3270
WELCH, GONZALES, A S D GUTHRIE
VOL.
[CONTRIBUTION FROM SOUTHERN REGIONAL RESEARCH LABORATORY,~ UNITED STATES
26
I>EP4RTMENT Ob' .\ORICUI,TIJRE]
Derivatives of Unsaturated Phosphonic Acids CLARK M. WELCH, ELWOOD J. GOSZALES,
JOHN I). G U T H R I E
AND
Received December 27, 1960 SaIts of vinylphosphonic acid and derivatives of the type CH,-CHP(0)(X)OCH2C€12CI where X = C1, N ( C H J ) ~and OCHI have been prepared starting from the commercially available bis(2-chloroethyl) vinylphosphonate. Diethyl 1( and 2)propynylphosphonate has been prepared from propargyl bromide and diethyl phosphonate. The molar refractions and infrared absorption spectra of several of these materials have been determined, and the significance of the spectra is discussed.
A number of esters of vinylphosphonic acid have previously been prepared by the dehydrohalogenation of the corresponding 2-chloroethylphosphonates.2 Vinylphosphonic acid itself was unknown until recently made by the pyrolysis of 2-chloroethylphosphonic dichloride, followed by hydrolysis. 3 The vinyl group of the esters is known to be moderately reactive toward nucleophilic reagents. Addition reactions occur with thiols,db amine~,4~,g nitro alkane^,^^ active methylene compounds such as malonic ester,4e and dialkyl phosphonates4',g in the presence of alkaline catalysts. Vinylphosphonates also undergo the Diels-Alder reaction with dienes,5 and may be polymerized6" or copolymerized6bwith other olefins. Certain of the esters have been used to stabilize polymers to heat and light7 and to impart flame and shrinkage resistance to textiles.8 The present research has shown the readily available bis(2-chloroethyl) vinylphosphonate to be a convenient starting material for the preparation of a variety of derivatives of vinylphosphonic acid. The ester was easily saponified by 20-50% aqueous sodium hydroxide, both of the 2-chloroethyl groups
being removed. A moderate amount of gas evolution occurred which may be duc t o the formation of acetylene, ethylene oxide or both. To facilitate product purification, the crude aqueous sodium vinylphosphonate was converted to bcnzylammonium hydrogen vinylphosphonate, which could be recrystallized from absolute ethanol and thus separated from inorganic salts. When bis(2-chloroethyl) vinylphosphonatc in an inert solvent was heated with phosphorus pentachloride, a rather rapid reaction occurred with removal of only one of the 2-chloroethyl groups from the ester molecule : 0
+
C H ~ = C H P ( O C H ~ C H ? C ~ ) ,PCI, --+
0
I
C H e C H P ( C1 )OCII?CH,Cl
+ POC13 + ClCHzCHzCl
A 62% yield of 2-chloroethyl vinylphosphonochloridate resulted. Removal of the second 2chloroethyl group proved unexpectedly difficult, even when 2-chloroethyl vinylphosphonochloridate was heated with phosphorus pentachloridc in the absence of solvent, and the vinylphosphonic dichloride obtained mas grossly impure. The facile preparation of 2-chloroethyl vinylphosphonochloridate makes this compound available for the synthesis of amides and esters. Reaction with dimethylamine in the presence of triethylamine in benzene solution gave 2-chloroethyl N,Li-dimethyl-P-vinylphosphonamidatein 66:; yield. Reaction of the phosphonochloridate with methanol in the presence of triethylamine in bcnzene gave 2-chlorocthyl methyl vinylphosphonatc in 74% yicld. Table I lists the dciisity, refractive index, and molar refraction determined for thc compounds. Table I1 givcs infrared spectral data. The reaction of sodium diethyl phosphite with propargyl bromide was studied as a means of prcparing diethyl 2-propynylphosphonatc :
