Halogenation
Tm
far-ranging utilization of halogen compounds in modern industry closely reflects the general economy in the production figures for chlorine and fluorine compounds. O u t p u t for 1957 and 1958 is in accord with the prevailing trend of business. However, over-capacity for chlorine was foreseen more than two years ago. Apparently the indefatigable optimism of the industry kept rhe yearly increase of chlorine production a t 10 to 10.5% for the past three decades. Undoubtedly the recession speeded u p production adjustments in accordance with more realistic market evaluations. Fortunately, the buffer capacity of the major U.S. chemical concerns is
LEO R. BELOHLAV, a native of Austria, received his Ph.D. in 1953 from Vienna University. He has held staff positions a t Vienna University, Harvard University, and Purdue University and i s presently employed with Great Lakes Chemical Corp. He is a member of the ACS, Association of Harvard Chemists, and Sigma Xi. EARL T. McBEE, who has authored I/EC's halogenation reviews since 1948, i s head of the chemistry department at Purdue University, where he received his Ph.D. in 1936. His major interests include synthetic organic chemistry, reaction mechanisms, and organic halides. The Modern Pioneer Award for original investigations in the chlorination of hydrocarbons and the Sigma Xi Award for fluorination contributions are among his honors. McBee is chairman o f the U. S. Naval Powder Factory Advisory Board, a fellow of the Indiana Academy of Science, and holds memberships in many other prof essionaI and honorary societies.
1 102
sufficiently large to support aggressive research activities in the face of decreased earnings. T h e yearly increase in rate of publications remains undaunted by economic trends. The unique characteristics of fluorine, and the considerable difficulties that had to be overcome to produce and handle the gas, rendered standard methods of halogenation inapplicable. I n the past 2 years specific fluorinating reagents have become realities Last year the development of perchloryl fluoride as a reagent for replacing active halogens by fluorine marked the beginning of this new trend. This year researchers a t D u Pont added sulfur tetrafluoride to the list of discriminating fluorinating agents. Only a short time ago a laboratory curiosity, it is under development for large scale production. I t proved to be a specific reagcnt for replacing carbonyl groups by CF2 groups in excellent yields. As a counterpart to perchloryl fluoride, it offers access to a whole array of ne\v fluorine compounds. Two recent developments in chlorine chemistry may be singled out for special mention. O n e appears to be a likely prospect for industrial utilization: the one-step photo-oximation of alkanes with nitric oxide and chlorine in the presence of hydrogen chloride under the catalytic effect of ultraviolet irradiation. As in the reaction of nitrosyl chloride with alkanes, the new process does not require the low temperatures and high dilutions necessary for the classical nitrosylation. I t opens a new route to cyclohexanone oxime, the starting material for e-caprolactam a n d the synthetic fibers based on it. Interesting experiments were performed a t Du Pont on reactions in flames; passing dilute aqueous solutions of acetic acid and sodium chloride through flames resulted in surprisingly high yields of well-defined halogen compounds. An increasing number of publications and patents on halogenated steroids indicate preliminary success in separating desirable pharmacological properties
INDUSTRIAL AND ENGINEERING CHEMISTRY
"
--
~~
-
~
.
Production. Short Tons 1957 1958
Chlorine HCl
HF CClr CsHsCl C2Cll CgHCla DDT 2,4-D 2,4,5-T
3,917,419 926,754 84,796
3,599,214 828,157 83,991
Pounds 321,398,961 309,818,922 373,319,736 377,450,522 196,354,093 188,276,844 318,949,745 294,627,670 123,757,530 143,216,244 33,413,442 30,930,937 5,053,339 3,638,452
by the introduction of halogen substituents.
Chlorination Paraffin Hydrocarbons. I n a continuous German process a mixture of chlorine and methane and/or chlorinated derivatives is treated ivith or \vithout inert gas a t 320" to 390' C. under adiabatic conditions (27A). The process employs a reaction chamber of 6.8 to 23 cu. meters and is provided with a circulation device. T h e supply of fresh gas mixture rates from 200 to 4000 cu. meters per hour. T h e reaction is variable in a wide range of composition of reactants, limited only by the explosive range of the respective mixtures. Methane was chlorinated economically to chloroform in a one-step process by use of a fluidized bed reactor and concomitant injection of liquid carbon tetrachloride to act as a reaction modifier by providing efficient heat transfer during the exothermic gas phase reaction at 650' to 775' F. Up to 51% of the final chlorinated materials were recovered as chloroform (57A). A new approach to moderation of the gas phase chlorination of lower acyclic hydrocarbons by chlorine is offered in a Japanese patent (544). At the beginning of the reaction tetrachloroethylene absorbs chlorine under the formation of hexachloroethane, obviating explosion hazards. T h e reaction between tetrachloroethylene and chlorine begins a t about 250' C. a n d increases spontane-
.___..
ously because of exothermicity. .4t higher temperatures the hexachloroethane dissociates into tetrachloroethylene a n d chlorine, the latter serving for chlorination. This dissociation proceeds smoothly a t 300' C. Passing 480 parts of sulfur trioxide into 120 parts of ethane over 900 parts of sodium chloride a t 400' C. gave 25yc conversion per pass to chlorine-containing materials composed to 90% of ethyl chloride. T h e molten salts were heated to release sulfur trioxide and treated with hydrogen chloride and sulfur to give sulfur dioxide which was oxidized to sulfur trioxide a n d recycled ( I 7'4). Small amounts of mercury, iron, or copper compounds a t a temperature of 200' to 450' C. catalyze this reaction efficiently. T h e process is applicable to bromide. A specially designed apparatus has been described ( 2 Q A ) . Excellent yields of ethyl chloride were claimed for a combined chlorinationhydrochlorination process ( S A ) . A mixture of chlorine (71% by weight) a n d ethane reacted thermally a t 425' C. a n d 80 p.s.i. with a contact time of 3 seconds, resulting in complete conversion of the chlorine. A gaseous hydrocarbon feed mixture containing 52cc ethane a n d 47y0 ethylene was subsequently mixed Lvith a recycled stream from the first step, resulting in a n over-all mixture containing 5570 ethane, l7yO eth>-lene, a n d 227, hydrogen chloride. This mixture was subjected to hydrochlorination in the presence of a catalyst consisting of cuprous chloride-promoted zinc chloride on a porous aluminous support a t 175' C. a n d 250 p.s.i. with a throughput rate of 1 pound of feed per hour. Propane was chlorinated in contact with a moving bed of mullite a t 360' to 395' C. O n e to 4Cc of monochloride was observed in the resulting mixture a t a chlorine-alkane ratio of 1.58 to 2.38. .At higher chlorine concentrations the yield of di- a n d trichloride was raised to 807, (89A). tert-Hydrocarbons were converted to tert-alkyl chlorides with tert-butyl chloride a n d 96Yc sulfuric acid (97A). X mixture of 1.8 moles of 2-methylpentane a n d 1 mole of tert-butyl chloride reacted with one volume of sulfuric acid for 2 hours at 0 ' C . a n d 2 p.s.i. pressure afforded a 26 mole % conversion to 78.5% 2-methyl-2-chloropentane. This offers a convenient way to reduce the 2methylhexane (3.3Yc)a n d the 3-methylhexane (13.3%) of commercial heptane to 5.57, total without the excessive rearrangements a n d side reactions of processes employing aluminum chloride. Light-induced chlorination of hexane using a 1 to 1 mixture of chlorine a n d hydrocarbon afforded 16% sec-hexyl chloride, 15.7% n-hexyl chloride, a n d
