US3431184A - Electrochemical cyanation of selected aromatic compounds - Google Patents

Description

United States Patent 3,431,184 ELECTROCHEMICAL CYANATION 0F SELECTED AROMATIC COMPOUNDS Sam Andreades, Wilmington, DeL, assignor to E. I. du

Pont de Ncmours and Company, Wilmington, DeL, a

corporation of Delaware No Drawing. Filed Feb. 16, 1966, Ser. No. 527,752 US. Cl. 294-59 12 Claims Int. Cl. Btlllr 1/00; (107a 121/60, ]2]/50 ABSTRACT OF THE DISCLOSURE Mono and dicyano carbocylic aromatic and nitrogen heterocyclic aromatic compounds are produced by passing a direct current of electricity through a solvent or mixture of solvents containing a cyanide-containing compound and a carbocyclic aromatic or nitrogen heterocyclic compound. The aromatic reactant contains 1-4 rings and bears not more than four substituents. The process is conducted at a temperature of about -50 to +100 C. at an anode potential (versus a Saturated Calomel Electrode) of the order of +0.5 to +3.5 volts using an essentially inert anode.

Description of the invention This invention relates to a matic nitriles.

More specifically, this invention relates to electrochemical cyanations, e.g., the introduction of cyanide functionality into carbocyclic and heterocyclic compounds to produce aromatic nitriles.

The process of this invention comprises passing a direct current of electricity through a medium containing an aromatic compound and a cyanide-containing compound to introduce nitrile functionality into the aromatic reactant. Depending upon the aromatic reactant, the product produced contains one or more nitrile groups.

The process comprises electrolyzing at an anode potential below that at which substantial attack of the solvent occurs, an aromatic compound composed of carbocyclic or nitrogen heterocyclic rings having an aromatic system of double bonds. Carbocyclic and heterocyclic aro matic compounds which can be electrochemically cyanated by the process of this invention contain 14 aromatic rings bearing not more than four substituents wherein the substituents are selected from the group alkyl containing up to 12 carbon atoms, F-, NC-, Cl-, Br, O N-, alkyl-O- containing up to 12 carbon atoms, phenyl, phenoxy, or alkyl-S containing up to 12 carbon atoms. Compounds containing not more than three aromatic rings are preferred.

Aromatic compounds used include substituted and unsubstituted benzenes, naphthalenes, anthracenes, phenanthrenes, Chrysenes, pyrenes, pyridines, and quinolines. The naphthalene, pyridine and quinoline reactants have at least one unsubstituted alpha position and anthracene is unsubstituted in the 9 position. Chrysenes should have position 2 unsubstituted and preferably one or more of positions 4, 5, 6, 10, 11 and 12 should also be unsubstituted. In the pyrenes at least two of positions 3, 5, 8,

process for preparing aroand 10 are unsubstituted. The numbering used for chrysenes and pyrenes conforms to the following formulas:

It is preferred that not more than one NC, Br, or O N group be present on one ring of aromatic compound and is is further desirable that at least one alkyl- O- or al'kyl-S- substituent be present when the aromatic compound has NC or Br-- substituents.

Compounds suitable as the aromatic reactant include: toluene, o-xylene, m-xylene, p-Xylene, mesitylene, 1,2,3,5- tetramethylbenzene, dodecylbenzene, n-hexylbenzene, cumene, 4-n-hexyltoluene, chlorobenzene, 2'cyanoaniso1e, methyl-4-butoxybenzene, 4-chlorotoluene, 4-chloroethylbenzene, 1,3,5-trimethoxybenzene, butyl hydroquinone dimethyl ether, butyl resorcinol dimethyl ether, 1,2-dimethyl-4,5-dimethoxybenzene, fluorobenzene, bromobenzene, 4-bromotoluene, 4-nitrotoluene, 4-nitroanisole, dodecyl phenyl ether, dodecyl phenyl sulfide, methyl phenyl sulfide, n-heXyl phenyl sulfide, 4,4-dimethoxydiphenyl ether, 4,4-dimethoxydiphenyl, 4-phenoxybenzonitrile, dibutylcatechol dimethyl ether, dibutylanisole, 4-bromodiphenyl ether, 4-chlorodiphenyl, 4-nitrodiphenyl ether, a-methoxy naphthalene, ,B-methoxynaphthalene, 2,5-dimethoxynaphthalene, 1-dodecylnaphthalene, 1,4,5-trimethoxynaphthalene, 1 methoXy-4-chloronaphthalene, 1,5 dimethyl-4- 35 methoxynaphthalene, l-naphthonitrile, dodecyl l-naphthyl sulfide, dodecyl l-naphthyl ether, 1,4-dimethylnaphthalene,

