US2134712A - Production of alkyl phenol sulphonates - Google Patents

Description

. Patented Nov. 1, 1938 UNITED STATES PRODUCTION OF ALKYL PHENOL SULPHONATES No Drawing. Application September 25, 1935, Serial No. 42,159

Claims.

This invention relates to the production of chemical compounds suitable for use as detergents,foamingagents,wettingagents and the like. It relates more particularly to a method of mak- 5 ing products which are nuclear alkyl derivatives of phenol sulphonic acids in which the alkyl group contains at least 12 carbon atoms, more particularly 12 to 23 carbon atoms and especially 14 to 19 carbon atoms.

According to the present invention an olefine hydrocarbon containing at least 12 carbon atoms (preferably 12 to 23, and especially 14 to 19, carbon atoms) is condensed with phenol or a cresol,

preferably with the aid of a metal halide condensing agent,, to produce the corresponding nuclear alkyl phenol, and the resulting alkyl phenol is sulphonated.

The alkyl phenol sulphonic. acid com unds, obtained in accordance with the present invention, are derivatives of phenol (hydroxyben- Zene) and of the cresols (1.2-, 1-3- and 1.4- methyl-hydroxybenzene) corresponding with the general formula in which A represents hydrogen or a methyl group, R represents an alkyl hydrocarbon radical linked to the nucleus of the phenol by a nonterminal carbon atom of the alkyl hydrocarbon radical and containing 12 or more (preferably 12 to 23, and especially 14 to 19) carbon atoms, and

M represents hydrogen or a metal, particularly an alkali metal, or an ammonium or organic ammonium radical. For convenience they will be hereinafter referred to as alkyl phenol sulphonates, which term generically includes the phenol and cresol derivatives in the form of the free acids or their salts. 4

The invention is particularly concerned with the production of alkyl phenol sulphonates from olefine hydrocarbons containing at least 12 carbon atoms, and preferably containing at least 7 of said carbon atoms in a straight chain, and

prepared, for example, by the decarboxylation of higher fatty acids or esters, the dehydration of an alcohol containing at least 12 carbon atoms, the removm of hydrogen halide from an alkyl halide containing at least 12 carbon atoms, or in any other manner.

Olefine hydrocarbons containing at least 12 carbon atoms in a straight chain and having a double bond, even when the double bond is between the ultimate and penultimate carbon atoms, condense, in accordance with the present invention, with phenol and its monomethyl derivatives to produce alkyl phenols and cresols in which the alkyl radical is not linked to the phenol nucleus by an end carbon atom but by an intermediate carbon atom. It has been found when the said alkyl phenols are sulphonated and the resulting alkyl phenol sulphonates are employed in the art, particularly in the form of their soluble salts, and especially their alkali metal salts, very advantageous detergent, wetting and foaming action is obtained. Without limiting the invention to any theoretical considerations, it appears the branched carbon chain alkyl radical which results from the process of the present invention, contributes to the valuable properties of the products. The invention is accordingly of particular advantage in that it permits the production of branched chain nuclear alkyl derivatives of phenol and cresol sulphonic acids from readily available, straight-chain olefine hydrocarbons which, in turn, can be obtained from natural products, such as higher fatty acids and their esters (as for example by decarboxylation, pyrolysis, etc.) The invention is also of value in permitting the obtainment of branched-chain, nuclear alkyl derivatives of phenol and cresol sulphonicacids from readily available hydrocarbon material containing straightor branchedchains, such as petroleum distillates, as for example, by halogenation followed by dehalogenation.

The invention will be illustrated by the following specificexamples in which the parts are by weight and temperatures are in degrees centigrade. It will be understood by those skilled in the art that the scope of the invention is not limited to these specific examples.

Example l.-700 parts of an olefine with a boiling point ranging from 237 to 262 and having an average carbon content of 14 to 15 carbon atoms (and obtained by the dechlorination of the monochlor hydrocarbon separated by fractionation from the products resulting from chlorination of petroleum distillates which boil at approximately 250 at atmospheric pressure), 700 parts of phenol, and 350 parts of anhydrous zinc chloride are mixed and heated together while agitated under a reflux condenser at a temperature around to for from 5 to 16 hours. The condensed mass is diluted and washed with water until reasonably free of water-soluble impurities, and the crude brownish oil is distilled in vacuo. .The distillate boiling between 195 and 240 at mm. pressure is collected. It is a faintly colored to water-white oil, insoluble in water and dilute caustic soda.

