INDUSTRIAL A N D ENGINEERING CHEMISTRY
286
VoI. 15, No. 3
Disubstituted Guanidines’ By Winfield E. I. D U
FONT DE
Scott
NBMOURS & CO., SALES DEPARTMENT, TECHNICAL LABORATORT, WILMINQTON, DEI,.
Evidence in favor of the amino form of disubstituted guanidines has been given, and the formula of diphenylguanidine hydrosulfide and its function in acceleration is discussed. Tetraphenylbiguanide and diphenylguanidine trithiocarbonate haue been prepared and described. A proposed mechanism for the formation of thiourea deriuatives and the decomposition of certain difhiocarbamates has been given, and also the formula for the reacfion product of aniline. carbon disulfide, and diphenylguanidine. The effect of zinc oxide on the tensile and elongation of rubber compounded with di-o-tolylguanidihe has been shown. The rela-
tive curing power of di-p-tolylguanidine. di-o-folglguanidine, and diphenylguanidine, when compounded in molecular proportions, is in the order named, the first being the strongest. I t requires 25 per cent more diphenylguanidine than di-o-tolglguanidine to produce the same acceleration. Their relative ualues at lower uulcanization temperatures haue been shown. Basic zinc carbonate has the same eflect as zinc oxide when compounded with disubstitufed guanidines. The use of methylenedianilide in connection with di-o-tolylguanidine shows a slowing-down effect of the rate of vulcanization in the initial stages of the cure, when methylenedianilide is not suficiently compensated for by an increase in sulfur.
HE FIRST work on disubstituted guanidines as vulcanization accelerators was published by Kratz, Flower, and Coolidge,2who pointed out the high curing power of diphenylguanidine as compared with certain other accelerators in use at that time. Twiss3 worked with a monosubstituted guanidine, aminoguanidine bicarbonate, and King4 recommended the use of certain urea derivatives such as guanidine. Bedford and Sebrells have published more on the vulcanizing reactions of diphenylguanidine than any other investigators. Disubstituted guanidines, usually written as imines, may exist in either the amino or imino forms, owing to a tautomeric hydrogen atom, thus:
I n this case the amino form would react with carbon disulfide to produce thiocarbanilide and thiocyanic acid. Since the reaction of diphenylguanidine and carbon disulfide probably proceeds through the intermediate formation of a dithiocarbamate, as is the behavior of other amines, the conclusions of Weith and Schroeder seem unwarranted. Reactions of the amino form of diphenylguanidine have been shown by Rathke and Oppenheim18who found that by the action of phenyl mustard oil, a t room temperature, triphenylguanylthiourea is produced. It was also shown that diphenylguanidine reacts with phenylcyanamide in a similar way to form triphenylbiguanide. The writer has found that carbodipheaylimide reacts with diphenylguanidine to form the new base, tetraphenylbiguanide.
