E. T. MCBEE AND H. B. HASS Purdue University and Purdue Research Foundation, Lafayette, Ind.
The literature of the past few years discloses much active interest in the chlorination of organic compounds. Some of the recent discoveries in this field are reviewed and discussed. Among them are the substitutive chlorination of olefins, peroxide-catalyzed chlorinations with sulfuryl chloride, chlorinations in intimate contact with a liquid mass of metallic chlorides, preparation of
polychloropropanes, chlorination of natural gas, chlorination of aromatic compounds, chlorinolysis of paraffin hydrocarbons, high-pressure chlorination of paraffin hydrocarbons, hexachloroethane as a chlorinating agent, the use of a capillary for introducing chlorine into material to be chlorinated, chlorination of esters, and chlorination of rubber. chlorine molecules. If this latter conclusion is correct, one should find in a repetition of Brown, Kharasch, and Chao's experiment a t elevated temperature that a reaction which produces racemization a t 0" C. will yield an optically active product a t 300-400" C. Vaughan and Rust (68) found that the rate of reaction of ethane with chlorine in the gas phase at moderate temperature is directly proportional to the concentration of the paraffin and the chlorine. This is in agreement with the results reported by Pease and Walz (46) for the thermal chlorination of methane. Apparently the chain mechanism predominates a t these conditions (vapor phase and moderate temperature), and the thermal bimolecular processes become important only a t higher temperatures. The latter in the case of ethane is above 270" C. The so-called induced substitution into paraffins and saturated chlorides which occurs simultaneously with the addition of chlorine to a copresent olefin is apparently a chain mechanism initiated by the addition reaction. This conclusion is based on the fact that such induced substitution is greatly diminished by the presence of oxygen. The addition reaction which may occur to some extent by association in solution is little affected by oxygen. Chain reactions may be promoted in a number of other ways. It has been pointed out many times that light and heat cause the chlorine molecule to become dissociated into chlorine atoms, a component in the established mechanism. Also, carbon surfaces tend to promote reaction (%), but this may be interpreted as the effect of more surface area (68) acting to produce more chlorine atoms. Presumably, the increased surface area
HE mechanism of the substitutive chlorination of saturated hydrocarbons has been a subject of repeated discussions ever since Pease and Walz (46) pointed out that the methane-chlorine reaction is strongly inhibited by oxygen. These authors did not attempt to decide between the two most obvious chain mechanisms, 2 and 2A: Clz + 2c1* (1) Cl*+CH(+CHaCl+H*; H * + C l z + H C l + C l * (2) C1* CH,+HCl f CHa*; CH,* Cls-CHsClf C1* (2A)
+
+
Brown, Kharasch, and Chao (3) brought forward strong evidence in favor of mechanism 2A. They prepared active amyl chloride (1-chloro-2-methylbutane) and showed that 1,2-dichloro-2-methylbutane,which is one of the products formed in its chlorination, is optically inactive. This result is to be expected if the intermediate is the free radical CHs
I
C2H5-C-CH2CI,
since such entities do not retain a stable
I steric configuration.
While these results seem unequivocal for the conditions employed (0' C. with free chlorine, 80' C. with sulfuryl chloride and peroxides), it would be premature to conclude that this mechanism holds for all conditions. Vaughan and Rust (68) presented evidence which indicates t h a t a t rather high temperatures, substitutive chlorination may occur by a thermal bimolecular metathesis between hydrocarbon and 137
INDUSTRIAL AND ENGINEERING CHEMISTRY
138
Vol. 33, No. 2
Courtesy, Shell Development Company
SEMICOMMERCIAL GLYCEROL UNIT
acts also to terminate chains. The termination of a chain may occur in several ways: the collision of a radical or atom with a solid surface such as the wall, collision of a radical or atom with oxygen, and the combination of radicals and atoms. Recently (6.2) i t was shown that very small amounts of tetraethyllead, which presumably yields ethyl radicals when heated, accelerate gas- and liquid-phase chlorinations enormously. Also, hexaphenylethane, which yields triphenylmethyl readily, catalyzes liquid-phase chlorination, and azomethane acts as a catalyst in the vapor phase. These results constitute additional evidence in support of the chain mechanism. The formation of olefins and chloro-olefins during the chlorination of many saturated compounds at elevated temperatures is a fact well established. Such side reactions cannot be explained as simple pyrolysis of chlorinated producOs because with comparable experiments much higher temperatures are usually required to obtain the same degree of olefin formation in the absence of free chlorine. It seems likely that at least some of this secondary reaction occurs, as by "induced" decomposition (62). A newly formed energyrich alkyl chloride may lose energy by losing hydrogen chloride or by collision with another alkyl chloride which, by reason of its acquired energy, undergoes disruption.
