Patented on. 20, 1.942 I . 2,299,411

' UNITED "STATES PATENT OFFICE

CATALYZED HYDROBROMINATION OF UN SATURATED ORGANIC COMPOUNDS Fredericlr Rust and William E. Vaughan, ' Berkeley, Calif., assignors. to Shell Develop ment Company, San Francisco, Calif., a corpo ration of Delaware No Drawing. 4 Application August 25, 1941, Serial No. 408,212 -

9'Claims. (01. 260-663) ' This invention relates to an improved process for the hydrobromination of unsaturated organic hydes and metal alkyls which tend to initiate I compounds, and more particularly to improve the reaction chains. v ments in the method of controlling the addition It is known that the presence of peroxide: orv of hydrogen bromide to unsymmetrical organic of peroxide-forming compounds in unsaturated compounds containing at least one ole?nic or organic compounds, e. g. unsaturated hydrocar acetylenic linkage to produce addition products bons, is undesirable. For example, organic per of a predetermined character. oxides, when present even in relatively small con It is known that hydrogen halides may be centrations, tend to catalyze the polymerization of a large number of unsaturated hydrocarbons, . added to unsaturated hydrocarbons and to var 10 ious unsaturated derivatives thereof. In fact, and particularly diole?ns. As to the “abnormal” in 1870 Markowniko? stated that “if an addition ofhydrogen bromide to unsaturates by metrical hydrocarbon combines with a halogen effecting the reaction under the deliberate in acid, the halogen adds to the carbon atom with ?uence, of light, and particularly of ultra-violet fewer hydrogen atoms, i. e. to the carbon atom radiations having wave-lengths of below about which is more'under the in?uence of other car' 2900 to 3000 Angstrom units, such processes ne bon atoms.” The same investigator further de cessitate the use of special equipment, such as termined that when a hydrogen halide is added reaction vessels provided with or containing to a halogenated unsaturated compound such as lamps made of quartz Or other suitable mate rials, e. g. calcium ?uoride, capable ‘of trans vinyl chloride or a chlorinated propylene (i. e. 20 to unsaturated hydrocarbons wherein one of the mitting rays of the de?ned wave-length, or re unsaturated carbon atoms carries a halogen atom, action- vessels consisting of such materials or or wherein these unsaturated carbon atoms con containing openings or windows made of such tain dissimilar numbers of halogen atoms di material. - rectly attached thereto), the halogen atom of It has now been discovered that'unsaturated the hydrogen halide will add to the double bonded organic compounds of the class more fully de (unsaturated) carbon atom which carries the scribed hereinbelow may be reacted with hydro greater number of halogen atoms, while the hy gen bromide to effect directional addition thereof drogen atom of the hydrogen halide molecule via the so-called “abnormal” addition, 1. e. con trary to the course stated or suggested by attaches to the adjacent unsaturated carbon 30 atom. The above type of hydrohalogenation is Markowniko?, this reaction being eifected in the termed "normal” to distinguish it from the “ab absence of the undesirable peroxides or peroxide normal” addition of a hydrogen halide, in which forming compounds, and without the necessity the hydrogen and halogen atoms are added in ' of employing any special equipment or appara positions which are interchanged with respect tus which was heretofore necessary when the to addition according to the‘ above-outlined reactions were effected under conditions requiring Markownikoff rule. ‘ irradiation of the reactants. According to the Various methods have been proposed for con present process, such “abnormal” addition of the trolling the described hydrohalogenation reac hydrogen bromide to the unsaturated organic compounds is attained by effecting the reaction tion so as to form reaction products in which 40 the hydrogen halide has been added contrary in the presence of ketones containing a bromine atom on the carbon atom in alpha position with to the above Markowniko? rule. For instance, it ‘respect to the carbonyl group. has been proposed