2,S-dimethylnaphthalene, wphenylnaphthalene, l-chloroanthracene, 1-chloro-4-methoxyanthracene, 1-methoXy-4- 4O methylanthracene, l-nitroanthracene, l-cyanoanthracene,

l-dodecylanthracene, dodecyl anthryl ether, 1,4-dimethoxyanthracene, 2,6-dimethoxyanthracene, 1,4,5-trimethoxyanthracene, 1,4 diethylanthracene, 1 phenoxyanthracene, 1,2,4,S-tetramethylanthracene, l-chlorophenanthrene, l-cyanophenanthrene, l-nitrophenanthrene, l-bromophenanthrene, l-methylphenanthrene, 1,4-dimethylphenanthrene, 1,S-dimethylphenanthrene, 1,4,5,8-tetramethylphenanthrene, 1,4,8-trimethylphenanthrene, l-chlorochrysene, 1,4-dimethylchrysene, l-methylchrysene, 1- methoxychrysene, l-heptylchrysene, 1- octachrysene, 1- methylthiochrysene, 1-dodecylthiochrysene, l-dodecyloxychrysene, 1-chloropyrene, l-methylpyrene, l-hexylpyrene, l-methoxypyrene, 4-chloropyrene, 3,4 lutidine, 2,4-lutidine, 4-phenylpyridine, 4-methoxypyridine, 2-ethoxypyri- 55 dine, 2-dodecylpyridine, 2-methylthiopyridine, 2-hexylthiopyridine, Z-methylpyridine, S-methylpyridine, 3 -methoxypyridine, 3-ethoxypyridine, 3-propoxypyridine, 3,4- dimethoxypyridine, 4-dodecyloxypyridine, 4-dodecylthiopyridine, lepidine, 4-hexylquinoline, B-methylquinoline, 4- phenoxyquinoline, 4-phenylquinoline, 4 -methoxyquinoline, 4-hexylthioquinoline.

Many other aromatic compounds, not listed above, can be used as the aromatic reactant.

Cyanide-containing compounds useful in electrochemical cyanations as the source of cyanide ion and as the electrolyte comprise hydrogen cyanide, and salts, and mixtures thereof, and mixtures containing any cyanide salt soluble in the reaction medium. Examples of cyanidecontaining salts are: the alkali-metal cyanides, mercurous cyanide, cuprous cyanide and quaternary salts such as R NAg(CN) and (R) XCN wherein X is nitrogen, phosphorous or arsenic and R is a group selected from phenyl, .aralkyl containing up to 18 carbon atoms and alkyl containing up to 18 carbon atoms. Examples of the latter class of cyanide-containing compounds are: tetramethylammonium cyanide, octadecyltrimethylammonium cyanide, dioctadecyldimethylammonium cyanide, benzyltrimethylammonium cyanide, tetramethylphosphonium cyanide and tetr-aphenylarsonium cyanide. Mercurous cyanide, R NAg(CN) and cuprous cyanide are generally used in catalytic quantities with other cyanide-containing compounds; when used, they sometimes have a catalytic effect on the electrochemical cyanation. The quatern ry ammonium, phosphonium and arsonium salts are readily prepared by the metathetical reaction of the corresponding quaternary halide and an alkali-metal cy nide in an organic solvent. Alkali-metal chloride precipitates from the reaction mixtures. The quaternary cyanide is soluble in the organic medium. The quaternary cyanides are isolated by evaporation and crystallization techniques.