9 One of the interesting recent developments in the field of chlorination is the technique of using a molten salt bath in direct contact with the reagents. Low-melting mixturbs of substances such as sodium, calcium, and aluminum chlorides
are maintained a t a suitable temperature, and the chlorine and the material to be chlorinated are bubbled through. The agitation thus produced in the bath facilitates good control of the temperature which, in these extremely exothermic reactions, is highly desirable. Since metallic halides frequently serve as catalysts for the pyrolysis of organic chlorides, salt bath chlorinations may be controlled to yield olefins or chloro-olefins as well as saturated substitution products. The fission of carbon-carbon bonds to yield products of fewer carbon atoms than the starting material has also been reported to occur under these conditions. Grebe, Reilly, and Miley (16) patented a process for preparing carbon chlorides which consists essentially in passing a mixture of chlorine and a saturated aliphatic hydrocarbon or its partially chlorinated derivative into molten metal chlorides maintained at a temperature above 250' C. The following equations were given to illustrate the reaction:
+ +
CzH~C12f 3C12 + CzCI4 4HC1 C,HBCI~ 6CIz 4 CzClr f CCla f 6HC1 CsHs 8C12 -+ CaC14 CCL 8HC1
+ +
+
(3) (4) (5)
More recently, this work was extended to chlorinations in which the reaction products contain hydrogen in addition to carbon and chlorine. Reilly disclosed the preparation of 1,1,2-trichloroethane (61) and the chlorination of acetylene (5S), ethylene chloride (60), ethane (49), and benzene (68). In the preparation of 1,1,2-trichloroethane, ethylene chloride is chlorinated in a molten salt bath a t 300" to 425" C. If a higher bath temperature is employed, the principal products are di- and trichloroethylene. Acetylene is mixed with a nonflammable chlorinated hydrocarbon such as carbon
'CHLORINATION'
Febniary, 1941
tetrachloride and chlorinated under the surface of a molten metal chloride a t 175-250" C. to yield tetrachloroethylene as the principal product. For the production of ethyl chloride and vinyl chloride, ethane and chlorine are passed into a molten bath a t 250450" C. Essentially the same technique is used to prepare chlorobenzene from benzene.
+ Clz
-C
CHz=C-CHzCl
+ HC1
(6)
&Ha 3-chloro-2-methylpropene
CHa-C=CHz CHa I
+ Clz
-+
CHs-C=CHCl
C=CHn+C CHs
c1
The chlorination of olefins has been the subject of much study. Groll, Hearne, Rust, and Vaughan (g0) extended the work of Deansley (9)on the chlorination of olefin-paraffin mixtures. "Induced" substitution is observed when ah olefin is chlorinated in the liquid phase. This induced substitution occurs on the dichloride addition product or copresent saturated hydrocarbons. I n the chlorination of ethylene in the liquid phase, no vinyl chloride was obtained. Also, only small amounts of unsaturated monochlorides result in the liquid-phase chlorination of propene and butene. Hence, it appears that if substitution into olefins occurs by induction, the effect is not very pronounced. It has been shown that addition and concurrent substitution occur in the dark tit temperatures ranging from -10 to +150" C., provided a liquid phase is present, but no gas-phase thermal reaction occurs over this same temperature range. Approximately 50 per cent of the total chlorine reacted with a propane-propene mixture a t 22" C. by induced substitution, either with or without illumination. One per cent of oxygen greatly reduced the amount of chlorine reacting by substitution. These results may be interpreted by assuming that induced substitution is a chain reaction initiated by irradiation or the addition reaction of chlorine and olefins and that the latter occurs most readily in a liquid medium. This phenomenon has been considered to result from specific molecular transfer of the relatively high heat of formation of dichlorides (67,68). Such a transfer of energy may cause the dissociation of a chlorine molecule and thus initiate a chain reaction which yields substitution products. There is considerable evidence to indicate that both addition and substitution reactions of olefins with chlorine occur, a t least in part, particularly a t high temperatures by chain mechanisms. Therefore, it is partioularly interesting to note that the substitutive chlorination of olefins is catalyzed by low concentrations of oxygen (64). This has been explained by assuming that radicals are produced by the interaction of olefin and oxygen and that the ethylenic radicals differ from alkyl radicals in being less readily eliminated by oxygen. In the course of their careful work on the mechanism of the chlorination of olefin hydrocarbons, Rust and Vaughan found that olefins inhibit high-temperature chlorination reactions. Such inhibition of reactions by olefins in which. chain mechanisms are believed to occur have been noted before, but the true mechanism of what occurs is not known. Burgin, Engs, Groll, and Hearne (4) studied the influence of many factors on the chlorination of olefins containing an unsaturated tertiary carbon atom. The following reactions occur normally during the chlorination of isobutene:
