VINYL-ALKYL C. E. SCHILDKNECNT, A. 0. ZOSS, AND CLYDE MCICINLEY General Aniline nnd Film Corporation, Easton, Pa.
T h e literature related to simple urlsubstituted F i n y l allq 1 ethers is reviewed. New data are presented on the purification and properties of the vinyl alkyl ether monomers. Special attention is given to vinyl methyl, vinyl n-butJ1, and vinyl isobutyl ethers, which have been made available for dekelopment purposes in this country by application o f the Reppe synthesis. Correct physical data on these materials are of special interest both because,the monomers are com-
pariltively unstable and because Elheis behavior in polymerization is greatly influenced by certain types of impurities. Chemical reactions of the vinyl alkq-1 ethers include addition to the double bond, hydrolysis, and polymerization. Some preliminary work on the polymerization of vinyl alkyl ethers is described together with observations on several commercial polyvinyl alkyl ethers from abroad.
HIS paper discusses simple compounds of the type CH2=CHOR, where R is an alkyl group free from unsaturation and both the vinyl and R groups are free from halogen or other substitution. Vinyl methyl ether, vinyl n-butyl ether, and vinyl isobutyl ether are the members of the series which received most attention and whose polymers are discussed. The n e x data presented from this laboratory comprise the major part of the material under the headings Purification, Physical Properties, and Polymerization, as well as Properties and Stabilization of the Polymers. B large part of the information on the synthesis of vinyl alkyl ethers arid their chemical reactions is taken from the literature. All data not otherwise designat'ed are from these laboratories. .The authors examined much of the published work critically in the laboratory, including that of Reppe in Germany and ShostakovskiI in Russia, Some discrepancies with their work arc not,ed. SYNTHESIS
In 1878 \Tislicenus (63) prepared vinyl ethyl ether by heating chloroacetal v i t h sodium: OGH; . .
i
CHnCICH
OCzH, 130" C. ___f
Na
'\
CH2=CH
+ KaC1+ KaOC2H6
(1)
OCBHI
Vinyl chloride can be used as a vinylating agent, but, under the conditions illustrated in Equation 6, the reaction is slow,-about 12 hours are required for an 85% yield. An excess of the alcohol can be used as solvent for the liquid phase reaction in an autoClare (58):
A German patent of 1918 (37) disclosed the reaction of acetylene with cold, concentrated sulfuric acid to obtain vinyl sulfuric acid, which gave vinyl ethyl ether on treatment mith ethanol. Vinyl ethyl ether was also said to be obtained by reaction of absolute alcohol with acetylene at 80" C. using mercuric phosphate catalyst dispersed in ligroin (8). However, the action of acetylene upon alcohols in the presence of mercury salts or acidic catalysts gives primarily acetals, and good yields of vinyl alkyl ethers are not obtained. I n 1930 Reppe (39) applied for patents on the use of acetylene at relatively high pressures to prepare vinyl alkyl ethers directly from alcohols using alkaline catalysts:
I t mas established that the boiling point and specific gravity are higher than those of diethyl ether. Vinyl ethyl ether was prepared by Claisen by the combined action of phosphorus pentoxide and quinoline on acetal ( 7 ) : OCzHj
/
CHjCH
\
OCi" / + CH?=CH
+ CzHsOH
(2)
OCzH5
Chalmers (5) was unable to dehydrate ether alcohols such ab 2-butoxyethanol directly but treated the bromoether with alkali t o obtain vinyl n-butyl ether: CH20HCH20C4Hs PBro CH2BrCH20C4Hs
CH2BrCH20C4Hg
+ KaOH --+ CHn=CHOC4Hs + KaBr +- HOH
(3)
(4)
Vinyl alkyl ethers can be prepared by passing the vapors of acetals over hot contact catalysts such as porous clays, or silver or palladium deposited on asbestos (8 57):
OR
OH
T
CH=CH Diluted
C. + ROH lq5O0 ------+ NaOR
CHzxCHOR
(7)
In order to avoid explosions, a diluent such as nitrogen was used along with the acetylene. A number of chemical and engineering devices have been developed in Germany and independently in this country to make the use of acetylene in the Reppe vinylation safer. Some of these precautions developed in Germany are described in reports issued by the United States Government (3,Q). The vinylation with acetylene and alkaline catalysts can be carried out not only with the liquid alcohol under pressure, but also in gas phase over contact catalysts (48). I n liquid phase the total pressure used depends primarily upon the vapor pressure of the particular alcohol a t the reaction temperature. The use of a large excess of caustic was proposed as a means of reducing the pressure necessary in vinylating lower boiling alcohols (47). Another method by which the operating pressure with lower alcohols can be reduced is to use inert, high boiling diluents (19). However, pressures as high as 30 atmospheres may be used for preparing vinyl methyl ether.