Electrochemical cyanations can be conducted in any of the various types of electrolysis cells commonly used for electrolytic reactions (A. Weissberger, Tecniques of Organic Chemistry, vol. II, Interscience Publishers, Inc., New York, 1956, 385). These cells are modifications of the simple electrolysis cells comprising two electrodes, one being a cathode and the other an anode, which are suspended in an electrolyte, medium. Some electrolysis cells are divided, that is, the anode and the cathode are suspended in separate media, which is connected by means of a semi-permeable membrane. Divided cells can be used where the aromatic reactant or solvent is susceptible to reductionfor example, nitrobenzene. In general, most electrochemical cyanations can be conducted in undivided electrolysis cells. Various electrical conductors can be used as the material of construction for the cathodes and anodes for electrochemical cyanation. The efficiency of the electrochemical cyanation is dependent upon the composition of the electrodes and the aromatic reactant, as well as other factors.

In general, inert electrodes with oxygen overpotentials between nickel and gold, including carbon, are used as the anode in the process of this invention. Copper, tin, zinc, and silver may be used in certain cases. However, they tend to dissolve during electrolysis to form cyanide complexes which makes their use inconvenient. Platinum, palladium, rhodium, carbon, lead, lead dioxide, and nickel are examples of useful anode materials. Preferably the materials used as cathodes have a hydrogen over-potential less than that of mercury and the cathode material is inert to the electrolyte. However, the restriction that the cathode be inert can be obviated to some extent by use of a divided cell which permits an electrolyte to be employed in the cathode compartment different from that in the anode compartment. Materials especially useful as the cathode include copper, nickel, lead, iron, zinc, platinum, rhodium and palladium.

The configuration of the electrodes can be varied. For example, except for mercury, bars, strips and gauzes composed of the above materials can be used. In the Examples given below, an undivided electrolysis cell consisting of a stationary cylindrical platinum gauze cathode and a rotating cylindrical platinum gauze anode was used. These electrodes were constructed of concentric -mesh platinum gauze cylinders. The operating electrode had a surface area of from 150 to 200 square centimeters (determined by a modified B.E.T. method). The anode was rotated at about to 300 revolutions per minute. The

cell capacity was about 400 milliliters. The anode potential was monitored using a Saturated Calomel Electrode (S.C.E.). This cell was constructed in such a manner that a relatively large ratio of electrode surface area to the volume of electrolyte medium was obtained. Relative motion between the electrolyte medium and the electrodes was produced by rotating the anode. Relative motion between electrodes and medium can be obtained by circulation of the medium through a cell equipped with stationary electrodes.

Solvents used as the cell medium comprised acetonitrile, methanol, N,N- dimethylformamide, N,N-dimethylacetamide, nitrornethane, acetone and mixtures of these solvents. Aqueous mixtures of these solvents can be used. Acetonitrile, which has a relatively large negative and positive discharge potential and possesses good solubilizing characteristics for aromatic reactants and cyanidecontaining compounds is a preferred solvent. Methanol is also a preferred solvent.

In general, any electrolyte which is soluble in the medium and which contains an anion which is not easily oxidized can be used in conjunction with the cyanidecontaining compounds. Examples of co-electrolytes which can be used are: tetraethylammonium perchlorate, tetrapropylammonium p-toluenesulfonate and tetrabutylammonium perchlorate. Other substances such as a small amount of sulfuric acid in some cases improve the conductivity of the electrolysis medium and promote electrochemical cyanation. Preparation of these electrolytes has been described, R. Shriner, R. Fuson and D. Curtin, Systematic Identification of Organic Compounds, 5th edition, J. Wiley and Sons, New York, 1964.

