitric acid is employed. N,N-Dimethylperfluoro-p-toluidine, N,N-dimethylperfluoro-2,4-xylidine, N,N-dimethylperfluoro-5-aminoindane undergo similar transformations. N-Nitroso derivatives were converted by a mixture of HNO₃ and H₂SO₄, HNO₃ or NO₂BF₄ into the corresponding N-nitro derivatives. Formation of the corresponding N-nitroso-N-methyl derivatives occurs when N,N-dimethylpentafluoroaniline, N,N-dimethylperfluoro-p-toluidine are treated with HNO₂.

Full text of DOI:10.1016/S0022-1139(02)00066-0

Journal of Fluorine Chemistry 116 (2002) 3–8
Interaction of N,N-dimethylperfluoroarylamines with
nitric and nitrous acids
Vyacheslav E. Platonova,*, Alois Haasb,1, Meinolf Schelvisb,
Max Liebb, Kira V. Dvornikovaa, Ol’ga I. Osinaa
aN.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, 9 Lavrentieva ave., 630090 Novosibirsk, Russia
b
¨ ¨ ¨
Fakultat fur Chemie, Ruhr-Universitat Bochum, FNO 034/036, D-44780 Bochum, Germany
Received 1 October 2001; accepted 20 December 2001
Dedicated to Prof. D.W.A. Sharp in recognition of his contribution to J. Fluorine Chemistry
Abstract
N,N-Dimethylpentafluoroaniline enters easily into reactions with a mixture of nitric and sulphuric acids or nitric acid with conversion of the
side chain. In the reactions with mixtures of HNO3 and H2SO4, the formation of N-nitroso-N-methyl and N-nitro-N-methylpentafluoroanilines
is observed. The ratio of these products was found to depend on the ratio of the acids: the formation of N-nitro-N-methylpentafluoroaniline
increases with the quantity of sulphuric acid; N-nitroso-N-methylpentafluoroaniline is obtained when only nitric acid is employed. N,N-
Dimethylperfluoro-p-toluidine, N,N-dimethylperfluoro-2,4-xylidine, N,N-dimethylperfluoro-5-aminoindane undergo similar transforma-
tions. N-Nitroso derivatives were converted by a mixture of HNO3 and H2SO4, HNO3 or NO2BF4 into the corresponding N-nitro derivatives.
Formation of the corresponding N-nitroso-N-methyl derivatives occurs when N,N-dimethylpentafluoroaniline, N,N-dimethylperfluoro-p-
toluidine are treated with HNO2.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Polyfluoroaromatic chemistry; N,N-Dimethylperfluoroarylamines; Nitric and sulphuric acids; Nitrous acid; Nitronium tetrafluoroborate;
N-Nitroso-N-methylperfluoroarylamines; N-Nitro-N-methylperfluoroarylamines
1. Introduction
methyl-2,4,6-trinitroaniline [2], it seemed reasonable to
think that the corresponding N-nitro-N-methyl derivative
should be the final product from treating N,N-dimethylpen-
tafluoroaniline with a mixture of HNO3 and H2SO4. To
check this, we have investigated the reactions of N,N-
dimethylperfluoroarylamines with mixtures of HNO3 and
H2SO4 and with HNO3 alone.
We have shown previously that treatment of N-alkylper-
fluoroarylamineswithnitricacidreadilygivesN-nitro-N-alky-
lperfluoroarylamines; in the case of N-alkylperfluoroanilines,
the formation of small amounts of N-nitroso-N-alkylpenta-
fluoroanilines was also detected. Replacement of amino
hydrogen by nitro via electrophilic attack by nitronium cation
was proposed to explain the formation of N-nitro derivatives
(Scheme 1) [1].