180
February 1947
INDUSTRIAL AND ENGINEERING CHEMISTRY
181
tion during distillation. Antioxidant-type stabilizers are not effective in preventing polymerization catalyzed by inorganic acidic substances. Vinyl alkyl ethers up to the vinyl butyl ethers can be satisfactorily distilled at atmospheric pressure if the precautions just described are observed. German methods of treating vinyl ether monomers were described in reports published by the United States Government (9, 1 1 ) . PHYSICAL P R O P E R T I E S
Table I gives physical properties of purified vinyl methyl ether, vinyl n-butyl ether, and vinyl isobutyl ether. Vinyl methyl ether is a gas a t normal temperature and pressure but is readily condensed to a colorless mobile liquid. All the other vinyl ethers discussed in this paper are colorless liquids under ordinary -40 -20 0 20 40 60 80 100 I20 140 160 conditions. Boiling points attributed to vinyl methyl TEMPERATURE,%. ether in the literature and in German reports Figure 1. M u t u a l Solubilities of Vinyl E t h e r s and W a t e r (7-14" C.) are not in agreement with the value reported here.' Reppe is quoted in a recent report (60) as giving the boiling point of vinyl methyl ether a t 9" C. Russian workers reported Both primary and secondary alcohols can be vinylated readily 9" to 10' C. (16). The boiling range of purified vinyl methyl by the Reppe process. Vinylation of tertiary alcohols usually ether was found in this laboratory to be between 5 " and proceeds more slowly. Varying amounts of the acetal are obtained as a side product, depending upon the conditions. 6 " C. under the best conditions of distillation. The vapor pressure of vinyl methyl (Figure 2) is 760 mm. a t a temperature just above 5" C. PURIFICATION Melting points of the three vinyl alkyl ethers have not been Vinyl alkyl ether monomers should nor+ally be stored containpreviously reported. Melting points were determined under dry ing an alkaline stabilizing agent, such as potassium hydroxide or nitrogen according to a procedure based on the work of Glasgow, triethanolamine, in order t o minimize or prevent such chemical Streiff, and Rossini (17). A copper-constantan thermocouple changes as hydrolysis in the presence of water or polymerization was used together with a Leeds & Northrup potentiometer No. from the action of acidic contaminating materials. Stabilized 8662. vinyl alkyl ethers can be c;tored for a year or more a t room temperature. When required in a substantially pure form free of stabilizer, portions should be washed and distilled. When purified T A B L ~I. PHYSICAL PROPERTIES OF T H R E E VIXYL ALKYL monomers are kept in refrigeration, precautions should be taken ETHERSOF THE TYPECH2=CHOR to prevent contact with water. Alkyl Group Methy Isobutyl n-Butyl In order to purify vinyl n-butyl ether or vinyl isobutyl ether, Molecular wei5ht 58.08 100.16 100 10 which contain free alcohol and stabilizing alkali, the ether is Boiling point, C. 5.0-6.0 82.9-83.2 93.3-93.8 washed several times with an equal volume of water, or until there Melting point, C. - 122 -112 - 92 Density, d ? ? 0.7511 ... .. is essentially no further change in the volume of the ether. DurDensit;, d a z ... 0.7644 0.7727 ing washing a t room temperature the pH of the aqueous phase Refractive index, n - g 1.3947 ... ... preferably should not fall below 8. The washed material is dried Refractive index, nW . . 1.3938 1.3997 Speoific heat, cal./&am a t by a neutral or alkaline drying agent. For example, the liquid 254 c. ... 0,555 0.553 Latent heat, cal./gram . . 7 4 . 4 (83' C.) 7 7 . 