CHs--C=CHa
'-1
Secondary reactions
Gblsrination of Olefins
Primary reactions
CH
139
+ HC1
&Ha I-chloro-2-methylpropene
(7)
CHa-C=CHa
+ HCl * CHa-'$-CHa
(9)
'
bH&l 3-chloro-2-(chloromethy1)propene
c1
t/ll?L
'
CHp&-CHaCl
+ HCl
I
+
CHs-C-CHnCl
(11)
&Ha 1,2-dichloro-2-rnethylpropane
The chlorination of tertiary olefins such as isobutene and "tertiary amylene" (a mixture of 2-methyl-1-butene and 2methyl-%butene) differs from that of the secondary olefins, since even in the liquid phase in the absence of light, the principal reaction is the formation of the unsaturated monochlorides. The addition reaction in the vapor phase is accelerated by light, but other factors such as temperature, phase, and surface, and impurities such as nitrogen, moisture, and oxygen do not affect the ratio between addition and substitution. None of the conditions investigated affect the ratio of 1-chloro-2methylpropene to 3-chloro-2-methylpropene which is about 3 and 97 per cent, respectively. Only 5 to 10 per cent of the chlorine reacts by addition. Carefully purified isobutene resembles ethylene in that it does not react with chlorine in the vapor phase in the absence of light a t 150" C. If porous material is used, such as calcium chloride or a tile pipe reactor which may serve LIS a catalytically active surface, or if a liquid medium is present, reaction occurs. Therefore it is concluded that the reaction is initiated or takes place a t the wall. A mixture of 2-methyl-1-butene and %methyl-%butene acts similarly to isobutene, yielding about 60 per cent 3chloro-2-methyl-1-butene and 40 per ceht l-chloro-2-xhethyl%butene as the principal unsaturated monochlorides. Straight-chain olefins in the liquid phase add chlorine readily to yield the corresponding dichlorides. Hence, to obtain a high yield of unsaturated monochlorides, it is important to prevent the presence of a liquid phase (8, 18,17, 18, 19). By using a technique which has been applied to the chlorination of paraffins (91,88,24, 86),the straight-chain olefins were chlorinated at high temperatures to yield preponderantly unsaturated monochlprides of the allyl type (17). Propylene and chlorine were preheated to 200-600" C. and mixed a t a jet. The yield of dichloropropane was in consequence reduced to less than 1 per cent. The maximum yield of unsaturated monoohlorides obtained a t 600" C. waB 85.5 per cent, which represents a yield of 82 per cent allyl chloride; whereas when the gases were mixed a t low tern-
INDUSTRIAL AND ENGINEERING CHEMISTRY
140
peratures and allowed to react a t elevated temperatures, the yield was about 11-12 per cent lower. Light and catalysts act only to increase the reaction velocity in the chlorination of straight-chain olefins. The optimum temperature range is 300" to 600" C. and the yield increases with temperature. The substitution reactivity of olefins varies with the nature of the groups attached t o the doubly bound carbon atoms. The reactivity varies in the order ethylene < propene < 2-butene < 2-pentene < isobutene and other tertiary olefins. Stewart, Dod, and Stenmark (56) found that the ratio of substitution to addition in the reaction of chlorine with olefins depends upon the concentration of the reactants. I n general, excess olefin increases substitution while excess chlorine decreases substitution. Tishchenko and co-workers (60) reported on the chlorination of several olefins. They obtained all of the products of the chlorination of isobutene reported by Burgin, Engs, Groll, and Hearne (4) with the exception of 3-chloro-2-methylpropene. However, in the chlorination of 2-methyl-1-butene, Tishchenko found the unsaturated monochlorides to be chiefly 2-chloromethyl-1-butene. Since the hydrogens on carbons alpha to a double bond are activated, both Zchloromethyl1-butene and 3-chloro-Zmethyl-1-butene should be expected from the chlorination of 2-methyl-1-butene. Presumably all of the theoretically possible monochloro-olefins would be formed under suitable conditions, but l-chloro-2-methyl-lbutene should be present in the smallest percentage.