T
RNH
RNH
I C+NH I
7-
I II
C-NHz RN
RNH
Symmetrical trisubstituted guanidines can exist in the one form only, since tautomers are identical. Marckwald6 has shown that the diphenyltolylguanidine prepared from thiocarbanilide and p-toluidine is the same as that prepared from phenyl-p-tolylthiourea and aniline. The imino formula for disubstituted guanidines was established by Weith and Schroeder,’ and was based upon their statement that carbon &sulfide reacts with diphenylguanidine to produce thiocarbanilide and thiocyanic acid. They state that the amino form would produce phenyl mustard oil and phenylthiourea in this way:
+c
~-NH%
L-NH-t:
This compound crystallizes from alcohol in needles, melting a t 136” C. The total nitrogen calculated for C~OHBN~ is 17.28; found, 17.08. Tetraphenylbiguanide forms a crystalline hydrochloride that is quite soluble in alcohol but insoluble in cold water. Owing to its rather weak basicity, tetraphnylbiguanide is onIy a mild accelerator. Since diphenylguanidine shows the characteristic reactions of a rather strong base, it is to be expected that it will form NHn NHz salts analogous to those of ammonia and the stronger organic I I bases. This is indeed the case. Bedford and Sebrells SCN C=S C = N D CS .S indicate diphenylguanidine hydrosulfide as diphenyltriaminomercaptan, resulting from the addition of hydrogen sulfide to It would be just as logical to assume that the reaction would the double bond between the central carbon atom and imino nitrogen. These writers claim that their hydrogen sulfide addition product a “free” amine, but this cannot be true -for it will not form a salt by reacting with another molecule of an acid, neither does it react with carbon disulfide in the C-NH.H CS.S + C - S H -I-HSCN mann&stated, which is claimed as proof of the existence of a “free amino group.” As evidence of the existence of a sulfohydryl group, it is stated that the hydrogen sulfide 1 Presented before the Division of Rubber Chemistry a t the 64th Meetreaction product of diphenylguanidine shows characteristic ing of the American Chemical Society, Pittsburgh, PP., September 4 to 8. reactions with metallic hydroxides and oxides-i. e., the for1922. mation of metallic mercaptides. No such behavior is to be 2 THISJOURNAL, 12 (1920), 319. found, for metallic hydroxides and oxides that react with 8 J . SOC.Chem. I n d . . 26 f1917), 786. Met. Chem. Eng., 15 (1916), 23. diphenylguanidine hydrosulfide decompose it into the free 6. THISJOURNAL, 14 (19221, 30. guanidine derivative and the metallic sulfide or hydrosulfide8 A n n . , 286 (1895), 353. ’
+
+-
+
4
7
Be?., 7 (1874), 945.
BW., i a (IS~Q), 774; aa (isgo), 1669.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
March, 1923
the same behavior as is found with ammonium sulfide. T h e formula for diphenylguanidine hydrosulfide is written as follows:
o y C=N, H Ha C > d H
or
SH
C>yH O h
C-N,
reaction of aryldisubstituted guanidines and carbon disulfide may be represented as €ollows: RNH IC-NHz
I
Ha
f CSa
----f
II
SH
4- H 9 f CS2
+ S II
H
I is q l l + HaN-C I + C-N-C--S-N-C RNH
I1
ACTIONOF HYDROGEN SULFIDE AND CARBON DISULFIDE ON DIPHE NYLGUANIDINE Further evidence in favor of the foregoing formula for diphenylguanidine hydrosulfide is shown by the fact that this disubstituted guanidine reacts with hydrogen sulfide and carbon disulfide to form diphenylguanidine trithiocarbonate.
C-NHa
I
RN
I
2
RNH C-N-CSSH
I/ RN RNH C-N-C-SHS/I
c)y
287
RN
/I
H
I1
RN
RN
RNH
RNH
RN
RN
H
II
RN
RN
The diphenylguanidine salt of diphenylguanyldithiocarbamic acid, for example, decomposes into carbodiphenylimide, hydrogen sulfide, and diphenylguanidine thiocyanate. Carbodiphenylimide and hydrogen sulfide immediately unite to form thiocarbanilide. By boiling carbon disulfide containing an excess of diphenylguanidine, some of the hydrogen sulfide escapes so that a part of the carbodiphenylimide reacts with carbon disulfide to form phenyl mustard oil. Weith has shown11 that carbodiphenylimide reacts with carbon disulfide to produce phenyl mustard oil. A similar decomposition of the aniline salt of phenyldithiocarbamic acid would produce phenyl mustard oil and aniline, which unite to form thiocarbanilide. The dithiocarbamates of primary amines are less stable than those of the secondary amines, where decomposition to form a mustard oil is impossible. One molecule each of aniline, carbon disulfide, and diphenylguanidine react to produce the diphenylguanidine salt of phenyldithiocarbamic acid, rather than the compound indicated by Bedford and Sebrell.6 The formula for this compound is:
"0 I
This compound is not formed by the action of carbon disulfide on diphenyltriaminomercaptan. Bedford and Sebrell5 state that the reaction above produces either a thiourea derivative or a dithiocarbamate, depending upon the amount of hydrogen sulfide employed. The product which they term a dithiocarbamate is not really such a compound, for the sulfur of the thiol group is not attached to nitrogen, the normal structure of such salts. Diphenylguanidine trithiocarbonate can be prepared from an alcoholic or aqueous acetone solution of diphenylguanidine containing a slight excess of the solid guanidine, by the addition of carbon disulfide and immediately passing hydrogen sulfide into the solution. This trithiocarbonate crystallizes in orange-yellow needles, melting with decomposition by heating rather quickly to 88" to 89" C. I n other solvents such as ether, benzene, carbon tetrachloride, and chloroform, its insolubility causes precipitation as a sticky resin mixed with a small amount of the dithiocarbamic acid derivative of By treating with hydrochloric acid this product is decomdiphenylguanidine. Trithiocarbonic acid is obtained by posed into the original constituents. By heating in boiling treating the thiocarbonate with a mixture of ice and strong benzene, hydrogen sulfide is evolved, forming principally hydrochloric or sulfuric acid. This offers a quick and con- triphenylguanylthiourea,which was found to melt a t 156" to venient method of preparing trithiocarbonic acid. Di- 157" C . (uncorrected), instead of 150" C. given by RathkeS8 phenylguanidine trithiocarbonate decomposes slowly on The heat decomposition of the dithiocarbamate mentioned standing, with the loss of hydrogen sulfide and some carbon above proceeds similar to the above-mentioned diphenyldisulfide. The decomposition product contains diphenyl- guanidine salt of diphenylguanyldithiocarbamic acid. I n guanidine, its thiocyanate, and thiocarbanilide, together this case, however, instead of carbodiphenylimide being produced from the acid portion of the salt, phenyl mustard with a t least one other compound. oil is formed. Thus, the decomposition products are phenyl It was shown by Hoffman9 that carbon disulfide reacts with diphenylguanidine to produce thiocarbanilide and di- mustard oil, hydrogen sulfide, and diphenylguanidine. The phenylguanidine thiocyanate. The mechanism of this mustard oil and the base unite to form triphenylguanylthioreaction has never been clearly shown, though it probably urea. proceeds through the formation and subsequent decomposiACTIONOF DISUBSTITUTED GUANIDINES DURING tion of a dithiocarbamate, as is the case with aniline and VULCANIZATION carbon disulfide. Owing to the structure of such a dithioDiphenylguanidine decompose's slowly at temperatures carbamate, it does not decompose into hydrogen sulfide, a n amine, and qustard oil, for under such conditions di-diphenyl- above its melting point, with the formation of ammonia, guanylthiourea would be formed. Neither does the reaction aniline, and triphenyldicarbimide, according to Rathke and Oppenheim.8 The ammonia is a powerful accelerator, while proceed through the formation and decomposition of a thiuramdisulfide, according to Fromm,10 for here the thiourea the other compounds are relatively weak in their accelerating action. This decomposition is not the primary vulcanil;ing derivative would also be formed. The mechanism of reaction, for di-o-tdylguanidine, which is more stable toward ' Bn.. 8 (1870), 460. I'
I b d , 4 1 (lSO9), 1948.
11 Bar..
7 (1876), 1308.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
288
heat and which melts at 179” C., is quite appreciably more active than the diphenyl derivative. Diphenylguanidine hydrosulfide does not decompose into thiocarbanilide and ammonia at vulcanization !temperatures, so its action is that of a h~drosdjkleaccelerator as has been previously stated.12 I
I
Vol. 15, Nop3
time for a set cure (nonporous vulcanizate), but larger amounts of the oxide do not produce correspondingly shorter set cures. A series of formulas with increasing amounts of zinc oxide up to 3 per cent on the rubber is shown in Table I. All cures were made at 141.5” C., corresponding to 40 lbs. steam pressure. Disubstituted guanidines used in this work passed a standard 200-mesh sieve. I n Fig. 1 the time-tensile and time-elongation curves marked A, B, C , etc., represent the corresponding formulas in Table I. TABLE I
900 BOO
roo
4000
30 )?IO.