68y0 of mixed dichlorohexanes. With a mixture of 1,4-hexane to chlorine 15.77c dichlorohexane (containing 4% of the 1,6-isomer) a n d 84% of polychlorinated products were observed (584). T h e solvent effect in free radical chlorination of 2:3-dimethylbutane a n d isobutane was studied. Chlorination of 2,3-dimethylbutane in aliphatic solvents gave a mixture of 607, 1-chloro-2,3dimethylbutane a n d 407, 2-chloro-2,3dimethylbutane. I n aromatic solvents the tert-chloride \vas generally the major product (90yc) in a n 8,21 benzene solution. It was concluded that the chlorine radical forms a vcomplex with the aromatic nucleus, less reactive a n d therefore more selective than the free chlorine radical (74A). Under ultraviolet irradiation a 1 to 1 mixture of heptane a n d chlorine a t 14' to 16" C . gave a mixture of 12.3yc sec-heptyl chloride. 11.S% prim-heptyl chloride: and 76.2% dichloroheptane (59A). Cobaltous chloride (l5yc) on pumice was the most efficient catalyst investigated in this type of reaction (57'4). Photochemical chlorination irith chlorine a n d sulfuryl chloride gave different products in the chlorination of branchedchain hydrocarbons. This was ascribed to an equilibrium: SO2 C1. @ S02C1. and the loLver activity a n d greater selectivity of the SO2C1. radical. I n aromatic solvents little difference is noted, possibly because of a similar type of complexing with the aromatic solvent (76A). T h e relative reactivities of 16 different C H bonds toward C1. radicals have been measured in the presence of aliphatic solvents, benzene, tert-butylbenzene, a n d carbon disulfide (75A). T h e results support the conclusion that the solvent can greatly influence the reactivity of chlorine radicals. Bromine promotes the conversion of 1,2-dichloroethane to tetrachloroethane by hydrogen chloride a n d oxygen. Liquid phase chlorination of 1 l-difluoroethane under ultraviolet irradiation gave high yields of 1 1-difluoro-2-chloroethane
+
~
~
( m 4 ). Unsaturated Hydrocarbons. T h e rate-controlling mechanism of the hydrogen chloride addition to ethylene has been established a n d the constants for the rate equation calculated. T h e mechanism appears to be a surfacecontrolled mechanism in Lvhich tivo adjacent sites are involved (87.4). T o prevent local concentrations and decrease the amount or aluminum chloride catalyst required during reaction of ethylene a n d hydrogen chloride, molten aluminum chloride was sprayed into the feed stream of ethylene and hydrogen chloride (56.4). .A technical propylene-propane mixture (78Yc pro-
HALOGENATION
pylene) was treated a t 95' to 100' C. with carbon tetrachloride a t 80 to 280 a t m . With a propene-carbon tetrachloride ratio of 1.4 in the presence of 1% benzoyl peroxide 1,1~1,3-tetrachlorobutane was obtained with a maximal yield of SOYc> besides smaller amounts of isopropyl chloride a n d chloroform. A maximum yield of 25Yc of tetrachloro3-methylhexane was obtained with a propene-carbon tetrachloride ratio of
2 (P3A). T h e chlorination of isobutylene was studied in detail. A chlorine-isobutylene mixture of 1 to 2. Lvith 2 seconds' residence time a t 70' to 80' C . a n d without catalyst resulted in 81% substitution a n d 197c addition (8L7a4). \Yith activated carbon as a catal>-st. the temperature rose spontaneously to 200' C. a n d about equal amount; of substitution and addition products were isolated. FVhen the gases !\.ere preheated to 250' C. prior to entering the reactor, the temperarure rose to 410' to 450' C . and 70% substitution products were obtained. \Vhen diisobutylene was atirred in a stainless steel autoclave for 60 hours a t 0 ' to 25' C. in contact with anhydrous hydrogen chloride a t 100 p.s.i. pressure, conversion to alkyl chloride was 1 0 0 ~ ~ . U p to 84Yc of the end product boiled lvithin the range of octyl chlorides, being composed of about equal amounts of 2-chloro-2,4,4-trimethylpentane.2chloro-2,3,4-trimethylpentane.a n d 3chloro-2,3~4-trimcthylpentane (77.4). T h e relative reactivity of a number of aliphatic olefins in the addition of dichlorocarbene to form dichlorocyclopropane derivatives has been determined. Reactivity increases with increasing degree of substitution in accordance with the hypothesis that CC:l2 is electrophilic( 74A). Butadiene reacts Jvith chloride ion in the presence of a free radical provided by hydrogen peroxide a n d a salt such as ferrous chloride in a solvent such as acetone? Ivhich dissolves the diene to give a product characterized as dichlorohlonochlorodimethyl octane (26.4). ether \vas added to 2-chloro-1,3-butadiene under the catalytic action of zinc chloride to give 74.5y0 C H ~ O C H ~ C H Z CCI=CHCH2C1. I n a n analogous reaction chloromethyl butyl ether added to chlorobutadiene to afford 60.87, of the adduct (95.4). I n a three-step synthesis diacetylene \vas chlorinated in carbon trtrachloride betbyeen - 30 C. and room temperature to afford hesachloro-2-butene. Further chlorination under irradiation with ulrraviolet light for 3 to 4 days gave octachlorobutane. Subsequent treatment with alcoholic sodium hydroxide yielded hexachlorobutadiene (80.4). Hydrogen chloride and 1,4-butynediol in a molar ratio of 3 to 1 reacted in the vapor phase over a
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SEPTEMBER 1959