I n the presence of organic peroxides (go), many compounds are chlorinated in the dark a t refluxing temperatures with sulfuryl chloride to yield RC1, sulfur dioxide, and hydrogen chloride. For example, cyclohexane does not react with sulfuryl chloride in the absence of light and catalysts a t its boiling point, but the addition of 0.001 mole of benzoyl peroxide to the reaction mixture causes the reaction to go to completion in 15 to 30 minutes. As in the chlorination of paraffins with elemental chlorine, the secondary hydrogen a t o m are substituted more readily than the primary ones. It is more difficult to introduce the second chlorine atom into the molecule, and it tends not to substitute on the same carbon as the first one; a third chlorine is not placed on a carbon atom by this process. This chlorination method is particularly suitable for introducing chlorine into the side chain of aromatic compounds having active nuclei; for example, the chlorination of m-xylene with sulfuryl chloride in the presence of peroxides yields only m-xylyl chloride. Diphenylmethane, oand p-nitrotoluene are not chlorinated by this method. Aliphatic acids and acid chlorides are readily chlorinated by this same process (SI). All of the theoretically possible monochlorides are obtained; the hydrogens in the beta and gamma positions are substituted more readily than those in the alpha position. Many of the facts indicate that this substitution occurs by a chain reaction. The following reactions have been advanced tentatively (29): Cd&CO-oO-cOC& -+ ~ C K H f~ 2 *c02 C&* f Sozclz + sozc1* +*CKHLCI SO%Cl* -t so2 c1 CI* RH + R* HC1 R* SO&L + RCI SOzCl*
++
+++
The reaction of sulfuryl chloride with olefins to form the corresponding dichlorides is also catalyzed by organic peroxides (30). This has been assumed to proceed by a chain reaction in which the chlorine atom reacts as follows:
Vol. 33, No. 2
The teim "chlorinolysis" has been suggested (38, 40) to designate a chlorination reaction performed under conditions which came a rupture of the carbon-carbon bond in the reactant molecules to form chloro compounds with fewer carbon atoms. The explosive limits of mixtures of chlorine and dichloropentanes were determined, and the upper limit was found to be below the theoretical amount of chlorine required to substitute all of the hydrogen atoms remaining in the dichlorides. The use of chlorine as a diluent is an important advance in high-pressure chlorination technique. Organic substances may be perchlorinated or chlorinolyzed by mixing the total quantities of reactants and obviating the need of a multiple-stage process involving recycling. Thus, it should be economical to convert petroleum hydrocarbons to carbon tetrachloride and hexachloroethane; the latter is readily pyrolyzed to tetrachloroethylene and chlorine. The chlorination of propane a t pressures as high as 4000 pounds per square inch (23,SO) further substantiates chlorination rule 11: "In vapor-phase chlorination of saturated hydrocarbons, increased pressure causes increased relative rates of primary substitution." It appears that pressure alters the relative chlorination rate of the primary and secondary hydrogen atoms in propane by effecting a greater absolute concentration of hydrocarbon in the vapor phase. From a practical point of view for obtaining high yields of primary substitution products, an increase in pressure above 1000 pounds per square inch seems unprofitable.