The electrochemical cyanation process of this invention is conducted at a temperature of about 50 to C. depending upon the medium. The electrolyte should be in the liquid state. Pressure under which the electrochemical cyanation is conducted is not critical. Reaction pressures of subatmospheric and superatmospheric can be used. In general, the process is conducted at, or near, atmospheric pressure, i.e., at a pressure in the range of 0.5-10 atmospheres.

The amount of current passed through the electrolysis cell should equal at least one Faraday per mole of aromatic reactant in order to obtain good yields. A large excess of current (2-3 Faradays per mole of aromatic compound) is desirable to improve the yield of nitrile product. Some product will be formed at lower levels of current consumption, that is, less than one Faraday per mole of aromatic reactant.

The anode potentials cited in the examples below were measured with respect to a Saturated Calomel Electrode (S.C.E.) and were usually of the order of +0.5 to +3.5 volts. Cyanide ion is oxidized at these potentials. Anode potentials higher than +3.5 volts may sometimes be used. However, potentials strong enough to cause substantial oxidation of the solvent are preferably avoided. The potential drop between anode and cathode in general will be considerably larger than 3.5 volts.

The products obtained by electrochemical cyanations fall into three classes, (a) wherein the original substituents on the aromatic compound are unchanged except for the introduction of one or more cyano groups, (1)) in which one or more of the original substituents on the aromatic compound has been replaced by cyano groups and (c) wherein original substituents on the aromatic compound are replaced by cyano groups and additional cyano groups are added. Alkyl substituted aromatic compounds, anisole, m-dialkoxybenzenes and anthracene yield products falling into the first class and oand p-dialkoxybenzenes yield products falling within the second class. Electrochemical cyanation of p-xylene anisole, m-dialkoxybenzene and anthracene give 1,4-dimethyl-2-cyanobenzene, p-methoxybenzonitrile, 2,4-dialkoxybenzonitrile and 9,10-dieyanoanthracene, respectively; 0- and p-dialkoxybenzenes give 2- and 4-alkoxybenzonitriles, respectively.

The following examples further illustrate the invention. The number of Faradays of electricity passed through the cell is determined by continuously recording and integrating the number of amperes of electricity passed through the cell as a function of time. The number of Faradays is calculated from the number of ampere-hours consumed. Voltages at the anode are expressed with reference to a Saturated Calomel Electrode. Temperatures are expressed in degrees centigrade.

EXAMPLE I Electrochemical cyanation of p-xylene p-Xylene (20.0 g.), g. of potassium cyanide and 110 ml. of methanol were electrolyzed under a nitrogen atmosphere using an anode potential of 3.5 v. for 3 hours and 3.0 v. for 18 hours. The cell voltage drop was varied from 4.0-5.5 v. in the course of the reaction. Total current consumed was 1.3 Faraday. After electrolysis, the methanol was evaporated from the dark orange mixture. The residue was treated with 100 ml. of water and ex tracted four times with 50-ml. portions of ether. The combined ether layers were dried and distilled. After removal of the ether, distillation of the extract gave: fraction 1, B.P. 67-69 (1.5 mm., 7.6 g.); fraction 2, B.P. 70l13 (1.5 m., 2.0 g.); fraction 3, B.P. 1l3-l40 (1.5 mm, 1.3 g.); fraction 4, B.P. 140-l82 (1.5 mm., 1.3 g.); fraction 5, B.P. 183 (1.5 mm., 0.5 g.). Fractions 1 and 2 were colorless, 3 and 4 were yellow and 5 was orange. Slight decoposition occurred during the distillation of 4 and 5. Fractions 25 showed strong nitrile infrared absorption and were largely 2,5-dimethylbenzonitrile, while fraction 1 showed only weak nitrile absorption. Fraction 1 was almost pure p-(methoxymethyl)toluene.

The nitrile products were purified by liquid chromatography on neutral alumina (activity grade 1) in benzene. 2,5-dimethylbenzonitrile and the hydrolysis product of the nitrile, 2,5-dimethylbenzamide, were obtained.