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Specific fluorinating agents have become reality y-Al20, catalyst with a contact time of 5 to 8 seconds a t 15.5' C. to produce addition compounds with a total conversion of 43y0. T h e products contained 4.8% 1,4-dichloro-Z-butene and 38.9% a-chlorocrotonaldehyde. A silica gel catalyst yielded 7% of 1,4-dichloro2-butene (75A). Chlorination of 1,4dichloro-2-butyne in carbon tetrachloride a t 65' afforded 74.47,hexachlorobutane. Lowering the reaction temperature to -60' C. increased the yield to 97.6yc,. Chlorination of 1,2,3,4-tetrachlorobutadiene in carbon tetrachloride in the presence of antimony(II1) chloride for 3 to 4 hours a t 50" C. led to 1,1,2,3,4,4-hexachloro-2-butene in SOYo yield; in sealed tubes under ultraviolet irradiation a 91% yield was obtained after 30 hours (82A). u-Chloroalkyl nitriles, C1(CHZCH 2 ) nCY ( n = 1 to 6), were prepared by condensation of cyanogen chloride and ethylene in the presence of sodium cyanide and catalytic amounts of azodiisobutyronitrile a t 120' C. under 5000p.s.i. pressure ( 4 2 A ) . w-Dichloro-olefins of the general formula R . C H = C C l ? react in acetic acid in the presence of mercuric acetate with bromine or chlorine according to the equation: RCH=CC12 Clz CH3COOH -+ R C H C l - eel?OCOCH3. O n hydrolysis RCHClCOOH was obtained (67A). T h e gradual replacement of fluorine by chlorine in the reaction of perfluoropropene with aluminum chloride was investigated thoroughly. Replacement occurs first in the two 1- positions; only after complete chlorination of the 1- position the 3position is attacked. Replacement of the fluorine atom in the 2- position occurs last (65A). a-Chlorostyrene oxide was obtained by low temperature chlorination of styrene oxide under ultraviolet irradiation of carbon tetrachloride. T h e compound is useful for the preparation of epoxy resins in which one carbon atom of the epoxide linkage also bears an ether oxygen (50A). Preparation of chloroalkyl alkenyl aryl ethers of the general formula CHz==C(R)-ArOC,Hn,Cl (R = H, CHs; Ar = arylene; n = 8) and their polymers has been claimed ( 72A). Cycloalkanes. The thermal chlorination of cyclopentane in a column filled with glass beads showed little influence of temperature variations near 250' C. T h e use of moist chlorine favored formation of monochloro derivatives. T h e same phenomenon was observed in the chlorination of cyclohexane a t 320' to 340' C. (60A). Octachloromethylenecyclopentene was prepared by photochlorination of a Cg chlorohydrocarbon with a minimum of three chlorine
+
1 104
+
atoms in the presence of a porous surfaceactive catalyst a t 250' to 460'. T h e resulting mixture of four isomers was separated by conventional methods (47A). Treatment of cyclohexanone with acetyl chloride in ethylene dichloride with catalytic amounts of aluminum chloride afforded a 64Yo yield of 1acetyl-2-chlorocyclohexene. Cyclopentanone gave 3 1Yc 1-acetyl-2-chlorocyclopentene ( 4 7 A ) . Of particular interest is a detailed study of the replacement of a hydroxyl function of hydroxy cholestene by chlorine. 4~-Hydroxycholest-5-enegave 68chlorocholest-4-ene on treatment with thionyl chloride in ether; hp-hydroxycholest-4-ene gave 4~-chlorocholest-5-ene. The competition by S ,, and Sv? type replacements could be eliminated by inactivating the liberated hydrogen chloride by complexing with the ether solvent. Aromatic Compounds. Experimental evidence explains the selective formation of monochlorobenzene in the catalytic chlorination of benzene in the liquid phase at 50' to 65" C. as a consecutive competitive reaction between the benzene and chlorobenzene formed during the reaction. The relative reaction rates were estimated in terms of the ratio between the reaction velocities of benzene and chlorobenzene for each catalyst. A ratio of 7 to 9 was found for anhydrous ferrous chloride, 11 for kaolin, 16 for bentonite, and 25 to 40 for a Japanese acid clay. This surprising influence of the catalyst was explained by selective adsorption of benzene by the silica gel in the acid clay, which was assumed to have surface-activitv centers of FelOs ( 6 4 4 . Isomerization of dichlorobenzene under the influence of aluminum chloride a t 120' to 160' was investigated. 4 n American patent claims conversion of o - dichlorobenzene ivith lOyo aluminum chloride in the presence of hydrogen chloride a t elevated pressures to m-dichlorobenzene with a yield of u p to 50% (70A). A Russian group established the equilibrium composition, reached a t 160' in 50 hours in the presence of aluminum chloride. T h e resulting mixture contained 16% o-, 30% p-3 and 54yo m- isomer. Simultaneously 1.6% chlorobenzene resulted from disproportionation ( M A ) . Acid-catalyzed chlorination of toluene by hypochlorous acid occurs 60 times faster than chlorination of benzene, affording a mixture of 74.6Yo o-, 2.2% m-, and 23.2% p- isomer. Chlorination of tert-butylbenzene with hypochlorous acid in acetic acid resulted in 42% of the pchloro derivative. This indicates an appreciable steric hindrance in the ochlorination of tert-butylbenzene (13il).
INDUSTRIAL AND ENGINEERING CHEMISTRY
Isomer distribution in the noncatalyzed chlorination of toluene in carbon disulfide a t 25" C. was determined. T h e reaction mixture, obtained in 78 to 81% yield, contained 79.8% o-, 0.5% m-: and 39,7y0 p- isomer. T h e ratio of chlorination of benzene and toluene under these conditions is 1 to 344. Chlorination of m-xylene gave 23.0% of the 2-chloro and 77.0y0 of the 4chloro derivative (6.4). I n the presence of hexamethylenetetramine, m-xylene was chlorinated exclusively in the side chain even in the presence of iron compounds. Illumination with ultraviolet light afforded a n 80%. yield of the corresponding hexachloroxylene. A mixed catalyst composed of a trialkarylphosphite and urea in chlorination of rn-xylene minimized darkening of the reaction mixture (&A, d9-4). T h e rates of chlorination of polvmethylbenzene in acetic acid a t 30' decrease in the order pentamethylbenzene > isodurene > metadurene > durene (2.4). New experimental evidence \vas cited in favor of a mechanism for chloromethylation in which formaldehyde and hydrogen chloride form a HOCH2+ ion which attacks the aromatic nucleus, yielding a benzyl alcohol which then reacts with hydrogen chloride to form the chloromethyl derivative (55A). Anilidest toluidides, and benzamides were chloromethylated with dichloromethyl ether and sulfuric acid a t 5" to 15' C. (77A4). Sitroaromatic compounds could be chloromethylated by using dichlorodimethyl ether in chlorosulfonic acid a t 60' C. p-Nitroethylbenzene gave 437, 2-chioromethyl-4-nitroethylbenzene and 10% of the corresponding 2,6-bischloromethylated derivative. p-Kitroisopropylbenzene gave 507, 2-chloromethyl - 4 - nitroisopropyl - benzene. p-Nitro-tert-butylbenzene did not react (69A). 1,2-Dihydronaphthalene reacted with paraformaldehyde and hydrogen chloride to give 1,2-dihydro-3chloromethylnaphthalene (67A). Treatment of benzofuran-2-carboxylic acid esters with paraformaldehyde and zinc chloride in chloroform introduced a chloromethyl group into the 5- position (52A). A new class of substituted aromatic compounds was made accessible by reaction of perchloryl fluoride with aromatic compounds in a Friedel-Crafts type reaction. Benzene: fluorobenzene, and pxylene afforded the corresponding perchloryl derivatives. Perchlorylbenzene could be subjected to nitration, yielding m-nitroperchlorylbenzene. T h e perchloryl function was not affected by reduction of the nitro group to the amine. Perchloryl derivatives are stable during vacuum or steam distillation but can be detonated by vigorous shock or
HALOGENATION
_.......__.__._. .~...._......_....___.___ ...._.__. __._.____._..__._....~~..~~.~~-~~.~~~..~...........-..