Levine and Cass disclosed several processes pertaining to the catalytic chlorination and dehydrochlorination of hydrocarbons. I n the chlorination of 1,2-dichloropropane,the trichlorides which are formed consist substantially of the 1,1,2-and 1,2,3-trichloropropane and the ratio of the two isomers can be controlled by variations of the catalyst and temperature (3s). l,l,l-Trichloropropane may be prepared in good yields by eliminating hydrogen chloride from 1,1,2-trichloropropanee. g., with aqueous sodium hydroxide a t 75" C. (6)-and then adding hydrogen chloride to the resulting 1,l-dichloropropene, suitably in the presence of aluminum chloride a t >lo" C. (36). l,l,l-Trichloropropane had been previously reported in the literature, but the physical constants demonstrate conclusively that the earlier work resulted in a misidentification. Independent research in the Purdue laboratory (16) has shown excellent agreement with the data of Levine and Cass and has confirmed their identification of this compound. The expected 1,1,1,2-tetrachloropropaneis obtained when chlorine is added to 1,l-dichloropropene substantially in the absence of light and in the presence of ferric chloride (6). This same tetrachloride yields l,l,2-trichloropropene upon dehydrochlorination in the liquid phase with an alkali or alkaline earth metal hydroxide (7). Pentachlorostyrene may be obtained by chlorinating ethylbenzene in the presence of a catalyst that promotes nuclear substitution-e. g., iron filings-to obtain ethyl pentachlorobenzene (3.4) and subsequently chlorinating the latter in the presence of light but in the absence of a catalyst at 60-200" C., followed by heating above 300" C. (37). Cyclohexene
,
..
.
February, 1941
141
is made by a similar loss of hydrogen chloride from monochlorocyclohexane (36). Mathes (4%') discusses the Raschig process for the preparation of phenol, which is being used in this country a t the present time. This process which operates continuously, without pressure and catalytically, involves the chlorination of benzene with hydrogen chloride and oxygen to give chlorobenzene and subsequent hydrolysis with water to give
perature can be avoided. Also a large total quantity of chlorine may be added to a given amount of hydrocarbon without forming explosive mixtures or recycling unreacted material. The I. G. has issued a series of patents (27) describing the halogenation of a wide variety of paraffinic, alicyclic, and aromatic hydrocarbons and their monohalogenated derivatives; the halogen is introduced through one or more capillary jets into the vapor of the material to
Courtesy. Shell Development Company
EQUIPMEKT USEDIN
THE
HIGH-TEMPERATURE CHLORINATION OF PROPYLENE
phenol and hydrogen chloride. Recently (1) Durez Plastics and Chemicals, Inc., announced the opening of a new synthetic phenol plant which employs the Raschig process. This plant is said to be the largest of its kind in the world. Hexachloroethane is a by-product of the chlorination of acetylene which (except for military use in smoke bombs) finds little application. Base1 and Schaeffer (1)suggested converting this to tetrachloroethylene and simultaneously utilizing the chlorine thus liberated for converting ethylene or acetylene to tetrachloroethylene. Active carbon is suggested as the catalyst. The use of an organic chloride as the source of the chlorine for a substitutive chlorination has the advantage of a smaller evolution of heat and would thus facilitate temperature control. It might well deserve thorough study as a general chlorination method. A related process by the same authors employs pentachloroethane and acetylene. Tetrachloroethylene may also be obtained by passing 1,1,2,2-tetrachloroethaneand chlorine a t elevated temperature over a catalyst of high surface activity such as activated carbon. The technique of introducing chlorine a t high velocity through a capillary to the material to be chlorinated has found wide application since it was first described in 1935 (11). The advantage is that the halogen can thus be introduced to the hydrocarbon while the latter is a t reaction temperature without formation of flame or soot a t the point of mixing. Thus any undesired reaction which might occur a t low tem-