vto effect the hydrohalogena~ These bromoke tion reaction in the presence of various perox tones apparently act as sensitizers to initiate the reaction mechanism, and also as compounds ides, such as hydrogen peroxide, acetyl peroxide, 45 'which affect the direction of ascaridole, and the like, as well as of compounds _ addition of the of the type of oxygen, air or ozone, all of which bromine atoms to the unsaturates treated. For tend to form peroxides when contacted with example, as shown in the examples, when hydro unsaturated hydrocarbons. Also, it has been gen bromide is mixed with propylene, and when found that hydrogen bromide may be added to the addition reaction is not controlled by any the unsaturated, organic compounds in a manner means, such as the addition of peroxides or the‘ use of ultra-violet radiations, the reaction prod contrary to Markowniko?’s rule by e?'ecting the uct predominates in, or even reaction under the deliberate in?uence of ultra consists solely of isopropyl bromide. On the other hand, the ad violet. radiations in the presence or absence of dition of even small sensitizers of the ‘class ofacertain 'ketones, alde- 55 quantities of a bromoketone, e. g. bromo-acetone; e?ects a directional control 2 2,299,411‘ unsaturates may contain one or'more halos of the addition reaction, the prodllct consisting‘ atoms attached to saturated and/or unsaturated of substantially pure n-propyl bromide. The carbon atoms. Representative examples of these bromoketones promote the "abnormal” addition . . compounds are: vinyl halides, allyl halides, crotyl of the hydrogen bromide eyen when the reaction halides, methallyl halides, and the like_._ Other thereof with the unsaturated organic compounds examples of substituted unsaturated hydrocar is e?ected in the dark and at normal tempera“, bons are methyl. acrylate, methyl methacrylate, tures, i. e.v in the neighborhood of about 25° C. divinyl ether, diallyl‘ ether, dimethallyl ether, and ‘ to about 15° C., or even at considerably lower The advantages of the present the like. ‘ ' - - temperatures. 10' A particularly suitable group of organic .com process over the previously known processes of ‘pounds which may be reacted with hydrogen “abnormal.” addition of hydrogen bromide_ will‘ bromide via abnormal addition comprises the be readily apparent to those skilled in the art, compounds, and particularly the hydrocarbons, in it being noted that the process does not require which the unsaturated linkage is in the terminal any special equipment, or the use of elevated or alpha posit'on. Also, aliphatic hydrocarbons temperatures, a d does not result in the presence and their various substituted derivatives, e. g. of undesirable peroxides in the reactants and/or halo-substituted derivatives, containing unsatu reaction products. ' - rated linkages both in alpha and omega positions The compounds which, according to the proc-‘ (1. e. terminal positions) may be readily hydro‘ es of the invention, promote'the abnormal hy brominated via abnormal addition to produce drobromination of‘ the unsaturates even when compounds in which both terminal carbon atoms the reaction is e?ected in the dark and at nor have bromine atoms attached thereto. Another 'mal temperatures of about 20° C. or even at group of organic compounds which may be em lower temperatures, are bromoketones contain- 1 - played as the primary material comprises or in- ‘ me a bromine atom directly linked to the carbon . cludes organic compounds wherein an ole?nic atom in alpha position with respect to thecar 25 linkage is in non-terminal position between two 7 bonyl group. The bromoketones may contain carbon atoms having a dissimilar number of hy alkyl, aryl or aralkyl radicals attached to the ' drogen atoms attached to'each of said unsatu; carbonyl group. The following is a list of rep rated carbon atoms due, for example, to various resentative hydrobromination-promoting bromo substituents attached thereto. For instance, the ketones: broino-acetone, alpha-bromo-acetophe 30 double bond may be between two carbon atoms Y none, alpha-bromo-cyclohexanone, alpha-alpha’ which are of secondary and tertiary character, dibromo-acetone, alpha-alpha-dibromo-acetone, respectively. Another example is a compound in 3-bromo-butanone-2, 1-bromo-butanone-2, 1 which the unsaturated carbon atoms are both phenyl-l-bromo-acetone, alpha-bromo-aceto primary or both- secondary, but have unequal , acetic acid and the like, and their homologues. 