high temperature: they are insoluble in lvater, soluble in organic solvents, and resistant to a series of reducing agents such as stannous chloride-hydrochloric acid, zinc-hydrochloric acid, hydrogen-palladium, and lithium aluminum hydride (38A). The reaction of nitryl chloride with aromatic compounds was reinvestigated. rinisole was chlorinated, while phenol \vas nitrated preferentially. Both reactions proceeded simultaneously in the case of naphthalene and h>-droquinol diethyl ether in methylene chloride at -20" C. (7011). With olefins nitryl chloride forms nitro-chloro adducts, h e nitro group being attached to the trrniinal position irrespective of the elrctronic demands of the substituents. Styrene gave a mixture of dichlororthylbenzene and nitrostyrene (resulting from CBH5CHC1CH2K02)(30A). A ne\\. route to aromatic carboxylic acid chlorides was found by treatment of the trichlorometh>-l derivative with titanium dioxide (or vanadium pentoxide) : 2C:,HjCC13 Tion4 2C6H5COCl TiC:l, (78A). A stoichiometric mixture of the two reactants is heated to 200' to 300' C. T h e volatile inorganic chloride is distilled off and the acid chloride subsequently distilled under vacuum f 78.li. 'I reatment of 1,l - diphenylethylene wirh iodine chloride gave 1,I-diphenyl2-chloroethylene. Styrene on reaction with iodine chloride afforded a mixture of meso- and DL-stilbene dichloride. Iodine chloride acted as a chlorinating agent (-l0.i). Oxygen Compounds. Methanol is converted to methyl chloride by reaction with hydrochloric acid in 65 to 7!17~ zinc chloride solution at elet ated pressures. Thus, aqueous hydrogen chloride and methanol, mixed Xcirh methyl chloride, methylene chloride, and chlorororm kvere fed into an autoclave \vhich was kept at 8 p.s.i. The overhead vapors were passed into another autoclave under identical conditions. T h e yield of methyl chloride after the first step was 6 S 5 and after the second step 9 7 7 ~ (4.3.4). Chlorine could be introduced into the cu-position of several tert-trichloromethylalkanoIs by treatment with sulfiiryl chloride in the presence of benzo)1 peroxide a t 50' to 120' C. Thus 1.1 -1 - trichloro - 2 - hydroxy - 2 - methylbutane gave 1*1)1,3- tetrachloro - 2hydroxy 2 - methylbutane (&A). T h e rrnction of 3-(a-tetrahydrofuryl)propanol with hydrochloric acid and zinc chloride resulted in ring opening under the forIllation of 1,7-dichloroheptene and 1,4,7trichloroheptane. Dimethyl ether was chlorinated to ~,vm-dichloromethy1ether smoothly and \viihout danger of explosions by passing
+
-
+
dimethyl ether and chlorine into dichlorodimethyl ether (62A). Total yield of chlorination products was 7570 of the gas introduced. A very useful chlorinating agent was 1:1,1'-trichlorodimethpl ether prepared by chlorination of dimethyl ether ( 7 2 4 ) . I t converts readily carboxylic acids, their sodium salts. and anhydrides into the corresponding acid chlorides. T h e reaction of an olefin of the general formula RCH=CH* with trichlorodimethyl ether opened a new route to a-p-unsaturated aldehydes. A compound of similar reactivity is the 1:ldichlorodiethyl ether which also converts carboxylic acids (not oxalic or succinic acids) to the corresponding acid chlorides a t 40'. The preparation of a more accessible substitute, 1.1:2triehlorodiethyl ether, has been described. Chlorinated ethers as halogenating agents are particularly useful in the preparation of acyl chlorides which must be completely free from compounds such as thionyl chloride? phosphorus trichloride, and phosphorus oxychloride (34-4). Chlorination of dioxane with elemental chlorine a t 90' to 150' C. gave good yields of trichloroacetyl chloride (46'4). Ethylene oxide reacts with carbonyl halides COX? (X = F, C1, Br) in the vapor phase in the presence of 0.01 to 77, H X (X = C1, Br, I) to give haloethyl haloformate (27A). A41keneoxides generally give compounds of the general formula CICH?-CHRO2CCl (28A). Several variations for the production of acid chlorides Tvere the subject of patent claims. Plcid chlorides were produced by the reaction of chlorine with primary hydrazides of carboxylic acids in the presence of hydrogen chloride. T h e hydrazide in the form of its hydrochloric acid salt is suspended in an anhydrous medium which resists the action of elemental chlorine-e.g., alkyl chloride or nitroparaffin (7A). .A continuous process for the preparation of organic acid chlorides employs thionyl chloride vapors countercurrently in the reaction vessel. Yields of better than 90% are claimed (37A). The formation of dichloroacetyl chloride in the production of chloroacetyl chloride from elemental chlorine and ketene is eliminated if the reaction is performed in the liquid phase with sulfur dioxide as a solvent (79'4). A novel method for the formation of haloacetic acid was discovered. Passing a 2% aqueous solution of acetic acid containing 5.57, sodium chloride through a 1 to 1 hydrogen-oxygen flame (contact time 0.003 second), collecting and cooling the mixture, recycling for a total of 10 cycles, and extracting the mixture with ether gave a liquid composed of 76.8Yc
chloroacetic acid, S.4'3c succinic acid, 10.7C;; hydroperoxyacetic acid, and 7.170 glycolic acid (SA). cu:a - Dichloropropionic acid and chloroform were produced, starting with methyl ethyl ketone or sec-butanol. Chlorination in water at SOo to 100' C . gives a mixture of tri- and tetrachlorides. Further chlorination over activated carbon at 130' to 180' C. afforded the corresponding penta-chloroketone, which can be cleaved by base into chloroform and cup-dichloropropionic acid (78.4). Thermal chlorination of methyl benzoate a t 149' C. with elemental chlorine gave a mixture of benzoyl chloride and chloromethyl benzoate. Chlorination a t 29" C. under the catalytic influence of light gave mainly trichloromethyl benzoate. 4 68% yield of monochloroethyl benzoate could be obtained by chlorination of ethyl benzoate. Isopropyl benzoate gave 60.77, of a mixture composed of CY- and 8-monochloro and 8-polychloro esters. Dimethyl terephthalate afforded '95.7% of a monochlorinated ester (88A). For the halogenation of acrylic acid esters and their homologs, tertiary nonheterocyclic organic bases such as dialkylaniline or carboxylic amides appear the catalysts of choice (33A, %?A). Heating vinyl acetate in carbon tetrachloride under reflux for 10 hours with cata1)-tic amounts of benzoyl peroxide gave 62% 1,3,3,3-tetrachloropropylacetate. A similar reaction with chloroform gave a yellow undistillable product which appeared to be CCls[CH.