I N V E S T I G A T I O N OF T H E D I P O L E - D I P O L E

I N T E R A C T I O N OF P H O S P H O R Y L C O M P O U N D S

W I T H T H E M E D I U M BY T H E M E T H O D OF

I R S P E C T R O S C O P Y

R. R . S h a g i d u l l i n , V. E. B e l ' s k i i , L . K h . A s h r a f u l l i n a , L . A. K u d r y a v t s e v a , a n d B. E. I v a n o v

UDC 541.67:543.422.4:547.1'118

The d ipole-d ipole interaction (DDI) of phosphoryl compounds (PC), in contrast to the interaction with various proton donors and Lewis acids, has prac t ica l ly not been investigated. It is known only that the frequency of the valence phosphoryl vibrations (up= O) in the IR spec t ra of PC depends substantial ly on the nature of the solvent [1], decreas ing in polar media. This permi t s the use of vp= O for evaluating the ability of PC for DDI. According to the existing concepts, the mechanism of DDI can be either averaged over all possible orientations of the molecules or can include a definite orientation of the interacting dipoles [2, 3]. In the la t ter case, the energy of interaction depends on the products of the dipole moments (DM), while statist ical averaging leads to a dependence of the energy on the product of the squares of the DM of the interacting molecules [4]. In view of this, it is of interest to study the nature of the var ia t ion of the f re - quency vp= O in various media for PC differing substantially in DM.

E X P E R I M E N T A L M E T H O D

The PC used in the work were synthesized, and the industrial prepara t ions purified by the well known methods. After purification, the solvents were tested for the absence of mois ture according to the IR spec t ra in the region of the valence vibrations of the hydroxyl group. The frequencies v p = 0 were mea- sured on a UR-20 spect rophotometer (slit p rog ram 4, ra te of scanning 25 cm- i /min , t ime of deflection of pen 16 sec, scale of recording 40 mm/100 cm-i) . The experimental reproducibi l i ty of the frequencies was :~1 cm -i. Solutions with a concentrat ion of 0.05-0.1 M with a layer thickness of 0.005 and 0.011 cm in cuvettes of NaC1 were investigated.

The measured values of ~p=O of the investigated ser ies of PC in various solvents are cited in Table 1. The band vp= O for some of the compounds considered is of a do~r nature, due to rotational i somer i sm

TABLE 1. Values of Up= O of the Investigated Compounds in Various Media

Compound Medium I I

(.n-BuO)3PO [ (EtO)2P(O)Cl EtOP(O)Et, (MeO)2P(O)Me (Me2N)~POI Et3PO Ph3PO I I

Vapor n-CnHlr n-CTH~8 C6H6CHs C8H6 CC14 C1CH2CH~CI CHaCN Me2SO CHCla

t 717.1%8 i290,1310 i27t, 1288 t290, i310 t265, t280 t285, t300 t264, 1280 i283, t298 t260, t278 1280, t293

t2607-t270 t284-- t269 t278_1288

t274 t~6 1262 i2t6 t262 t21t i254, t264 t209 t253, t266 1207 t249

t244, t254 1~9 t244, t255 tt97 t243, t250

- - t242

i239 i229 t228 12t4 12t3 t209 1203 1203 t203

t191 tt80 tt78 1'176

1 1 6 4 t163

t213 1203 1202 1201

1192

A. E. Arbuzov Institute of Organic and Physical Chemist ry , Kazan' Branch of the Academy of Sci- ences of the USSR. Translated f rom Izvest iya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2502-2504, November, 1973. Original ar t ic le submitted March 2, 1973.

�9 Consultants Bureau, a division of Plenum Publishing Corporation, 227 fflest 17th Street, New York, N. Y. 10011. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission of the publisher. ,4 copy of this article is available from the publisher for $15.00.

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T A B L E 2. P a r a m e t e r s of Eq. (1) f o r the I n v e s t i g a t e d Corn )ounds

No. in order Compound 1~, - D a b r s *

ChPO [t] (MeO)~P (O) Me (MeOhP (O) H [11 (BuO)aPO (EtO)2P (O) C1 EtOP (0) Et~ (Me~N)aPO EtaPO Ph3PO

2,4 2,86 2,94 3,t 3,09 3,29 4,3t 4,4 4,49

0,895 i,0 1,016 1,009 i,t34 i ,2t7 t ,220 1,453 t,1t3

183 0

--7,5 t5,5

--i21,2 --314,9 --3t5 --642 --i34,6

0,966 t,0 0,989 0,993 '0,995 0,983 0,985 0,991 0,99

*Standard deviation.