2. Results and discussion
We have now investigated the behaviour of N,N-dialkyl-
perfluoroarylamines with HNO3. Interaction of the N,N-
dialkylamino group with nitronium cations with formation
initially of N-nitroammonium cations ArFNþ(Alk)2NO2
was expected, and since it is well known that nitration of
N,N-dimethylaniline with HNO3–H2SO4 gives N-nitro-N-
We have found that treatment of N,N-dimethylpenta-
fluoroaniline (1) with mixtures of HNO3 and H2SO4 gives
N-nitroso-N-methylpentafluoroaniline (2) and/or N-nitro-N-
methylpentafluoroaniline (3) depending on the conditions
(Scheme 2, Tables 1 and 2). Thus when compound 1, HNO3
and H2SO4 were used in the ratio 1:5:3, respectively N-nitro
derivative 3 was obtained. The formation of the N-nitroso
derivative 2 along with 3 occurred when the relative quantity
of sulphuric acid was diminished; N-nitroso derivative 2 was
obtained as main reaction product when neat nitric acid was
employed.
* Corresponding author. Tel.: þ7-3832-34-4437; fax: þ7-3832-34-4752.
E-mail addresses: platonov@nioch.nsc.ru (V.E. Platonov),
alois.haas@ruhr.uni.bochum.de (A. Haas).
1 Co-corresponding author. Tel.: þ49-234-32-23004;
fax: þ49-234-32-14541.
0022-1139/02/$ – see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 1 1 3 9 ( 0 2 ) 0 0 0 6 6 - 0

4
V.E. Platonov et al. / Journal of Fluorine Chemistry 116 (2002) 3–8
Scheme 1.
Scheme 2.
A negligible quantity of tetrafluoro-p-benzoquinone was
N,N-dimethylperfluoroarylamines with HNO3, namely N,N-
dimethylperfluoro-p-toluidine (4), N,N-dimethylperfluoro-
2,4-xylidine (5) and N,N-dimethylperfluoro-5-aminoindane
(6). The generality of the nitrosation was thereby demon-
strated, since the corresponding N-nitroso derivatives (7–9)
were obtained. Reactions of amino derivatives 1 and 4 with
formed in the reaction of compound 1 with HNO3, and the
order of mixing compound 1 and HNO3 did not change the
main reaction course.
The conversion of compound 1 with HNO3 to N-nitroso
derivative 2 prompted us to study the reactions of other
Table 1
Interaction of N,N-dimethylperfluoroarylamines 1, 4–6 and N-nitroso-N-methylperfluoroarylamines 2, 7, and 8 with HNO3
Compounds
HNO3 (d 1.51) g
Molar ratio
Temperature
Time (h)
Yield of reaction
Ratio of reaction products
(by 1H and 19F NMR)
(mmol)
(8C)
product mixture (g)
Number
g (mmol)
Compound numbers
Ratio
1
1.0 (4.7)
1.0 (4.7)
1.0 (4.7)
1.0 (4.7)
0.5 (2.4)
0.5 (2.4)
0.5 (2.2)
1.0 (3.8)
0.5 (1.9)
0.5 (1.9)
0.5 (1.6)
1.0 (3.1)
0.1 (0.4)
0.08 (0.3)
1.2 (19.0)
1.5 (23.8)
0.44 (7.0)
0.44 (7.0)
1.15b (11.9)
0.75 (11.9)
0.42 (6.7)
1.2 (19.0)
0.9b (9.3)
0.75 (11.9)
0.55 (8.7)
1.0 (15.9)
0.07 (1.1)
0.06 (1.0)
1:4
1:5
1:1.5
1:1.5
1:5
1:5
1:3
1:5
1:5
1:6
1:5
1:5
1:3
1:3
0
20
20
20
20
75
20
20
60
80
20
20
20
20
0.5
0.5
0.5
0.5
0.5
0.5
1.0
0.5
1.0
1.0
0.5
3.0
0.5
0.5
0.90
0.92
0.89
0.90
0.40
0.42
0.40
0.85
0.40
0.37
0.47
0.90
2:3
2:3
2:3
2:3
2
80:1
9:1
1
1
14:1
9:1
1a
1
1
2:3
3
3:1
2c
4
7
4
7
4
7:10
8
3.6:1
5
6
9
7c
8c
–
d
10
16
d
–
a To HNO3 was added 1.
b HNO3 (d 1.39) was used.
c Reaction was carried out by analogy with procedure 3.1.
d Extract with chloroform (ꢀ0.5 ml).
