LETTER
1121
Can Nitroalkanes be Obtained Directly from Alcohols and Sodium Nitrite in
Acetic Acid – Hydrochloric Acid Mixture?
Mieczys aw M kosza,* Micha Barbasiewicz, Krzysztof Wojciechowski
Institute of Organic Chemistry Polish Academy of Sciences, ul. Kasprzaka 44/52, P.O.Box 58, PL 01-224 Warszawa 42, Poland
E-mail: icho-s@icho.edu.pl
Received 17 April 2001
times of the products in the crude reaction mixtures ob-
Abstract: The report that nitroalkanes can be obtained from ali-
tained according to the procedure of ref. 1. In all instances
phatic alcohols and sodium nitrite in acetic acid - hydrochloric acid
we have not detected even traces of the expected nitroal-
mixture was shown erroneous. Under these conditions no nitroal-
kanes. The reaction mixtures contained nitrites and unre-
acted alcohols, and in the case of the reaction with
4-methoxybenzyl alcohol small amounts of anisaldehyde
were also detected. In the 1H NMR spectra the diagnostic
chemical shifts of the α-methylene protons of the standard
1-nitrohexane and 4-(nitromethyl)anisole did not match
the signals in the NMR spectra of the crude products ob-
tained from the corresponding alcohols. Similarly, the 13C
NMR chemical shifts of the obtained products did not fit
the shifts of the standard nitroalkanes. Also the IR spectra
of the crude reaction mixtures did not show the character-
istic bands in the region of 1550 cm-1 corresponding to the
nitro group.
kanes but alkyl nitrites were formed.
Key words: nitroalkanes, alkyl nitrites, sodium nitrite, acetic acid,
hydrochloric acid
In the July 2000 issue of Synlett the communication enti-
tled A Simple and Highly Efficient Procedure for the prep-
aration of Aliphatic Nitro Compounds Directly from
Alcohols by Baruah, Kalita and Barua was published.1
The results presented in this Letter appeared very interest-
ing but unusual to us. According to the described proce-
dure aliphatic nitro compounds were prepared in high
yields from primary, secondary and tertiary alcohols, also
of benzylic character via simple treatment with sodium ni-
trite and a mixture of acetic and hydrochloric acids in
dichloromethane, conditions very similar to those routine-
ly applied in the synthesis of alkyl nitrites.2
Thus, there is no doubt that the results presented in ref. 1
are erroneous and that under the described conditions only
alkyl nitrites are produced. This is obvious from the mech-
anistic considerations because the reaction between alco-
hols and sodium nitrite in acidic medium can proceed via
addition of NO+ to the oxygen in the case of primary alco-
hols, or via an addition of carbocation to nitrite anion for
tertiary and benzylic alcohols, always with formation of
nitrites but not nitro compounds.
The striking discrepancy between the common knowl-
edge and these reported unexpected results, and our con-
tinuous interest in the chemistry of nitroalkanes prompted
us to verify this procedure. Here we report that these re-
sults are entirely erroneous.
Since nitroalkanes are important and versatile starting ma-
terials in organic synthesis6 it seems necessary to inform
the scientific community that they cannot be obtained as
reported in reference 1.
To verify these results we have chosen three alcohols of
different
character
which according
to the
communication1 were efficiently converted into nitroal-
kanes (Table in ref. 1 entries 4, 10, and 12). We used as
simple primary aliphatic alcohol 1-hexanol analogous to
entry 12, as a tertiary alcohol 1-methylcyclohexan-1-ol
(entry 10), and 4-methoxybenzyl alcohol (entry 4).
References and Notes
(1) Baruah, A., Kalita, M., Barua N. C. Synlett 2000, 1064.
(2) Noyes, W. A., Org. Synth. Coll. Vol. II. p. 108. 1-Hexyl
nitrite, 1H NMR δ (CDCl3) 0.84-0.95 (m, 3H, C-6 CH3), 1.20-
1.49 (m, 6H, C-3,4,5 CH2), 1.65-1.82 (m, 2H, C-2 CH2), 4.69
(t, 2H, J = 6.6 Hz, C-1 CH2). 13C NMR δ (CDCl3) 13.8, 22.5,
25.5, 28.9, 31.4, 68.4. IR 1650, 1605 cm-1. MS (m/z,%): 85
(2), 71 (2), 60 (16), 55 (15), 43 (100).
We have repeated several times the reported procedure1 of
synthesis of nitroalkanes from these alcohols and have
found that the only nitrogen containing products are the
corresponding alkyl nitrites. By comparison of the ob-
tained compounds3 with the corresponding nitro
compounds4 and 1-hexyl nitrite2 prepared independently,
we could prove that there are not even traces of the nitro
compounds in the reaction mixture. Selected data of the
alkyl nitrites obtained in the reactions performed accord-
ing to the procedure presented in ref. 1 and data of the ni-
tro compounds prepared by known methods are collected
in the Table.
(3) The crude reaction mixtures obtained following the procedure
described in ref. 1.
1-Hexyl nitrite obtained from hexyl alcohol, 1H NMR δ
(CDCl3) 0.77-1.07 (m), 1.14-1.46 (m), 1.65-1.81 (m, 2H, C-2
CH2), 4.69 (t, 2H, J = 6.6 Hz, C-1 CH2). 13C NMR δ (CDCl3)
13.9, 22.5, 25.6, 29.0, 31.4, 68.4. IR 1650, 1605 cm-1. MS (m/
z,%) 85 (2), 71 (2), 60(16), 55(21), 43(100).
1-Methylcyclohexyl nitrite obtained from 1-
methylcyclohexanol, 1H NMR δ (CDCl3) 0.77-1.00 (m),
1.23-1.34 (m), 1.47-1.78 (m), 2.00-2.13 (m). 13C NMR δ
We compared the GC5 retention times of the independent-
ly obtained standards of nitroalkanes with the retention
Synlett 2001, No. 7, 1121–1122 ISSN 0936-5214 © Thieme Stuttgart · New York
Ma?kosza
