Oxidation with nitric acid of aliphatic alcohols and diols to carboxylic acids

Full text of DOI:10.1134/S1070428007050235

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2007, Vol. 43, No. 5, pp. 773−774. © Pleiades Publishing, Ltd., 2007.
Original Russian Text © N.V. Svetlakov, V.G. Nikitin, E.A. Nikolaeva, 2007, published in Zhurnal Organicheskoi Khimii, 2007, Vol. 43, No. 5,
pp. 775−776.
SHORT
COMMUNICATIONS
Oxidation with Nitric Acid of Aliphatic Alcohols and Diols
to Carboxylic Acids
N. V. Svetlakov, V. G. Nikitin, and E. A. Nikolaeva
Kazan State Technological University, Kazan, 420015 Russia
Received October 30, 2006
DOI: 10.1134/S1070428007050235
of HNO3 with alcohols would be a nitric acid ester [13],
and the formation of the final product, carboxylic acid,
would depend on the chemical stability of the nitrate.
Aliphatic hydroxy compounds are oxidized to carbonyl
derivatives by various oxidants, like potassium per-
manganate, chromium compounds, silver carbonate,
ruthenium(VIII) oxide, nickel peroxide, potassium
persulfate, etc. [1–3]. The oxidation of these compounds
with nitric acid is performed far less often, although this
oxidant is of great practical interest because of its low
price and availability.
Primary aliphatic alcohols with a normal backbone of
any length (pentyl, hexyl, octyl, decyl, and undecyl) are
readily oxidized with nitric acid into the corresponding
carboxylic acids in 75–90% yield, and this procedure can
serve a preparative method for these acids.
It was shown that the oxidation of primary alcohols
with nitric acid gave rise as a rule to carboxylic acids
with the same number of carbon atoms, and the oxidation
of secondary alcohols occurred with a rupture of
a carbon–carbon bond [4–11]. Thus the following acids
were obtained at oxidation with nitric acids: from
trimethylenechlorohydrin, chloropropionic [4], from
glycerol, glyceric [5], from ethylene glycol, oxalic [6–9],
and from triethylene glycol, glycolic [10] acids. The
difficulties of this process consist in the choice of the
reaction conditions and mainly in the separation of reaction
products that even has been claimed in a patent [11].
The isoamyl alcohol contains a relatively labile hydrogen
at the tertiary carbon atom; however undet the chosen
conditions the oxidation with the nitric acid does not affect
the C–H bond, and the main product obtained is isovaleric
acid.
The oxidation of dihydric primary alcohols depends
on their structure as we have demonstrated by an example
of 1,6-hexanediol and ethylene glycol. With two
hydroxymethyl groups far removed from each other the
1,6-hexanediol behaved like monohydric alcohols and at
treatment with the 75–85% nitric acid at 25–30°C easily
underwent oxidation giving the adipic acid. The reaction
occurred similarly to that with the monohydric alcohols
with strong heat evolution and nitrogen oxides liberation,
but the precipitation of adipic acid began immediately in
the course of diol addition to HNO3.
We investigated the oxidation of some primary
monohydric and dihydric alcohols containing a fairly long
alkyl chain (from pentanol to undecanol), and also of
ethylene glycol and 1,6-hexanediol.
The said alcohols suffered oxidation when treated with
30% and more concentrated HNO3. In oxidation of
monohydric primary alcohols at 25–30°C the concentra-
tion of 70–85% is optimal. The reaction occurred with
a high rate, with evolution of heat and nitrogen oxides,
but is easily controlled by alcohol dosage and cooling the
reaction mixture. Nitric acid of 75% and higher
concentration contains a nitronium cation [12], therefore
it is presumable that the primary product of the reaction
The ethylene glycol oxidation also involved both
hydroxy groups giving the oxalic acid, but it possessed
certain specific features. For instance, on mixing the
components the temperature first insignificantly increased,
and after a short interval it rose to 60–65°C simultaneously
with vigorous liberation of nitrogen oxides. The reaction
mixture even required additional heating for the comple-
tion of the reaction. The relative stability of the ethylene
glycol against the oxidation with the nitric acid may be
773

SVETLAKOV et al.
774
for 4–5 h. The moderate nitric oxides evolution was
controlled by the rate of heating. On cooling the mixture
crystals of oxalic acid precipitated, were filtered off, and
dried in air. Yield 17 g (69%). On recrystallization from
water and drying in air oxalic acid dihydrate was obtained,
mp 101°C (mp 101.5°C [14]).
due to the stabilizing effect of the nitrate groups formed
by esterification of the glycol.
Oxidation of alcohols. General procedure. To
80% nitric acid [63 g (1.0 mol) calculated on 100% HNO3]
at 25–30°C was added while stirring 0.2 mol of an
appropriate alcohol. The reaction occurred with evolution
of heat and nitrogen oxides that caused the brown color
of the reaction mixture. After the end of heat evolution
the reaction mixture was maintained for 3–4 h at 30°C
till decoloration, then it was poured into 50 ml of cold
water, extracted with chloroform (3×50 ml), the extract
was dried with Na2SO4, the chloroform was distilled off,
and the carboxylic acid obtained was purified by
distillation.
b. On mixing the components the reaction mixture
was maintained at 20°C for 7–10 days; therewith the
crystals of oxalic acid started to precipitate in 2–3 days.
Yield 80–85%.
In this study commercial primary alcohols were used
and the 97% nitric acid of technical grade that was diluted
with water to the required concentration. IR spectra were
1
recorded on a spectrophotometer UR-20. H NMR
Valeric acid was obtained from pentanol. Yield 90%,
bp 186–187°C, nD20 1.4076 (bp 187°C, nD20 1.4086 [14]).
spectra were registered from solutions in acetone-d6 on
a spectrometer Tesla-497 at operating frequency 100
MHz at room temperature, internal reference HMDS.
Caproic acid was obtained from hexanol. Yield 87%,
bp 202°C, nD20 1.4136 (bp 202°C, nD19.6 1.4145 [14]).
REFERENCES
Caprylic acid was obtained from octanol. Yield 82%,
bp 139–140°C (22 mm Hg), nD20 1.4275 (bp 237.5°C, nD21
1.4268 [14]).
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Capric acid was obtained from decanol. Yield 80%,
bp 136–138°C (8 mm Hg), mp 30°C (mp 31.5°C, bp
268°C [14]).
Undecanoic acid was obtained from undecanol. Yield
86%, bp 225–227°C (160 mm Hg), mp 29–30°C {mp
29–30°C, bp 228°C (160 mm Hg) [14]}.
Isovaleric acid was obtained from 3-methyl-1-butanol
(isoamyl alcohol). Yield 20.5 g (81%), bp 175–176°C,
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Adipic acid. To 80% nitric acid [63 g (1.0 mol)
calculated on 100% HNO3] at 25–30°C was added by
small portions 23.6 g (0.2 mol) of 1,6-hexanediol. The
separation of adipic acid started already during addition
of the diol. After the end of diol addition the reaction
mixture was maintained for 3–4 h till decoloration. Then
the adipic acid was filtered off and dried.Yield 13 g (45%),
mp 152°C (from water) (mp 151–153°C [14]).
Oxalic acid. a. To 80% nitric acid [63 g (1.0 mol)
calculated on 100% HNO3] at 25–30°C was added
12.5 g (0.2 mol) of ethylene glycol. After mixing the
reagents the reaction mixture self-heated with vigorous
nitrogen oxides liberation. When the mixture heated to
60–65°C it was cooled with water to 20°C, then gradually
heated to 85–90°C and maintained at this temperature
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