176
INDUSTRIAL AND ENGINEERING CHEMISTRY
(89) Nesmeyanov, A. N., Ber., 62B,1010 (1929). (70) Nesmeyanov, A. N., Org. Syntheses, 12, 54 (1932). (71) Nesmeyanov, A. N., Glushnev, N. I., Epivanskii, P. T., and Felgontov, A. I., Ber., 67B,130 (1934). (72) Nesmeyanov, A. N., and Kahn, E. Y . ,Ibid., 62B,1018 (1929). (73) Nesmeyanov, A. N., and Kocheshkov, X. A., Ibid., 63B, 2496 (1930). (74) Nesmeyanov, A. N., and Makalova, L. G., Ibid., 66B, 199 (1933). (75) Newstrom, J. E., and Kobe, K. A., J. Am. Chem. SOC.,57,1640 (1935). (76) Peters, W., Ber., 38, 2587 (1905). (77) Pope, W. J., and Gibson, C. S., J . Chem. Soc., 101, 736 (1912). (78) Raiziss, G. W., U. 9. Patent 1,554,293 (Sept. 22, 1925). (79) Ibid., 1,630,072 (May 24, 1927). (80) I b i d . , 1,967,686 (July 24, 1934). (81) I b i d . , 1,985,949 (Jan. 1, 1935). (81A) Rao, S., and Seshadri, T. R., Proc. I n d i a n A c a d . Sci., 11A, 23 (1940). Reissert, A,, Ber., 40, 4209 (1907). Roeder, G., and Blasi, N., Ibid., 47, 2748 (1914). Sandin, R . B., J . Am. C h e m . Soc., 51,479 (1929). Sasano. K. T.. and Medlar. E. M.. J . Infectious Diseases. 59. 35 (i938). ’ Sohems. W., and Bonrath, W., Brit. Patent 307,532 (Dec. 8. 19i7). . Schepss, W., and Bonrath, W., French Patent 661,893 (Dee. 8, 1927). Schepss, W., and Bonrath, R., German Patent 484,995 (Dee. 10, 1926). Schrauth, W., and Schoeller, ]I7., Ber., 45,2808 (1912). Sharp, F. L., Brit. Patent 406,725 (March 5, 1934). Smith, L. I., and Taylor, F. L., J . Am. Chem. Soc., 57, 2370 (1935). Ibid., 57,2460 (1935). Spiegler, L., U. S.Patent 2,089,006 (Aug. 3, 1937). Steinkopf, W., Ann., 413, 310 (1917). Ibid., 413,329 (1916). Steinkopf, W., and Bauermeister, M., Ibid., 403, 50 (1914).
Vol. 33, No. 2
(97) Steinkopf, W., and Kohler, W., Ibid., 522,25 (1936). (98) Swaney, M.W., Skeeters, M. I., and Shreve, R. N., IND. EXQ. CHEM.,32, 360 (1940). (99) Taube, C., German Patent 548,902 (Aug. 9, 1928). (100) Taube, C., U. 9. Patent 1,786,094 (Deo. 23, 1930). (101) Ukai, T., J.P h a r m . Soc. J a p a n , No.548,873(1927) (102) I b i d . , 48,374 (1928). (103) Vecchiotti, L., Gazz. chim. ital., 44,34 (1914). (104) Ibid., 56,216 (1926). (105) I b i d . , 58,231 (1928). (106) Vecchiotti, L., and Copertini, S., Ibid., 59, 524 (1929). (107) Vecchiotti, L., and Michetti, A.,Ibid., 55, 372 (1926). (108) Vecchiotti, L., and Speranzini, G., Ibid., 59,363 (1929). (109) Waters, W. A,, N a t u r e , 140,468 (1937). (110) Weed, L. A., and Ecker, E. E., J . Infectious Dbseases, 49, 441 (1931). (111) Ibid., 51,309 (1932). (112) I b i d . , 52, 354 (1933). (113) Whitmore, F. C., “Organic Compounds of Mercury”, A. C. S. Monograph, New York, Chemical Catalog Go., 1921. (114) Whitmore, F. C., and Culhane, P. J., J . Am. Chem. Soc., 51, 602 (1929); Whitmore, F. C., Culhane, P. J., and Nehr, H. T., Org, Syntheses, 7, 3 (1927). (115) Whitmore, F. C., and Fox, A. L., J . Am. Chem. Soc., 51, 3363 (1929). (116) Whitmore, F. C., and Hamilton, F. H., Ibid., 45, 1066 (1923). (117) Whitmore, F. C., Hamilton, F. H., and Thurman, N., Org. Syntheses, 3, 99 (1923). (118) Whitmore, F. C., and Hanson, E. R., Ibid., 4, 13 (1925). (119) Ibid., 4,37 (1925). (120) Whitmore, F. C., Hanson, E. R., and Carnahan, F. L., J . A m , Chem. Soc.. 51. 894 (1929). (121) Whitmore, F:C.,’ and Isenhour, L. L., Ibid., 51,2785 (1929). (122) Whitmore, F. C., and Middleton, E. B., Ibid., 43, 819 (1921). (123) Whitmore, F. C., and Perkins, R. P., Ibid., 51, 3352 (1929). (124) Whitmore, F. C., and Sobatzki, R. J., Ibid., 55, 1128 (1933). (125) Whitmore, F. C., and Thorpe, M. A.,Ibid., 55,782 (1933). (126) Whitmore, F. C., and Woodward, G. E., Org. Syntheses, 7, 58 (1927).