--CH(OCOCH3) ]gCH ?CH ZOCOCH 3 (8744). Chlorination of dimethyl oxalate in carbon tetrachloride with elemmtal chlorine a t 75' to 85' C. under the catalytic action of ultraviolet light yielded bistrichloromethyl oxalate. Distillation of a mixture of chlorobenzene and bistrichloroniethyl oxalate with catalytic amounts of pyridine (or activated carbon) with a slow increase in pot temperature formed oxalyl chloride. Phosgene was formed simultaneously (76A). Treatment of glyoxal with methanolic hydrogen chloride at 40" to 50' C. and subsequent introduction of dry hydrogen chloride a t 0' C. yielded dichloroglycol dimethyl ether, CH3O C H C I C H C I O C H ~ . Similarly, CHIOCHBrCHBrOCHS and C2H;OCHCICHC10C2H5 were prepared ( 5 A ) . Chlorination of ethylene carbonate under illumination in a chlorinated solvent a t 75' to 120' C. afforded tetrachloroethylene carbonate; ethylene bischlorocarbonate afforded tetrachloroethylene bischlorocarbonate. These esters are stable under neutral and acidic conditions (77A). Nitrogen Compounds. Phenyl phosphonic dichloride is a useful reagent for
VOL. 51, NO. 9, P A R T II
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1105
UNIT PROCESSES __-_---.________________________________--~--~~.~~~~ replacement of a hydroxyl group by chlorine in nitrogen heterocycles. The reaction is similar to phosphorus oxychloride. T h e best effect is shown when the oxygen function occupies a n a- or y-position with reference to the hetero atoms. The high boiling point of the reagent (258' C.) allows reaction in an open vessel. T h e hydrolysis products are water-soluble (73.4). Chlorination of terminal dinitriles iYC(CH,).CN a t atmospheric pressure with or without iodine as a catalyst or under pressure in sealed tubes with liquid chlorine opened a convenient route for the synthesis of CY,LY+Y',LY'tetrachlorodicarboxylic acids (9OA). The vapor phase reaction of chlorine and pyridine leading to 2-chloropyridine at 325" to 355" C. can be moderated by the presence of steam; the molar ratio of chlorine, pyridine, and steam can be widely varied. Yields u p to 77% (based on pyridine consumed) are claimed (79A). €-Caprolactam, because of its unique capability for polymerization, has become a basic raw material for artificial fibers. This has led to extensive researches into improvement of its synthesis. '4 photochemical process was developed reacting nitric oxide and chlorine in the presence of hydrogen chloride with cyclohexane under irradiation with ultraviolet light below 420 mp. Yields of 65 to 70y0 (based on chlorine used) have been realized. T h e reaction is generally applicable to all alkanes
oxime as the starting material in this reaction, the yield was 42y0 (23A, 25A, 36A). The reaction of nitrosyl chloride with olefins has been investigated. 3-Methylbutene added nitrosyl chloride in diethyl ether a t 3' to 11" C . to give a mixture of 4-chloro-2-methyl-2-butene, 3,4-dichloro-2-methylbutene, 3-chloro-4nitro-2-methylbutene, and small amounts of l-nitroso-l,2-dichloro-3-methylbutane (63A). In other cases an oxime is formed predominantly (68A). Cyanuric chloride could be formed in 97Yc yield by polymerizing cyanogen chloride in an azeotropic mixture of hydrogen chloride and dimethyl ether (86A). Fusing dimethylamine hydrochloride with dicyandiamide at 140" C., dissolving the cooled melt in water, and adding chlorine a t 10' afforded 2-chloro-1,ldimethylbiguanide hydrochloride with 34.9yC active chlorine. At 18" to 20" C. the 2,4-dichloro derivative with 58 to 60% active chlorine was obtained. Chlorobiguanides are stable when dry, losing only a small amount of active chlorine during long storage ( 3 2 A ) . Chlorination of S-methyl .Y,,V..'V'-trimethylisothiourea Ivith elemental chlorine and carbon tetrachloride a t 0" to IOo C . gave quantitatively C-chloro-.Y,S,h"-trimethylformamidine hydrochloride (45-4). Oxazol-2-ones could be chlorinated in good yields to 2-chloro-oxazols with phosphorus trichloride and triethylamine. T h e chlorine in the 2- position is extremely reactive with alkoxide, amines, and alkali salts of active methylene compounds (37-4). Miscellaneous. Dimethyl sulfide could be chlorinated stepvise. gixing the full range of possible products. -4 special apparatus assures optimal yields ( 3 A ) . Addition of sulfur monochloride, S2C12: to halo-olefins of the general type RCH-CC12 yielded disulfides (96-4). '4 new route for the preparation of alkanesulfonyl chlorides halogenates thiolacetates ivith elemental chlorine in water ( 4 A ):
(53A). e-Caprolactam is also a convenient starting material for lysine, both oxygen and nitrogen functions being preformed in the molecule. T h e basic synthetic problem is the monohalogenation in a-position to the carbonyl function. Reaction with phosphorus pentachloride and phosphorus oxychloride at 70" C. (35A) or reaction with phosphorus pentachloride in chloroform and simultaneous introduction of elemental chlorine at 20' to 45" C. (7A) afforded the a,adichloro derivative. -4lthough the yields could be improved to 90% by slight variations, a monochlorinated product could not be isolated even by decreasing the amount of halogenating agents (24'4, 9311). T o obrain the monochloro compounds, the dichloro derivative is dehalogenated catalytically at low pressures. &,a-Dichloro-6-caprolactam can be synthesized starting from cyclohexanone oxime by chlorination with phosphorus pentachloride at 85' C . with xylene as solvent ( Z M ) . Surprisingly, direct monobromination could be realized in 65 to 67Yc by bromination of ecaprolactam with phosphorus tribromide and elemental bromine in benzene as a solvent. Using cyclohexanone-
1 106
(CH )?C=CH-CH?CH1
(CHj)?CH-CH( CHzCH ,)SCOCH,
Chlorination of benzo-2.1,3-thiadiazole in the presence of iron shavings a t 60°C. gave the 4,7-dichloro- derivatives after treatment of the crude reaction product with 10% alcoholic potassium hydroxide, Chilling the crude reaction product in ethanol gave up to 227, of two isomers of tetrachlorotetrahydrobenzo-2,1,3-thiadiazole (66'4).
