ISSN 0036-0244, Russian Journal of Physical Chemistry A, 2009, Vol. 83, No. 3, pp. 509–510. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © Yu.A. Lisitsyn, L.V. Grigor’eva, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 3, pp. 596–597.
SHORT
COMMUNICATIONS
Electrosynthesis of Anisidines
in Aqueous Sulfuric and Acetic Acids
Yu. A. Lisitsyn and L. V. Grigor’eva
Butlerov Chemical Institute, Kazan State University, Kazan, Tatarstan, Russia
Received December 18, 2007
Abstract—The influence of the concentrations of acetic and sulfuric acids on the efficiency of anisole amina-
tion by means of hydroxylamine and Ti(IV)/Ti(III) mediator was studied. Ortho- and para-anisidines were ob-
tained with the total yields of about 79% by current and hydroxylamine.
DOI: 10.1134/S0036024409030327
The indirect cathode amination of aromatic com- tors, and phases XE-60, SE-30, and OV-17. Quantita-
pounds with the Ti(IV)–hydroxylamine system in tive analysis of anisidines was performed using a flame
0.5–7 M aqueous solutions of sulfuric acid gave the ionization detector and a glass column with length
corresponding monoamine isomers [1, 2]. However, 2500 mm and inside diameter 3 mm (5% XE-60 on
in the functionalization of substrates with low solu- Chromaton N-AW (0.160–0.200 mm)). The column
bilities in water, the current efficiency was only temperature was 150°ë; the carrier gas (helium) flow
slightly higher than 10% even after incomplete con- rate was 15 ml/min.
version of NH2OH [3]. The major reason for this was
The amination of anisole in 1.5 M H2SO4 showed
the disappearance of main part of the aminyl radicals
that the presence of small amounts of AcOH in the
caused by their interaction with titanium(III) ions
catholyte led to a decrease rather than increase in the
[1, 2].
efficiency of substitution. The dependence of the cur-
In this work, the amination of anisole was used to
show that the rate of the formation (competing with
substitution) of ammonia (ammonium) can be sub-
stantially decreased by the introduction of acetic acid
(AcOH) into the sulfuric acid electrolyte; acetic acid
is fairly inert with respect to amino radical intermedi-
ates [4].
rent efficiency of anisidine formation on the content of
the organic solvent was minimum in a 10 M solution.
However, usingAcOH concentrations higher than 12 M
was restricted by the solubility of Ti(IV) complexes in
aqueous–organic catholytes. We found that the problem
of complex solubility was absent in more acid aque-
ous–organic media. Taking into account this and the
character of the dependence of the yield of anisidines
on the molar ratio of H2O/H2SO4 [5], we performed pre-
liminary electrolyses of the Ti(IV)–NH2OH–anisole
system in 6 and 9 M H2SO4 containing maximum pos-
sible concentrations of CH3COOH (11 and 7.6 M,
respectively).
The amination of anisole was performed in a glass
electrochemical cell, in which the cathode and anode
spaces were separated by a ceramic diaphragm. An
aqueous solution containing 0.2 M NH2OH, 0.1 M
Ti(IV), and the required concentrations of H2SO4 and
AcOH served as a catholyte. The electrolysis of
argon-deaerated high-dispersity emulsion of anisole
(5 ml, 0.046 mol) in catholyte (25 ml) was performed
at 40°ë and a current density on a mercury cathode
of 2 mA/cm2. As in [3, 5], the amount of electricity
passed during electrolysis was generally 250 C.
The products of anisole amination in these electrolytes
were ortho- and para-anisidines (para : ortho ~ 1.8). The
highest total current efficiency of amino compounds
formation was obtained in 6 M H2SO4; because of the
chain mechanism of electrochemical amination [1, 2],
After electrolysis, the catholyte was diluted with the yield of anisidines was 152%. When electrolysis
water to a ~1 M concentration of H2SO4 and neutralized was performed by passing the amount of electricity
by successively treating it with saturated aqueous solu- necessary for the complete exhaustion of hydroxyl-
tion of NaOH and NaHCO3. The anisole amination amine in a one-electron process (482.4 C) through the
products were extracted with chloroform and analyzed electrolyte, the catholyte acquired a violet coloration
on a Chrom-4 chromatograph. For qualitative analysis, characteristic of Ti(III)-containing solutions. The addi-
we used flame ionization and heat conduction detec- tion of hydroxylaminium sulfate to the sample taken
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Lisitsyn