60
90
120
I50
160
I-THE EFFECT OF T R E ADDITION OF SMALL AMOUNTS OR Z I N C TO A DI-0-TOLYLQUANIDINE
OXIDE
STOCK
EFFECTOF ZINCOXIDE The polymerizing effect of certain zinc compounds such as the oxide, carbonate, or basic carbonate is quite marked when used in connection with disubstituted guanidines, By using only 0.5 per cent of zinc oxide on the rubber content, a shorter elongation and higher tensile strength of the vulcanized product are obtained. These effects are the reverse of depolymerization, and are supposed to be due to a higher state of polymerization or larger and fewer aggregates of the rubber complex. This stiffening action of small amounts of zinc oxide is physicothemical and must be distinguished from the use of zinc oxide as a filler. Zinc carbonate and basic zinc carbonate also produce high tensile strength when used with disubstituted guanidines. Such activators probably form derivatives corresponding to the complex zinc ammonia compounds, zincates, and thiozincates. A discussion of such compounds and the action of zinc oxide with both mercapto and hydrosdjide accelerators will be given at a later date. Certain other metallic oxides and carbonates, notably litharge and white lead, do not show any marked polymerizing effect when used with disubstituted guanidines in heat cures, and their action is largely additive. Small amounts of litharge with guanidine derivatives do not produce “snappy,.” high-tensile stocks, probably owing to the fact that lead is quickly removed from the system as the inactive sulfide. Antimony pentasulfide shows no effect when compounded with guanidine derivatives. The result seems to be entirely the additive action of the two Compounds. Antimony pentasulfide does not act as a retardant, although it appears to reduce the effect of zinc oxide to some extent. I n a tube stock containing 10 per cent of antimony pentasulfide on the rubber, 1.5 per cent of zinc oxide shows about the same effect as 1 per cent of zinc oxide, where none of the pentasuliide is used in oonnection with diphenyl- or di-o-tolylguanidine. With di-0-tolylguanidine as the accelerator, 0.5 per cent of zinc oxide on the rubber content appreciably reduces the 11 Scott and
Bedford, THIS JOURNAL, 13 (19211,125.
Smoked sheet Zinc oxide Sulfur Di-o-tolylguanidine
A 100 0 3.0 0.5
B 100 0.5 3.0 0.5
C 100 1.0
D 100 1.6 3.0 0.5
3.0 0.5
E 100
F 100 3.0 3.0 0.5
2.0 3.0 0.5
The 15-min. cure with Stock A, containing no zinc oxide, was blown-i. e., contained gas pockets, and was very much undervulcanized-while all the others were “set” and showed tensiles ranging from 1200 to 1700 lbs. per sq, in. Each increase in the amount of zinc oxide used is distinctly s h o w by higher ultimate tensile strength, as well as in the shorter elongation. I n addition to a quicker initial cure, small amounts of zinc oxide produce a less “tender” stock. By examining the time-elongation curves (Fig. 1) it will be seen that 3 per cent of zinc oxide almost entirely overcomes depolymerization or “reversion” caused by longer curing time. This does not mean that Stock F will show better aging qualities than B In a stock containing no “filler,” 0.5 to 1 per cent of zinc oxide on the rubber content is sufficient to activate an accelerator of the type of di-o-tolylguanidine. When less than 1 per cent of I;inc oxide is used, it readily disappears as such, so that at the optimum cure (1hr. with the stocks above) the test