UTILIZATION OF POLYCHLOROPROPANES AND HEXACHLOROETHANE E. T. ICICBEE, H. B. HASS, T. H. CHAO, Z. D. WELCH, AND L. E. THOMAS Purdue University and Purdue Research Foundation, Lafayette, Ind.
IT T H E fifth article of a series on the syntheses of natural
I
gas hydrocarbons (81, the chlorination of propane to obtain 1,3-dichloropropane and the synthesis of cyclopropane from this dichloride were discussed. This process yields a relatively high percentage of the other dichlorides of propane. During vapor-phase thermal chlorination of propane a t 400” C., the dichlorides are formed in the following relative proportions : 2,2-dichloropropane, 25.5 per cent; 1,l-dichloropropane, 19.6; 1,2-dichloropropane, 35.6; 1,3-dichloropropane, 19.3. Also, a large potential supply of 1,2-dichloropropane is available from propylene. The most promising potential industrial use of 1,3-dichloropropane a t present is in the synthesis of cyclopropane. 1,2Dichloropropane is sold commercially for use as a solvent particularly for fats, oils, waxes, gums, and resins, as a substance for making cleaning and scouring compounds and spotremoving agents, and as an intermediate in organic synthesis. Other uses suggested for 1,2-dichloropropane are with methanol or ethanol in the preparation of lacquers containing cellulose acetate (1.41, and as a fumigant when mixed with carbon tetrachloride (,9,9,l,??j, 1,l-Dichloroproptane and 2,2dichloropropane have never been available in commercial quantities, hence they have no reported comm t rcial value.
I n considering these t v o dichlorides as industrial solvents, either in pure form or mixed with 1,2-dichloropropane, the relative stability of the compounds as compared to other chlorinated solvents is important.
Stability Tests on Dichloropropanes In determining the relative stability of the different chlorides, they were refluxed with water in the presence of three different reagents-reduced iron, sodium bicarbonate, and cupric oxide. Iron equipment is most frequently encountered in commercial apparatus, and reduced iron was expected to act as a reducing agent; sodium bicarbonate gives a slightly alkaline solution for hydrolysis; cupric oxide possesses a possible replaceable oxygen. The tests with reduced iron were carried out as follows: Five grams of the organic chloride were mixed with Z grams of iron powder and 100 ml. of distilled water. The order of mixing was always iron, chloride, and water. The mixture was gently refluxed, and a t the end of each 12-hour period the flask was immersed in ice water for 10 minutes. One milliliter was removed by a calibrated pipet for testing. Five milliliters of fresh 3 per cent hydrogen peroxide solution were added to the 1-id. sample in an Erlenmeyer flask, and the
February, 1941
INDUSTRIAL AND ENGINEERING CHEMISTRY
contents shaken for 3 minutes. The sample was then diluted to about 5 ml. by distilled water and titrated with 0.025 N sodium hydroxide. The neutral point could not be accurately determined because of the brown precipitate of ferric hydroxide. Therefore the base was added in excess, and the mixture allowed t o stand until the precipitate settled to the bottom; then i t was back-titrated with 0.025 N hydrochloric acid. A suitable correction was made for the hydrogen peroxide.
A new term "chlorinolysis" has been proposed to describe the process of chlorinating an organic compound under conditions which rupture the carbon-carbon bonds and yield chlorocarbons with a smaller number of carbon atoms than the starting material. This process was conducted by mixing dichloropropanes with the quantity of chlorine necessary to yield exclusively carbon tetrachloride and hexachloroethane and submitting the mixture to thermal reaction at superatmospheric pressure. Octachloropropane, hexachloroethane, and 1,2-dichloropropane were pyrolyzed to obtain useful products in good yields.
