Oxidation of magnesium with benzoyl chloride in a mixture of tetrahydrofuran and benzene

Article abstract of DOI:10.1023/A:1019583513232

The kinetic features of magnesium oxidation with benzoyl chloride in a mixture of tetrahydrofuran and benzene were studied. A reaction mechanism was suggested, involving attack of the oxidant molecule adsorbed on the metal surface by a similar molecule from the bulk of the solution.

Full text of DOI:10.1023/A:1019583513232

Russian Journal of General Chemistry, Vol. 72, No. 5, 2002, pp. 678 680. Translated from Zhurnal Obshchei Khimii, Vol. 72, No. 5, 2002,
pp. 728 730.
Original Russian Text Copyright
2002 by Maslennikov, Sergeeva, Spirina, Kazakina.
Oxidation of Magnesium with Benzoyl Chloride
in a Mixture of Tetrahydrofuran and Benzene
S. V. Maslennikov, V. P. Sergeeva, I. V. Spirina, and S. V. Kazakina
Research Institute of Chemistry, Lobachevskii Nizhni Novgorod State University, Nizhni Novgorod, Russia
Received June 19, 2000
Abstract The kinetic features of magnesium oxidation with benzoyl chloride in a mixture of tetrahydro-
furan and benzene were studied. A reaction mechanism was suggested, involving attack of the oxidant
molecule adsorbed on the metal surface by a similar molecule from the bulk of the solution.
Among organic compounds capable of oxidizing
metals, a particular place is occupied by acyl halides.
On the one hand, significant polarization of the car-
bon halogen makes these compounds reactive in or-
ganic and organometallic syntheses. However, acyl
halides can also react with polar substances that are
usually used as solvents in organometallic syntheses
In Fig. 1 the rate of magnesium concentration at
various temperatures is plotted vs. the initial concen-
tration of benzoyl chloride. The apparent activation
energy calculated from the experimental data is 16
1
1 kcal mol . From the slope of the straight line in the
coordinates logV logc B0 C, we calculated the reaction
order with respect to the oxidant, which amounted
to 2. These results suggest that oxidation of magnesi-
um with benzoyl chloride is described by the Ealy
[1, 2]. Such processes are catalyzed by Lewis acids
3]. It was also shown in [3] that at common temper-
[
atures benzoyl chloride does not react with zinc in
benzene, carbon disulfide, carbon tetrachloride, and
petroleum ether. According to [4], aliphatic acyl bro-
mides react with beryllium in diethyl ether and diox-
ane slowly, whereas in anhydrous ethyl acetate the
reaction is very vigorous. In aromatic hydrocarbons,
beryllium bromide formed in the process catalyzes the
reaction of acyl bromides with the solvent molecules,
yielding the corresponding ketones. Thus, when study-
ing the reactivity of acyl halides toward metals, the
possible reactions of the oxidant with the solvent and
with primary reaction products should be taken into
account [5].
3
I
II
III
IV
V
2
6
4
1
2
0
In this work, we chose tetrahydrofuran (THF) as
solvent, in view of the following facts. First, accord-
ing to the published data [6] on the dependence of the
magnesium oxidation rate V on the donor number or
ionization potential of the solvent (dioxane, methyl
acetate, ethyl acetate, diethyl ether, tetrahydrofuran,
and diglyme were tested), in THF, other conditions
0.2
0.4
0.6
0.8
cBC, M
Fig. 1. Rate of magnesium oxidation with benzoyl
chloride as a function of the benzoyl chloride concentra-
tion in THF benzene (c
1) 298, (2) 303, and (3) 313. Other compounds added to
the initial solution of benzoyl chloride: (I) 0.0022 M
MgCl , (II) 0.005 M MgCl , (III) 0.1 M -chlorobutyl
8.0 M). Temperature, K:
THF
(
being the same (benzoyl chloride concentration c0
BC
0
.5 M, 298 K), the rate of the reaction with benzoyl
2
2
chloride is the highest. Second, the rate of magnesium
oxidation with benzoyl chloride is much higher than
the rate of reaction of benzoyl chloride with THF.
Third, -chlorobutyl benzoate formed by the latter
reaction was inert toward magnesium under the reac-
tion conditions (Fig. 1).
benzoate, and (IV) 0.3 M -chlorobutyl benzoate. (V) The
initial reaction mixture contains the products of reaction
of benzoyl chloride with magnesium in the same con-
centration as formed in the liquid phase after complete
consumption of the oxidant (c 0.3 M) and removal
of magnesium chloride.
0
1
070-3632/02/7205-0678$27.00 2002 MAIK Nauka/Interperiodica