INDUSTRIAL AND ENGINEERING CHEMISTRY
I
._-a
CH3COSH light 4 6 %
-
Fluorination Paraffin Hydrocarbons. An apparatus has been described for fluorinacion of hydrocarbons at 100' to 400" C. in the presence of a n inert gaseous diluent, using silver: cobalt, manganese, or cerium fluoride as catalysts. Heptane could be fluorinated in good yields to fluoroheptanes with 1 to 3 hydrogen atoms per molecule. Benzene yielded perfluorocyclohexane in 78% yield (based on the liquid fraction) (25B). 1,l-Difluoroethane substantially free from vinyl fluoride \vas produced by passing ethylene into liquid hydrogen fluoride containing 0.1 to 5% stannic chloride (7723). Catalysts such as titanium(1V) chloride or antimony pentachloride were used with or without inert support (78B, 19B). Anomalous substitution was observed in the fluorination of sym-tetrachloroethylene in hydrogen fluoride in the presence of antimony pentafluoride and chlorine in an autoclave at 1 2 0 ° C . and 30-atm. pressure; 1:I ,l-trifluoro-2-chloroethane\\-as obtained (ZZB). A mixture of 5 parts of antimony(II1) chloride. 25 parts of pentachloroethane, 5 . 5 parts of hydrogen fluoride, and 0.3 part of chlorine afforded 92% of 1!l-difluoro-1,2.2-trichloroethane when heated to 110" to 140" C. T h e catalyst could be re-used (7B). .i mixture of antimony(II1) fluoride and antimony(V) chloride heated in 1:2,2-trifluoro-l,1,2-dichloroethane. cooled, and decanted was used as a fluorinating agent. Fluorination of a relomer of trichlorobromomethane and 1;I-dichloroethylene with this mixture at 66" C. afforded fluorohalohydrocarbons of the general formula CFCl?(C:H&CIF),,Br (n>l) (QB). Perchlorofluorocarbons could be enriched in fluorine by treatment with elemental fluorine or chlorine trifluoride under the catalytic influence of aluminum fluoride at 250°C. (ZJB). Alkenes. Trichlorobromomethane gave simple addition products with a number of haloolefins. The addition proceeded smoothly except Ivhen the halogen atoms were located both on a carbon atom having a double bond and on the carbon atom adjacent to it. The addition product of trichiorobromomethane to 2-rrifiuoromerh>-lpropene was used as an intermediate for the preparation of 2-trifluoromethyl-2-difluoro-l,3butadiene (2OB). T h e tendency towards formation of the cyclobutane ring has been noted in several instances of fluorocarbons with multiple C-C bonds. Bistrifluoromethylacetylene forms a white crystalline tetramer when heated under autogenous pressure. Perfluoropropene gave perfluorodimethylcyclobutane ( 3 B ) . Pyrolysis of phosphorus pentafluoride,
*
HALOGENATION carbon tetrafluoride, sulfur hexafluoride, and arsenic(II1) fluoride above 1700" C. and subsequent contact of the gaseous product with fluidized carbon below 500' C. yielded tetrafluoroethylene ( J B ) . R F S F j and (RF)?SFI (RF = perfluoroalkyl) tend to form perfluoroalkyl radicals at elevated temperatures (5B). R$F; also forms fluorine radicals. Schiemann reaction of 4-aminoacenaphthene vielded 4-fluoroacenaphthene. T h e 2-fluoro- and 3-fluoro- derivatives and corresponding naphthalic acids were prepared (26B). Hexafluorobenzene \vas obtained by pyolysis of tribromofluoromethane at pressures of 4.5 atm. of nitrogen in platinum tubes at 540" to 550' C. Optimal yields were better than j5Yc ( 7 7B). The side product consisted mainly of bromofluoro derivatives of ethane. propane: benzene, and toluene. Feasible routes for the synthesis of wfluorostyrene Ivere investigated. Dehydration of the alcohol CsHj-CHOHCH2F pro\-ed impossible because of the presence of a strong hydrogen bond. Eventually the synthesis could be achieved by a reaction sequence involving halogenation and subsequenr dehalogenation with zinc metal. The compound obtained was apparently the trans- isomer ( 2 B ) . T h e compound could be polymerized by ionic catalysts (SnCla). Peroxidic catalysts proved ineffective. Oxygen Compounds. A comparative study reveals the superiority of tosylate o w r methane or benzene sulfonate in the metathetical reaction of tosylate with potassium fluoride to give the corresponding alkyl fluoride. Yields range from 75 to 90yc ( 7B). A hydroxy group is replaced by fluorine by simultaneous treatment of the alkanol ivith phenylsulfonyl fluoride and anhydrous potassium fluoride (23B). Diethyl difluoromalonate, 5-ethyl-5-fluorobarbituric acid, ethyl 2,2-difluoroaceroacetate, 3,3-difluoro-2,4-pentanedione> and diethyl 2fluoro-2-phenylmalonate have been obtained in excellent yields by treatment of the corresponding parent compound lvith perchloryl fluoride (72B). Between 250' and 300" C. carbonyl fluoride reacted with trifluoromethyl hypofluorite to give perfluorodimethyl peroxide. The compound could also be obtained by direct combination of fluorine with carbon monoxide or carbonyl fluoride. The peroxide is stable, nonexplosive, and reacts only slowly ivith a n aqueous iodide solution (75B).Trifluoromethyl hypofluorite could be synthesized by treating a mixture of equal amounts of potassium cyanate and potassium fluoride with a 1 to 10 mixture of elemental fluorine and nitrogen at 45" to 50" C. (6B). T h e most important development in the field of fluorine chemistry is undoubtedly the discovery of a new specific
fluorinating agent, sulfur tetrafluoride, previously obtained only in trace amounts as a by-product in the fluorination of sulfur. Before evaluation of the potential of this new compound, feasible preparation of sulfur tetrafluoride had to be found. Two routes led to the desired product: Reaction of sulfur dichloride with sodium fluoride in acetonitrile: 3SC12 4 S a F 50--70"- SFI SsC12 4NaC1. Fluorination of sulfur with io2000 dine pentafluoride: IFb S -+ SFI
+
+
+
+
+The I?. latter reaction affords particularly
pure sulfur tetrafluoride. I n contrast to the extremely stable sulfur hexafluoride, sulfur tetrafluoride is readily hydrolyzed by water and attacks a series of organic compounds. \Vith nitriles, cyanates, and thiocyanates, compounds of the general formula R-NSF2 are formed. Compounds of the type RNSF2 are readily hydrolyzed by water to give a primary amine, hydrogen fluoride, and sulfur dioxide. Of particular importance is the reaction of sulfur tetrafluoride Xvith carbonyl compounds (13B, 7 6 3 ) . The oxygen is replaced in excellent yields by t\vo fluorine atoms; carboxyl and carbomethosy groups are generally perfluorinated to a trifluoromethyl group. Primary and secondary amides are attacked under cleavage of the carbon and nitrogen bond; in tertiary amides the oxygen of the carbonyl group is replaced by fluorine. Halogen substituents. heterocyclic nitrogen atoms, and multiple bonds are not affected in the reactions with sulfur tetrafluoride. Trifluoromethoxybenzene was synthesized b) fluorination of trichloromerhoxybenzene (28B). 6-Deoxy-6-fluoro-a-~-galactoseand 5deoxy-5-fluoro-a,+-D-ribosewere obtained by exchange reactions between methanesulfonyl esters and potassium fluoride in refluxing ethylene glycol (27B). Nitrogen Compounds. Electrochemical fluorination of methyl dimethylaminoacetate and dimethylaminodimethylacetamide (CH2)3NCH2CON(CHa)?yielded about 6'30 (CFa)iNCF&OF besides perfluorotrimethylamine, (CF3)g S C O F : and the oxazolidine (2QB): (CF3)2N-CF-O-CFz-K(CF3)-CF2.