100 parts by weight of the resulting oil are mixed with 148 parts by weight ofsulphuric acid monohydrate at 30, then heated to 70-75 and held there until a sample is completely soluble in water and in neutral, acid or alkaline aqueous solutions, and a neutral 0.2 per cent solution does not precipitate calcium salts from a soluble calcium salt solution containing the equivalent of 0.224 gram calcium oxide per liter. The sulphonation mix is poured into water, diluted to a final volume of 450 to 600 parts, and made neutral (for example, to delta paper, Congo paper,

brilliant yellow, or brom-phenol-blue) with alkali, for example caustic soda, or potashor their equivalents. The neutral solution is evaporated to dryness. If desired, the neutral solution can be clarified by filtration'before being evaporated to dryness.

The product thus obtained is a mixture of alkyl phenol sulphonates, sodium sulphate and some impurities. The chief components are alkyl phenol sulphonates having the probable formula wherein Re represents an aliphatic hydrocarbon group, M represents an alkali metal or equivalent derived from the base used for neutralization, and p is 1 or 2 but mainly 1. For the most part, the alkyl phenol sulphonates contain branched carbon chains in the groups represented by Re and these groups are connected to the phenol nucleus by primary, secondary or tertiary carbon atoms. The chief components of the mixture contain 14"or 15 carbon atoms in the alkyl group represented by Re.

Imthe form 01- the alkali metal and alkaline earth metal salts it is a friable solid, faintly colored light brown to white, readily reduced to a comminuted or powdery form (resembling powdered soap) and readily solube in water.

Exampe 2.The sulphuric acid monohydrate in Example 1 is substituted by 200 parts of 66 B. sulphuric acid which is fed slowly to the agitated alkyl phenol at a temperature of -70. The mixture is slowly heated to 90-100 and held at this temperature for one hour, or until a sample is completely soluble in water and does not precipitate calcium salts (as in Example 1).

Example 3.--100 parts of the alkyl phenol employed in Example 1 are mixed slowly with 50 parts of chlorsulphonic acid, and the mix is heated to 70-90 until evolution of hydrochloric acid practically ceases and a sample of the sulfonation mass is completely soluble in water and does not precipitate calcium salts (as in Example 1). The sulphonation mass is then diluted with water, "neutralized with alkali, filtered and evaporated to dryness, etc., as in Example 1. The resulting alkyl phenol sulphonate is similar to that produced in Example 1.

Example 4.100 parts of the alkyl phenol used in Example 1 are mixed with 24 parts of acetic anhydride, and while the mass is agitated, 32 parts of 26% oleum are added slowly, so

5 that the temperature of the mix does not exceed 50. Thereafter, the temperature is slowly raised to 95 and held there until a. sample of the sulphonation mass is soluble in water and does not precipitate calcium salts. The sulfonation mass is diluted with water to approximately 450 to 600 parts and neutralized with alkali. The solution is clarified by filtration, if necessary, and evaporated to dryness. The product is similar to that obtained in Example 1. Emmple 5.To parts of the alkyl phenol used in Example 1, while being agitated, 64 parts of 65% oleum are added slowly. The temperature during addition of oleum is held at 30 while the finishing temperature is not allowed to exceed 45. The sulfonation is complete when a sample is completely soluble in water and does not precipitate calcium salts from dilute solutions. The sulphonation mass is diluted, neutralized, filtered and evaporated to dryness as described in previous examples.

The products of the above examples contain inorganic salts (alkali metal sulphates) in admixture with the alkyl phenol sulphonates. When it is desired to employ the alkyl phenol sulphonates in a form free from inorganic salts, they may be obtained from the mixed products produced by such processes as are given in the above specific examples by taking advantage of the solubility of the alkyl phenol sulphonate salts in alcohol and other organic solvents. Thus a mixture of a salt of the sulphonated product and an inorganic sulphate may be extracted with alcohol, and the resulting extract may be evaporated to leave a residue of the purified salt of the sulphonated product, as illustrated by the following specific examples.