sheets are translucent. By using basic zinc carbona%e the rubber becomes translucent in a shorter time than with zinc oxide. RELATIVE ACCELERATING ACTIONOF CERTAIN DISUBSTITUT~D GUANIDINES Certain other disubstituted guanidines, among which are the ditolylguanidines, have appreciably more accelera$ing power than diphenylguanidine, when compounded in molecular proportions or even when equal weights of the different accelerators are used. The activity of di-p-tolylguanidine, di-o-tolylguanidine, and diphenylguanidine is in the order I
I
I
I
I
4000
t 0
70 0
3000
2000
H , 0.453 D-oTG
J, 0.453 D-p-TG I
I
I
Tme o i c u r e Ln-in. FIG.2 - T H B TIONS
OF
I
1
I
I50 180 30 60 90 120 RELA‘I‘IVE ACCELERATING EFRECT OF EQUIMOLECULAR PORDIPHE$NYLQUANIDINE, DI-0-TOLYLGUANIDINE, AND Dry$TOLYLQUANIDINB
INDUSTRIAL A N D ENGINEERING CHEMISTRY
March, 1923
I
I
crj
2000-1)
I
I
p
,/
1
-;
I
I 60
FIQ.3-A
180
I20
1
I
I
I
I
P
I
240
I
I S.oo%ZnO 2 4. I 5 % Z n,fO H),COJ
G I 1000-s
~ r n bf e c l reAm i A
289
300
COMPARISON OF DIPHENYLGUANIDINE AND DI-O-TOLYLGUANIDINE AT DIEWERENT CURING TEMPERATURES
named, the first being the strongest. The stock formulas used in comparing the above accelerators are shown in Table 11. TABLEI1 Smoked sheet Zinc oxide Sulfur Diphenylguanidine D i-o-tolylguanidine D i-$-tolylguanidine
G
H ~-
100 1
100 1 4
4 0.400
0.453
1 100 1 4
0.453
The two ditolylguanidines were compounded in molecular proportions based upon 0.4 per cent of diphenylguanidine on the rubber. Cures were made a t 15-min. intervals from 15 min. to 3 hrs., as were all other curing tests connected with this work. The vulcanization temperature was 141.5' C. Time-tensile and time-elongation curves are shown in Fig. 2. The higher accelerating power of the tolylguanidines is due to their slightly greater basicity as compared with diphenylguanidine.
will be noticed by reference to Fig. 3 that nearly the same relative behavior is found as when vulcanization is carried out at 141.5' C., although the difference is somewhat in favor of the 0-tolyl derivative. This indicates, as was stated above, that the activity of this disubstituted guanidine is not dependent upon its decomposition, but rather upon the ease with which it unites with hydrogen sulfide to form a hydrosulfide which is analogous to ammonium sulfide.
ACTIONOF BASICZINC CARBONATE
It was stated above that basic zinc carbonate has an effect with substituted guanidines similar to that of zinc oxide. From similarity of basic properties of the two compounds a similar effect is to be expected, although larger amounts of the basic carbonate are required to produce the same results. Fig. 4 shows the effect of an equimolecular portion of basic zinc carbonate based on a stock containing:
........ ........... ................. . ..
Smoked sheet.. Zinc oxide., Sulfur Di-o4olylguanidine. ,
COMPOUNDING: EQUIVALENT OF DI-0-TOLYLGUANIDINE AND DIPHENYLGUANIDINE
w -
Since di-o-tolylguanidine shows more accelerating power than diphenylguanidine when used in equimolecular proportions or even when equal weights are used, it was desired to determine the compounding equivalents of these two accelerators. (By "compounding equivalents" is meant the amount of one accelerator that shows the same vulcanizing power as a given amount of another.) The following stock was taken as a basis of comparison:
........ ...........
Smoked sheet., Zinc oxide.. Sulfur.. Diphenylguanidine.
............... ....