EXAMPLE II Electrochemical cyanation of p-xylene The procedure of Example I was repeated using 10.0 g. of potassium cyanide, 110 ml. of methanol, 0.1 g. of cuprous cyanide and 20.0 g. of p-xylene. Electrolysis was carried out at 35 C. at a potential of +3.5 v. and

a total current consumption of 1.11 Faraday over a 19- r hour period. Workup in the usual manner gave 2.2 g. B.P. -60" (3 mm.) and a remaining red residue of 22 g. The distillate was a mixture of methyl p-methylbenzyl ether and p-toluic aldehyde.

The residue was eluted from a column of 300 g. of neutral alumina (activity grade 1) with benzene to obtain fraction 2 (0.674 g.) and fraction 3 (10.24 g.). Elution with ether gave fraction 4 as 2.18 g. Fractions 2-4 showed strong nitrile absorption at 4.5 1. By vapor phase chromatographic analysis, fraction 2 was 31% p-(methoxymethyl)toluene and 34% 2,5-dimethylbenzonitrile. Fraction 4 was 38% of the methyl ether and 18% of the nitrile. Fraction 3, which contained about 50% nitrile and 50% of the ether, was rechromatographed on 300 g. of alumina to yield 3.5 g. of pure 2,5-dimethylbenzonitrile, established by comparison of its infrared spectrum and its gas chromatographic retention time with those of an authentic sample. An addition 5.1 g. of the nitrile was obtained by further treatment of fraction 3.

A similar electrolysis was carried out using tetraethylammonium cyanide (preparation described below) instead of potassium cyanide. Cuprous cyanide was added. Cyanation again occurred but in lower yield. In addition, it was observed that more oxidation of a Xylene methyl group to an aldehyde occurred when the tetraethylammonium salt was used in place of the potassium salt.

EXAMPLE III Electrochemical cyanation of biphenyl A solution of 10.0 g. (0.065 mole) of biphenyl, 10.0 g. (0.153 mole) of potassium cyanide in ml. of methanol was electrolyzed using an anode potential of +1.75 v. The current dropped from 2.5 amp to 0.3 amp in two hours. Total current consumed was 0.5 Faraday in 23 hours. The mixture slowly turned orange as electrolysis proceeded and at the end of the electrolysis the current level has dropped to 0.03 amp. The mixture was Worked up in the usual manner and the final distillation gave 2.0g. of biphenyl and 2.8 g. of p-phenylbenzonitrile, B.P. 139 (0.5 mm.) with a residue of 2.1 g. The distillate was purified by chromatography on alumina. using benzene as the eluent. p-Phenvlbenzonitrile eluted as the only early product and crystallized. The chromatographic cuts were combined and recrystallized from hexane to give pure product, M.P. 83-84.

Analysis.Calcd for C H N: C, 87.12; H, 5.06; N, 7.82; M.W., 179.21. Found: C, 86.97; H, 4.96; N, 7.75.

The n.m.r. spectrum showed aromatic absorption at 2.6 which appeared to include an A-B pattern derived from the two kinds of protons on the ring bearing the nitrile group, viz., the protons adjacent to the CN group and those adjacent to the C 11 group.

EXAMPLE IV Electrochemical cyanation of anthracene (3N EtrNCN CHsCN Electr. 0N

Part A A solution of 50 g. of sodium cyanide: in 1.5 liters of methanol was added to a stirred solution of 100 g. of anhydrous tetraethylammonium chloride in 200 ml. of methanol. The entire operation was conducted under nitrogen. The reaction mixture was filtered and the filtrate was evaporated to dryness under reduced pressure. The residue was extracted with 1 liter of dry acetonitrile. The extract Was then evaporated under reduced pressure. Crystals of Et NCN formed during the concentration. When about 200 ml. of solution remained, 47 g. of Et NCN was collected on a filter and was washed with acetonitrile.

