1088
MULDAKHMETOV et al.
=
(2VO
V )/2V .
H O
W, ml min 1
The best results were obtained when the electrolytic
reduction of nicotinic acid ethyl ester was performed
in aqueous alcoholic solution (Fig. 2), which may be
due to higher solubility of the starting ester in an
aqueous organic solution.
The pyridine molecule is not a regular hexagon: it
has a dipole moment due to nonuniform charge distri-
bution [4]. The nitrogen atom in pyridine is an elec-
tron acceptor withdrawing the electron density from
the ring. Furthermore, formation of two bonds and
one bond between the o-C atoms and N atom of the
ring results in orientation of the nitrogen lone electron
pair outside the ring, which favors complexation with
Lewis acids and solubility in proton-donor solvents.
V, ml
Fig. 2. Hydrogen uptake rate W as a function of volume V
of hydrogen taken up in (1) aqueous and (2) aqueous alco-
holic NaOH solutions.
In aqueous alkali, the hydrogen uptake does not go
to completion (it does not exceed 74 78%), and the
1
mean hydrogenation rate is 0.8 (ml H ) min . On
2
As organic solvent we used ethanol. The catholyte
adding ethanol to the catholyte, the hydrogen uptake
accelerates [2 (ml H ) min ] and reaches 100%. An
was a 1 : 1.5 mixture of alcohol with 20% aqueous
NaOH, and the anolyte was 20% NaOH. The electrol-
ysis was performed with gentle stirring (50 60 rpm)
at a current of 1.0 A and solution temperature of 20
1
2
analysis shows that electrocatalytic hydrogenation of I
on the cathode occurs with a substance yield of 98%
and current efficiency of 63%, following the scheme
4
0 C, until the hydrogen uptake ceased; the amount of
2
O
O
Raney nickel on the cathode surface was 1.0 g dm .
After the electrolysis completion, the target product
was extracted from the catholyte with ether and puri-
fied by common procedures. According to Faraday’s
law, 300 ml of hydrogen should be absorbed by 0.78 g
of the ester. The system was sealed, and gases evolv-
ing from the cathode and anode compartments could
be collected in 500-ml graduated gas burets.
C
C
+ 6H O + 6e
2
OC H
OC H
2
5.
2
5
N
I
N
H
II
The structure of nipecotic acid ester II was proved
1
by IR and H NMR data, and the composition was
confirmed by elemental analysis. The IR spectra were
recorded on an Avatar-320 spectrometer from mulls in
From the volume of the released oxygen and hy-
drogen, we calculated the reduction rate W, hydrogen
uptake percentage, hydrogen utilization coefficient ,
and current efficiency.
1
mineral oil, and the H NMR spectra, on a Tesla BS-
5
87 spectrometer (80 MHz) in DMSO-d relative to
6
HMDS. The IR spectrum of II contains a strong band
at about 1740 cm 1 caused by stretching vibrations of
1
The reduction rate, (ml H ) min , was calculated
the C=O group and a broad absorption band at about
2
1
by the equation
3440 cm belonging to NH stretching vibrations.
1
In the H NMR spectrum, the methylene protons of
W = k(2VO
V )/
,
the piperidine core give a multiplet at 1.5 2.0 ppm,
and the methyl protons of the ethoxy group give a
triplet at 1.25 ppm (J 7.0 Hz).
H
where V and V are the volumes (ml) of the released
O
H
oxygen and hydrogen, respectively; t, process time
min); and k, barometric coefficient for converting the
gas volumes to normal conditions.
(
CONCLUSION
The hydrogen utilization coefficient, i.e., the ratio
of hydrogen added to the organic substrate (pyridine
ring) to the total volume of hydrogen released at the
cathode, was calculated by the formula
A procedure was developed for electrolytic syn-
thesis of nipecotic acid ethyl ester in aqueous alco-
holic alkali solution on a copper cathode with Raney
nickel. The target product is prepared with almost
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 80 No. 7 2007
Muldakhmetov