OXIDATION OF MAGNESIUM WITH BENZOYL CHLORIDE
679
Rideal mechanism involving attack of the oxidant
molecule adsorbed on the metal surface by a similar
molecule from the bulk of solution [7]. In Fig. 2 the
rate of magnesium oxidation is plotted vs. THF con-
centration in the reaction mixture. In the coordinates
1
1
.6
.2
(
b)
6
4
0.8
3
of the Kirkwood equation [8] logV (
1)/(2 + 1),
0
0
.4
.0
where is the dielectric permittivity of the liquid
2
phase, the plot is linearized (Fig. 2b). This means that
the event determining the reaction rate involves the
polarized benzoyl chloride molecule whose reactivity
increases as the THF content and hence the dielectric
permittivity of the liquid phase are increased.
0.32 0.34 0.36 0.38 0.40
1
(
1)/(2 + 1)
(a)
Thus, the pattern of the reaction of benzoyl chlo-
ride with magnesium can be represented as follows:
2
0
C H C(O)Cl + C H C(O)Cl
6
5
6 5
C H C(O)C(O) C H .
6
5
6 5
///Mg///
This scheme is consistent with the detection of
hexamethylbenzil as the reaction product of magnesium
and 2,4,6-trimethylbenzoyl chloride [9]. The data ob-
tained in [4, 5] on oxidation of beryllium with aliphatic
acyl chlorides are also nicely consistent with this
scheme. According to [4, 5], the primary reaction
product is acylmagnesium halide RC(O)MgX, as sug-
gested by the formation of the aldehyde on saponifica-
tion of the reaction mixture. Acylmagnesium halide
further reacts with acyl chloride to form the corres-
ponding diketone. A similar mechanism was suggested
in [10, 11] for oxidation of lanthanides with benzoyl
chloride in THF.
4
8
12
cTHF, M
Fig. 2. (a) Rate of magnesium oxidation with benzoyl
chloride (c 0.3 M) in THF benzene at (1) 298, (2) 303,
and (3) 313 K as a function of THF concentration;
(b) logarithm of the oxidation rate at 293 K vs. the
Kirkwood function of the solvent.
0
amount that is formed by the end of the kinetic experi-
ment, and on adding a solution of the reaction products
(after complete consumption of benzoyl chloride and
removal of magnesium chloride; Fig. 1).
The reaction of magnesium with a benzoyl chloride
solution (c0 0.5 M, 298 K; metal-to-oxidant ratio
EXPERIMENTAL
BC
3
: 1), performed to 20% conversion, gave the fol-
Magnesium wire (0.5 mm in diameter) and magne-
sium turnings [MCh-1, GOST (State Standard) 804
lowing products (per mole of converted benzoyl chlo-
ride): 0.1 mol of C H C(O)C(O)C H , 0.48 mol of
MgCl , and 0.03 mol of C H C(O)(CH ) Cl formed
by the reaction of THF with the oxidant. After remov-
al of volatiles (including unchanged benzoyl chloride)
at 5 10 mm and 298 K and treatment of the
6
5
6
5
8
6, 99.9% main substance] were used without addi-
2
6
5
2 4
tional surface treatment. Organic solvents were puri-
fied and dried by standard procedures [14]. Liquid
mixtures were degassed by repeated freeze pump
thaw cycles. The initial solutions were prepared and
the reaction product analyzed with protection from
ambient air.
2
residue with water to remove MgCl , a yellow resin-
2
ous substance was obtained. Its IR spectrum contained
strong absorption bands at 1590 and 1620 cm 1 as-
signable to the C=C bond conjugated with the ben-
zene ring [12]. Similar compounds were formed in the
reactions of sodium with aliphatic acyl chlorides in
ether [13].
Analytically pure grade benzoyl chloride was used
without additional purification. Anhydrous magnesi-
um chloride was prepared as described in [15] and
analyzed according to [16]; the main substance con-
tent in the product was 99.8%. -Chlorobutyl benzo-
It should be noted that in the initial stages the
2
0
reaction products do not affect noticeably the reaction ate was prepared according to [17]; n 1.5183 (pub-
D
lished data [17]: n2 1.5186).
0
rate. For example, the rate of magnesium oxidation
did not change when concentration of -chlorobutyl
benzoate in the initial mixture had been increased
from 0.1 to 0.3 M (Fig. 1). No changes were observed,
D
The dielectric permittivities of THF benzene mix-
tures were calculated by the equation suggested in
[18]. The reaction kinetics was monitored resisto-
either, on adding MgCl in an amount equal to the
2
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 72 No. 5 2002