Example 6.'I'he sulphonation mixture resulting Jrom the process of above Example 2 is diluted with 1750 parts of 70% denatured alcohol, and neutralized with solid soda ash (NazCOa). The mixture is filtered and the filtrate evaporated to dryness to obtain the sodium salt of the alkyl phenol sulphonic acid practically free from salts of inorganic acids. The resulting product is similar to that obtained in Examples 1 and 2 but it does not contain the inorganic salts present in that product, and it is soluble in benzene, alcohol and other organic solvents.

Example 7.-The neutralized solution of the sulphonic acid obtained by the process of above Example 5 is treated with such an amount of alcohol that the resulting alcohol solution in water contains more than 50% alcohol. The solution is filtered to remove precipitated impurities which are mostly inorganic salts, and the filtrate containing the sulphonate is evaporated to dryness to yield the dry sulphonate practically free from inorganic salts. The product, which is similar to that obtained in Example 6, is suitable for use in organic solvents as a cleaning composition and is an excellent emulsifier.

Instead of adding alcohol to the dilution mass, the dry crude sulphonate may be repeatedly extracted with alcohol, and the alcohol extracts combined, filtered and evaporated to dryness.

Example 8.--A mixture of 15 parts zinc chloride, parts of the olefine used in Example 1, and 100 parts of phenol is refluxed with agitation for 15 hours at to The mixture is cooled, and the liquid portion is decanted therefrom and distilled in vacuo. The distillate boiling between 150 and 225 at 7 mm. pressure is collected. It is an oil comprising an alkyl phenol mixture in which the alkyl group contains an averagev of 14 to 15 carbon atoms.

To 20 parts of this-oil there is slowly added, with agitation, 20 parts of sulphuric acid monohydrate, the temperature being maintained at 28 to 30. The mixture is stirred at 30 to 35 for 2 hours or until the sulphonation is completed, then diluted with 800 parts of water, neutralized with caustic soda, and evaporated to dryness. The product is similar to that obtained in Example 1.

Example 9.-To 100 parts of an alkyl phenol obtained by condensing phenol with an olefine of boiling range 232 to 255 (and derived from chlorinated petroleum distillates of about the same boiling range), as per methods described herein, 64 parts of 65% oleum are added at such a rate that the temperature of the mixture does not exceed 30. The temperature thereafter is raised to 35 to 45 and held at that point till a sample of the sulphonation mass is completely soluble in water and does not precipitate calcium salts from dilute solutions. The mass is diluted with water, and the resulting solution is neutralized with caustic soda, filtered and evaporated to dryness. Or, the solution or final product may be extracted with alcohol of greater strength than 50% and the extract evaporated to dryness to yield an alkyl phenol sulphonate practically free from inorganic salts, as described in Examples 6 and '1 above. The resulting product is chiefly an alkyl phenol sulphonate in which the alkyl group contains about 14 to 15 carbon atoms but averages somewhat lower than the product of Example 1.

Instead of the alkyl phenol product employed in the above examples for the production of alkyl phenol sulphonates, other alkyl phenols and cresols may be employed. The following additional examples in which the parts are by weight and the temperatures are in degrees centigrade, illustrate the preparation of such alkyl phenol products.

Example 10.-An admixture of 50 parts of cetcne (obtained by pyrolysis of spermaceti), 50 parts of phenol and 50 parts of fused, powdered zinc chloride is refluxed and agitated for 16 hours. The reaction mass is washed with water and fractionally distilled. The fraction boiling between 238 to 252 at 13 mm. is separately collected. It is a white oil, insoluble in water and has a specific gravity less than 1.

Example 11.--A mixture of 50 parts of phenol, 50 parts of 1.2-heptadecene (obtained by distillation of a mixture of oleic acid and sodium ethylate), and 25 parts of anhydrous zinc chloride is heated with stirring at 90 to 120 for 15 hours. The resulting reaction mass is washed with water and then subjected to fractional distillation. The portion boiling between 220 and 270 at 15 mm. is separately collected. It is a colorless, or nearly so, oil consisting mostly of heptadecyl phenol.

By carrying out the condensation in the presence of 10 parts of concentrated sulphuric acid at 6 to 12, in place of zinc chloride, followed by washing and distilling the resulting product and collecting, the fraction distilling between 220 and 270 heptadecyl phenol is also obtained.

As above indicated, changes may be made in the process hereinbefore described without departing from the scope of the invention. Thus phenol, ortho-, meta-,or para-cresol may be employed.