It may be concluded from the data of Table I that 2,2-dichloropropane gives a great deal more acid when it is refluxed with water in the presence of iron than 1,l-dichloropropane and 1,2-dichloropropane. 2,2-Dichloropropane is slightly less stable than carbon tetrachloride but reacts a t about the same rate. 1,2-Dichloropropane is slightly more stable than 1,ldichloropropane. Finally, 1,2-dichloroethane is the most stable of the chlorides studied under the experimental conditions given. I n another series of experiments (Table 11) 0.1 mole of the chlorides was refluxed with 100 grams of distilled water in the presence of 0.2 mole of sodium bicarbonate. One-milliliter samples were taken every 12 hours, and the chloride ion was determined by Volhard's method. I n the slightly alkaline solution the order of stability is somewhat different. Carbon tetrachloride is relatively inert to hydrolysis in sodium bicarbonate solution; the order of increasing hydrolysis for the other chlorides is as follows: 1,l-dichloropropane, 1,2dichloropropane, 1,2-dichloroethane, and 2,2-dichloropropane. These same dichlorides, 1,l-, 1,2-, and 2,2-dichloropropane and 1,2-dichloroethane, were refluxed with water in the presence of cupric oxide for 50 hours. 2,2-Dichloropropane was the only one which reacted appreciably.
hexachloroethane were obtained. I n a similar manner they chlorinated isobutyl iodide and obtained octachloropropane. Iodine trichloride was assumed to be the chlorinating agent. Cahours ( 1 ) reported the preparation of a liquid octachloropropane boiling a t 280" C. with a specific gravity of 1.80. Prins ( I S ) started with hexachloropropene and chlorine in the presence of sunlight and synthesized octachloropropane. Hartmann (7) reported the chlorination of several hydrocarbons in the presence of chlorine carriers such as iodine and antimony pentachloride and obtained carbon tetrachloride, hexachloroethane, hexachlorobenzene, and hexachlorobutadiene. Dichloropropanes, both as mixtures and pure compounds, were chlorinated in the liquid phase a t atmospheric pressure in the presence of light to yield octachloropropane. A typical experiment was conducted in the following manner : The material to be chlorinated, which in this case consisted of 752 grams of a mixture of 1,l-, 1,Z-, and 2,2-dichloropropane, was placed in a flask fitted with a condenser, a thermometer, and a chlorine inlet which extended well below the surface of the liquid. The flask was surrounded with four 60watt lamps to provide light which greatly accelerates the reaction. During the early stages of the reaction after the induction period, chlorine reacted readily with the organic chlorides and was added at such a rate t h a t the heat of reaction maintained the reacting mixture near the boiling point. As the specific gravity increased or as the material approached complete chlorination, the reaction became increasingly sluggish. When the specific gravity of the liquid had increased t o approximately 1.7, the rate a t which chlorine reacted was slow, and much of the chlorine escaped through the condenser. For this reason, only 50 per cent of the chlorine which was introduced into the reaction flask was utilized. The temperature a t the start of the experiment was approximately 90" C., the boiling point of the dichlorides, and it was increased gradually until at the end it was approximately 200" C. Previous experiments indicated that considerable cleavage of the carbon-carbon chain occurred a t higher temperatures with
TABLEI. RELATIVE STABILITY OF ORGANIC CHLORIDES IN PRESENCE OF IRON AND WATER
--
Diahloropropanes-CClr Time 1,l-Dichloro- 1,2-Diohloro- 2,2-DiohloroHOUTS c Milliequivalents of acid forme12 24 36 48 60 72 84 96
4.10 8.44 14.33 14.32 18.40 22.60 26.25 23.21
Very little work has been done on the perchlorination of aliphatic hydrocarbons other than methane and ethane. Chlorine derivatives of propane were chlorinated t o octachloropropane by Krafft and Merz (11) using iodine trichloride as the chlorinating agent in sealed tubes for several hours at 200" C . At a higher temperature carbon tetrachloride and
3.73 6.39 6.02 6.03 6.01 9.26 12.11 13.19
68.70 68.09 60.69 59.27 59.26 59.26 70.86 67.57
1 &Dichloroethane
42.80 46.23 48.08 47.76 46.44 48.29 61.09 61.19
0.91
0.00 0.00
0:67 0.62 0.88
..
TABLE11. RELATIVE STABILITY OF ORGANIC CHLORIDE IN PRESENCE OF SODIUM BICARBONATE SOLUTIONS
-
Diohlorppropanes 1,2-Diohloro1,l-Dichloro- 1,2-Diohloro- 2,2-Diohloroethane H O U T ~c Milliequivalent8 of chloride {on 8.30 48.60 1.20 8.00 12 15.23 92.16 10.21 22.98 24 19.23 93.62 12.67 34.21 36 25.89 99.96 16.83 49.36 48 29.40 97.17 59.47 18.30 60 33.00 97.05 24.21 72 30.24 97.13 22.61 84 41.61 102.31 23.94 96 7 -
Synthesis of Octachloropropane
177
Time
... ... ...
CCL 0.00 0.00 0:oo
0:oo
..