680
MASLENNIKOV et al.
metrically [19]; the procedure was modified to ex-
clude contact of reactants with ambient air.
Petrov, E.S., Zh. Obshch. Khim., 1995, vol. 65, no. 1,
pp. 1600 1603.
1
1. Novotorova, M.N., Syutkina, O.P., Rybakova, L.F.,
and Petrov, E.S., Zh. Obshch. Khim., 1998, vol. 68,
no. 1, pp. 73 75.
REFERENCES
1
2
. Coppinger, A.M., J. Am. Chem. Soc., 1954, vol. 76,
no. 7, pp. 1372 1381.
1
1
2. Bellamy, L.J., The Infra-Red Spectra of Complex Mol-
ecules, New York: Wiley, 1957.
. Pearl, I.A., Evans, T.N., and Dehn, W.M., J. Am.
Chem. Soc., 1938, vol. 60, no. 15, pp. 2978 2980.
3. Palston, A.W. and Selby, W.M., J. Am. Chem. Soc.,
1
939, vol. 61, no. 5, pp. 1019 1020.
3
4
. Varvoglos, G.A., Ber., 1937, vol. 70, pp. 2391 2396.
. Lapkin, I.I. and Povarnitsyna, T.N., Zh. Obshch. Khim.,
14. Gordon, A.J. and Ford, R.A., The Chemist’s Com-
panion. A Handbook of Practical Data, Techniques,
and References, New York: Wiley, 1972.
1
968, vol. 38, no. 1, pp. 99 102.
1
5. Zakharov, V.A., Makhtarulin, S.I., and Ermakov, Yu.I.,
USSR Inventor’s Certificate no. 726702, 1980, Byull.
Izobret., 1981, no. 13, p. 266.
5
6
. Lapkin, I.I., Anvarova, G.Ya., and Povarnitsyna, T.N.,
Zh. Obshch. Khim., 1966, vol. 36, no. 11, pp. 1952
1
953.
1
6. Charlot, G., Les methods de la chimie analytique.
Analyse quantitative minerale, Paris: Masson, 1961,
. Sergeeva, V.P., Maslennikov, V.P., Spirina, I.V., and
Maslennikov, S.V., Vestn. Nizhegor. Gos. Univ., Ser.
Khim., 1998, no. 1, pp. 153 164.
4
th ed. Translated under the title Metody analitiches-
koi khimii. Kolichestvennyi analiz neorganicheskikh
soedinenii, Moscow: Khimiya, 1965, p. 678.
7
8
. Maslennikov, S.V. and Spirina, I.V., Zh. Obshch.
Khim., 1998, vol. 68, no. 2, pp. 300 302.
1
7. Organic Syntheses, Blatt, A.H., Ed., New York: Wiley,
. Entelis, S.T. and Tiger, R.P., Kinetika reaktsii v zhid-
koi faze. Kolichestvennyi uchet vliyaniya sredy
1
944. Translated under the title Sintezy organiches-
kikh preparatov, Moscow: Inostrannaya Literatura,
953, coll. vol. 4, p. 528.
(
Kinetics of Liquid-Phase Reactions. Quantitative
Consideration of Solvent Effects), Moscow: Khimiya,
975, p. 209.
1
1
1
8. Chirkov, N.M., Entelis, S.G., and Kondrat’eva, G.P.,
Vysokomol. Soedin., 1961, vol. 3, no. 6, pp. 1044
1053.
1
9
. Gray, A.R. and Fuson, R.C., J. Am. Chem. Soc., 1934,
vol. 56, no. 3, pp. 739 741.
9. Zhukov, S.A., Lavrentyev, I.P., and Nifontova, T.A.,
1
0. Rybakova, L.F., Syutkina, O.P., Stepanova, T.A., and
Kinet. Catal. Lett., 1977, vol. 7, no. 4, pp. 405 412.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 72 No. 5 2002