100 3 4 0.5
With this formula as a control stock, di-o-tolylguanidine was substituted for diphenylguanidine, and the amount used was decreased by definite amounts until the time-tensile and timeelongation curves practically coincided. Fig. 3 shows that 4 parts of di-o-tolylguanidine is equivalent to 5 parts of diphenylguanidine. It was thought that on account of the rather high melting point of di-o-tolylguanidine, it might be less effective than the diphenyl derivative at lower vulcanizing temperatures. Cures were run at 134' to 134.5' C. and 125.3' to 625.8' C., corresponding to 30 and 20 lbs. of steam, respeetively. It
100 3 3 0.5
3000
2000
1000
30 FIG.
5-THE
QUANIDINB B Y
90
60
EFFECT PRODUCED
18
REPLACIHO 1.0 PART OR DI-C-TOLYL6.0 PARTS OR METBYLBNBDlANIk.itlDB BY
INDUSTRIAL A N D ENGINEERING CHEMISTRY
290
Curve 1indicates the results of 3 per cent of zinc oxide on the rubber, while Curve 2 shows the effect of the basic carbonate. No such high ultimate tensile strength is found with the basic carbonate, but the tensiles and elongations for the shorter cures are remarkably close together. By comparison with A of Fig. 1 the effect of basic zinc carbonate is readily apparent. Using basic zinc carbonate, the rubber becomes translucent in 30 min. at 141.5’ C. (the temperature a t which the cures represented in Fig. 4, were made), showing a rapid disappearance of the basic carbonate as such.
tolylguanidine and methylenedianilide it was thought that some effect of the unstable trithiocarbonate or dithiocarbamate might be shown. It was found that in low sulfur stocks, such as have been used throughout this work, an initial retarding effect is brought about unless the methylenedianilide is compensated for by an increase of sulfur sufficient to bring about its sulfur reaction. A mixture of methylenedianilide and di-o-tolylguanidine is less likely to “scorch” than when the guanidine is used alone in a highly compounded stock. To bring out the combined effect of di-o-tolylguanidine and methylenedianilide, the following stock was used:
METHYLENEDIANILIDE AND DI-O-TOLYLGUANIDINE I n the discussion of the chemistry of diphenylguanidine given above, it was stated that this compound reacts with hydrogen sulfide and carbon disulfide to form a trithiocarbonate. A number of accelerators, such as hexamethylenetetramine, anhydroformaldehydeaniline, and methylenedianilide react with sulfur to produce both hydrogen sulfide and carbon disulfide. By employing a mixture of di-o-
Vol. 15, No. 3
........ 100 ........... 3 ............... 3 0.4 ..... 0 . 5
Smoked sheet.. Zinc oxide.. Sulfur.. Di-0-tolylguanidine., ... Methylenedianilide
This formula is the same as that shown in F, Table I, in which 1 part of di-o-tolylguanidine has been replaced by 5 parts of methylenedianilide. Fig. 5 shows the tensile and elongation comparison of the two stocks.
T h e Beta-Chlorovinyl Chloroarsines”’ By W. Lee Lewis and G. A. Perkins NORTHWESTERN UNIVERSITY, EVANSTON, ILL.,
N a dissertation by J. A. Nieuwlandls there appears the following paragraph :
I
AND
BUREAUOF SCIENCE, MANILA,P. I.
Following ts a reoiew of work. upon the absorption of acetylene by arsenic chloride in the presence of aluminium chloride. Further proofs of the structures and the physical properties of p-chlorooinyl diqhhloroarsine. bis-8-chlorovinyl chloroarsine, and tris-6chlorooinyl arsine, together with a theory of the mechanism of the absorption reaction, are presented. The methods of preparation, purification, analysis, and interconversion of the three chlorooinyl arsines are discussed.