be halogenated, which is a t such a temperature that the reaction product quickly condenses to a liquid and is removed from the reactor. Another modification of the same general procedure (18)consists in flowing one hot gas into the other through a thin porous layer or fine-meshed tissue of a stable contact material such as quartz. Hennig (16) discloses the preparation of carbon tetrachloride by passing mixtures of aliphatic hydrocarbons of 2 to 3 carbon atoms or their chlorinated derivatives with excess chlorine over materials of large surface area a t temperatures from 400" to 700" C. High yields of carbon tetrachloride are reported. The Standard Oil Development Company in the course of the study of highly polymerized hydrocarbons has found methods (66) for introducing sufficient halogen to yield a product containing between 10 and 20 per cent of halogen. Presumably such a material could be converted to a vulcanizable hydrocarbon if suitable methods can be evolved for removing halogen acid and if the over-all process does not result in a serious reduction in the average molecular weight. Waddle and Adkins (6s) chlorinated esters of trichloroacetic acid and thus obtained, after saponification, chloroalcohols except in cases where alkali would be expected to split the chloroalcohol to other compounds such as aldehydes or epoxy derivatives. Because of the importance in organic synthesis of substances with two functional groups and the ready availability of many alcohols, this process is
INDUSTRIAL AND ENGINEERING CHEMISTRY
142
worth noting. While not all of the isomers to be expected were isolated, they are presumably to be found in the 25 per cent of the product which was unaccounted for. Recently sodium nitrate was prepared by the action of nitric acid upon sodium chloride. The nitrogen appears as nitrosyl chloride, and hence the chlorinating action of this substance upon saturated hydrocarbons first reported in 1934 (11) has been reinvestigated by Moyer (43)who successfully chlorinated such hydrocarbons as pentane and benzene with this reagent at temperatures above 200’ C. Whiston showed in 1920 (64) that nitrosyl chloride is a powerful inhibitor for the photochlorination of methane. This appears to be a case in which elevated temperature suffices to overcome the inhibition of a reaction. The chlorination of saturated alicyclic compounds is beginning to attract some of the attention which it deserves. As recently as 1937 Ellis (10) stated that no work had appeared until then on the chlorination of cyclopentane. The following year Zal’kind and Markov (66) described the chlorination of cyclopentane and the subsequent conversion of monochlorocyclopentane to cyclopentene which was hydrated by 80 per cent sulfuric acid to cyclopentanol. Dicyclopentyl adipate and glutarate were prepared and recommended as plasticizers for cellulose nitrate, Gandini (14) chlorinated menthane and camphane. He reported that the action upon menthane of chlorine dissolved in carbon tetrachloride yielded as the principal monochloride 4chloromenthane and as the principal dichloride 214dichloromenthane:
1$
Numbering system of menthane
The chlorination of benzene is important and has been the subject of considerable study. Certain processes (41, 47) use catalysts such as zinc chloride. Recently a patent was issued to Reed (48) in which the process of chlorinating bengene with chlorine and sulfur dioxide or similar compounds was disclosed. At 0-20’ C. p-chlorophenyl chlorosulfite results, while a t higher temperatures p-dichlorobenzene is also formed. Aluminum chloride was used as a chlorine carrier in the chlorination of phenol to pentachlorophenol (69). I n a similar process an increased yield of Halowax (polychlorinated naphthalene) was obtained by chlorinating naphthalene in the presence of aluminum oxide (61). A chlorinated rubber has been developed within recent years which possesses clarity and flexibility. This substance may be used to formulate many products such as paints, varnishes] plastics, etc. A solution of rubber in a volatile solvent such as carbon tetrachloride is treated with elemental chlorine (3.3, &, 46) or with a hypohalite of an organic carboxylic acid (18). ~~~~~~~~~~~~
Cited
(3) Anonymous, News Ed. (Am. C h m . SOC.),18, 921 (1940). (2) Basel and Schwffer, French Patent 832,749 (Oct. 3, 1938); U. S. Patents 2,139.219 (Dec. 6, 1938). 2,168,213 (May 16, 1939), 2,178,622 (Nov. 7. 1939). (3) Brown, Khsrasch, and Chao, Div. Organic Chem., Detroit meeting, A. C. S., 1940. (4) Burgin, En@, Groll, and Hearne, IND.ENG. CHEM.,31, 1413 (1939). (6) Cam, Brit. Patent 471,186 (Aug. 30, 1937).