1 ( 9 3 . ~ 5C.) ~ monomer may be dried by standing over solid potassium hydroxVapor pressure, mm. Hg a t ide for 24 hours at room temperature. It can be treated further 250 c. 1550 77 51 pressure, Ib./sq. in. for the removal of traces of alcohol and other impurities by stand- . Vapor sbs. a t 70' F. 28 1.3 0 8 Solubility in water, wt. % ing over sodium wire a t room temperature or by heating with a t 25o.c. 0.82 < 0.10 her. Tiicse products hav:: not been ree Experimental. ported from Germany. Russian workers reported viscous liquid pJIyviny1 alkyl ethers. but not rubberlike or solid hinh Under favorable conditions vinyl alkyl ethers interpolymerize polymers (64, 66, 66). In working JTith the polyvinyl ethers our or form mixed polymerizat'ion products with certain unsaturated laboratory has found it convenient to use the abbreviations compounds, including many vinyl compounds, ethylene a,pPIW, PVI, and PYX (Table V). dicarboxylic acids and their esters, and acrylic esters (4,16,85,61). STABILIZATION OF POLYVIKYL ETHERS. High polymers Of For example, by interpolymerization of vinyl chloride with minor vinyl alkyl ether require special treatment to render them stable amounts of vinyl isobutyl ether, products can be obtained of not only t o heating and light exposure, but even to aging at room modified flexibility and solubility in organic solvents. Such an temperature. Although this fact was disclosed in a British patent interpolymer was Vinoflex MP 400, manufactured in Germany. (bS),it has not been adpquately appreciated Some of the prodInterpolymers of acrylic esters with vinyl alkyl ethers were manuucts which were manufactured abroad and offered in this country factured by I. G. Farbenindustrie under the name Scronals before the war left considerable improvement to be desired in this (10, 11). For carrying O L ~ L int~erpolgmeii7;a~ion, bulk, solution, respect. The rubberlike or solid polymers without stabilizers, or emulsion methods can be used, depending upon the particular even after they were treated for the removal of catalyst residues or monomers involved. If Jyater is present in the system employed purified by reprecipitation from solvents, are transformed over n for interpolymerization, a pH of 8 or higher should be maintained period of weeks or months at room temperature into balsamlike or throughout the process to prevent hydrolysis of the vinyl alkyl liquid products. The breakdomn is accelerawd by heating or in ether monomer. light. It was observed in this laboratory that brcakdown or Table V describes some polymers of vinyl methyl ether and depolymerization near room temperatures may also be catalyzed vinyl isobutyl ether used abroad. These products ~vereformerly by adding small amounts of acidic compounds which act as polycalled LLltonals, but the name was changed t o Igcvin follomd meiization catalysts at low temperatures. I n general, degradation by a letter indicating the alkyl group of the vinyl ether. Igevin products are not monomers but include the free alcohol, aldehydes, I or Igevin J indicates polyvinyl isobutyl ether. Polyvinyl ethers and sirupy low polymers. The breakdown is retarded in atmosTere used abroad as adhesives and plasticizers and in compositions phr.res low in oxygen. for impregnating and coating paper and textiles. The Igevin M or polyvinyl methyl ether products made abroad vere all of relaTALilX \'I[, ~ P . i B I L I Z A T I O X O F POLYVTNYI. ??