2,3 0

1,4 0,8 0,7 t ,0

, i ,0 t ,4 t , t

[5, 6]. In c a l c u l a t i o n s f o r fou r and f ive compounds (Tab le 2), we u s e d the v a l u e s of up___ O of t he h i g h - f r e - q u e n c y c o m p o n e n t s of the doub le t . We shou ld m e n t i o n the c o r r e l a t e d sh i f t of the f r e q u e n c i e s of the c o m - ponen t s of the doub le t wi th a change in the so lven t , which is e v i d e n c e tha t the n a t u r e of the i n t e r a c t i o n of t h e two i s o m e r s wi th the m e d i u m is a n a l o g o u s .

R E S U L T S A N D D I S C U S S I O N

F o r a l l the i n v e s t i g a t e d P C , the in f luence of the m e d i u m on up= 0 o c c u r s a c c o r d i n g to one m e c h a n i s m . Th i s is c o n f i r m e d b y the e x i s t e n c e of a l i n e a r r e l a t i o n s h i p b e t w e e n the f r e q u e n c i e s vp= 0 of v a r i o u s PC wi th v a r y i n g na t , : r e of the s o l v e n t . The l i n e a r i t y of the func t ions

"v~ = a'Vst + b, (1)

w h e r e v i and Vst a r e the f r e q u e n c i e s v p = O of the P C c o n s i d e r e d and the s t a n d a r d PC; a and b a r e cons t an t , i s o b s e r v e d wi th high c o r r e l a t i o n c o e f f i c i e n t s r , wh ich w e r e d e t e r m i n e d by the m e t h o d of l e a s t s q u a r e s (Tab le 2). ]:t shou ld be no ted tha t a c c o r d i n g to [1] the r e l a t i v e a b i l i t y fo r i n t e r m o l e c u l a r i n t e r a c t i o n is Con- v e n i e n t l y c h a r a c t e r i z e d b y the q u a n t i t y (v ~ vi)/v~, Where v ~ is the f r e q u e n c y fo r the gas p h a s e . H o w e v e r , in the i n v e s t i g a t e d s e r i e s of PC, the f r e q u e n c y v p = O in t h e l v a p o r cou ld be m e a s u r e d oMy f o r a few c o m - pounds a s a r e s u l t of the low v o l a t i l i t y of m o s t of the i n v e s t i g a t e d PC . Ths u se of Eq. (1) i n s t e a d of

(,~o _ ~ d / , ~ , o = a ' ( , , ~ t ~ - ~ , ~ t ) / ~ t ~ ( 2 )

l e a d s to the f0act t ha t the i n t e r a c t i o n wi th the m e d i u m is c h a r a c t e r i z e d b y the qua n t i t i e s a : a' (v]/V~ and 0 0 b = ( l - a ) vii2st. The r a t i o v i /Vs t f o r the i n v e s t i g a t e d compounds is c l o s e to one; t h e r e f o r e the va lue of a

i s a su i t ab l e m e a s u r e f o r e v a l u a t i n g the a b i l i t y fo r t h e i r i n t e r a c t i o n with the m e d i u m . In the c a s e of p r e - d o m i n a n c e 0f o r i e n t e d i n t e r a c t i o n of the p h o s p h o r y l d i p o l e s wi th the m e d i u m , we should e x p e c t l i n e a r i t y of the v a r i a t i o n of the q u a n t i t y a a s a func t ion of the DM of the c o r r e s p o n d i n g P C . A c o m p a r i s o n of the v a l u e s of a f r o m T a b l e 2 wi th the DM [7, 8] i n d i c a t e s the a p p r o x i m a t e l y l i n e a r r e l a t i o n s h i p s b e t w e e n t h e m ; the equa t ion a = 0.227p + 0.37 i s c h a r a c t e r i z e d b y a c o r r e l a t i o n c o e f f i c i e n t of 0.90. * The s p e c i f i c s of the o r i e n t a t i o n s DDI shou ld p e r h a p s be b e t t e r d e s c r i b e d on the b a s i s of the DM of t he bonds , but the d a t a on the DM of the P ----O bond in v a r i o u s PC n e c e s s a r y f o r such a c o n s i d e r a t i o n a r e not ye t a v a i l a b l e .