Anaiysis.Calcd for C H N C, 69.17; H, 12.90; N, 17.93. Found: C, 69.82; H, 12.96; N, 17.77.

On dilution with tetrahydrofuran, the filtrate yielded an additional 28 g. of Et NCN, which was recrystallized from acetonitrile before use.

Part B A solution containing 0.53 g. (3 mmoles) of anthracene and 6.0 g. (38.5 mmoles) of tetraethylammonium cyanide in 300 ml. of acetonitrile and 100 ml. of ether was electrolyzed for 0.6 hour at an anode potential of 2.0 v. Total current passed was 0.027 Faraday. After completion of the electrolysis, half of the acetonitrile and ether was evaporated, the mixture was diluted with water and filtered to give 0.373 g. of crude 9,10-dicyanoanthracene. This solid was dissolved in boiling benzene and the solution filtered to remove some dark amorphous impurities. On cooling, the solution deposited 73 mg. of greenish yellow needles of 9,10-dicyanoanthracene, M.P. 340341 (dec., sealed capillary, lit. M.P., 334). The infrared spectrum was identical to that of an authentic sample.

7 Analysis.-Calcd for C H N C, 84.2; H, 3.5; N, 12.3; M.W., 228. Found: C, 84.3; H, 3.88; N, 11.35; M.W., 228 (mass spec).

EXAMPLE V Electrochemical cyanation of diphenyl ether Electr.

A solution of 10.0 g. of potassium cyanide, 20.0 g. of diphenyl ether (0.117 mole), 0.1 g. of cuprous cyanide and 110 ml. of methanol was electrolyzed at an anode potential of +0.5 v. for 1.5 hours, +1.75 v. for 2 hours, +2.5 v. for 2 hours, and +3.0 v. for 21 hours for a total current consumption of 0.4 Faraday. The mixture was worked up in the usual manner. Final distillation gave fraction 2, BF. 8990 (1.5 mm., 10.3 g.) which was essentially pure diphenyl ether, fraction 3, Bl. 90-145 (1.5 mm., 0.7 g.) which was a mixture of a nitrile and a material absorbing at 6.0 1. in the infrared spectrum and fraction 4, 13.1. 145-l67 (1.8 mm., 0.9 g.) which showed strong 6.0 1 absorption. A residue of 4.2 g. black liquid was obtained. The residue and fraction 4 were combined and chromatographed on 150 g. of alumina. Elution with benzene gave 2.8 g. (0.0144 mole) of analytically pure p-cyanophenyl phenyl ether. The n.m.r. spectrum showed only a strong symmetrical aromatic multiplet centered at 2.41. The yield was 27.3 percent at 45 percent conversion.

Analysis.-Calcd for C H NO: C, 79.99; H, 4.65; N, 7.17; M.W., 195.22. Found: C, 79.47; H, 4.74; N, 6.73; C, 80.05; H, 4.72; N, 6.91; M.W., 179 (cryoscopic in benzene).

EXAMPLE VI Electrochemical cyanation of pyridine ON Q Q H2804 Electr.

A solution consisting of 10.0 g. of anhydrous hydrogen cyanide and 100 ml. of pyridine allowed no current flow at an applied potential of 5.0 v. (anode potential +3.0 c.). Therefore, 0.6 g. of concentrated sulfuric acid was added. At this point, a current of 0.6 tained at an anode potential of +3.5 v. but the current again dropped as 17 ml. of cyclopentene were added, and levelled ofi at 0.1 amp. In 5.5 hours, 0.065 Faraday was consumed. The mixture was worked up by evaporation of the pyridine, dilution of the concentrate with water and extraction of the aqueous solution thus obtained with several portions of ether. The combined ether extracts were dried over anhydrous sodium sulfate and distilled to remove starting material to a 13.1. of 48.5" C. at 76 mm., leaving a residue of 0.5 g. This residue was largely 2-cyanopyridine as shown by IR comparison with an authentic sample. Current yield, 15%.

