THE ELECTROCHEMICAL REDUCTION

ORGANOPHOSPHORUS COMPOUNDS

Ya. A. Levin, Yu. M. Kargin, V. S. Galeev, and V. I. Sannikova

OF SOME

UDC 541.138.3 + 661.718.1

We have found that esters of acids of phosphorus having a phenyl or/?-styryI radical attached to an atom of tri- or tetracoordinated phosphorus are capable of undergoing reduction at the dropping mercury electTode. In dimethylformamide solution, this process takes place in one or two one-electron stages (Table i). The transfer of the first electron is not connected to an appreciable extent with'irreversible chemical reactions, since in commuted polarograms an anode wave is found in the same region of poten- tials. This justifies our considering the process in its first stage as A + e~A-. Compound (IV) forms an exception, this possibly being connected with the rapid dimerization of the anion-radicals formed into the dianion disulfide. The lower spin density on the sulfur atom in the anion-radical of compound (XI) pre- vents dimerization. The second stage of the reduction, judging from commuted polarograms, is irreversible. All the/?-phosphorus-substituted styrenes investigated (V)-(XII) (Table i) are reduced 0.4-0.5 V more readily than styrene (El/2 = --1.98 V). Attention is attracted by the fact that compounds (V) and (XII) with tri- and pentavalent phosphorus are reduced at the same potential. Phosphonothioic and phosphinothioic esters are reduced more readily than the corresponding phosphonic and phosphinic acids. Here we may see an analogy with the change in acidity in the transition from (RO)aP(O)OH to (RO)2P(S)OH [i]. Within the class of compounds of the type CGHsCH- CH--P(O)XY, where X and Y are alkyl or alkoxy groups (V)- (IX), El/2 depends linearly on ~p [i], r = 0.995 and p = 0.075 V/unit of ffp.

T A B L E 1. H a l f - w a v e P o t e n t i a l s of the E s t e r s of Some A c i d s of P h o s p h o r us

i �9 ,, ! -

No. Compound --E,/2, V --E,/, V No. Compound -E( , , v --E%, V

I

II

III

IV

V

VI

/OC,Hs

0

Cel l s_p /0C~H~

o /OC=H5

C,H,--~\II O

C.H~__p/OC~H~

C, H6--CH= /OC~Hs

~ C H - - ~ \ O C 2 H s O

C.H~--CH=

~ C H _ P < OC3HT-n rl OC.H,-n 0

2,06

2,08

1,93

1,53

1,45

1,47

VII C~H6--CH= /OC4H,-n

=CH--P-- ~ \OC~H0-n

r C,H~--CH= /OC,H5

=CH--~(-,O~H5 0

IX C.H~--CH= /OC,tt~-n

=Cl'I--~QC, H,_n

X ] C.I-Is--CH=

- -Ct t - - \ 0 C2H~

XI ~ C.H~--CH= ] /O02H6 =CH--['-,Or

XII | C,H~--0H= / /OC~H~ =CH--P\oc2H 5

1,48

1,52

1,53

1,40

1,39

1,45

t,84

1,90

1,87

2,04

1,78

1,85

A. E o A r b u z o v I n s t i t u t e of O r g a n i c and P h y s i c a l C h e m i s t r y , A c a d e m y of S c i e n c e s of the USSR. T r a n s l a t e d f r o m I z v e s t i y a A k a d e m i i Nauk SSSR, S e r i y a K h i m i c h e s k a y a , No. 2, pp. 411-412 , F e b r u a r y , 1968. O r i g i n a l a r t i c l e s u b m i t t e d J u l y 12, 1967.

401

Es t e r s of isopropenylphosphonic and-phosphinic and of phenylphosphonic and -- phosphinic acids a re also reduced at a dropping m e r c u r y e lec t rode with El/2 values close to the beginning of the background discharge.

EXPERIMENTAL

A LP-60 Heyrovsky sys t em polarograph was used to r e c o r d the po la rograms . The dropping m e r c u r y e lec t rode with forced detachment of the drops had m = 0.366 mg/sec and t = 0.50 sec. The compar ison e lec t rode was the bottom layer of me rcu ry , the potential of which was taken as zero . Dimethylformamide, purif ied by Thomas and Rochow's method [2], was used as the solvent. The background e lec t ro ly te was t e t rae thy lammonium iodide (0.08 M). The concentrat ion of the depolar izer was 1 �9 10 -3 M. No cor rec t ions were made for the potential drop in the solution, since it did not exceed 3 inV. The dissolved oxygen was driven off by the passage of e lec t ro ly t ic hydrogen. The commuted polarograms were obtained by means of a Kalousek commutator with switching schemes I and II [3]. The switching f requency was 10 Hz, t empe ra - t a r e 25 ~: 0.1% Compounds (II), (HI), (V)-(VIII), (XI), and (XII) were synthesized by published methods [4-7]. (I) was synthesized in a s imi la r manner to (V) (bp 93-95~ (0.04 mm); d42~ 1.1114; nD 2~ 1.4961), and (IV) was obtained f rom the corresponding thioacid chloride and ethanol in the p resence of t r ie thylamine [bp 93~ (0.09 mm); d420 1.1821; nD2~ 1.5536]. Compounds (IX) and (X) have not been descr ibed previously . (IX) was obtained s imi la r ly to (VIII) using butyl bromide (50 h at 150-155~ yield 50%; bp 162-163~ (0.04 mm); d420 1.0355; riD2~ 1.5268. Found %: P 11.63. C16H2502P. Calculated %: P 11.04. (X) was obtained in a s imi la r manner to (III), yield 51%; bp 140-141~ (0.08 re_m); d~ ~ 1.1249; riD2~ 1.5665. Found %: P 15.50. C10H1302P. Calculated %: P 15.81. The s t ruc tu re and pur i ty of aU the compounds investigated was con- f i rmed by thei r IR, Raman, and UV spec t ra .

C O N C L U S I O N S

1. The polarographic reduct ion of e s t e r s of a number of organophosphorus acids in d imethyl form- amide solutions has been studied.

2. A mechanism for this p rocess has been proposed.

3. Some cor re la t ions have been found between the s t ruc tu re and the El/2 values of the compounds

studied.

1.

2. 3.

4. 5. 6. 7.

L I T E R A T U R E C I T E D

M. I. Kabachnik, In the collection: The Chemis t ry and Applications of Organophosphorus Compounds [in Russian], Izd. Akad. Nauk SSSR (1962}, p. 24. A. B. Thomas and E. G. Rochow, J. Amer. Chem. Soc., 79, 1843 (1957). J. Heyrovsky and J. Kuta, Pr inc ip les of Polarography [Russian t ransla t ion f rom the Czech], "Mir ~

(1965), p. 448. A. E. Arbuzov, Russ . F iz . -Khim. Obshchestva, 42, 395 (1910). A. N. 1)udovik and D. Kh. Yarmukhametova, Izv. Akad. Nauk SSSR, Otd, Khim. Nauk, 1952, 902. K. N. Anisimov and A. N. Nesmeyanov, Izv. AN SSSR, Otd. Khim. Nauk, 1955, 1003. Ya. A. Levin and V. S, Galeev, Zh. Obshch. Khim., 3._~8, 1327 (1967).

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