35 numbers of halogen atoms, such as chlorine, Although there is no intention of. being lim bromine, ?uorine and/or iodine atoms, attached ited by any theory of the case, it is believed at to them. the present time that the abnormal hydrobromi The abnormal addition of the hydrogen bromide nation reaction occurs with the following or some to the above-de?ned class of unsaturated organic similar reaction chain mechanism which is ini compounds in the presence of the speci?ed group . tiated by the reaction of the bromo-ketones with ‘ of bromoketones may be effected in the vapor or '. the hydrogen bromide: liquid ‘phase, or- in a two-phase liquid-vapor , ' system. Generally, no heating of the reactants is 45 necessary. In fact, in many instances the re-; action, although it'may be realized in the vapor phase and at temperatures of above 25° C., is preferably eii'ected in the liquid phase and at temperatures which are evenvbelow 0° C. Thev '50 reaction temperature, however, should not be be low that at which thelunsaturated hydrocarbon‘ treated or the speci?c bromo-ketone employed The becomes congealed. ‘It was also found that the wherein R denotes any organic radical. abnormal addition according to the present proc quantity of the bromoketone or mixture of bromo 55 ess, when-the reaction'is e?ected in the presence ketones to be added to the reactants may vary of the bromoketones, proceeds regardless of the within relatively‘ wide limits, it being understood presence or absence of a liquid phase or film in that the amount should be su?icient to initiate ' the reaction zone. and maintain the reaction chain mechanism. ' The reaction may be effected in a batch, inter The unsaturated organic compounds ‘which mittent or continuous manner. When the proc process of this 80 ' may be treated according to the - ess is executed batch-wise, the reactants, together invention include hydrocarbons containing one with a suitable amount of the bromoketone, may or more ole?nic and/or acetylenic linkages. Ex be conveyed under any desirable‘ or optimum amples of such. hydrocarbons are ethylene,'_ pressure and temperature into a suitable con butene-l, butene-2, isobutylene, pen-. ’ propylene, 65 tainer, and then allowed to stand tor a period of tone-1, pentene-2, hexene-i, 4-methyl-pentene-1, - time suillcient to permit the desirable or optimum 4,4-dimethyl-pentene-1, d-methyl-pentene-z, oc degree of conversion. Although the reactants tene-i, decene-l, cetene-l, styrene, cyclohexene, may be kept in the-dark, it is frequently possible to' 3 - methyl - cyclohexene, 1,4ddiphen‘yl - butene-2, ' 1,3, pentadiene '- 1,4, subject the. reactants'to the simultaneous action butadiene - 1,3, pentadiene - of light and of- the bromoketones, such a pro , hexadiene-pl',5,vhexadiene-l,4, acetylena'propyne, 70 butyne-l, pentyne-2, heme-1,, cetyne-l, cotyl cedure increasing the rate of conversion to the acetylene. phenyl-acetylene. ‘and the like. The desired products. ‘ l above compounds, and theirvarious homologues, _ The following examples, which are to be con the nucleus and/or in the strued as illustrative only, represent a speci?c . may be substituted in embodiment of the invention. It is to be under-k substituents in various degrees.