-
178
INDUSTRIAL AND ENGINEERING CHEMISTRY
the formation of carbon tetracliloride and hexachloroethane. The weight of the chlorinated product was 1750 grams. The crude product, which was substantially all octachloropropane, mas purified by crystallization from alcohol and by vacuum sublimation, hexachloroethane being the first sublimate. The presence of hexachloroethane could be explained by assuming either that chlorides of ethane were present in the starting material which had been made by a commercial chlorination of natural gas or that cleavage of some cliloropropane molecules had occurred. The latter absuniption mas proved to be correct by conducting a similar chlorination with 1,3-dichloropropane made from 1,Y-propanediol, n-hich was therefore entirely free of ethane deriratives. Hexachloroethane was found to be present in small quantities in the octachloropropane from this chlorination.
1.80
1.70 1.60 0 ci
;;1.50 f 1.40
A 8 C
SULFUR DIOXIDE SULFUR PC15 AND ACTIVATED
1.30
D
(NO CATALYST)
* t P
BETWEEN POINTS I AND 2 , NO ILLUMINATION
1 1.10 0
I I
500 1000 1300 WEIGHT OF CHLORINE USED, GRAMS
FIGURE 1. PHOTOCHEMICAL CHLORINATION OF 1,2-DICHLOROPROPANE
I n view of the fact that the chlorination proceeds slonrly even at temperatures as high as 200" C. when the specific gravity reaches approximately 1.7, a search 17-as undertaken for a catalyst hich would cause the hydrogen atoms of hexachloropropanes and lieptachloropropanes to be substituted more readily. The following substances were tried: sulfur, selenium, SOz, PCls and activated coconut charcoal, CoCI2.6H20,SbC15,BiC13, ZnCL, HgC12, and CdCle. Kone of these substances seemed to have any effect in causing the chlorination to proceed more rapidly during the last stages of the reaction. The metallic chlorides caused considerable cleavage of the carbon-carbon bonds and thus increased the yield of hexachloroethane and carbon teti achloride. Figure 1 shows the increase in specific gravity of the reacting mixture in the photochemical chlorination of 1,2dichloropropane a t 95-200" C. plotted against the weight of chlorine added. The efficiency of tlie chlorine conbuniption decreases with an increase in specific gravity. Sulfur dioxide actually increases the rate of chlorination during the early stages of the reaction; however, in curve A of Figure 1, no light was used until the specific gravity was 1.25. I n an attempt to improve the chlorine efficiency and to increase the rate of reaction by increasing the chlorine concentration, dichloropropane mas mixed with liquid chlorine and sealed in Carius tubes for chlorination. It was found that 0.02 mole of chloride could be mixed with 0.12 mole of chlorine or the theoretical quantity of chlorine for conversion to octa-
Vol. 33, No. 2
chloropropane and heated to 135" C. without explosion. If a substantially higher temperature was used, the tube was broken t'o small pieces, probably because of the vapor pressure of the reactants and not because of an explosive react,ion between the chlorine and dichloropropane. After several hours considerable chlorine substitution had occurred, and the reaction became sloii- a t this temperature. The tubes were opened to allow hydrogen chloride to escape, and frerjh chlorine was added and tlie heat,ing resumed. If the final tJemperaturemas as high as 230" C., the product consisted of carbon tetrachloride and hexachloroethane, but if it was not greater than 200 C., t>heproduct TTas principally octachloropropane. O
Chlorinolpsis of Chloropropanes The term "chlorinolysi '' has been adopted by the aut1ioi.s for the process of convert ig organic compounds into chlorine compounds x i t h fever c rbon atoms by means of chlorine. For example, propane or cliloropropanes can be converted into carbon tetraciiloiicle and hexachloroethane under suitable conditions. This term "chlorinolysis" is analogous to the familiar terms Iiydrogeiiol , hydrolysis, alcohol and ammonolysis. The Carius tube experiment x i t h high clilorine concentration in which carbon t'etrachloride and hexachloroethane Iyere obtained as products was tlie starting point for the investigation of high-pressure liquid-phase chlorination or chlorinolysis of polychloropropanes. Figure 2 shows a drawing of the apparatus used. An experiment was conducted in the following manner : The chlorine tank, S, was detached from the apparatus at coupling U . This tank 17-asthen cooled by solid carbon dioxidc and filled with the desired amount of liquid chlorine, the tank being weighed before and after the addition of this reagent. The material to be chlorinated and carbon tetrachloride, which was added as a diluent to reduce the explosion hazard, were added to the high-pressure storage bomb, D. Chlorine tank S was attached to coupling 0 , and valves E and T were opened to allow the chlorine to pass into D and dissolve in the material to be chlorinated. Since the contents of the tank were a t room temperature and in the dark, no detectable amount of reaction occurred during mixing. Tank S was heated by a bath of warm water to vaporize all of the chlorine quickly. When the chlorine had been added to bomb D,valves E and T were closed. The desired pressure for the reaction was obtained by adding nitrogen to storage bomb D through tubing A from a cylinder of commercial nitrogen. To start a chlorinolysis, valve G was opened and the reactants passed into reactor I . The reactor was made of a/,,inch (4.75-mm.) i. d. X .g/l~-in~h (14.3-mm.) 0 . d. seamless nickel tubing vith a capacity of 7.45 ml. in the hot zone. Hath I< contained sodium nitrate and potassium nitrate maintained at the desired temperature by heating elements controlled by a Leeds & Northrup Microniax pyrometer. The product passed from the wat,er cooler, L, through a regulating valve where the pressure was released to atmospheric. Any desired exposure time could be obtained by proper regulation of valve M. As the product collected in N , the hydrogen chloride escaped as a gas and was absorbed in water scrubber R.