-ljLTYI. f?TIilSR 'PO tively low solution viscosity. -4s prepared for text'ile applications, HZATISP polyvinyl methyl ether was called Appretan JTrL (26). (Initial polymer viscosityh van/(' = 4.0) PROP~RTIES OF POLYVIXYL ALKYLETHERS. Table VI shows vsD.'C after Ileatiiig the solubilit,y of polymers from vinyl methyl ether, vinyl n-but'yl Agent Added (1.0%) 1 Ilr. a t 150' C. ether, and vinyl isobutyl ether in a few common solvents. It is Controls (no added agent) 0.54-0.68 urPn n 70 noteworthy that polyvinyl methyl ether dissolves both in organic Phenyl ethyl ether 0.78 Triethanolamine 1.10 solvents, including benzene, and in cold water. However, the Diphenylguanidine 1.14 polymer precipitates from water solution on warming to near 3.61 8-Saphthglamine Phenvl-a-naphthylamine 4.02 35' C. Polyvinyl methyl ether was used abroad for heat sensi4,4'-biaminodiphenylaniline 4.16 4.17 Phenyl-&naphthylamine tization of Buna NK and other synthetic latices in a dip 1-Amino-&naphthol a , 02 coating process for fabricating gloves (55). This heat' sensitizing Hydroquinone 1.80 (3-Xaphthol 1.50 process permits making relatively thick-walled articles quickly 2,6-Dichloro-4-tei.t-amylpheiioi 1.56 4-lert-Butylphenol 2.60 in a single step. Certain American synthetic rubber latices are 4-tert-Butyl-m-cresol 3.46 sensitive to precipitation by polyvinyl methyl ether. However, a Polymers were heated in air in iorced draft oven. the pH and other factors are critical, and temperatures higher b Viscosities nere determined using solutions of 1.0 gram polymer per 100 ml. benzene a6 25' C. and an Ostwald-Fenske viscometer. than 35" C. must be used. Depending upon the conditions of polymerization vinyl isobutyl ether can give (a)sticky balsamlike polymers, ( b ) a tacky, The incorporation of 0.574 or more of antioxidant-typc st ibbilizers or of certain sulfur compounds is effect,ive in preventing or retarding the breakdown and changed of proper.ties on aging (493. OF POLYVINYL ETHERSAT 25" C. TABLE VI. SOLUBILITY Stabilized high polymers prepared in the summer of 1943 remain (6% polymer shaken a t room temperature with solvent) rubberlike solids substantially free of odor and unchanged in Polyvinyl Polyvinyl Polyvinyl Isobutyl Ether Methyl Ether %-Butyl Ether solution viscosity. Table VI1 shows the effects of incorporating 0 0 Water 1.0% of various agents in stabilizing a polyvinyl ,n-butyl ethcr 0 0 Methanol against breakdown on heating. The controls without added Acetone 0 0 Methyl ethyl ketone agent were transformed from a rubberlike solid with pressureEthyl acetate i sensitive tack to a viscous, sticky liquid by heating 1 hour at Benzene n-Heptane 150' C. Stabilized polymers, which retained their chain lengt,h Chloroform as measured by viscosity in benzene solution, were subst,antially
TABLE v.
SOME POI,Y-\IERS OF V I N Y L .L\LKYL
~
ETHERS
C
9
++
+ +
:
+ + ++
+++ ++
February 1947
INDUSTRIAL AND ENGINEERING CHEMISTRY
unchanged in character. \Vhere stabilizers were less effective, intermediate semisolid products resulted. I n addition to the results shown in Table VII, the following were found to be good or moderately effective stabilizers: di2-naphphenylamine, N,N'-di(P-naphthyl)-p-phenylenediamine, thalenethiol, thioxane, and mercaptobenzothiazole. Among inorganic compounds which had a stabilizing effect were alkaline and alkaline earth sulfides and polysulfides (49). Organic compounds which had little or no effect included ammonium stearate, stearylamine, propylene diamine, cyclohexylamine, quinoline, carbazole, thioglycolic acid, diphenyl sulfone, acetic acid, and diethylene glycol. Certain oxidizing agents, such as benzoyl peroxide, catalyzed the breakdown of the polymer. High polymers of other vinyl alkyl ethers in addition to polyvinyl n-butyl ether were found to require stabilization. Table VI11 shows the effects of added stabilizers upon samples exposed to sunlight. The breakdown of the polymer a t room temperature in brown bottles was considerable, but light had an additional action retarded by the stabilizers.