Table 2
Reaction of N,N-dimethylpentafluoroaniline (1) and N-nitroso-N-methylpentafluoroaniline (2) with mixtures of HNO3 and H2SO4
Compounds
Number
Molar ratio
Temperature (8C)
Yield of reaction
Ratio of 2:3a
(by H and 19F NMR)
compound:HNO3:H2SO4
product mixture (g)
g (mmol)
1
1
1
2
0.50 (2.4)
0.50 (2.4)
0.50 (2.4)
0.50 (2.2)
1:5:1
1:5:2
1:5:3
1:5:3
16
18
20
20
0.35
ꢀ1.1:1
0.35
0.40 (70%)
0.41 (77%)
ꢀ1:1.8
3
3
a Traces of tetrafluoro-p-benzoquinone were present.

V.E. Platonov et al. / Journal of Fluorine Chemistry 116 (2002) 3–8
5
Scheme 3.
concentrated HNO3 are influenced by the reaction tempera-
ture; an elevated temperature favouring formation of N-nitro
derivatives 3 (2: 3 ¼ 3:1 at 75 8C) and 10 (Scheme 3 and
Table 1) as minor products. When diluted HNO3 (65%) was
employed, the compounds 1 and 4 afforded only the corre-
sponding N-nitroso derivatives 2 at 20 8C and 7 at 60 8C,
respectively (Table 1). In the reactions of compounds 4, 5,
and 6 with concentrated HNO3 at 20 8C, formation of the
corresponding N-nitro derivatives were not detected
(Scheme 4). N-Nitroso derivatives 2, and 7–9 consist of E
and Z isomers with the former prevailing (E:Z ꢀ2.2–3.0:1).
The structures of E and Z isomers of N-nitroso derivatives 2,
7–9 are considered in detail in [3].
The formation of N-nitroso derivatives in the reactions of
compounds 1, 4–6 with HNO3 can be rationalised by a
mechanism involving the decay of intermediate nitroammo-
nium cations to aminium radical cations (A) and nitrogen
dioxide, as shown in Scheme 5 (cf. [1]). Proton elimination
from A, giving aminomethyl radicals (B), as outlined in the
literature [4,5], followed by combination of radicals B with
nitrogen dioxide can give nitrites (12), which, on loss of
formaldehyde, will provide N-nitroso derivatives 2, and 7–9.
Earlier, similar conversion of a nitrite was postulated to
occur during nitrosation of diethylamine by sodium nitrite in
the presence of formaldehyde in the pH range 6.4–11.0 at
room temperature [6]. The transformation of carbinolamines
into amines and carbonyl compounds is well known [7], of
course, but if N-methyl derivatives 14 were formed as
intermediate products from 13 the corresponding N-nitro
derivatives 15 would be expected as the main products in the
reactions between compounds 1, and 4–6 and nitric acid [1].
Since the reactions of N,N-dimethylperfluoroaryl amines
with HNO3 gave N-nitro derivatives as minor products, or
seemingly not at all, formation of N-nitroso derivatives 2,
and 7–9 directly from nitrites 12 seems to be the preferred
process.
Although formation of the N-nitro-N-methyl derivative 3
from compound 1, and a mixture of HNO3 and H2SO4 (see
Scheme 2) could be assumed to involve conversion of nitrite
12 (ArF ¼ C6F5) by H2SO4 into the corresponding alcohol
13 (ArF ¼ C6F5) followed by loss of formaldehyde and
electrophilic nitration of N-methylpentafluoroaniline thus
generated, formation of 3 could occur as a result of con-
version of N-nitroso derivative 2 (produced directly from 12,
as in Scheme 5) by HNO3–H2SO4. Note that, we have shown
that treatment of N-nitroso derivative 2 with a mixture HNO3
and H2SO4 (ratio 1:5:3, respectively) or with NO2þBF4ꢁ in
sulfolane–dichloromethane at 16–25 8C produced N-nitro
derivative 3 plus traces of tetrafluoro-p-benzoquinone in the
former reaction (see Table 2). N-Nitroso derivatives 2, 7, and
8 are smoothly converted by 100% HNO3 to the correspond-
ing N-nitro derivatives 3, 10, and 16 (Scheme 6).