( 1 ) One of the laboratories of the Southern Utilization Research and Development Division, Agricultural Research Service, U.S. Department of Agriculture ( 2 ) A. H. Ford-Moore and J. H . Williams, J . Chem. SOC., 1465 (1947); R f . I. Kabachnik, P. A. Rossiiskaya, and N.N. Novikova, Hull. m a d . sci. C.IZ.S.S., Classe sci. cham., 97 (1947); ref. Ga. 1 3 ) AT. I. Kahachnik and T. Ya. Medved. Imest. d k a d . X a i ~S.S.S.R., i Otdel. Khim.Sauli, 2142 (1959). ( 4 ) ( a ) P. 0. Tawnclg, U. P. Patent 2,535,172 (1050); ( b ) P. 0.Tawneg, U.S.Patent 2,535,174 (1950); (e) P. 0 . Tawiicy, tJ. S.Patrnt 2,570,503 (1051); ( d ) P. 0 . Tawney, C . Y. Paten't 2,535,175 (1950); ( e ) P. 0. Tanney, U. S. Patent 2,535,173 (1950); A. N . Pudovik and 0 . N. Grishina, Zhur. Ohshchel Khim., 23, 2GT (1953); ( f ) E. C. Ladd and hl. P. Harvey, U. S.Patent 2,651,656 (1953); (9) A. hT. Pudovik and G. 31. Denisova, Zhur. Obshchei Khim., 2 3 , 2 6 3 (1953). (5) J. B. Dickey, H. \Ti. Coover, Jr., and N. H. Shearer, Jr., U. S.Patent 2,550,651 (1051); E. C. Ladd, U. S.Patent CH=CCH,Br T a P ( 0 ) ( O C 2 H 5 )+ ? 2,622,096 (1952). ( 6 ) (a) % I. Kahachnik, I. B d . acacl. sei. L-.R.S.S., Classe CH-CCI~ZP(O)(OC~€I~'~ sci. chirn., 233 (1047). ( b ) C. L. Arcus and R. J. S.Mattheir-s, The analogous reaction with allyl bromide ha? J . Cheni. Soc., 4607 (1956). ( 7 ) D. H. Chadaick, U. S. Patent 2,784,171, (1957); been describcd by Pudovik and F r ~ l o v aThe . ~ tendR. J. Slocombe, U. S. Patent 2,784,169 (1057); D. H. Chad(9) A. N. Pudovik and ;21. 31. Frolova, Zhiir. Obshrhei wick, U. S. Patent 2,784,206 (1957). Khini., 22, 2052 (1953). (8) F. Ward, Brit. Patent 765,222, Example 11 (1957).
+
SEPTEMBER
1961
3271
DERIVATIVES O F UNShTURATED PHOSPHONIC rlCIDS
TABLE I THEMOLARREFRACTION OF U N S A T U R A TPHOSPHATES ED Mr,i Cpd.
d2S
ny
Found
Calcd.a
CHZ-CHP(OCHI)OCTTZCHZCI 0
1,239
1.4548
40.40
40.56
CHz=CHP [S(CH~)z]OCHzCHzCl
1,171
1.4723
47.19
47.08
1,104
1.4164
42.59
43.40
0
I
0
C1H3?(0C&)l
a Calculated from atomic refractions using 4.27 for P and 2.45 for N,as found by M. I. Kabachnik, R i d . acad. sei. U.R.S.S., Classe sci. chim., 219 (1948); and G. M. Kosolapoff and L. B. Payne, J . Org. Chem., 21, 413 (1956), respectively. A
mixture of diethyl 1-propynylphosphonate and 2-propynylphosphonate. TABLE I1 I N F R A R EABSORPTION^ D
831 855 918 932 065 983 1031-34 1053 1070 1196 1277 1305 1405 1458 1610 1869 1961 2460 2849 2094 3400
OF
UKS.ATURATED PHOSPHONATES
(19) (8)' (IO)' (12) (20) (27) (86) (79)' (46) (8) (17)
(9) (11)
(7) (4)d
(1) (1) (2)
(3) (1 1) (4Id
I305 1404 1464 1484 1613 1946 2475 2817 2994-3021 3378
a Figures i n parentheses are molar ahsorptivities in arbitrary units. propynylphosphonate. ' Shoulder. Water band.
ency of excess phosphite to react further with the initial productg was avoided in the present experiments bv the use of inverse addition. A 36% yield of isomeric diethyl propynylphosphonates was obtained. Tests for a terminal acetylenic grouping were obtained with alkaline sodium 3,S-dinitrobenzoateIO and with alkaline mercuric cyanidp. The infrared absorption ( 3 , Table 11) shows that both isomers were present, with diethyl l-propynylphoFphonate greatly predominating. A very strong peak a t 2208 cm.-l is clearly within the range characteristic of C=C stretching in disubstituted acetylenes." A much weaker peak a t 2092 cm.-l (10) B. C. Saunders and B. P. Stark, Tetrahedron, 4, 197 (1958); ref. 14.