O F POLYVINYL n-BT;TYL ETHERT O TABLE VIII. STABILIZATION
SUNLIGHT" viscosity vaP/C* Controls in brown Tests in Agent Added (1%) bottle light 0.41 None 1.37 3.00 4-tort-Butylmetacresol 3.50 4.20 Phenyl-a-naphthylamine 4.30 a Polymers exposed to diffused north light through window 12 days a t room temperature. * Viscosities were determined using solutions of 1.0 gram polymer per 100 ml benzene a t 25" C. and a n Ostwald-Fenske viscometer.
185
TABLE x. STABILITY O F POLYVINYL n-BUTYL ETHERTO DILUTE AQUEOUSHYDROCHLORIC ACIEAT pH 2 Viscosity v l p / C * Time of Treatment a t 100" C. 0.10 g./lOO mi. 0.20 g./lOO ml. Control untreated 3.8 4.1 10 minutes 3.9 4.2 1 . 0 hour 3.9 4.1 5 . 0 hours 3.9 4.1 Flow time of 10 mi. benzene, seo. 7 9 . 1 (tube 11) 5 7 . 3 (tube I) Viscosities of benzene solutions determined a t 25" C. using Ubbelohde viscometer tubas.
--
*
using t w o different conc?ntrations and t v o different viscometer tubes showed essentially no change. Stabilized polyvinyl alkyl ethers are also relatively stable t o alkali. EFFECTOF MILLIKGPOLYVINYL ALKYLETHERS.The British patent mentioned (25) states that antioxidant-type stabilizers are effective in preventing breakdown of polyvinyl ethers by kneading and other mechanical treatment. The present authors found that this is not always true in the caSe of working polyvinyl alkyl ethers on the rubber mill. As in the case of many rubbers, the milling of polyvinyl ethers containing antioxidants near room temperature has more rapid degrading action than milling a t moderately elevated temperatures-for example, 60' C. Khether or not profound changes occur on the rubber mill seema to depend most upon the internal structure of the polymer as related to the method of polymerization. The case of polyvinyl isobutyl ethers of higher viscosity is particularly interesting in this respect.
H2C'
.'
/ Table IX shows the results of a heat stability test of 1 hour a t 160' C. in a forced air draft oven on some vinyl alkyl ethw polymers. A sample of Igevin J (60) procured from Sweden, but of German origin, was poorly stabilized, judging from its odor and the loss in volatiles in vacuum. Breakdown of this sirupy polymer had apparently reached equilibrium, since the viscosity was not further decreased on heating. Oppanol C (German vinyl isobutyl ether, high polymer) is not very stable to heating. An old sample of Appretan WL, polyvinyl methyl ether, became largely insoluble in benzene. A smaller amount of change mas shown by three experimental polyvinyl ethers containing stabiliaing agmts.
TABLE IX. HEATSTABILITY TEST Viscosity v S p / C Before After heating heating0 Remarks 0.13 0.14 Odor Igevin J ( 6 0 ) b Oppanol C 4.3 1.7 Softer, more tacky, flowed PVI (1527-10) 6.5 4.1 Nontacky, still granular P V N low (G14.55) b 0.73 0 . 6 1 Little change PJ'S medium (G1259) 6.5 4 7 Pressure tack retained: still granular Appretan WL (old sample) Incompletely sol. Tack retained One hour a t 160" C. in air. b Viscosities determined a t 0.50 gram per 100 ml. benzene; others a t 0.10 gram per 100 ml benzene.
In sharp contrast to the vinyl alkyl ether monomers, the polymers are resistant to hydrolysis by dilute acids. Table X summarizes an experiment in which strips of a rubberlike polyvinyl n-butyl ether containing an antioxidant-type stabilizer were immersed at 100' C. in water acidified with hydrochloric acid to maintain a pH of 2. That the aqueous phase penetrated into the polymer was shown by a cloudy opacity which developed during contact with the water. After the treated strips were dried, there was no evidence of change in color, tackiness, or rubberlike extensibility. Viscosities of the polymers in benzene solution
Figure 4.