In the hydrocarbon field, the conversion of certain ali-
phatic tert-amines on nitrosation into sec-nitrosamines and
carbonyl compounds has been described [8], and nitrosation
of N,N-dialkylanilines at the para position discussed [9]. We
Scheme 4.

6
V.E. Platonov et al. / Journal of Fluorine Chemistry 116 (2002) 3–8
Scheme 5.
found that formation of N-nitroso derivatives 2, 7, and 8,
respectively from the compounds 1, 4, and 5 and HNO2
(NaNO2 þ HCl) took place less readily than that from their
monomethyl analogues [3]. This transformation is viewed as
occurring via N-methyl derivative 14 as shown in Scheme 7,
which is similar to that offered previously for nitrosation of
tert-amines [8].
The lower reactivity of compounds 5 and 6 than com-
pounds 1 and 4 (see Table 3) towards HNO2 could be
accounted for by the greater hydrophobicity of the first
two polyfluoroarenes [10]. The steric effect of the ortho
CF3 group in compound 5 also could retard transformation
of the N(CH3)2 group by HNO2.
Scheme 6.
Scheme 7.

V.E. Platonov et al. / Journal of Fluorine Chemistry 116 (2002) 3–8
7
Table 3
Interaction of N,N-dimethylperfluoroarylamines 1, and 4–6 with HNO2
Amine
NaNO2
(mmol)
g
Molar ratio
HCl (ml)
Temperature
Yield of reaction
Ratio of reaction products
(by 1H and 19F NMR)
(8C)
product mixture (g)
Number
g (mmol)
Compound numbers
Ratio
1
4
4
5
5
6
0.5 (2.4)
0.3 (1.1)
0.5 (1.9)
0.3 (1.0)
0.5 (1.6)
0.5 (1.5)
0.33 (4.8)
0.16 (2.3)
0.39 (5.7)
0.13 (1.9)
0.22 (3.2)
0.22 (3.2)
1:2
1:2
1:3
1:2
1:2
1:2
5
4
5
4
5
5
20
20
60
20
60
20
0.41
0.25
0.41
0.24
0.45
0.41
1:2
4:7
1:4
1:2
1:5
4:7
5 and 8a
5:8
6 and 9a
2:1
a Traces.
3. Experimental
into cold water. The organic material was extracted with
chloroform (0.6 ml twice), washed with water (3 ml) three
times. The organic phase was dried over MgSO4, filtered and
the solvent was removed by using a Rotavapor at room
temperature. Experimental data and analytical results are
provided in Table 2.
19F and 1H NMR spectra were recorded on a Bruker AC-
200 instrument at 188.3 and 200 MHz in CHCl3 solution; the
standards were hexafluorobenzene and hexamethyldisilox-
ane. IR spectra were measured in CCl4 on a UR-20 spectro-
meter. UV spectra were recorded on a Specord UV–VIS
instrument using solutions in EtOH. The molecular weight
of 6 was determined by vapor-phase osmometry in acetone
on a Knauer instrument. The presence of N-nitroso-N-
methyl, N-nitro-N-methylperfluoroarylamines and tetra-
fluoro-p-benzoquinone in the reaction product mixtures
was determined by a comparison of their 19F and 1H
NMR spectra with the spectra of authentic samples [1,3].
3.3. Reaction of N-nitroso-N-methylpentafluoroaniline
ꢁ
(2) with NO2þBF4
A stirred solution of compound 2 (0.3 g, 1.3 mmol) in dry
sulfolane (2 ml) and dry dichloromethane (ꢀ5 ml) was
treated with NO2BF4 (0.18 g, 1.4 mmol) for 2 h at 20–
25 8C. The reaction mixture was quenched with ice and
water and the organic material was extracted with chloro-
form (0.25 ml twice), dried over MgSO4, filtered and ana-
lysed by 19F NMR spectroscopy. Compounds 3 and 2 were
present in this mixture in the ratio 4:1, respectively.