Data for two typical experiments are given in Table 111. The results from these and many similar chlorinolysis experiments indicate a new approach to the utilization of paraffiii hydrocarbons and their partially chlorinated derivatives. Polychloropropanes and chlorine may be mixed and converted into carbon tetrachloride and hexachloroethane in a one-pass process. It is not necessary to resort to low concentrations of chlorine and hence to recycling of the partially chlorinated product because the theoretical or excess quantities of chlorine may be mixed directly with the mat'erial to be Chlorinated. Carbon tetrachloride was added as a diluent to decrease the explosion hazard. A more careful determination of explosion
179
INDUSTRIAL AND ENGINEERING CHEMISTRY
February, 1941
The first experiment (38, Table IV) was conducted a t the boiling point of octachloropropane, and the products, carbon tetrachloride and tetrachloroethylene, were alTABLE 111. CHLORINOLYSIS OF POLYCHLOROPROPANES lowed to distill off as formed. Expt. No. 177 198 Since this did not yield satisfacChloropropane Chloropropane, moles C8H3Cl5 1 0 0CsHaC12 6 tory results, experiment 42 n a s Chlorine, moles 3 2 3 6 conducted a t 300" C. in a sealed 1 0 1 0 CCh, moles 7 46 7 0 tube. The increase in temperature Reactor, ml. Temperature C 300 360 caused an increase in yield, hence 1250 (87.0) 5 l Z 55O (87 ') Pressure, lb /sa in (kg /sq. om ) 4 38 Exposure time, min experiment 51 was conducted in the vapor phase a t 400" C. Product, grams 430 278 cc14 (total) 203 188 with a still better yield and with a much shorter exposure CzCh 215 37 18 3 time. CzCla CaH,Clg 32 Many experiments were conducted using aluminum chloride as a catalyst, and a few are reported in Table IV. It \vas found that by using aluminum chloride a better yield of carbon tetrachloride and tetrachloroethylene was obtained The reactor was made of nickel which has little catalytic at a much lowertemperature and shorter time. The reaction effect on the dehydrochlorination of Partially chlorinated temperature was varied from 750 to 1250 c,,and the catalyst hydrocarbons and subsequent polmerization Of the chlorofrom 0.003 to 3.8 per cent by 17 eight without any appreciable olefin t o carbonaceous material. Reaction temperature may effect. In experiment B the reaction time was only be varied considerably, but if it is much lower than 300" C. and the yield was 91.8 per cent. perric chloride was found to the substitution occurs only slowly in the absence of light. be ineffective as a catalyst for the decomposition of actaAlso, if the temperature is substantially above 400" C.: unchloropropane at 1000 C. Calbon tetrachloride was emdesirable side reactions occur. Several different pressures ployed as a solvellt for the catalyst and the clllorohave been used, and there appears to be no upper limit except carbon. that imposed by the apparatus. As the pressure approaches atmospheric, more and more of the reaction occurs in the vapor Pyrolysis of Hexachloroethane phase. This is undesirable for several reasons. More carSeveral chlorinolysis reactions which are being investigated bonaceous material is formed because of the longer exposure in this laboratory yield products which contain substantial times necessitated by smaller concentrations of chlorine. quantities of hexachloroethane. This chlorocarbon is also a The higher the concentration of chlorine, the greater the opby-product in the preparation of chloroform and methylene portunity for olefinic material and free radicals to react with chloride. A simple process for the conversion of hexachlorochlorine instead of polymerizing or decomposing to a carethane to tetrachloroethylene has commercial potentiality bonaceous deposit. A larger reactor is necessary for the because the latter compound is an important solvent. Faravapor-phase reaction, and finally a higher temperature is reday (4)prepared tetrachloroethylene by passing hexachloroquired. ethane through a heated tube containing porcelain chips. Carbon tetrachloride is obtained almost exclusively, according Pyrolysis of Octachloropropane to Hartmann (7), when hexachloroethane is heated a t 450" C. The discovery that propane and chlorides of propane can be with antimony pentachloride. Hexachloroethane has been treated with several reducing agents to yield tetrachloroconverted in good yields to octachloropropane led to a careful ethylene; Sabatier and Maillie (16) passed hexachloroethane investigation of the pyrolysis of the latter substance into the useful products carbon tetrachloride and tetrachloroethylene. and hydrogen over reduced nickel a t 270" C., Geuther (6) used zinc and sulfuric acid as reducing agents, and Regnault (15) employed alcoholic potassium hydrogen sulfide. Goldschmidt (6) treated hexachloroethane with "molecular" silver a t 280" C. and obtained tetrachloroethane. It is known that the reaction,
mixtures of chlorohydrocarbons with chlorine was determined later and is reported in the paper on page 181.