EXAMPLE VII Electrolytic cyanation of anisole CHsCN Electr.

level was about 0.6 amp. giving a total current consump- 7 amp was obtion of 0.313 Faraday. Approximately of the acetonitrile was removed under vacuum on a rotary evaporator and the remaining crude liquid was diluted with 100 ml. of water. The aqueous mixture was then extracted five times with SO-ml. portions of ether. The combined ether layers were dried and distilled. After removal of the ether, a fraction B.P. 86 (0.8 mm., 0.3 g.) showed a strong doublet nitrile band in the infrared spectrum. This fraction was identified as anisonitrile by comparison of its infrared spectrum with an authentic sample. Total yield was 5%.

EXAMPLE VIII Electrochemical cyanation of p-dirnethoxybenzene EtaNCN CHaO--OCH: omoQ-orv ornoN Electr.

A solution of 30.0 g. (0.192 mole) of tetraethylammonium cyanide and 10.0 g. (0.0725 mole) of p-dimethoxybenzene in 375 ml. of anhydrous acetonitrile was electrolyzed at an anode potential of +2.0 v. vs. Saturated Calomel Electrode (S.C.E.) for 15 hours. The current decreased slowly from 1.0 amp to 0.5 amp. A total of 0.5 Faraday was passed. The mixture was worked up in the usual manner which included evaporation of most of the acetonitrile, addition of water, repeated extraction of the aqueous layer with ether, aqueous washing and drying of the ether layer, and evaporation of the ether. The remaining 9.5 g. of crude liquid product was shown to be 47% anisonitrile and 53% dimethoxybenzene by gas chromatographic analysis. The product contained at least of the above mixture. The anisonitrile was isolated by preparative gas chromatography and shown to be identical with an authentic sample by its infrared spectrum. The total conversion was 47% and the yield was 95 In another experiment, electrolysis was carried out until 0.02 Faraday was passed. Analysis of the product indicated a current efficiency of 30%.

When the preparation was conducted in acetonitrile containing 5% water, 0.73 Faraday was passed, and, in addition to the anisonitrile, 1 g. of p-methoxybenzamide was isolated and recrystallized from CH CN; M.P. 153-5 (lit., from H O, 163).

Analysis.-Calcd for C H O N: C, 63.51; H, 5.99; N, 9.26. Found: C, 63.01; H, 5.82; N, 9.41.

EXAMPLE IX Electrolysis of tetraethylammonium cyanide in the presence of p-dimethoxybenzene at a low anode potential EMNCN CH30- OCH3 CH30 C N CHaCN Electr.

The previous electrolysis in the presence of p-dimethoxybenzene was repeated using an anode potential of +0.9 v., which is suflicient to oxidize cyanide ion in acetonitrile solution but is below the half-wave oxidation potential of p-dimethoxybenzene. Under these conditions, 30 hours was required to pass 0.03 Faraday. At the end of this time, the solution contained 3% anisonitrile and 97% p-dimethoxybenzene. The results appear to indicate a current efficiency of 100% at low conversions.

EXAMPLE X Electrochemical cyanation of veratrole CHsCN 0 CH3 0 CH3 Electr. CN 0 CH3 A solution of 10.0 g. (0.072 mole) of veratrole and 30.0 g. (0.192 mole) of tetraethylammonium cyanide in 375 ml. of acetonitrile was electrolyzed with an anode potential of +2.0 v. until 0.41 Faraday was consumed. After working up in the manner described above, 10.88 g.

of liquid remained which was approximately 78% veratrole and 18% o-methoxybenzonitrile by gas chromatographic analysis. Distillation of the liquid gave a fraction B.P. 69-93 (0.6 mm.), 1.7 g. which was 87% veratrole and 13% o-methoxybenzonitrile and a fraction B.P. 93- 110" (0.6 mm), 1.2 g. which was 68% o-methoxybenzonitrile. The nitrile, isolated by preparative gas chromatography from these fractions, was shown to be identical with an authentic sample by its infrared spectrum. The product was obtained in 20% conversion (94% yield), while the current efficiency was The process of this inVentiOn is useful for the manufacture of a variety of nitrile-containin g compounds. These nitrile-containing compounds are useful as intermediates for the production of dyes, polymers, and pharmaceuticals. For example, p-methoxybenzonitrile can be converted into esters which are used as odorants and o-methoxybenzonitrile can be converted into salicylates which are useful as anti-oxidants.