A series of fluoronitriles \vas synthesized by metathetical reactions of the corresponding chloronitriles with potassium fluoride and sodium fluoride in a mixture of ethylene and trimethylene glycol a t 180' C.(8B). Treatment of sodium difluoroacetate with phosphorus tribromide and reaction of the resulting acid bromide with mercuric oxide yielded mercuric difluoroacetate. Subsequent reaction with io-
dine afforded a mixture of difluoroiodomethane and difluoromethyl difluoroacetate (27B). Chlorine-substituted triazines are readily converted to the fluorine analogs by treatment with antimony(II1) fluoride in the presence of anrimony(II1) chloride and elemental chlorine at 1CO0to 180°C. Cyanuric fluoride \vas prepared from cyanuric chloride. Perfluoro-s-trianines exhibit unusual thermal stability and are very resistant TO oxidative and reductive degradation (70B). Miscellaneous. Fluororhioethers wxre prepared by reaction of the corresponding chlorine compounds ivith anhydrous hydrogen fluoride in copper vessels a t room temperature. The resulting compounds are very sensitive toward moisture and attack glass. The corrosivr s!,m-difluorodimethyl thioether decomposes at room temperature (7JB). Bromination
Unsaturated Hydrocarbons. Hydrogen bromide reactcd uirh vinylidine chloride under irradiation \vith uliraviolet light io Sivr 1.1-dichloro-2-bromoethane and ?l,6yc of 1,1.3.3-tetrachloro4-bromobutane. The reaction proceeded faster though \vith reduced >-ieldsin quariz than in borosilicate glass (7C). Bromine chloride reacted with propene in aqueous hydrochloric acid to give 2-chloro-3-bromopropane and 2bromo-3-chloropropane in a ratio of 54 to 46. The t\vo possible bromohydrins \vex also produced; the ratio of primary to secondary alcohol was 21 to 79. Although the total amount of bromohydrins decreases from 70 to 60 and 51yc as the hydrochloric acid concentration is increased from 1.0 to 2.0 and 3.0.21, those ratios remain constant. S o indication of dichloride or chlorohydrin formation was found (ZC). Cnder illumination methylacetylene and hydrogen bromide reacted rapidly in liquid phase, yielding stereospecifically cir-1-bromo-1-propene. Reaction in the gas phase was markedly accelerated by light and oxygen. The stereochemistry of this addition, however. is obscured by the rapid equilibration of the product. The equilibrium ratio in the gas phase between cis- and transisomer was 4.14 (ZJC). Bromination of the unsaturated alcohol (CH,) &(OH)C_C--CH=CH2 and its diethyl analogs lvith elemental bromine in chloroform resulted in predominant addition to the vinylic double bond (78C). Stereospecific radical addition of hydrogen bromide to 1-substituted cyclohexene could be established unambiguously (8C). I n the reaction of l-halocyclohexene with hydrogen bromide less than 0.5y0of the trans-adduct could be detected in the reaction product. Ap-
VOL. 51, NO. 9, PART II
e
SEPTEMBER 1959
1107
UNIT PROCESSES
~~.-~~.....
parently the addition occurs in 2 steps:
identification of these aromatic hydrocarbons. Derivatives of 24 different \ ,' ' /' methylnaphthalenes have been prepared 1. Br . C=C+Br-C--C. addition and their melting points determined / \ / ' \ ( 2 a ' ) . Naphthalic acid was brominated with elemental bromineat 180" to 200'C. \. i i I 2. Br-C-C. HBr -+ Br-C-C-H in 65% oleum to give hexabromonaph/ \ I 1 thalic acid, which forms deeply colored complexes with pyrene: ethylpyrene! + Br . transfer and perylene (7C). Until recently a radical mechanism Ionic addition of hydrogen bromide to was generally accepted for the reaction 1-chlorocyclohexene and l-bromocyclohexene in excess liquid hydrogen bromide of .V-bromosuccinimide with aromatic in the presence of small amounts of ferric compounds such as toluene. fluorine, and acenaphthene. Extensive nuclear subchloride gave 1,l-bromochloro- or 1,ldibromocyclohexane. If more ferric stitution can be achieved with 'V-bromosuccinimide at the expense of brominachloride is present, the initially formed tion of the carbon atom adjacent to the gem-dihalide can beconverted to trans-1,4aromatic ring when a highly polar soldibromocyclohexane by halogen exvent such as propylene carbonate is change and rearrangement. By using varying amounts of ferric chloride the folused (27C). Ionic mechanism can apparently also be forced upon the reaction lowing reaction sequence was established when boron trifluoride is added to for this reaction (QC): l-chlorocyclohexthe reaction mixture. Fluorene yielded ene 1-bromo-1-chlorocyclohexane -+ largely a nuclear-substituted product 1,l-dibromocyclohexane cis-1,2-diwith ,I'-bromosuccinimide: with only bromocyclohexane 1,3-dibromocyclohexane -+ tra~~s-l,4-dibromocyclohexar~e, small amounts of the 9-bromo derivative. A well-established correlation between The bromination of thujone with elethe strength of an aromatic acid and the mental bromine gives thujone dibromide, bromination product of its allylic ester for which Wallach originally proposed was discovered. Larger proportions of structure I. Based on chemical and abnormal-Le., 1.3-brotnine-adducts, spectroscopic data structure I1 is postuwere obtained from the allyl esters of lated instead (5C): comparatively weak aromatic acids rather than from those of stronger acids. This is consistent with the mechanism involving a cyclic intermediate cation where combination with bromide ion could give the vicinal or nonvicinal dibromide. I n chloroform allyl p-anisate gave 2 parts of 1,3-dibromo-2-propyl I 11 anisate and 3 parts of 2,3-dibromopropyl anisate. Allyl p-chlorobenzoate yielded Cycloalkanes. Bromination of the 1 part of the 1,3-dibromo and 6 parts of chloride of trans-2-meth) Icyclohexane-lthe 2,3-dibromopropyl ester. In the pcarboxylic acid and subsequent esterifinitro- and 2,4-dinitrobenzoate only the cation give predominantly an isomer of vicinal dibromides could be detected the a-bromo ester in which the methyl ( 76C). and carboxyl group are cis to each other. Bromoazomethines formed in the reT h e 2-phenyl analog leads to the isomer action of aminodibenzofuran with benin which phenyl and carboxyl groups zylbromide in dimethylsulfoxide. Apoccupy trans positions (75C). parently a N-aralkyl derivative is formed Aromatic Compounds. I n comprefirst. Subsequent bromination on the hensive investigations on the partial rate aliphatic carbon atom attached to the factors of aromatic substitutions the nitrogen and spontaneous loss of hydrorelative bromination rates of fluorogen bromide gives rise to the azomethine. bromomesitylenes, cyanomesitylene, and I n some instances the intermediate could cyanodurene have been measured in nibe isolated (6C). tromethanes (72C). Bromination rates Oxygen Compounds. An improved for hydroxymesitylene and the methoxy laboratory method for gas phase reaction and methylthio derivatives of mesitylene of ethylene oxide and hydrogen bromide and durene have been measured in aceto form bromohydrin in 87 to 92y0 yield tic acid. The methoxy and methylthio has been described (77C). Diacetyl regroups were strongly activating in the acted with elemental bromine at 20' to durene series and moderately deactivat30' C. to give monobromodiacetyl. The ing in the mesitylene series (73C). monoxime proved useful as a herbicide, Side-chain bromination of di- and bactericide, and fungicide (4C). N-Brotrimethylnaphthalenes with N-bromomosuccinimide reacted with dihydropysuccinimide under the catalytic influence ran to give 3-bromo-5,6-dihydro-4Hof benzoyl peroxide was proposed for pyran, 2,3-dibromotetrahydropyran, and