817 969-76 1004 1055-64 1094 1157 1258 1:370 1391 1439 1415 1613 1795 1852 1931 1061 2002
838-47 855 93 1 963 988 1032 1073 1085 1192-1208 123-45
(6) (19) (4Id
.4mixture of diethyl 1-propynylphosphoriate and 2-
corresponds t o the same vibration in a terminal acetylenic group adjacent to a negatively substituted carbon atom. Weak absorption a t 3200 cm.-' corresponds to =CH stretching, again attributed to small amounts of diethyl 2-propynylphosphonate. Traces of a third isomer, diethyl propadienylphosphonate, may be indicatedll b y very weak absorption a t 1961 em. characteristic of allenes. It is evident that the triple bond in propargyl bromide shifts to a considerable extent during reaction with either sodium diethyl phosphite or (11) L. J . Bellamy, The Infrared Spectra oj Complex Molecules, John Wiley and Sons, Inc., New York, 1954, pp. 49-52.
3272
IVELCH, GOSZSLES, A S D GUTHIZIE
VOL.26
with triethyl phosphite. ,Jacobsen et a1.12 obtained a The integrated intensity of the entire band is an 5% yield of diethyl 1-propynylphosphonate using additive function of the number of such groups the triethyl phosphite route. Their product failed The peak a t 1484 cm.-' is missing from to show infrared absorption a t 2100 or 3300 cm.-I the spectrum of conipotind 1 (Table 11) and so is characteristic of a terminal acetylenic group. apparcritly due to an Y-methyl group. The splitting Failure to obtain a precipitate with ammoniacal of the entire band seems more pronounced in Ssilver nitrate was probably inconclusive, since the methyl derivatives than in O-methyl derivaproduct obtained in the present work also failed tives.19f21-23 However, 0-ethyl derivatives usually to give the test, and other studies have shown that show two well defined peaks, as may be seen a t certain monosubstituted acetylenes having phos- 1439 and 1475 em. for diethyl propynylphosphophony1 groups do not give an insoluble silver or nate. copper derivative.13 EXPERIMENTAL Hunt, Saunders, and Simpson prepared several ethynylpho~phonates'~ in semipurified form, and Benzylainnionium hydrogen vinylphosphonafe. T o 56 ml. of noted C=C stretching absorption at 2075 cm.-' water in a 300-ml. round bottomed one necked flask was This is in good agreement with the value of liquid added 24 g. (0.60 mole) of sodium hydroxide pellets. As cyanoa~etylene'~and for diethyl 2-propynylphos- soon as solution was complete, 23 g. (0.10 mole) of his(2chloroethyl) vinyl phosphonate (commercial grade)24 was phonate noted here. However, they found H-C= added to the warm mixture, which was then swirled. After stretching absorption a t 3165 em.-' which is 40 a f e x minutes the t\vo phases merged, accompanied by gas cm.-l below that given by solid or liquid cyano- evolution. The mixture was refluxed 1 hr. and was chilled acetylenelsand is 125 cm.-llower than for diethyl 2- and filtered under suction to remove a brown, solid byproduct. T o the filtrate mas added 22 ml. of concd. hydropropynylphosphonate. The replacement of -CH2chloric acid, giving a pH of about 5. The solution was P(0)(0R)2by-P(0) (OR)zin the monosubstituted evaporat'ed to about 80 ml., cooled. and freed of salts by acetylene would not be expected to produce such a suction filtration. The filtrate was further evaporated to 40 ml., cooled, and 10 nil. of concd. hydrochloric acid was large shift. The spectra of the vinylphosphonates studied added. It was cooled to 5' and again filtered by suction. The remaining salts were precipitated with 150 ml. of (1 and 2, Table 11) showed little similarity to acetone, followed by stirring and filtration. T o the filtrate spectra of alkyl acrylatesI6 or of acry10nitrile.l~ x a s added 12 ml. (0.11 mole) of benzylamine. The solution A strong sharp peak a t 831 cm.