Patent GB-468016-A (GB)
Title: A process of halogenating unsaturated organic compounds by substitution
IPC: C07C21/04
Filed: 1936-08-12
Abstract: Unsaturated organic compounds, containing an olefinic linkage between two non-tertiary carbon atoms of aliphatic character, at least one of which is secondary, are halogenated by substitution by effecting the halogenation with free halogen or agents yielding free halogen at a temperature above that at which halogen addition is favoured, which temperature exceeds 100 DEG  C. but is below that at which substantial degradation is favoured, e.g. at 200--500 DEG  C. The process is preferably effected by heating the unsaturated organic compound to the desired reaction temperature and then introducing the halogen, if necessary at high velocity to avoid flame, advantageously at a number of separated points along the reaction tube.  The process is applicable to the treatment of olefines from any source, e.g. those obtainable by the pyrolysis or cracking of mineral oils such as petroleum, petroleum products, coal tar, pitches, coal, peat, or shale oil, by the dehydration of alcohols or by the destructive hydrogenation of higher hydrocarbons.  The olefines may be employed individually, as admixtures of pure olefines, or in admixture with paraffin hydrocarbons whether or not containing the same number of carbon atoms per molecule, e.g. as a propanepropylene, butane-butylene, pentane-pentylene or hexane-hexylene cut.  Inert diluents, e.g. nitrogen, may be added in order to absorb heat, and oxygen may be used to inhibit the substitution halogenation of saturated organic compounds.  The products are preferably removed and separated as quickly as possible, e.g. by absorbing the hydrochloric acid formed in a solvent, e.g. water, or by fractionating the materials with or without previous neutralization.  The reaction may be effected photo-chemically and/or in the presence of halogenation catalysts, e.g. granular carbon, antimony chloride, or stannic chloride.  The products are allyl type halides, which may be used for the production of the corresponding alcohols, ethers, aldehydes and acids, or for the production of cellulose ethers by reaction with alkalized cellulose.  In examples: (1) chlorine and liquid b -butylene are introduced downward into a vertical glass tube the lower end of which is widened into a bulb containing a water spray; the heat of reaction raises the temperature to various degrees according to the proportions of the reactants, and there are obtained various proportions of unsaturated monochloride, saturated di- and trichlorides and saturated chlorhydrin; (2) a longer tube and higher temperatures are employed; (3) the chlorine and b -butylene are preheated; a mixture of a - and b -butylenes may be similarly treated; (4) propylene is treated with chlorine at 390 DEG  C., yielding allyl chloride; (5) 2-chlorbutene-2 is treated with chlorine at 350 DEG  C., producing a mixture of unsaturated dichlorides, probably 1 : 2- and 2 : 4-dichlorbutene-2; the product may be converted to chloroprene; (6) cyclohexene is treated with chlorine at 420 DEG  C. Other starting materials specified are b -chloropropylene, 1-chlorobutene-2, 1 : 1-dibromobutene-2, pentene-2, pentene-1, 3-methylbutene-1, 3 : 3-dimethylbutene-1, 7-methyloctene-2, hexadiene-1 : 5, 3-phenylpropene-1 and 4-phenylbutene-2.  Samples have been furnished under Sect. 2(5) of (A) allyl bromide, obtained by reacting propylene and bromine at 525 DEG  C.; (B) 1 : 2-dichlorbutene-2, obtained together with 2-chlorbutadiene-1 : 3 by reacting 2-chlorbutene-2 and chlorine at 500 DEG  C.