+
' X ~
+
-
1 108
- -
INDUSTRIAL AND ENGINEERING CHEMISTRY
both geometrical isomers of 2-succinaiiiid yl-3-bromotetrahydropyran. The character of the reaction product indicatcd a puldr mechanism. The polarizing effect of the oxygen cy to the double bond is considered responsible for increasing the nucleophilic character and favoring a polar mechanism (23C). Nitrogen Compounds. Rearrmgcment of ~~--bromosuccinirnidein tlic presence of allyl chloride and benzoyl peroxide in chloroform as a solvent {vas observed. The structure of the prcduct could be established as P-bromopropionyl isocyanate. S o rearrangement takes place in carbon tetrachloride, ethylene chloride, trichloroethylene, benzene, toluene, petroleum ether, nitromethane, dimethylsulfoxide, and excess allyl chloride. The effect of the olefin structure in this reaction is not clear. The reaction works also when allyl chloride is replaced by allyl bromide, methallyl chloride, 2,3-dibromopropene, 2-tcrt-butyl-3brornopropene. The rearrangement is formally similar to the Hofmann degradation Lvherc an h'-haloamine rearranges to isocyanate. However, a radical mechanism seems to be operative in the case of it7-bromosuccinimide rearrangement (74C). Heterocyclic compounds could be obtained in the reaction of dinitriles with hydrogen halides in benzene. Glutaronitrile in hydrogen bromide gave 2imino-6-bromopiperidine hydrobromide. Phenylsuccinonitrile yielded 2-imino-3( or 4-)phenyl-5-bromopyrroline hydrobromide. Fumaro nitrile afforded 2imino-3 (or 4-)> 5-dibromopyrroline. Glutaronitrile and hydriodic acid gave 2-imino-6-iodopiperidine hydriodide
(77C). Bromination of quinoline in concentrated sulfuric acid with catalytic amounts of silver sulfate at room temperature gave a mixture of 5-bromo-&bromo- and 5:8dibromoquinoline in 80% yield ( 3 C ) . 2:6-Dibromopyridine could be further brominated orer an iron(I1) bromidepumice catalyst at 480" C. and a contact time of 0.5 minute to a mixture containing 40 to 45% 2,3,6-tribromo- and 10 to 15% 2,3,5,6-tetrabromopyridine. Without a specific catalyst the 2,4,6-tribromopyridine was formed in a slow reaction. These brominations were not influenced by daylight or ultraviolet irradiation (IOC). Miscellaneous. Triphenvlphosphine reacted with bromoform a t its boiling point, at room temperature and ultraviolet irradiation, or at 80" in benzene under the catalytic influence of benzoyl peroxide, to form a phosphonium salt ( 7QC). Positive univalent halogen complexes of the general formula X(pyridine)tY (X = Br,I) (Y = F,SbF,,SOaF) could be prepared by action of bromine or iodine on silver fluoride or silver fluorosulfate
HALOGENATION
__..
dissolved in acetonitrile in the presence of pyridine (22C).
Iodination Halide exchange of chloro- and bromoalkenes icith iodide ion proceeds \\-irh measurable speed at 148'to 200' C. ( 7 0 ) . Elemental iodine catalyzes the addition of hydrogen iodide to cyclohexene in benzene as a solvent. In acetic acid. however. it decreases the reaction rate: tliongh lithium iodide shoivs a distinct catalytic effect in this solvent. The addition of hydrogen iodide to allyl chloride is s l o ~ cand is inhibited completely in acetic acid. Addition of hydrogen iodide to 1.2-dimerhylc)-clohexeneis very rapid. T h e dimethyl esrer of acetylene dicarhoxylic acid displays a decreased addirion rate of hydrogen iodide on addition of elemental iodine. T h e reaction is hastened \\-hen protopliiiic solvents arc added to the benzene used as solvent. These phenomena are accounted for by different mechanisms ( 9 0 ) . l-inylidene fluoridt. reactS therInally tcith iodine ar 183" C. and 3200 p.s.i. initial pressure to give mainly 1,l .l-trifluoro-2-iodoethanr and 1-flLioro-1-iodoethylene (5D). series of unsaturated compounds was treated \vith h>-drochloricacid solutions of iodine trichloride to give iodochloro compounds and the corresponding iodohydrins. Iodine chloride gave the same product ( 4 0 ) . An improved preparation of 2,4-dinitroiodobenzerie is based 011 a halide eschange i n 2,4-dinitrochlorobenzeneivith sodium iodide in dimeth>-lforrnamide (3D)3. .\ novel rearrangement \vas observrd with o-iodobenzo>-lperoside either in chloroform at room temperature or \chile standing as a solid for 6 iveeks. T h e product was accounted for by a "caged" radical mechanism accordins to the cqua'ion (GDj: A \
T h e iodoform reaction \vas reinvestigated to shed new light on the involved meclianism. I n the case of methyl ethyl ketone and acetone, the reaction \cent to completion in the presence of 0.002 equivalent excess alkali. I n the case of acetaldehyde a maskiiig effect was observed that may be due to aldol condensation at the higher pH level (700). I n very dilute solutions at 5 " C. 98c& of the acetaldehyde \vas converted to iodoform. T h e amounr of iodoform formed passed through a niaximum~cithincreasing alkali concentrations. -4large excess of iodine gave lower conversions. The formation of iodoform is suppiessed b) using 10c6 less alkali than reauired. Tivo alternative reactions are possible in principle. T h e reaction of iodine with acetaldehyde probably via a hypoiodite anion to produce iodoform, and the oxidation of acetaldehyde to acetic acid by unionized hypoiodous acid ( 2 0 ) . A stable solid complex between pentamethyleneterrazol and iodine chloride \cas prepared (8D). A nexc synthesis for 2,2'-dithionyliodonium salts was developed. T h e reaction of thiophene with iodine(1IIj trifluoroacetate afforded a 6?y0yield of product, while treating thiophene with iodate in acetic acid-acetic anhydride -sulfuric acid misrures gave only a 28yG yield ( I D ) ,
Literature Cited Chlorination tlhi hnagnostopoulos, C . E.! Hsu: E.-P. T. (to Monsanto Chemical CO.'~,U. S. Patent 2,836,502 (May 27! 1958). t2.4) Baciocchi. E., Illuminati, G., Chem. 3 b i d . (London) 1958, p. 917. ( 3 A ) Boberg, F.: LVinter, G.. hloos, J., A n n . 616, 1 (1958). (4.4)Bordwell. F. A.? Hewett, M'. A,, J . Org. Chrm. 22, 980 (1957). (5.41Borel-Maletra (to Societe industrielle
de produits chimiques), Brit. Patent 785,998 (Xov. 6, 195':. :&Ai Brown, H. C., Stock, L. M . , J . .Am, Chem. SCG.79, 5175 i1957). (7.4) Carpino, L. H. (to Research Corp.), U. S. Patent 2,845,429 (July 21. 1958). ( 8 A ) Cherniavsky, A. J. (to Shell Development Co. l , Ibid., 2,807,656 (Sept.
-7 6,, 1 9 i - i,. - I _
(9'4) Cleaver, Ch. S. (to F,. I. du Pont de Nemours Bi Co.j, Ibid., 2,833,822
(May 6, 1958'1. (IOA) Collis, hi. .J., Goddard, D. R., -anova, K. N.. L 112,346 (.July 2, 1958). 10.4) Erickson, F. B., Prill, I:. .I.. J . Or!. Ci7em. 23, 141 (1958).
'20.4) Farbwcrke Hoechst .A. G.: Brit. Patent 785,209 (Oct. 23, 1957i. , 2 l . V Ibzd.,789,314 (Jan. 22, 1958). 22.A Fox, J. E. (to hfonsanto Chcmical co.,.U. S. Patrnt 2,846,484 l.\ug. 5 , 1 O i 8 1. .,I_
23.4) Francis: W. C., Hopkins, Th. I