Preferably the proportion of olefine employed with respect to the phenol is such that not more than two alkyl radicals of the type represented by R in the foregoing formula are contained in the resulting alkyl phenol and preferably only one. Thus, at least 1.25 mols of phenol per mol of olefine is preferably employed in the condensation. A ratio as low as 1 to l or even lower may be employed, but the yield of the resulting alkyl phenol containing one long alkyl group will be less.

As condensing agents there may be employed anhydrous zinc chloride, anhydrous aluminum chloride, anhydrous antimonic chloride, anhydrous ferric chloride, sulphuric acid (66 B. monohydrate, oleum), etc. Anhydrous zinc chloride is preferred. While the zinc chloride and other metal halide condensing agents mentioned have been referred to as "anhydrous, it is noted that said condensing agents may be employed in a partially hydrated condition containing small amounts of water, for instance such as are absorbed from the surrounding atmosphere or otherwise in commercial operation, but insufficient to interfere with their action as condensing agents. The amount of condensing agent employed may vary.

The time during which the condensation reaction of the olefine and phenol may be carried out also may be varied. With zinc chloride as the condensing agent, the period of heating may be extended to 16 hours or more without seriously harming the quality or decreasing the yield of the alkyl phenol.

The crude alkyl phenol resulting from the condensation is preferably purified, as for example, by fractional distillation and collecting a middle fraction having in general a boiling point range of not more than 100 C. and the purified compound is preferably employed for sulphonation. Distillation is preferably carried out at a pressure not exceeding 30 mm. to avoid decomposition.

In sulphonating the alkyl phenol or cresol, an inert solvent and/or a sulphonation assistant may or may not be used. As sulphonating agents there may be employed sulphuric acids of various strengths (e. g., 66 B., sulphuric acid, sulphuric acid monohydrate, oleum), chlorsulphonic acid, etc. As solvents or diluent there may be employed any inert organic liquid which is not readily sulphonated; such as halogenated hydrocarbons of the aliphatic and aromatic series, as for example, carbon tetrachloride, dichlorethane, tetrachlorethane, dichlorbenzene, etc. As sulphonation assistants there may be employed the lower organic acids and/or their anhydrides, as for example, acetic acid, acetic anhydride, etc.

The sulphonation may be carried out with the aid of heating or cooling, as required, depending upon the ease of sulphonation of the alkyl phenol or cresol and the sulphonating power of the sulphonating agent. For example, temperatures as low as about and as high as about 140 C. may be employed. In general the more vigorous the sulphonating agent the lower is the preferred temperature. Ordinarily the completion of the sulphonation is carried out at a temperature in the neighorhood of about 25 to about 80 C. The ratio of sulphonating agent employed with respect to the alkyl phenol also may be varied. While the preferred amounts are given in the above examples, an amount of sulphuric acid or other sulphonating agent equivalent -to from 1 to about parts by weight of sulphuric acid monohydrate per part by weight of the alkyl phenol may be employed.

The extent to which the sulphonation is carried out may vary with the individual material being sulphonated and the use to be made of the sulphonated product. In general the extent of sulphonation of the alkyl phenol treated is such as to form chiefly the monosulphonic acids of the alkyl phenol, and to sulphonate impurities as well, if present. In some cases, a degree of sulphonation which corresponds with a product having maximum detergent properties is notv completely soluble in water to form a clear solution and/or may cause some precipitation of lime salts. (An aqueous solution of calcium chloride containing the equivalent of 0.224 gram of calcium oxide per liter of solution is merely employed in the above examples as a representative hard water solution for test purposes. It is to be noted that the invention is in no respect limited thereto.)

The alkyl phenol sulphonates may be produced in accordance with the present invention in the form of their free sulphonic acids or in the form of salts of metals (as for example, of the alkali metals) or of organic bases, or of ammonia, etc. The salts may be obtained in any suitable manner; for example by reacting the sulphonated product, either in the crude form resulting from the sulphonation or in a purified form, with a metal oxide or hydroxide, ammonia or an organic base, or of a suitable salt of one of these, in an amount adapted to form a neutral product. Among the bases, oxides and salts which may be combined with the sulphonated products to produce salts in accordance with the present invention are, for example sodium, potassium and ammonium hydroxides; sodium, potassium and ammonium carbonates and bicarbonates; ammonia; magnesium oxide; ethylamine; pyridine; triethanolamine; propanolamines; butanolamines; diamino propanol; ethylenediamine; triethylene tetramine; etc.