The foregoing detailed description has been given for clearness of understanding only and no unnecessary limitations are to be understood therefrom. The invention is not limited to the exact details shown and described, since obvious modifications will occur to those skilled in the art.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Process for electrochemical cyanation of aromatic compounds to produce aromatic nitriles and aromatic dinitriles comprising passing a direct current of electricity at an anode potential of between 0.5 to 3.5 volts through a solution containing an aromatic compound and a cyanide-containing compound, wherein said aromatic compound is selected from the group consisting of unsubstituted and substituted benzenes, naphthalenes, anthracenes, phenanthrenes, chrysenes, pyrenes, pyridines and quinolines wherein the substituents are selected from the group alkyl containing up to 12 carbon atoms, F-, Cl-, Br-, CN, O N, alkyl-O containing up to 12 carbon atoms, phenyl, phenoxy or alkyl-S- containing up to 12 carbon atoms; with the provisos that the substituted aromatic compounds have no more than four substituents; That when the aromatic compound is a naphthalene, a pyridine and a quinoline at least one alpha position is unsubstituted, when the aromatic compound is anthracene the 9 position is unsubstituted, when the aromatic compound is a chrysene the 2 position is unsubstituted, and when the aromatic compound is a pyrene at least two of the positions 3, 5, 8 and 10 are unsubstituted; wherein said cyanide-containing compound is selected from the group consisting of hydrogen cyanide, alkali-metal cyanides, (R) XCN wherein R is a group selected from phenyl, aralkyl containing up to 18 carbon atoms and alkyl containing up to 18 carbon atoms and X is selected from the group nitrogen, phosphorous and arsenic, cy-

anide mixtures containing cuprous cyanide, mercurous cyanide and (R) NAg(CN) wherein R is a group selected from phenyl, aralkyl containing up to 18 carbon atoms and alkyl containing up to 18 carbon atoms, and mixtures of said cyanide-containing compounds; and wherein the electrochemical cyanation is conducted in a solvent, in which the aromatic and cyanide-c0ntaining compounds are at least partially soluble.

2. Process of claim 1 wherein the aromatic compound contains up to three substituents.

3. Process of claim 1 wherein the solvent is identical with the aromatic reactant.

4. Process of claim 1 wherein a non-cyanide-containing salt is added to the solution, said non-cyanide-containing salt being at least partially soluble and containing an anion which is not easily oxidized.

5. Process of claim 1 wherein the solvent is selected from the group acetonitrile, methanol, N,N-dimethylformamide, N,N-dimethylacetamide, nitromethane, acetone, mixtures of these solvents, and aqueous mixtures of these solvents.

6. Process of claim 4 wherein the non-cyanide-contaim ing compound is tetraethylammonium p-toluenesulfonate.

7. Process of claim 4 wherein the non-cyanide-containing compound is sulfuric acid.

8. Process of claim 1 wherein the is veratrole.

9. Process of claim 1 wherein the aromatic compound is anthracene.

10. Process of claim 1 wherein is diphenyl ether.

11. Process of claim 1 wherein is diphenyl.

12. Process of claim 7 wherein the aromatic compound is pyridine.

aromatic compound the aromatic compound the aromatic compound References Cited UNITED STATES PATENTS 2/1957 Kamlet 20472 5/1957 Hutchings 204-101 OTHER REFERENCES JOHN H. MACK, Primary Examiner. HOWARD M. FLOURNOY, Assistant Examiner.

U.S. Cl. X.R.