CzCla Ft. czc14
FIGURE 2.
HIGH-PRESSURE CHLORINATION APPARATUS
+ c12
is reversible; the equilibrium is greatly in favor of hexachloroethane a t low temperatures. The purpose of this investigation was to determine whether or not the reaction could be carried out by purely thermal means with good conversions and yields. The experimental work was performed as follows: The desired amount of hexachloroethane was placed in a glass container immersed in a n oil bath heated to 155" C. and sublimed into the reactor by passing a stream of air into the finely
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
180
TABLE IV. PYROLYSIS OF OCTACHLOROPROPANE Expt. No. CaCls, grams CCla, grams AlCls, grams Temp., C. Time, hr. Product, grams CClra
C2Ch
38 48
42 50
240 19
300 20
400 2.67
96 50 16 0.15 110200 3
19.5
17 22.1
37.6 22.4
79.5
88
.. . .
1
23 I15.2
Residue Yield of CClr and C?Cla, % a
51 50
..
14
48
69.4
..
..
A1 50 16 0.5
..
75
B5 60 32 1.0 100
C1 50 16 0.5 125
B3 50 16 2.0 100
50 16 0.5 100
5
5
5
5
5
3
28.8 32 4 3 . 5 1 9 . 5 1 8 . 8 18.: 8 6 2,7
29.4 20.7 6
81.6
85.6
85.6
86
Including solvent added.
TABLE V. PYROLYSIS OF HEXACHLOROETHANE Expt. No. 1.4 16 25 26 27
Temp. C. 565 600 565 566 565
TABLE VI.
CzCh
Grams 50 50 100 100 100
Contact Time See. 3.1 2.9 2.8 2.7 2.7
Conversion
CCla
CsCla
Residue
Grams
Grams
Gmms
yo
4 8
26.8 25.5 55.5 55.8 55.7
3.1 1.0
89.0 83.0 93.0 94.0 93.5
5 7 10.0 10.4 10.4
7.0
6.5 6.0
HYDROLYSIS OF 1-CHLOROPROPENE AND 3-CHLOROPROPENE
Trial No. 1 2 11 12 7 8 Comoound 1-Chloro- 1-Chloro- 3-Chloro- 3-Chloro- 3-Chloro- 3-ChloroObsGd. wt., 1.80 grams 1.66 2.28 2.19 2.00 1.93 70-75 70-75 70-75 Temp., C. 70-?5 95-100 95-100 Time, hr. 0 5 5 5 4.5 4.5 Wt. hydrolysed, grams 0 0 2 28 2 19 1.95 1 84
divided solid a t a rate of 30 liters per hour. The mixture of hexachloroethane and air passed into a glass reactor (volume, 85.5 ml.) immersed in a molten nitrate bath. The organic product was condensed b y an ice-cooled trap and finally a solid carbon dioxide trap. The product was rectified to separate the carbon tetrachloride and tetrachloroethylene, leaving as a residue any unreacted hexachloroethane. No products, other than the free chlorine, were detected, and the reaction tube remained free from carbonaceous material. Several experiments madc at temperatures below 500" C. gave substantially no conversion of the starting material a t contact times of the order of 3 seconds. Excellent conversions were obtained at 550-600' C. The data for four representative runs are compiled in Table V. With a contact time of 2.7-3.0 seconds the conversion was 93-94 per cent. If the temperature is increased to 600" C., the conversion is substantially 100 per cent. The carbon tetrachloride presumably was a result of the following reaction: C,Cl,
+ Cln
---t
B
B1 50 16 0.5 100
2cc14
TABLE VII.
Vol. 33, No. 2
Experiments 14 and 16 were conducted in a n open tube whereas in 25, 26, and 27 the reactor was filled with glass wool. Apparently surface area has no effect on this reaction.
