OXIDIZING ALKOXYLATION OF PHOSPHINE IN ALCOHOLIC SOLUTIONS OF IODINE
2081
Fig. 1. (a) Conversion and (b) potentiometric curves of phosphine uptake by iodine solution. (w) Rate of phosphine uptake,
(
(
) potential, and (Q) amount of phosphine taken up. c (M): (1, 4) 0.8; and (2, 3) 0.4. c (M): (1) 0, (2, 3) 1.2, and
I2
Py
3
4) 12.4. c
(M): (1) 10.9, and (2) 9.8; (3) c
5.7; (4) No alcohol. p
PH3
10 (Pa): (1) 1.6, (2, 4) 3.3, and (3) 4.0.
BuOH
OctOH
T ( C): (1) 70, (2, 3) 50, and (4) 25.
phates [12]. The IR spectra of the trialkyl phosphates
obtained coincided with those of the reference samples
and contained characteristic bands of P=O ( = 1260
periment, the initial reddish brown solution of I is
decolorized, and a white precipitate of PyH HI is
2
formed. The uptake of PH by the pyridine-alcoholic
3
1
1
1
285 cm ) and P O C ( = 1020 1045 cm ) groups
13]. The 13C NMR spectra of the products contained
signals with chemical shifts (CH ) = 19.5 0.5,
solution is accompanied by the oxidizing alkoxyla-
tion of PH (2) with the formation of trialkyl phos-
[
3
phates in high yields (see table). The table illustrates
the effect of the temperature and concentration of io-
dine, phosphine, pyridine, and alcohol on the trialkyl
phosphate yield. Under the optimal conditions, the
yield is 100%. The increase in PyH concentration in
3
(
CH) = 29.5 0.5, and (CH ) = 73.6 0.5 ppm,
2
characteristic of trialkyl phosphates.
The PH I ROH system. The alcoholic solution
3
2
of I is fairly stable at 20 70 C. The I /I redox po-
2
2
the alcoholic solution of I from 1.2 to 7.4 M does
2
tential was constant for a long time (30 min). The I2
concentration did not change, and no products of al-
cohol oxidation with iodine were detected [14]. In-
not affect the tributyl phosphate (TBP) yield. At the
pyridine concentration of 9.9 M, the TBP yield de-
creases to 64%. The pyridine solution of I takes up
2
troduction of PH into this solution is accompanied by
PH , and a yellow precipitate of, probably, P I is
3
3
2 4
a cathodic shift of the redox potential from 0.8 to
formed [15], with no organophosphorus compounds
detected in the solution. The effect of alcohol on re-
0
.1 V because of the decrease in the I concentration
2
due to reaction (1). In the course of PH uptake by io-
action (2) was studied at the optimal [PyH]/[I ] ratio
3
2
dine alcoholic solution, I is reduced to RI and HI,
close to the stoichiometric ratio. The character of con-
2
and PH is oxidized to phosphoric acid by Eq. (1).
version and potentiometric curves of PH uptake by
3
3
The yield of organic phosphates is 1 2% (see the ta-
pyridine-alcoholic solutions of I are similar to those
2
ble). The W Q conversion and
Q potentiometric
for alcoholic solutions of I . The rate of reaction (2)
2
curves are descending (Figs 1a, 1b, curves 1). The
alcoholic solution of iodine eliminates from Ar PH3
grows with increasing concentration of I and PH ,
temperature, and alcohol acidity and decreases with
accumulation of PyH HI (Fig. 1).
2
3
mixtures even trace amounts of PH (< 10 Pa). The
3
PH uptake stops only when I is completely reduced
and, correspondingly, the reddish brown alcoholic
3
2
CONCLUSION
solution of I is decolorized.
2
At 20 70 C, pyridine-alcoholic solutions of I rap-
2
The PH I ROH PyH system. The pyridine-
3
2
idly take up PH from gas mixtures with selective
3
alcoholic solution of I is fairly stable at 20 70 C.
2
formation of trialkyl phosphates. The optimal condi-
The redox potential of the I /I couple remains con-
2
tions of this reaction are T = 25 50 C, p
1.4 2.3) 10 Pa, and cI2 = cPyH = 10 30 wt%
the remainder is ROH).
=
PH3
stant for 30 40 min. During this time, the I concen-
tration is also unchanged, and products of alcohol
and pyridine oxidation by iodine do not appear. In-
3
2
(
(
troduction of PH into the pyridine-alcoholic solution
3
REFERENCES
of I is accompanied by uptake of PH , decrease in
2
3
the I concentration, and cathodic shift of the redox
potential from 0.7 to 0.05 V (Fig. 1). During the ex-
1. Dorfman Ya.A., Yukht, I.M., Levina, L.V., et al.,
Usp. Khim., 1991, vol. 60, no. 6, pp. 1190 1228.
2
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 74 No. 12 2001