REACTION OF CU WITH BENZYL BROMIDE IN DMAA
457
ꢁ
ꢂ1
0 C min . Helium was the carrier gas at (a flow rate of
Table 1. Product composition in the oxidative dissolution of
copper in benzyl bromide–DMAA systems in the absence or
presence of radical traps
1
1
ꢂ1
ꢁ
ml min ). The injector temperature was 275 C and the
ꢁ
detector temperature was 290 C. Components were
identified by co-injection of authentic samples and GC–
MS. Quantitative analyses were based on measured
response factors using model mixtures.
Yield (mol.%)
a
DCPD /Cu (mol/mol) Ph—CH
b
c
D
Ph—CH —CH —Ph
2 2
2
0
1
2
5
0
72
85
100
100
28
15
0
Reagents
Copper powder of >99.99% purity was prepared by the
reduction of CuSO (analytical grade) with magnesium
powder (MP-1, Khlorvinil, Ukraine) in an atmosphere of
argon free of oxygen.
A copper wire (GOST 7262-54 Russia, Cu content of
a
Admixture with 1% dicyclohexylphospine.
Admixture with 1% toluene.
Admixture with <0.01% 4,4 -dimethylbiphenyl.
b
c
4
0
9
2
9.99%) 0.05 mm in diameter was held in DMAA for
4 h. Just before the experiment, the sample was purified
ꢁ
12
ꢁ
1
(96%), m.p. ¼ 51–52 C (lit m.p. ¼ 51–52 C). H NMR
mechanically to remove the swollen insulating film,
exposed to concentrated nitric acid for 5–10 s and washed
with water, acetone and then DMAA.
All organic compounds were obtained from commer-
cial sources. Benzyl bromide (Aldrich) was dried with
fused CaCl and distilled: b.p. 83.5–84 C/13 mmHg (lit
2
b.p. 83.5–84 C/13 mmHg). 3-Methylpyridine (Janssen)
was dried with fused KOH and twice distilled over KOH
(CDCl ): ꢁ ¼ 2.82 (s, 4H, —CH —), 7.02 (m, 10H, —Ph)
3
2
ppm. MS (EI, 70 eV): calculated m/z ¼ 182.11 (M);
þ
þ
found m/z ¼ 182 [M] (23), 91 [M/2] (100). Retention
time 17.8 min.
4,4 -Dimethylbiphenyl MS (EI, 70 eV): calculated
0
ꢁ
7
þ
m/z ¼ 182.11 (M); found m/z ¼ 182 [M] (100), 167
ꢁ
þ
þ
3
[M—CH ] (56), 152 [M—2CH ] (15). Retention
3
time 18.9 min.
ꢁ
20
D
in an inert gas atmosphere: b.p. ¼ 143.7–144 C; n
¼
8
ꢁ
20
D
1
cetamide was purified by slow double-vacuum distillation
.5067 (lit b.p. ¼ 144.0 C; n ¼ 1.5068). Dimethyla-
Identification of radical species in solution
9
ꢁ
over a large amount of P O : b.p. ¼ 83.5–84 C/
2
8
5
2
D
0
ꢁ
3
2 mmHg; n ¼ 1.4380 (lit b.p. ¼ 84 C/32 mmHg;
The reaction in the presence of a radical trap was studied
analogously to the above procedures, with dicyclohex-
yldeuterophosphine (DCPD) as the radical trap.
The residues of benzyl bromide and DMAA, as well as
1,2-diphenylethane and ꢂ-deuterotoluene, were detected
in the diethyl ether solutions. Table 1 summarizes the
20
nD ¼ 1.4380).
1
3
Other solvents were purified according to standard
10
procedures. They were freed from dissolved gases by
repeatedly freezing and thawing at reduced pressure and
stored in ampoules in the absence of air.
yields of organic reaction products.
1
ꢂ-Deuterotoluene H NMR (CDCl ): ꢁ ¼ 2.32 (m, 2H,
3
Reaction of benzyl bromide with copper:
general procedure
—CH —), 7.15 (m, 5H, —Ph) ppm. MS (EI, 70 eV):
2
þ
calculated m/z ¼ 93.07 (M); found m/z ¼ 93 [M] (100),
þ
þ
þ
2 [M—H] (93), 91 [M—D] (46), 66 [M—H—C H ]
2
9
2
þ
(9), 65 [M—C H D] (11).
2 2
A 1-g portion of Cu powder was dissolved in 10 ml of
DMAA and 5 ml of benzyl bromide in an argon atmo-
ꢁ
sphere at 50 C. After 5 h, the white precipitate formed
(
which rapidly became green in air) was filtered off in an
atmosphere of argon free from oxygen. The recrystalliza-
tion from 3-methylpyridine afforded 5.26 g (80%) of
Study of the reaction kinetics
The reactions of copper with benzyl bromide in DMAA
14
were studied by the resistometric method according to a
11
yellow crystals, which were stable in air . Analysis:
C H N CuBr (422.01) calculated: Cu, 15.40; Br, 18.90
C, 51.10; H, 5.00; N, 9.53; found Cu, 15.35; Br, 18.87 C,
15
well-known procedure in an atmosphere of water-free
argon free from oxygen.
18 21 3
5
Cu—N), 418 (w, Cu—N), 348 (s, Cu—N), 230 (vs, Cu—
1.00; H, 5.01; N, 9.77%. IR (mineral oil), ꢀ ¼ 480 (m,
Benzene was used as a neutral solvent for determina-
tion of the kinetic and thermodynamic characteristics of
the reaction of copper with benzyl bromide in the pre-
ꢂ1
Br), 225 (s, Cu—N) cm .
Organic products of reaction were extracted with
diethyl ether (20 ml). The residues of benzyl bromide
16
sence of DMAA.
The reaction was studied in kinetic mode, as evidenced
by the independence of the rate of copper dissolution in
the test media from the rate of stirring (Table 2 sum-
marizes the results of this study).
0
and DMAA, as well as 1,2-diphenylethane and 4,4 -
dimethylbiphenyl, were detected in the ether solution.
The isolated yield of 1,2-diphenylethane was 1.37 g
Copyright # 2004 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2005; 18: 456–461