Dehydrochlorination of 1,2-Dichloropropane
The vapor-phase chlorination of propane a t 400" C. yields 35.6 per cent of 1,2-dichloropropane in the total dichlorides. Also, 1,2-di84.6 91.8 chloropropane is available from the addition of chlorine to propylene. If one mole of hydrogen - chloride is eliminated from 1.2-dichloropropane, cis and trans 1-chloropropene, 2chloropropene, and 3-chloropropene are theoretically possible products. One of the products, 3-chloropene (allyl chloride), may be useful in the synthesis of glycerol. Essex and V a r d ( 3 ) report the preparation of 3-chloropropene from 1,2-dichloropropane by passing the latter over calcium chloride catalyst a t 300" t o 380" C. Klebanskii and Vol'kenshtein (10) obtained 1-chloropropene and propadiene by removing hydrogen chloride from 1,2-dichloropropane with a catalyst and base. The purpose of this investigation was to determine the effect of temperature, cxposure time, and catalysts upon the formation of chloropropenes from 1,2-dichloropropane. The experiments reported in Table VI1 were conducted in the folloT\-ing manner: 1,2-Dichloropropane was forced from a graduated cylinder at a constant rate into a n electrically heated glass vaporizer. The vapors passed into a Pyrex reactor (volume, 51 ml.) which was heated in a n electric furnace. A thermocouple well placed inside the reactor caused the gases to flow close t o the hot Tvalle and hence become heated quickly to the desired reaction temperature. The product passed immediately from the reactor to a watercooled condenser and solid carbon dioxide trap to collect all organic material. The hydrogen chloride was absorbed in sodium hydroxide solution. The organic product n as rectified t o separate the chloropropenes from the unreacted dichloropropane. Only traces of 2-chloropropene (boiling point, 23.5" C.) were found to be present in the mixture of chloro-olefins, and hence the analytical problem was a determination of the amounts of l-chloropropenes (cis boiling at 32.8' and trans boiling a t 37.4' C.) and 3-chloropropene (boiling a t 44.6' C.) in the mixture. The boiling points of trans 1-chloropropene and 3-chloropropene lie too close together for rapid and efficient separation by rectification. The chlorine in 3-chloropropene is attached to a carbon atom which is adjacent to a carbon atom with a double bond, and it is characteristically easy to remove by hydrolysis. However, the chlorine in 1-chloropropenes is attached to a carbon which also has a double bond, and such compounds are stable to hydrolysis. To prove that this mixture could be analyzed satisfactorily by selective hydroly29.5 17.2 6
32.4 20.7 5.8
DEHYDROCHLORINATION O F 1,2-DICHLOROPROPENE
R u n No.
20
28
21
24
25
26
27
29
35
1,2-Diohloropropsne, moles Temp., O C. Exposure time, sec. Catalyst HC1 removed moles 1- and 2-Chldropropene formed, moles 3-Chloropropene formed moles Mole ratio, 3-chloropro~ene/l2-chloropropenes 1 2-Dichloropropane pyrolyzed yo l:2-Dichloropropane converted' t o chloropropenes, yo yield
1.05 640 5.67
1.81 550 f 5 3.54
1.81 540 5 2.30
1.81 545 f 5 1.69
...
1.81 621 4-5 0.77
1.81 635 -I- 5 0.85
1.81 640 f 5 0.93
1.34 635 f 5 1.42
... 1.31
1.14 1.81 750 f 10 540 5 0.33 ... CYCls 1.17 0.33
BiCln 0.25
PKClz 0.17
+
+
+
30
31
+
32
1.81 1.81 540 f 5 465 5
+
0.82
0.83
0.44
0.31
... 0.80
1.19
... 1.27
0,223 0.305
0.270 0.411
0.152 0.227
0.0997 0.149
0.295 0.423
0.362 0.562
0.368 0.542
0.331 0.469
0.222 0.261
0.10 0.11
0.06 0.07
0.020 0.023
1.37 90
1.52 51.2
1.49 29.9
1.49 21.4
1.43 56.1
1.55 67.4
1.48 72.7
1.42 91.5
1.18 92.2
1.09 27.8
1.17 22.9
1.15 14.6
56
65
70
64
73
76
68
66
46
42.5
30.8
16.2
...
...
.. .
...
February, 1941
INDUSTRIAL A N D ENGINEERING CHEMISTRY
sis, samples of pure 3-chloropropene and l-chloropene were prepared and subjected to hydrolysis. Samples of the pure compounds were weighed in bottles fitted with ground-glass stoppers to eliminate evaporation. The bottle and sample were placed in a tube containing 25 ml. of a standardized alcoholic base which had previously been cooled in ice, and the tube was sealed. The glass stopper was removed from the weighing bottle, and the contents of the tube and bottle were thoroughly mixed by shaking. The results in Table VI show that a t 70" to 75" C. l-chloropropenes are not hydrolyzed a t all, but that 3-chloropropene is completely hydrolyzed. This same technique was used in analyzing mixtures of chloropropenes obtained by dehydrochlorination of l,Zdichloropropane, and the results are reported in Table VII. Three different temperature ranges were used, 540-550 ", 635-640", and 750" C. At 540" C. the best yield of chloropropenes was obtained with an exposure time of 2.30 seconds. Either longer or shorter exposure times caused a decrease in the yield. When the temperature was increased to 635" C. a maximum yield of 76 per cent was obtained with an exposure time of 0.85 second. The ratio of chloropropenes did not seem to vary appreciably with temperature, and 3-chloropropene was approximately 60 per cent of the total chloro-olefins. Catalysts
181
caused a lower yield of desired products even a t low conversion.