The reaction mixtures resulting from the sulphonation' of the alkyl phenol or cresol may also be directly employed for the formation of mixed products, as for example, mixtures of salts of the alkyl phenol sulphonic acid and of other acids present in said reaction mixtures, which mixtures of salts are also useful as such. Thus, the sulphonation reaction mixture resulting from the treatment of the alkyl phenol or cresol with an amount of sulphonating agent in excess of that theoretically required to effect the desired degree of sulphonation may be treated with a suitable inorganic or organic base or basic salt (as for example, one of those mentioned) and the resulting mixture of the salt of the sulphonated alkyl phenol or cresol and the organic and/or inorganic salt (as for example, sodium sulphate) may be jointly isolated from the reaction mixture and employed as such. If it is desired to produce a salt of the sulphonated alkyl phenol or cresol in a form substantially free from inorganic salts (for example, inorganic sulfates) this may be accomplished by taking advantage of the solubility of the salts of the sulphonated products in alcohol and other organic solvents as disclosed in the above examples.

The sulphonated products in the form of metallic salts or salts of inorganic bases are usually yellowish to white, friable solids; and in the form of salts of organic bases vary from viscous oils to semi-solids to solids. In general, the salts are readily soluble in water and in aqueous (neutral, acid or alkaline) solutions to form solutions which are faintly colored brown or yellow, which are of a soapy nature and which foam readily. Certain of the salts, such as the salts of the aromatic monoamines and the aliphatic and aromatic polyamines, are oils which generally are insoluble in water but soluble in organic solvents (as for example, benzene, gasoline, etc.) and in aqueous solutions of alkalis (presumably by conversion to the salts of the alkalis) This application is a continuation in part of my applications'Serial Nos. 691,081 and 691,082, filed September 26, 1933.

I claim:

1. A method of producing a nuclear alkyl derivative of a sulphonated phenol, which comprises condensing a member of the group consisting of phenol and its monomethyl derivatives with an olefine hydrocarbon containing at least 12 carbon atoms with the aid of a metal halide condensing agent, and sulphonating the resulting product.

2. A method of producing a nuclear alkyl derivative of a sulphonated phenol, which comprises condensing a member of the group consisting of phenol and its monomethyl derivatives with an olefine hydrocarbon containing at least 12 carbon atoms of' which at least 7 are in a straight chain, with the aid of a metal halide condensing agent, and sulphonating the resulting product.

3. A method of producing a nuclear alkyl derivative of a sulphonated phenol, which comprises forming a phenol compound containing a high alkyl substituent by condensing a phenol compound of the group consisting of phenol and its monomethyl derivatives with an olefine hydrocarbon containing at least 12 carbon atoms in a straight chain, with the aid of a condensing agent, the amount of olefine hydrocarbon not ex ceeding about that required to produce monoalkylation of the phenol compound, and sulphonating the resulting product.

4. A method of producing a nuclear alkyl derivative of a sulfonated phenol which comprises forming a phenol compound containing a high alkyl substituent by condensing a phenol compound of the group consisting of phenol and its monomethyl derivatives with an olefine hydrocarbon containing at least 12 carbon atoms in a branched, open-chain with the aid of a condensing agent, the amount of olefine hydrocarbon not exceeding about that required to produce monoalkylation of the phenol compound, and sulphonating the alkylated phenol compound.

5. A method of producing a nuclear alkyl derevative of a sulphonated phenol, which comprises forming a phenol compound containing a high alkyl substituent by condensing a phenol compound of the group consisting of phenol and its monomethyl derivatives with an open-chain olefine hydrocarbon containing at least 12 carbon atoms and having a double bond between the ultimate and penultimate carbon 'atoms, in the presence of a metal halide condensing agent, the amount of olefine hydrocarbon not exceeding about that required to produce monoalkylation of the phenol compound, and sulphonating the alkylated phenol compound.

6. A method of producing a nuclear alkyl derivative of a sulphonated phenol, which comprises condensing one mol of a phenol compound of the group consisting of phenol and its monomethyl derivatives with not more than one mol of an olefine hydrocarbon containing at least 12 carbon atoms with the aid of a zinc halide as a condensing agent, whereby an alkyl phenol compound is produced, and sulphonating said alkyl phenol com pound.