S u b s t i t u e n t s a t the p h o s p h o r u s u n d o u b t e d l y change the p o l a r i t y of the P = O bond, which a f f e c t s the f r e q u e n c y UP=O- The d e t e r m i n i n g r o l e of the induc t ive e f f ec t of s u b s t i t u e n t s on u p = O in t h i s

c a s e is we l l lmown [9-11]. The s a m e ef fec t has the b a s i c in f luence

zz ~,5~ o e

njL__ I i I ~' - 0 5 IO Z~ ~

F i g . 1. D e p e n d e n c e of t he c o e f - f i c i e n t a of Eq. (1) on the s u m of the Taf t i nduc t ion c o n s t a n t s Za* f o r s u b s t i t u e n t s a t the p h o s - p h o r u s . The n u m b e r s of the p o i n t s correspond to T a b l e 2.

on the change in the e n e r g y of the h y d r o g e n bonds of PC with p r o t o n d o n o r s [12]. E v i d e n t l y the induc t ive in f luence of s u b s t i t u e n t s a t the p h o s p h o r u s i s the d e t e r m i n i n g f a c t o r not on ly in the c a s e of i n t r a - m o l e c u l a r e l e c t r o n i c e f f e c t s on the f r e q u e n c y vp =O, but a l s o in the c a s e of i n t e r m o l e c u l a r i n t e r a c t i o n s a c c o r d i n g to v a r i o u s m e c h a n i s m (hyd rogen bond, d o n o r - - a c c e p t o r i n t e r a c t i o n , DDI). A c t u a l l y , a s i s shown in the f i g u r e , t h e r e is an i n t e r r e l a t i o n s h i p b e t w e e n the va lue of a and the s u m of the Taf t i nduc t ion c o n s t a n t E(~* fo r s u b s t i t u e n t s a t t he p h o s p h o r u s , c o r r e s p o n d i n g to the equa t ion a = - 0 . 0 5 2 5 Ecr* + 1.297 ( c o r r e l a t i o n coe f f i c i en t r = 0.80). Judg ing b y t h i s d e p e n d e n c e , the i n c r e a s e in p o l a r i t y of the P = O bond u n d e r the in f luence of the i nduc t ive e f f ec t l e a d s to an i n t e n s i f i c a t i o n of the DDI of v a r i o u s PC wi th the m e d i u m . * C a l c u l a t e d wi thout Ph3PO.

2443

CONCLUSIONS

i. The interaction of organophosphorus esters, amides, acid chlorides, and trialkyl(aryl)phosphine oxides, possessing a phosphoryl group, with the medium occurs according to the same mechanism, as is indicated by the linearity of the change in the frequency of the valence vibrations of the P = O bonds under the influence of the medium.

2. The interaction of phosphoryl compounds with the medium is intensified as their dipole moments increase, which may be due to the increase in polarity of the P -- O bond.

3. The ability of phosphoryl compounds to interact with the medium depends on the intermolecular effects of the substituents at the phosphorus, determined by the Taft induction constants.

LITERATURE CITED

i. L.J. Bellamy, C. P. Conduit, R. J. Pacl, and P. L. Williams, Trans. Faraday Soc., 55, 1677 (1959).

2. M. Horak and J. Pliva, Spectrochim. Acta, 21, 919 (1965). 3. M. Horak, J. Moravec, and J. Pliva, Speetrochim. Acta, 21, 919 (1965). 4. S .G. ]~ntelis and R. P. Tiger, Reaction Kinetics in the Liqu---id Phase [in Russian], "Khimiya" (1973). 5. F . S . Mortimer, Spectroehim Acta, 9, 270 (1957). 6. O.A. Raevskii, F. G. Khalitov, and-T. A. Zyablikova, Izv. Akad. Nauk SSSR, Set. Khim. (1972),

p. 348. 7. O.A. Osipov, V. I. Minkin, and A. D. Garnovskii, Handbook of Dipole Moments [in Russian] "Vys-

shaya Shkola" (1971). 8. P. mauret and J. 1 ). Fayet, Bull. Soc. Chem. France, 2363 (1969). 9. L . V . Bell, J. I-Ieisler, H. Tannenbaum, and J. Goldenson, J. Amer. Chem. Soc., 76, 5185 (1954).

10. C . E . Griffin, Chemistry and Industry, 1068 (1960). 11. L . C . Thomas and R. A. Chittenden, Spectrochim. Acta, 20, 467 (1964). 12. T. Gramstad, Spectrochim. Acta, 20, 729 (1964).

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