Literature Cited (1) Cahours, Ann., 76, 283 (1850); Beilstein's Handbuch der organischenChemie,Vol. 1,p. 108, Berlin, Julius Springer, 1918. (2) Dibble, J . Econ. Entomol., 26, 893 (1933). (3) Essex and Ward, U. S. Patent 1,477,047(Dec. 11, 1923). (4) Faraday, Ann., [2]18,53 (1821). (5) Geuther, Ibid., 107,212 (1858). (6) Goldschmidt, Ber., 14, 929 (1881). (7) Hartmann, Ibid., 24,1011-26 (1891). (8) Hass, McBee, Hinds, and Gluesenkamp, IND.ENG. CHEM., 28, 1178 (1936). (9) Hutson, J . Econ. Entomol., 26,291 (1932). (10) Klebanskii and Vol'kenshtein, J . A p p l i e d Chem. (U. S . S . R.), 8, 106-16 (1935). (11) Krafft and Merz, Ber., 8, 1296 (1875). (12) Munro and Fox, N. Dak. Agr. Expt. Sta., Bull. 278 (1934). (13) Prins, J . prakt. Chem., 89,418 (1914). (14) Reed, U. S. Patent 1,969,183(Aug. 7,1937). (16) Regnault, Ann., 33, 324 (1840). (16) Sabatier and Mailhe, Compt. rend., 138,409 (1904). THISpaper contains material abstracted from the Ph.D. theses of T. H. Chao and L. E. Thomas, and the M.S. thesis of Z. D. Welch.
CHLORINOLYSIS OF CHLOROPENTANES E. T. MCBEE, H. B. HASS, AND EARL PIERSON Purdue University and Purdue Research Foundation, Lafayette, Ind.
A high-temperature high-pressure chlorination of chloropentanes has resulted in the formation of hexachloroethane, carbon tetrachloride, and hexachlorobutadiene. The term "chlorinolysis" is proposed as being descriptive of the reaction. Explosions and carbonization are prevented by the use of excess chlorine. At 400' C. (752' F.) and a pressure of 1000 pounds per square inch the conversions to carbon tetrachloride and hexachloroethane are approximately 90 per cent, and the potential yield of these products approaches the theoretical value.
T
H E terms hydrogenolysis, hydrolysis, ammonolysis, and alcoholysis occur frequently in chemical parlance and indicate a chemical reaction in which hydrogen, water, ammonia, or alcohol, respectively, effects a rupture of the molecule undergoing these reactions. Following this analogy, the term "chlorinolysis" is suggested as affording an apt description of a chlorination reaction performed under conditions which cause a rupture of the carbon-carbon bonds in the reactant molecules to form chloro compounds with fewer carbon atoms. The chemical literature contains only a limited number of examples of chlorinolysis. Hartmann (3) chlorinated 2,5-
dimethylhexane, 2,7-dimethyloctane, l-iodohexadecane, hexadecanoic acid, and Pennsylvania petroleum with antimony pentachloride in sealed tubes a t temperatures of 60-320" C. (140-608" F.) and obtained carbon tetrachloride, hexachloroethane, hexachlorobenzene, and a compound having the empirical formula C4Cls (presumably hexachlorobutadiene). Krafft (4) chlorinated l-iodobutane and l-iodohexane in sealed tubes with iodine trichloride at 100-240" C. (212464" F.) and obtained carbon tetrachloride, hexachloroethane, and a compound which was considered to be hexachlorobutadiene. The only reference to a chlorinolysis reaction in which elemental chlorine was used as the chlorination agent is that of Grebe, Reilly, and Wiley (2) who patented a process for the preparation of chlorocarbons, principally carbon tetrachloride and tetrachloroethylene, by passing preheated chlorine and paraffin mixtures through a molten salt bath. From the limited number of references to chlorinolysis it is evident that this reaction has received but little attention, presumably because of the difficulties involved, the lack of industrial potentialities in chlorination by means of compounds of chlorine, and the frequent occurrence of carbonization and explosions when large amounts of chlorine are mixed with paraffins.
Explosibility of Dichloropentanes-Chlorine Mixtures
It was desired to apply the chlorinolysis reaction to the isomeric dichloropentanes derived from the thermal chlorination of mixtures of pentane and isopentane; however, there was considerable apprehension as to the possible consequences of