Representation of Polyvinyl Alkyl Ether Chain
With slow polymerization near -80" C., stabilized polyvinyl isobutyl ethers are obtained which are substantially nontacky and quite stable to milling. These polymers can be milled for half an hour a t room temperature with comparatively little breakdown in viscosity or increase in tackiness. Oppanol C, vinyl isobutyl ether high polymer submitted from Germany through United States Army Intelligence, was found to behave very differently on milling under the same conditions. Oppanol C breaks down rapidly on the mill, accompanied by a loud crackling noise, to give a soft, tacky polymer of low viscosity. The experimental polyvinyl isobutyl ethers which mill quietly and with little change can have viscosities, as measured in dilute solution in benzene, which lie in the same range as the viscosity of Oppanol C. Oppanol C is reported to have been made by rapid continuous polymerization of vinyl isobutyl ether a t about -40 o C. using boron fluoride as catalyst (11). The method is similar to that described in a United States patent (56). Incorporating a superior heat stabilizer &to Oppanol C did not improve its stability to milling. Differences in solubility behavior of the two types of polyvinyl isobutyl ether in paraffin wax, in Nujol, and in kit-butanol also indicate that differences exist between the internal structures of the polymer chains in the two cases. The degree of branching or the shapes of the chains (coil or spiral), as determined by the distribution of alkoxy groups on either side of the vinyl chain, may be involved. The latter effect was suggested by Huggins (%B) as a cause for differences between vinyl polymer chains produced by polymerization a t different temperatures. For example, the repulsion or crowding of
.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
186
,
neighboring large -OR groups (Figure 4), both lying in the plane above the paper, might cause a bending of the polymer chain. Table XI s h o w approximate molecular w-eights of some of the typec of polyvinyl ethers under consideration. These data were obtained b y the light scattering method b y P. P. Debye. The resuhs are tentative in t h a t any possible dissymmetry of the angular scattering \%asnot taken into account. All data were obtained by extrapolation to zero concentration in benzene solution. The procedure and apparatus \>ere described recently (12).
TABLE
XI.
hfOLECUL4R JvEIGIITS O F POLYVINYL ETHERS BY
Polymer Oppanol C PVI (302) PVN low (G1455) P V X medium (G1658) PVN high (G1256)
LIGHTSC.4TTERISG Physical Form Tacky rubbeTy solid h ontaoky solid Viscous liquid Soft rubbery solid Rubbery solid
qss/C
3101. Wt.
4,3 1.5 0.5 5.0 7.8
600,000 219,000 118,000 545,000 810,000
The physical properties of the polyvinyl alkyl cthcrs are interesting in relation t o the mechanism of pressure-sensitive tack and adhesion. Fractionation esperimeryts shoved t h a t pressuresensitive tack cannot be att,ributcd primarily t o a low viscosity sticky fraction contained i n the polyvinyl ethers. Although further x o r k is in progress, it niight be said t h a t vinyl ether polymers possessing “lively” pressure-sensitive tack are those having cornparatively low yield value or modulus, together TTith complete and rapid recovery for moderate deformations. Thus pressurescnsi tiT1.e tack may involve the elastomer adhesive surface conforming t o the hills and valleys of .(;he second surface, to bring about ,the condition of Johaiisson steel gage blocks, where s!iortrange molecular forces can act betn-ecu the .tvo materials. ACRNOWLEDGiMENT
The authors n-ish t o acknon-lcdgo the contributions of the folR. E. Christ, Joseph Copes, ,J. 17.Copenhaver, P. P. Debye, Frederick Grosser, P. ill. Kirk, I . \,-. Runyan, Sidney Siggia, Katherine Stewart, D. E. Stoke., and Robert Verbutg. For samples of Qppanol C the authors we indebted to E. J. Hobson of the Army &uar.iermsster Corps and ‘to G. LI. Kline of the Sational Bureau of Standards. l o \ ~ i n persons g toivard this paper:
LITERATURE CITED
(1) Baur, Karl, U. 8. Dept. of Commerce, Office of Pub. Board,
Rept. PB-652 (1946).
