SPECTROSCOPIC AND DIELCOMETRIC STUDY OF THE KINETICS
value was determined by extrapolation of the linear
1801
1
2
relation C0 = f(a0) to the initial concentration a0 =
b0 = 0.70 M. The smallest gain in the capacity of the
system was observed at a0 = b0 = 0.18 M (Fig. 4, 4).
No capacity gain was detected at all for more dilute
solutions (see table), whereas the concentration dis-
balance ( a m) was the greatest. Thus, the kinetic
relations holding in the reaction under study are
identical to those observed in the alcoholysis of
butyryl chloride in the same solvent. In the two
systems, accumulation of two intermediate products X
and Y occurs; the former prevails in dilute solutions,
and the latter, in concentrated.
0.3
0.2
0.1
0
3
15
30
45
60
Time, s
Fig. 3. Kinetic curves for (1) consumption of trichloro-
acetyl chloride, (2) accumulation of butyl trichloro-
acetate, and (3) accumulation of intermediate Y; a
=
0
In order to elucidate the structure of intermediates
X and Y [reactions (1) and (2)], the IR spectra of
dilute samples were recorded. In the IR spectrum of
a solution with the initial reactant concentrations a0 =
b0 = 0.01 M, we observed a broad absorption band
b
= 0.470 M (CCl , 20 C).
0
4
C, p
200
1
at 3300 cm and two bands in the region correspond-
1
ing to stretching vibrations of a free hydroxy group,
CM 110
1
1
1
CP 49
at 3644 and 3575 cm (Fig. 2; the band at 3300 cm
100
2
CP 53
2
is not shown). The bands at 3300 and 3644 cm
1
belong to n-butanol, and the band at 3575 cm , to
intermediate X, as far as just that intermediate
accumulates in dilute solutions.
0
1
3
Time, min
CM 59
C, pF
CP 42
3
60
In the IR spectrum of the reaction mixture with
a0 = b0 = 0.47 M, diluted by a factor of 47 (to a con-
centration of 0.01 M) with carbon tetrachloride, at
a moment corresponding to the maximal capacity, we
50
40
C0 33
C0 32
CM 36
4
CP 33
1
observed a broad band at 3300 cm , corresponding
0
1
2
3
4
to residual absorption of H-bonded hydroxy group,
and three bands in the region of stretching vibrations
Time, min
1
of free hydroxy group at 3644, 3630, and 3575 cm .
1
Fig. 4. Plots of the electric capacity vs. time for solu-
tions with various initial concentrations of trichloroacetyl
The band at 3644 cm
belongs to unchanged
1
n-butanol. The band at 3575 cm was assigned to
intermediate X, and the third band (3630 cm ), which
chloride and n-butanol (CCl , 20 C); concentration, M:
1
4
(1) 0.700, (2) 0.470, (3) 0.360, and (4) 0.180.
was not observed previously for this system, is likely
to arise from the second intermediate (Y). The stretch-
ing vibration frequency of the O H bond is reduced
due to the presence of CCl3 group in the -position
[3 6]. The OH group can be involved in intramolec-
ular hydrogen bond with chlorine atom of the CCl3
group in X, thus forming a five-membered H-chelate
ring [6, 7]. This also reduces the OH stretching vibra-
tion frequency. According to theoretical calculations
[8] (no experimental spectra of compounds X and Y
are available from the literature, except for our data
[1]), the OH stretching vibration frequency increases
as hydrogen atoms in the -positions are replaced
by chlorine. As a result, we have a frequency of
the -position with respect to the hydroxy group, is
larger (3630 cm ).
1
The formation in the system of two intermediate
products X and Y is confirmed by the variation of the
IR spectra of a dilute sample of the reaction mixture
with time (Figs. 2, curves 3 and 4): the intensity of
1
the band at 3630 cm decreases, while the band at
1
3575 cm becomes stronger. The former completely
disappears in 1 h after dilution, while the latter
reaches its maximal intensity (Fig. 2, curve 5). Curve
5 in Fig. 2 coincides with curve 2 obtained for the
system with a0 = b0 = 0.01 M. In such a way, the
system comes again to the equilibrium state via
accumulation of intermediate X, which is typical
of dilute solution.
1
3575 cm which is observed experimentally for
intermediate X. The OH vibration frequency in
molecule Y, which contains two chlorine atoms in
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 73 No. 11 2003