818
SHTEINBERG
shaped.” At low concentrations of PEG-400,when 1 >>
2
(K1[PEG]0 + K2K1[PEG]0 + K3K1[PEG]0[PNBA]0, the
expression for the initial rate is transformed to
O
B
O
C
O
O
O2N
O
H
W0 = kef[PEG]0,
O
N
H
O
and the rate varies by the linear law. At high concentra-
tions of PEG-400, when (K1[PEG]0 + K2K1[PEG]0
K3K1[PEG]0[PNBA]0) >> 1, the expression for the
O
H
2
O
+
initial rate takes the form
H
kef
W0 = —————————————–
ammonia molecule toward a nucleophilic attack at the
carbonyl carbon atom by acting as nucleophilic centers
of the resulting complex polyfunctional catalyst G, H.
K1 + K2K1[PEG]0 + K3K1[PNBA]0
Kef
= –———————–
Kef.1 + K2K1[PEG]0
EXPERIMENTAL
where Kef.1 = K1 + K3K1[PNBA]0, and tends to zero with
increasing concentration of the activator.
4-Nitrobenzoic and boric acids, 1,2,4-trichloroben-
zene, ammonia, and PEG-400 were purified and used as
described in [1–3].
Below are presented some specific features of PEG as
a constituent of a number of catalytic systems, including
those used in synthesis of carboxylic acid amides
[11–14]: (1) are used in peptide synthesis, with oxy
groups of PEG being good “anchor”” groups; (2) serve
as a basis for polymeric catalysts, can form a kind of
a void with easily changeable geometric shape, in which
a catalytic reaction occurs; (3) can react with water,
amines, amides, and polychlorobenzenes, with several
reagents at once bound along a single polymer chain.
This may lead to a cooperative action and manifestation
of a polyfunctional catalysis.
4-Nitrobenzamide was obtained in 1,2,4-trichloro-
benzene at 173°C, the resulting mixtures were analyzed,
and the purity of the substances purified was determined
as it was done in [1, 2]. Kinetic measurements were per-
formed using the procedure described in [4].
CONCLUSIONS
(1) In the reaction of boric acid with polyethylene
glycol of 400 brand, with increasing concentration of
PEG-400 and constant initial concentrations of reagents
and boric acid, a bell-shaped dependence of the initial
rate of 4-nitrobenzamide formation is observed, with
a clearly pronounced maximum.
It is not improbable that, in synthesis of PNBAm,
PEG performs in catalysis functions of this kind. Below
are presented two hypothetical structures of complexes:
G oxygen atoms of the PEG chain favor fixation of
PNBA in voids and further formation of its borate
ester; H oxygen atoms of the PEG chain favor fixation
of PNBA and ammonia in voids and further formation
of PNBA borate ester; the same atoms activate the
(2) The optimal molar ratio between boric acid and
PEG-400 for obtaining 4-nitrobenzamide with high
initial rate and yield is 1 : (1.5–2.5).
REFERENCES
O
1. Shteinberg, L.Ya., Zh. Org. Khim., 2003, vol. 39, no. 7,
O
H
O
H
O2N
C
O
B
O
pp. 1033–1035.
O
2. Shteinberg, L.Ya., Zh. Prikl. Khim., 2005, vol. 78, no. 10,
pp. 1745–1747.
3. Shteinberg, L.Ya., Zh. Prikl. Khim., 2006, vol. 79, no. 8,
O
O
pp. 1296–1299.
4. Shteinberg, L.Ya., Zh. Prikl. Khim., 2009, vol. 82, no. 4,
G
pp. 619–623.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 5 2011
Shteinberg