( 2 ) Baur, Karl (to I. G. Farbeniiidustrie A,-G.),U. 8. Patent 1,931,-
858 (Oct. 24, 1933). (3) Bounds, R . H., and Hasche, R. L., U. S. DeDt. of Commerce, Office of Pub. Board, Rept. PB-1069 (1946): (4) Carothers, W.H., Collins, A. M., and Kirby, J. E. (to E. I. du Pont de Nemours 8: Co., Inc.),U.R. Patent 2,066,330 (Jan. 5, 1937). (5) Chalmers, William, Can. J. Research, 7 , 464-71 (1932). (6) Ibid., 7, 472-80 (1932). (7) Claisen, L., Ber., 31, 1021 (1898). (8) Consortium fur elektrochemische Industrie G.m.b.€l., Brit. Patent 231,841 (Apr. 1, 1924). (9) Copeland, N. A., and Youker, bl. A., FIAT Final Rept. 720, U. S.Office of Military Govt. for Germany (Jan. 28, 1946). (10) Craemer, Carl, Kautschuk, 15, 23-7 (1939). (11) DeBell, J. M., Goggin, W.C., and Gloor, W. E., Q.11.C. Overseas Investigation Team Rept., Appendix 6 d , 160-1, Office of Quartermaster Gen., Nov., 1945. (12) Debye, P. P., J . Applied Phys., 17, 392-8 (1946). (13) Dolliver, M. 9., Gresham, T. L., Kistiakowsky, G. B.,Smith, E. A., and Vaughan, W. E., J . Am. Chem. SOC.,60, 441-2 (1938). (14) Egloff, Gustav, and H u h , George, Chen. Revs., 36, 114 (1945). (15) Favorskil, A. E., and Shostakovskit M . F., J. Gen. Chenz. (U.S.S.R.), 13,1-20 (1943). (16) Fikentscher, Hans (to I. G. Farbenindustrie A,-G.), U. S. Patent 2,016,490 (Oct. 8. 1935).
Vol. 39, No. 2
(17) Glasgov-. A . R., Jr., Streiff, A. J., and Rossini, %. D., J . Research Natl. Bur. Standards, 35, 355 (1946); Research paper RP1676. (18) Glasstone, S., “Textbook of Physical Chemistry”, p. 439, Yew York, D. Van Nostrand Go., Inc., 1940. (19) Halbig, Paul, and Rost, Theodor (to Consortium fur elektrochemische Industrie G.m.b.H.), German Patent 726,547 (Sept. 3, 1942). (20) Hasche, R. L., and Thompson, Benjamin (to Eastman Roda,k Go.), U. S.Patent 2,294,402 (Sept. 1, 1942). (21) Henning, F., Ann. Phueiiz. /41, 43, 293 (1914). ( 2 2 ) Huggins, bl. L., J. Am. Chem. Soc., 66, 1991-2 (1944). (23) I. G. Farbenindustrie -4.-G., Brit. Patent 482,512 (Mar. 28, 1938). (24) International Critical Tables, Vol. I, p. 276 (1926). (25) Jordan, Otto, Kollek, Leo, and Ufer, Hanns ( t o I. G. Farbenindustrie A.-G.), U. 8.Patent 2,054,019 (Sept. 8, 1936). (26) Kline, G . XI., U. S. Dept. of Commerce, Office of Pub. Board, OPB-8, pp. 28-32; also PB 949. (27) Kollek, Leo, Kunatstofle, 30,229-32 (1940). (28) Krzikalla, Hans, and Flickinger, Erich, U. 6 . Dept. of Commerce, Office of Pub. Board, Rept. PB-601 (1946). (29) Krzikalla, Hans, and F’oldan, Ernst, Ibid., Itept. PB-602 (1946). (30) Kuehn, Erich, and Hopff, Heinrich (to I. G. Farbenindustrie A.-G.), U. 8. Patent 2,061,946 (Nov. 24, 1936). (31) Leake, C . D., and Chon, Xei-Yu, Anesthesia and Analgesia, 10, 1--3 (1931). (32) Lowry, T. M., J . Chem. Soc., 105,91 (1914). (33) Marvel, C. S.,C. S. Dept. of Commerce, Office of Pub. .Board, PB-5521 and PB-11, 193 (1946). (34) Mueller-Cunradi, Martin, and Pieroh, Kurt (to I. C . Farbonindustrie A.