-l (12.04 p ) for was evaporated until its boiling temperature reached 90'. methyl 2 chloroethyl vinylphosphonate could cor- It was distilled under reduced pressure until the pot temperature reached 40-50" and the residue crystallized. respond t o the 12.3 p absorption noted by Walton The solid was dissolved in 150 ml. of hot absolute ethanol and HughesI6 for acrylates and acrylamides and recrystallized by cooling, followed b y suction filtration generally. The 963-965 cm.-l absorption given by a t 5". It weighed 7.2 g. and melted a t 191-195'. An additional 1.8 g. of this material was obtained on evaporation of the vinylphosphonates is probably due to P-0 the filtrate and recrystallization of the residue. The total stretching,lg with out-of-plane =CH2 and =CHyield was 4272,. Again recrystallized, the solid melted a t deformations occurring a t 983-988 cm.-' and 918- 196.0-197.0" (partial immersion thermometer). 932 cm.-', respectively. The in-plane =CHAnal. Calcd. for CgH14;"i03P:N, 6.51; P, 14.4. Found: and =CH2 deformations appear a t 1305 and 1404- N,6.48; P, 14.1. 2-Chloroethyl vinylphosphonochloridate. T o a 1-I., three1405 cm.-' flask equipped with a mechanical stirrer and a reflux 2-Chloroethyl N,N-dimethyl-P-vinylphosphona-necked condenser protected with a calcium chloride tube was added midate (2, Table 11) showed a broad and unusually 215 g. (1.03 moles) of phosphorus pentachloride and 170 intense peak a t 983-988 cm.-' which may have ml. of 1,1,2-trichloroethane. T o the stirred suspension was added 194. g. (0.83 mole) of bis(2-chloroethyl) vinylphosbeen due in part to a C-?,T ~ i b r a t i o n . ' Other ~ An exothermic reaction took place. The stirred characteristic features are a doublet a t 1073 and phonate. mixture was refluxed for 1 hr. during Tyhich the remaining 1085 cm.-l, and a peak a t 1484 cm.-l The latter phosphorus pentachloride dissolved. The solvent, phospeak is a part of the -CH, and -CH2deforma- phorus oxychloride, and ethylene chloride svere removed by tion absorption normally a t 1430-1485 cm.-l distillation at atmospheric pressure until the head temperature reached 120°. Distillation of the volatile materials was
(12) H . I. Jacobson, N. J . Griffin, S. Preis, and E. V. Jensen, J . Am. Chein. Sac., 79, 2608 (1957). (13) G. SI. Kosolapoff, private communication. (14) B. B. Hunt, B. C. Saunders, and P. Simpson, Chem. & Ind. (London), 47 (1960). (15) G. C . Turrcl. IT. D. Jones, and A. hlaki, J . Chem. Phys., 26, 1544 (1957). (16) W.L. Walton and R. B. Huehes. J . .4m.Chem. Sac., 79; 3985 (1957). (17) F. Halverson, R. F . Stamm, and J . J. Whalen, J . Chem. Phys., 16, 808 (1948). (18) L. J. Bellamy and L. Beecher, J . Chem. Sac., 475 (1952); 728 (1953); ref. 10, p. 267. (19) B. Holmstedt and L. Larsson, .Ida Chem. Scand., 5 , 1179 (1051).
completed under reduced pressure. The residue was distilled through a &in. Vigreux column at ca. 1 mm., giving 24 g. a t 55-96", 98 g. (6270 yield) a t 94-loo", and 11 g. at 100119". There was 16 g. of residue. The middle fraction was analyzed and used in subsequent syntheses. Anal. Calcd. for CaH7Cl2O2P: P, 16.4. Found: P, 16.1. Jfethyl 2-chloroeth yl vinylphosphonale. T o a 500-ml., three-necked flask fitted with a mechanical stirrer, reflux
Y
(20) S. A. Francis, J . Chem. Phys., 18, 861 (1950). (21) L. IT. Daasch and D. C. Smith, Anal. Chem., 23,853 (1951). (22) T . 8.Piper and E. G. Rochow, J . Am. Chem. SOC., 76, 4318 (1954). ( 2 3 ) H. Lenormnnt, BUZZ. Sac. Chim. France, 36 (1948). (24) Sample was prepared by the hlonsanto Chemical Co.
SE;PTEiM B E I