Pure arsenic chloride free from oxide did not show any reaction with perfectly dry acetylene. When aluminium chloride wasadded theabsomtion of the gas was effect;d with the evolution of considerable heat. The contents of the flask turned black. When decomposed by pouring the substance into cold water, a black, gummy mass separated out, and on standing for some time crystals appeared in the aqueous solution. The tarry substance possessed a most nauseating and penetrating odor and was extremely poisonous. Inhalation of the fumes, even in small quantity, caused nervous depression. No chlorine derivatives of acetylene were noted. Owing to the poisonous nature of the compound formed, their thorough investigation was postponed.
The importance of the substituted arsines in chemical warfare, together with the probability that there might be formed here one or more addition products of arsenic chloride and acetylene of a new order, led to a more careful investigation of Nieuwland’s reaction. I Received December 28, 1922. Published with the permission of Brigadier General Amos A. Fries, director of the Chemical Warfare Service. 9 The present paper is a partial report of an investigation carried out beween April l a and August 23, 1918, in Organic Unit No. 3, Offense Research Section, U. S. Chemical Warfare Service, stationed a t the Chemical Laboratory of the Catholic University of America, Washington, D. C The following men took part in the work in varying degree, and in the order listed: R. I,. Ginter, R. R . Williams, R. S. Bly, F. C. Vibrans, J. W. Rauth, W. N. Jones, W. T.Read, H. G. Seeley, G. 0. Gutekunst, H. R . Parker, H. P. Ward, R. A. Norton, 0. S. Levy, C. C. Curtis, Geo. Miller, Hugh Patterson, W. Hartman, H. R. Yon, Fred Cassebeer, F, C. Owens, E. W. Clark, H. W. Stiegler, P. F. Ziegler, C. W. Staples, J. A. Kerr, W. R. Crandell, E. M. Clarke, Alex Greenberg, F. 0. Krieger, E. Musser, L. L. Perry, G. F. Taylor, H. Abrams, R . 0. Davis. a Printed but not published. “Some Reactions of Acetylene,” p. 128, completed under direction of Dr. John J. Griffin a t the Catholic University of America in 1904.
PREVIOUS WORK to
The addition of acetylene both
with zation,and is recorded without by polymeriBaud,4 and a number of compounds of aluminium chloride, acetylene, and a third constituent, such as alcohol. have been isolated by Gangloff and Henderson.& Fischefl added arsenic chloride to the acids of the acetylene series, the addition of AsQ and chlorine taking place at the triple bond. Weak alkalies hydrolyze the chlorines attached to arsenic, yielding chloroarsenoso acids, which may be oxidized to the chloroarsono acids. Dafert? subsequently studied the reaction of acetylene upon arsenic chloride, and isolated a product to which he ascribed the formula AsCla.2CaHz. Dafert apparently regarded the substance as an association product rather than a secondary arsine, although the properties correspond to those of bis-p-chlorovinyl chloroarsine. He does not report finding the corresponding compounds of arsenic chloride with one and three molecules of acetylene, respectively. More recently Green and Prices have partially repeated and substantially confirmed the American work which had been reported in Chemical Warfare Communications in 1918. Lewis and StieglerQreported preliminary results on the derivatives of the chlorovinyl arsines, which work has subsequently been repeated and extended by Mann and Pope.l0 The authors and their collaborators reduced the reaction to controllable conditions, isolated three pure compounds from the reaction mixture, proved their nature, worked out methods of laboratory control, and submitted plans for large-scale production. In the later stages of the work J. B. Conantll and his
Comfit. rend., 130 (1900), 1319. J . A m . Chem. Soc., 39 (19171, 1420. a Ann., 403 (1914), 106. 7 Monatsh., 40 (1919), 313. 8 J . Chem. Soc., 119 (1921), 442. a Science, 56 (1922), 55. 10.7. Chem. Soc., 121 (1922), 1754. 11 Chemical Warfare Communications, Organic Unit No. 1, Offeqse Rmearch Section, U. S. Chemical Warfare Service, 4
6