Vol. 33, No, 2
Ibid., 471,187 (Aug. 30,1937). Cass, U. 8. Patent 2,111,043 (March 15, 1938). Conn, Kistiakowsky, and Smith, J . Am. Chem. SOC.,60, 2764 (1938). Deansley, U.9. Patent 1,991,600 (Feb. 19, 1935). Ellis, “Chemistry of Petroleum Derivatives”, Vol. I, p. 763 (1934). Ibid ,Vol. I, p. 1055 (1934). Engs and Redmond, U. 8. Patent 2,077,382 (April 20, 1937). Farmer and Barrett, Brit. Patent 492,767 (Sept. 27, 1938). Gandini, Gazz. chim. ital., 68, 779-92 (1938). Goldrick, Ph.D. thesis, Purdue Univ., 1940. Grebe, Reilly, and Miley, U. 8. Patent 2,034,292 (March 17, 1936). Groll and Hearne, IND). ENC. CH~M., 31,1530 (1939). Groll, Hearne, Burgin, and LaFrance, U. S. Patent 2,130,084 (Sept. 13, 1938). Ibid.,2,167,927 (Aug. 1, 1939). ENC. CHEM.,31, 1239 Groll, Hearne, Rust, and Vaughan, IND. (1939). Hass and McBee, U. S. Patent 2,004,072 (June 4,1935). Ibid., 2,004,073 (June 4, 1935), 2,147,577 (Feb. 14. 1939). Hass, McBee, and Hatch, IND.ENQ.CHEM.,29, 1335 (1937). H a s , McBee, and Weber, Ibid., 27, 1190 (1936). Ibid., 28, 333 (1936). Hennig, French Patent 836,979 (Jan. 31, 1939); U. S. Patent 2,160,574 (May 30, 1939). I. G. Farbenindustrie. French Patents 818,251 (Sept. 22, 1937), 822,862 (Jan. 10, 1938), 823,021 (Jan. 12, 1938); Brit,. Patents 474,922 (Nov. 15, 1937), 497,230 (Dec. 14, 1938). I. G. Farbenindustrie, French Patent 816,957 (Aug. 21, 1937); Brit. Patent 489,553, July 28, 1938; U. S. Patent 2,156,039 (April 25, 1939). Kharasch and Brown, J . Am. Chem. SOC.,61, 2142 (1939). Ibid.. 61. 3432 (1939). Ibid.; 62; 925 (1940).’ Lee, Chem. & M e t . Ew., 46, 456 (1939). Levine and Cass, Brit. Patent 471,188 (Aug. 30, 1937); U. 9. Patent 2,119,484 (May 31, 1938). Levine and Cam, Brit. Patent 497,581 (Dec. 15, 1938). Ibid., 503,615 (April 11, 1939); U.5. Patent 2,179,218 (Nov. 7, 1939). Leviniand Cass, U.8. Patent 2,183,574 (Dec. 19, 1939). Ibid., 2,193,823 (March 19, 1939). McBee, Hass, Chao, Thomas, and Welch, IXD. ENG.CHEX, 33, 176 (1941). McBee, Hass, and Pianfetti, Ibid., 33, 185 (1941). McBee, Hass, and Pierson, Ibid., 33, 181 (1941). Mares. U. S. Patent. 2.111.866 (March 22.. 1938). . Mathes, Angew. Chek.; 52, 591 (1939). Moyer, U.S. Patent 2,152,357 (March 28, 1939). North, Ibid., 2,148,830 (Feb. 28, 1938); Brit. Patent 489,954 (Aug. 5, 1938). Pease and Wala, J . Am. Chem. SOC.,53,3728 (1931). Peterson. U. S. Patent 2.140.715 (Dec. 20. 1938). Riith and Buchheim, German Patent 643,387 (April 10,1937). Reed, U.S. Patent 2,174,111 (Sept 26, 1939). Reilly, Ibid., 2,140,547 (Dec. 20, 1938). Zbid., 2,140,548 (Dec. 20, 1938). Ibid., 2,140,549 (Dec. 20, 1938). Ibid., 2,140,650 (Dee. 20, 1938). Ibid., 2,140,551 (Dec. 20, 1938). Rust and Vaughan, J. Ow. C h m . , 5,472 (1940). Standard Oil Development Co., German Patent 665,197 (Sept. 19, 1938). Stewart, Dod, and Stenmark, J . Am. Chem. Soc., 59, 1765 (1937). Stewart and Smith, Ibid.,51,3082 (1929). Ibid., 52, 2869 (1930). Stoesser, U. S. Patent 2,131,259 (Sept. 27, 1938). Tishchenko and co-workers, J . Gem Chem (U. S . S . R.),8, 1062, 1232 (1938); 9, 1258 (1939). Varozhtsov and Travkin, Org. Chem. I d (U. S . S. R.), 5 , 196 (1938). Vaughan and Rust, J . Ora. Chem., 5,449 (1940). Waddle and Adkins, J . Am. C h e a . SOC.,61, 3361 (1939). Whiston, J . Chem. SOC,,117, 183 (1920); J . SOC.Chem. Ind., 39, 384 (1920). (66) Zal’kind and iMarkov, J. Applied C h m . (U. S . S. R.),1 1 , 818 (1938).
PRBSBNTBD as part of paper No. 8 in the Symposium on Unit Processes before the Division of Industrial and Engineering Chemistry a t the 100th Meeting of the American Chemical Society, Detroit, Mioh. No. S appeara on pages 185 t o 188 of this issue.
The other part of paper