3.1. Interaction of N,N-dimethylperfluoroarylamines
with HNO3: general procedure
HNO3 (d 1.51) was added dropwise, with stirring to the
N,N-dimethylperfluoroarylamine. When the reactions were
carried out at 20 8C, the temperature rose to 30–45 8C at the
beginning of all the experiments as a result of the exothermic
reactions which ensued; this period was short and completed
in 3 min (cooling by water containing ice). The reaction
mixture was poured into cold water, and the organic material
was extracted with chloroform (0.3–0.5 ml twice), washed
with water (3 ml) three times, dried over MgSO4, filtered
and the solvent was removed by using a Rotavapor at room
temperature. The residue was analysed by NMR. Traces of
tetrafluoro-p-benzoquione were present in reaction product
mixture of compound 1. Results, reaction conditions and
experimental data are presented in Table 1.
3.4. Interaction N,N-dimethylperfluoroarylamines
with HNO2: general procedure
An aqueous solution of NaNO2 was added dropwise, with
stirring, to a mixture of N,N-dimethylperfluoroarylamines
and concentrated HCl over 1 h; reaction temperatures are
given in Table 3. The product was poured into water (10 ml)
and the aqueous mixture extracted with chloroform (0.5 ml
twice). The organic layer was washed three times with water
(5 ml), dried over MgSO4 and filtered. The solvent was
removed in vacuum, and the residue analysed by NMR.
Experimental data and analytical results are given in Table 3.
3.5. Synthesis of N,N-dimethylperfluoroarylamines 1,
and 4–6: general procedure
3.2. Interaction of N,N-dimethylpentafluoroaniline (1)
and N-nitroso-N-methylpentafluoroaniline (2) with a
mixture of HNO3 and H2SO4: general procedure
N,N-dimethylperfluoroarylamines 1, and 4–6 were
obtained by treatment of the corresponding perfluoroarenes
with a 30% aqueous solution of dimethylamine in isopro-
panol. Physical data of amines 1, 4, and 5 were in agreement
with literature data [11–13]. N,N-Dimethylnonafluoro-5-
aminoindane (6) was identified as follows: 19F NMR, dF
ppm: 57.0 and 55.3 (broadened peaks; 1-CF2 and 3-CF2),
A mixture of HNO3 (d 1.51) and concentrated H2SO4 was
added dropwise, with stirring, to compound 1 or 2. The
temperature of reaction mixture rose from 16 to 28 8C
during short period similar to 3.1. Stirring was continued
for 2 h at 16–20 8C and then the reaction mixture was poured

8
V.E. Platonov et al. / Journal of Fluorine Chemistry 116 (2002) 3–8
[3] V.E. Platonov, A. Haas, M. Schelvis, M. Lieb, K.V. Dvornikova, O.I.
Osina, T.V. Rybalova, Yu.V. Gatilov, J. Fluor. Chem. 114 (2002)
55–61.
33.7 (br; 4-F), 32.8 (tt, J ¼ 5 Hz, 2-CF2), 27.3 (t, J ¼ 17 Hz,
6-F), 20.3 (m, 7-F); 1H NMR, dH ppm: 3.06 (t, J ¼ 2:7 Hz,
N(CH3)2). IR 1500, 1510, 1640, 2945, 2900 cmꢁ1. UV, l
max., nm (log e): 227.8 (3.92), 287.5 (4.53). Anal., Calcd.
for C11H6N1F9: C, 40.87; H, 1.85; N, 4.33; F, 52.94%. MW
323. Found: C, 40.55; H, 1.76; N, 4.15; F, 52.94%. MW 324,
325.
[4] J.P. Dinnocenzo, T.E. Banach, J. Am. Chem. Soc. 111 (1989)
8646–8653.
[5] L.C. Portic, V.V. Bhat, C.K. Mann, J. Org. Chem. 35 (1970)
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[8] R.G. Coombes, Nitro and nitroso compounds, in: I.O. Sutherland
(Ed.), Comprehensive Organic Chemistry, Vol. 2, Pergamon Press,
Oxford, 1979, p. 364.
Acknowledgement
The authors thank Volkswagenstiftung for financial sup-
port of this work.
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(Ed.), Comprehensive Organic Chemistry, Vol. 2, Pergamon Press,
Oxford, 1979, p. 309.
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Press, Boca Raton, 1996, 8,140 pp.
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