‘ For instance, the 2,299,411 3 stood, howeverrthat thereis no intention oi being 0! hydrogen bromide to propylene, the step oi‘ by any details set iorth. adding to the reaction mass a bromoketone hav _ Emma‘ I ' ing a bromine atom on the carbon atom in alpha‘ Propylene and hydrogen bromide were intro positionwith respect to the carbonyl group. duced together with bromoacetone into a pm: 3. In a process ior eiiecting abnormal addition glass reactor in a liquid state and at a tempera oi hydrogen bromide to butene-l, the steps oi ture oi about -'78° 0., the volumetric ratio oi the adding bromo-acetone to the reaction mass, and three ‘compounds in the reactor being 17:9.5:1. eiiecting the reaction in the dark and at a tem-v The reaction vessel was then sealed and allowed perature not in excess or about 25‘? C. . to stand ior a period oi about ten minutes while 10 4. In a process for e?ecting abnormal addition completely ‘shielded even irom di?'used light. of hydrogen bromide to butene-l, the step of add 4 During this period oi time the temperature within ing to the reaction mass at bromoketone having a thereactor gradually rose to about 20° C. The bromine atom on the carbon atom in alpha posi reactor was then cooled by the use oi solid carbon tion with respect to the carbonyl group. dioxide, the product removed from the vessel. 15 5. In a process oi’ effecting an abnormal hydro washed with caustic soda solution and water, ‘bromination' by the additionoi hydrogen bromide dried, and distilled, An analysis oi the product to an aliphatic hydrocarbon containing an alpha ' ' obtained showed a substantially quantitative con ole?nic linkage, the steps oi adding to the reac version to n-propyl bromide (i. e. product of tion mass a bromoketone havinga bromine atom abnormal addition). This reaction product had on.the..carbon atom in alpha position with re an index oi refraction 19% equal to 1.4340, while spect to the carbonyl group, and eiiecting the that of pure n-propyl bromide is 1.4341. reaction in the dark and at a temperature not in excess oi about 25° C. trample II ' _ 6. In a process of e?ecting an abnormal hydro Approximately 4.4 cc. of butene-l, about 3.2 25 brominatiomthe step oi reacting hydrogen bro cc. of hydrogen bromide and 0.1 cc. oi bromo mide with an aliphatic hydrocarbon containing acetone were mixed together and kept in the dark“ an alpha ole?nic linkage in the presence of a ior a period oi ilve minutes. The reaction prod bromoketone having a bromine atom on the car uct was then worked up as in the previous ex bon atom in alpha position with respect to the ample. The yield was again substantially quanti 30 carbonyl group. _ ’ tative, the reaction product being substantially 7. In a process of effecting abnormal hydro pure n-butyl bromide having an index oi refrac bromination, the step oi reacting a hydrogen _ tion n=°D—l.44-(the theoretical being nan bromide with an organic compound unsaturated 1.4398) . . in alpha position in the presence oi a bromo Example 11! 35. ketone havinga bromine atom on a carbon atom Propylene and hydrogen bromide were reacted in alpha position with respect to the carbonyl under substantially the same conditions as those employed in ExampleI, with the exception that 8. The process according to claim 7, wherein the reaction is effected in the dark and at a the reaction time was lengthened to two hours 40 and that acetone was employed in lieu of the temperature not in excess oi about 25° C. ' bromo-acetone. As in the previous experiments, . “ 9. In a process of eiiecting abnormal addition the reaction was eiiected in the substantial ab of hydrogen bromide, the step oi reacting hydro gen bromide with a compound selected irom the sence oi light. The reaction product consisted group consisting oi unsaturated hydrocarbons solely of isopropyl bromide, i. e. product oi the 48 normal addition of the hydrogen bromide.‘ This containing at least ‘one ole?niclinkage in asym showed that ketones, when used alone, do not metrical position in the molecule, their halo-sub promote the abnormal addition which is realized stitution derivatives, .and symmetrical unsatu by the use oi the bromok'etones. rated aliphatic and alicyclic hydrocarbons con taining a halogen atom attached directly to only We claim as our invention: 60 1. In a process iore?ecting abnormal addition one oi the unsaturated carbon atoms in the pres oi hydrogen bromide to propylene, the steps of ence oi a bromoketone having a bromine atom on ' a carbon atom in alpha position with respect to adding bromo-acetone to the reaction mass, and the carbonyl group. eiiecting the reaction in the dark and at a tem perature not in excess 01' about 25' C. 55 FREDERICK RUST. 2. In a process for effecting abnormal addition WILLIAM E. VAUGHAN.