-G.), U. S. Patent 2,061,934 (Nov. 24, 1936). (35) Ostromislensky, I. I., J . Russ. Phys. Chem. Soc., 17, 1487 (1915j. (36) Otto, Michael, Gueterbock, Hermann., and Rellemanns, Alfrcd (to Jasco, Inc.), U. S.Patent 2,311,567 (Feb. 16, 1943). (37) Plauson’s Forschungsinstitut G.m.b.H., German Patent 838,281 (May 2 5 , 1918). (38) Reppe, Walter (to I. G. Farbenindustrie A-G.j, U. S. Patoni. 1,941,108 (Dec. 26, 1933). (39) Ibid., 1,959,927 (May 22, 1934). (40) Reppe, Walter, Office of Rubber Reserve, Tech. Rept. OPB-32 (July 25, 1945), and PB-13, 366 (1946). (41) Reppe, Walter, U. X. Dept. of Commerce, Office of Pub. Board, Rept. PB-2437 (1946). (42) Iieppe, Walter, and Baur. Karl (to I. G. Farbenindustrie A..-G.). German Patent 566,033 (Jan. 24, 1930). (43) Reppe, Walter, and Baur, Iiarl (to I. G. Farbenindustrie A.-G.), U. S.Patent 2,000,252 (May 7, 1935). (44) Keppe, Walter. and Kuehn, Eric, I b i d . , 2,098,108(Nov. 2, 1937). (45) Reppe, Walter, and Schlichting, Otto, Ibid., 2,104,000 (Dec. 28. 1937)‘ (46) Reppe. TValter, and Ufer, H a m s (to I. G. Farhcnindustrie A.-G.), German Patent 706,273 ( (47) Reppe, Walter, and ITolff, Werner (to 1. G. -4.-G.), U. 9. Patent 2,021.869 ( S o v . 19, 1935). (48) I b i d . , 2,066,076 (Dec. 29, 1936). (49) Schildknecht, C. E. (to General Aniline & Film Corp.), C. S. Patent 2,395,684 (Feb. 26, 1946). (50) Seiferle, E . J., Rept. of Fellowship in School of Agr., Pa.State College, t o General Aniline & Film Corp., Jan. 1, 1946. (51) Shostakovskii, M .F., D o k l n d ~Alzad. Xaulz. S.S.S.R., 41, 121--i (1943); B u l l . acad. sei. U.R.S.S., Classe sci. chem., 1543, 156-7. (52) Shostakovskii, M . F., J . Applied C h e w (U.G.S.R.), 16, 66-71 (1943). (53) Shost,akovakii, ?I. F., J . Gen. Chem. (U.S.S.R.), 14, 102-12 (1944). (54) Ibid., 14, 889 (1944). (55) Shostakovskif, M aF., and Bogdanov, I. F., J - A p p l i e d Chens. (U.S.S.R.), 15, 249-59 (1942). (56) Shostakovsltii, 11.F., and Sidelkovsltaya, J. Gen. Chem. (TJ.3. 8.R.). 13, 428-35 (1943). (57) Sigmund, Fritz, and Cchann, Reinfried, Jfonatsh., 51, 234--52 (1929). (58) Skrabal, Anton, arid Skrabal, Roman, Z . physik. C‘hem., A181, 449-68 (1938). (59) Tinimermans, J., B u l l . SOC. b e l g . ckim., 24, 24.4 (1910); Cltem Zentr., 1910,11, 442. (60) U. S. Dept. of Commerce, Office of Pub. Board, Rcpt. PB-1112. pp. 3-5 (1946). (61) Voss, Arthur, and Dickhauser, Exaid (to I. G. F’arbeni~idiistrie A-G.), U. S. Patent 2,047,398 (July 14, 1938). (62) Wang, Sheng-Niea, and Winkler, C. A., Can. J . Research, 21B, 97-110 (1943). (63) Wicilicenus, Johannes, Ann., 92, 106 (1878).