7. A method of producing a nuclear alkyl derivative of asulphonated phenol, which comprises condensing one mol of a phenol compound of the group consisting of phenol and its monomethyl derivatives with not more than one mol of an open-chain olefine hydrocarbon containing 12 to 23 carbon atoms with the aid of a condensing agent, whereby an alkyl phenol compound is produced, and sulphonating said alkyl phenol compound.

8. A method of producing a nuclear alkyl derivative of a sulphonated phenol, which come prises condensing one mol of a phenol compound of the group consisting of phenol and its monomethyl derivatives with not more than one mol of an open-chain olefine hydrocarbon containing 12 to 23 carbon atoms, of which at least seven are in a straight chain, with the aid of a condensing agent, whereby an alkyl phenol compound is produced, and sulphonated said alkyl phenol compound.

9. A method of producing a nuclear alkyl derivative of a sulphonated phenol, which comprises condensing one mol. of a phenol compound of the group consisting of phenol and its monomethyl derivatives with not more than one mol. of an open-chain olefine hydrocarbon containing 12 to 23 carbon atoms and having a double bond between the ultimate and penultimate carbon atoms, in the presence of a metal halide condenslng agent, whereby an alkyl phenol compound is produced, and sulphonating said alkyl phenol compound.

10. A method of producing a nuclear allgvl derivative of a sulphonated phenol, which comprises condensing one mol. of a phenol compound of the group consisting of phenol and its monomethyl derivatives with not more than one mol. of an olefine hydrocarbon containing 14 to 19 carbon atoms, of which at least '7 are in a straight chain, with the aid of a zinc halide as a condensing agent, whereby an alkyl phenol compound is produced, and sulphonating said alkyl phenol compound.

11. A method of producing a nuclear alkyl derivative of a sulphonated phenol, which comprises condensing at least 1.25 mols of a phenol compound of the group consisting of phenol and its monomethyl derivatives with one mol. of an olefine hydrocarbon containing at least 12 carbon atoms, of which at least 7 are in a straight chain and having a double bond between the ultimate and penultimate carbon atoms, with the aid of anhydrous zinc chloride, whereby the corresponding alkyl phenol compound is produced, and sulphonating said alkyl phenol compound.

12. A method of producing a nuclear alkyl derivative of a sulphonated phenol, which comprises condensing at least 1.25 mols of a phenol compound of the group consisting of phenol and its monomethyl derivatives with one mol. of an olefine hydrocarbon containing 14 to 19 carbon atoms in a straight chain and having a double bond between the ultimate and penultimate carbon atoms, with the aid of anhydrous zinc chloride, whereby the corresponding alkyl phenol com pound is produced, and sulphonating said alkyl phenol compound.

13. A method of producing a nuclear alkyl derivative of a sulphonated phenol, which comprises condensing at least 1.25 mols of a phenol compound of the group consisting of phenol and its monomethyl derivatives with one mol. of an olefine hydrocarbon containing 12 to 23 carbon atoms and resulting from the removal of hydrogen chloride from a chlorinated aliphatic hydrocarbon, with the aid of anhydrous zinc chloride, whereby the corresponding monoalkyl phenol compound is produced, and sulphonating said monoalkyl phenol compound.

14. A method of producing a nuclear alkyl derivative of a sulphonated phenol, which comprises condensing at least 1.25 mols of a phenol com pound of the group consisting of phenol and its monomethyl derivatives with one mol. of a mixture of olefine hydrocarbons containing 12 to 23 carbon atoms and resulting from the removal of hydrogen chloride from a mixture of chlorinated aliphatic hydrocarbons, with the aid of anhydrous zinc chloride, whereby a mixture of the corresponding monoalkyl phenol compounds is produced, and sulphonating said monoalkyl phenol compounds. 1

15. A method of producing a nuclear alkyl derivative of a sulphonated phenol, which comprises condensing at least 1.25 mols of a phenol compound of the group consisting of phenol and its monomethyl derivatives with one mol. of a mixture oi. olefine hydrocarbons containing 14 to 19 carbon atomsand resulting from the removal of hydrogen chloride from a mixture of chlorinated aliphatic hydrocarbons, with the aid of anhydrous zinc chloride, whereby a mixture of