Cyclic compounds containing halogen linked directly to carbon are heated with a double compound of cuprous cyanide with any of the nitrogenous compounds specified below, whereby halogen is replaced by the cyano group. The nitrogenous compounds capable of forming double compounds with cuprous cyanide are pyridine, quinoline and their hydrogenation products, benzyl cyanide, benzonitrile, cyclohexylamine, mono-, di- and trialkylamines, aralkylamines, arylamines, and alkylolamines; the nitrogenous compounds must not contain halogen. The proportion of nitrogenous compound must not exceed that necessary to produce the double compound and is generally about equimolecular with that of the cuprous cyanide. Other copper salts, however, such as cuprous chloride, may also be included in the reaction mixture, and if these are capable of combining with the nitrogenous compound the proportion of the latter may be correspondingly increased, provided that none is present in the free state; this may be ascertained by heating the mixture to above the boiling point of the nitrogenous compound, if necessary under reduced pressure, whereupon free nitrogenous compound, if present, is driven off. The halogenated compounds which may be treated include those of the benzene, naphthalene, anthracene, diphenyl, phenanthrene, pyrene or chrysene series, and halogenated pyridines, quinolines, azaphenanthrenes, quinazolines, pyrazines, diphenylene oxides, acridones, thioxanthones, carbazoles, anthrapyrimidines, and azabenzanthrones; compounds containing halogen linked to a nucleus and/or to a side chain may be treated; bromine and iodine compounds are preferred, but chlorine compounds in which the chlorine is especially reactive, by virtue of its position in the molecule or the presence of adjacent substituents, are also suitable; such chlorine compounds include o-chlorophthaloyl compounds such as 1-chloranthraquinone, 8-chloroquinolines, compounds containing a nitro group or a free or modified carboxylic group in o-position to chlorine, and compounds containing chlorine in a side chain, such as benzyl chloride. The proportion of cuprous cyanide to halogen compound is generally about that theoretically necessary, and the double compound of the cuprous cyanide with the nitrogenous compound may be produced in the reaction mixture; the cuprous cyanide also may be produced in the reaction mixture from a copper salt and an alkali cyanide. A diluent may be present, several being specified, and the reaction mixture may include also salts other than copper salts, e.g. ammonium salts or halides of alkali metals, aluminium, zinc, mercury or iron. In the examples: (1) o-chloronitrobenzene, cuprous cyanide and pyridine are heated to yield o-cyanonitrobenzene; 3-nitro-4-cyanotoluene, 3 - cyano - 2 - nitrotoluene, 5 - cyano - 4 - nitro - 2 - aminotoluene and 1 - cyano - 2 - nitro - 4 - chlorobenzene are similarly obtainable from the corresponding chloro compounds; (2) o-chlorobenzoic acid, cuprous cyanide and pyridine are heated in nitrobenzene to yield phthalimide, produced by isomerization of the o-cyanobenzoic acid first formed; derivatives of o-chlorobenzoic acid, such as 2-chloro-5-methylbenzoic acid, yield correspondingly substituted phthalimides; (3) 1 - chloro - 2 - aminoanthraquinone, cuprous cyanide and cyclohexylamine are heated in nitrobenzene to yield 1-cyano-2-aminoanthraquinone; pyridine, piperidine or triethanolamine may be used instead of cyclohexylamine; 1-cyano-4-(or 5-)aminoanthraquinone, 1-cyano-2 - amino - 3 - chloranthraquinone and 1 : 4-diamino-2-cyanoanthraquinone are similarly obtainable from the corresponding chloro compounds; (4) 1-amino-2-bromanthraquinone, cuprous cyanide and pyridine are heated in nitrobenzene to yield 1-amino-2-cyanoanthraquinone; 2-amino-3-cyano- and 2-cyano-3-hydroxy-anthraquinone are similarly obtainable from the corresponding bromo compounds; (5) o-bromotoluene, cuprous cyanide and pyridine yield o-cyanotoluene; (6) p-dibromobenzene, cuprous cyanide and pyridine yield p-dicyanobenzene; (7) p-bromaniline, cuprous cyanide and pyridine yield p-cyanoaniline; 1-amino-2-nitro-4-cyanobenzene is similarly obtainable from the corresponding bromo compound; (8) 8-chloroquinoline, cuprous cyanide and quinoline yield 8-cyanoquinoline; 5 : 8-dichloroquinoline similarly yields 5 : 8-dicyanoquinoline; (9) benzyl chloride is heated with cuprous cyanide, benzyl cyanide and cuprous chloride to yield benzyl cyanide; (10) b zl-bromo-8-azabenzanthrone, cuprous cyanide and pyridine are heated in nitrobenzene to yield b zl-cyano-8-azabenzanthrone; (11) 1 - amino - 3 - chloro - 4 - nitrobenzene, cuprous cyanide and pyridine yield 1 - amino - 3 - cyano - 4 - nitrobenzene; 1 - acetylamino - 3 - cyano - 4 - nitrobenzene, 1-acetylamino-3-cyano-4-nitrobenzene, 1-amino-2-chloro-4-nitro-5-cyanobenzene, 1-amino-2-methoxy-4-cyano-5-nitrobenzene and 1-oxalyl-amino-2-methoxy-4-cyano-5-nitrobenzene are similarly obtainable from the corresponding chloro compounds; (12) 2-chloro-5-nitrobenzoic acid, cuprous cyanide and pyridine are heated in dichlorobenzene to yield 4-nitrophthalimide (cf. example 2); 3-nitrophthalimide is similarly obtainable from 2-chloro-6-nitrobenzoic acid; (13) 2 : 4-dichlorobenzoic acid, cuprous cyanide and pyridine are heated in dichlorobenzene to yield 4-chlorophthalimide (cf. example 12); 3-chlorophthalimide is similarly obtainable from 2 : 3-dichlorobenzoic acid; (14) 1-chloro-8-nitronaphthalene, cuprous cyanide and pyridine are heated in nitrobenzene to yield 1 - cyano - 8 - nitronaphthalene; (15) dibromo-allo-meso-naphthodianthrone, cuprous cyanide and pyridine are heated in nitrobenzene to yield dicyano - allo - meso - naphthodianthrone, useful as a yellow-red vat dye for cotton; (16) o-dichlorobenzene is heated with cuprous cyanide, cuprous bromide and quinoline to yield o-chlorobenzonitrile; (17) o-chloronitrobenzene is heated with cuprous cyanide, sodium or potassium cyanide and pyridine to yield o-nitrobenzonitrile; a mixture of cuprous chloride and sodium cyanide may be used in place of cuprous cyanide; (18) 4-chloro-3-nitrobenzotrifluoride is heated with cuprous cyanide, cuprous chloride and quinoline to yield 4-cyano-3-nitrobenzotrifluoride; (19) 1-bromo-2-acetylaminonaphthalene, cuprous cyanide and pyridine yield 1-cyano-2-acetylaminonaphthalene; (20) 2 : 5-dichloroacetophenone, cuprous cyanide and pyridine yield 2 - cyano - 5 - chloroacetophenone; 2-cyanoacetophenone is similarly obtainable from 2-chloroacetophenone; (21) a -bromopyridine, cuprous cyanide and pyridine yield a -cyanopyridine; (22) 2 : 5-dichlorobenzoic ethyl ester, cuprous cyanide and pyridine yield 2-cyano-5-chlorobenzoic ethyl ester; esters of 2-cyano-4-nitrobenzoic acid and of 2-cyanobenzoic acid are similarly obtainable from the corresponding chloro compounds; (23) p-dichlorobenzene is heated with cuprous cyanide, cuprous bromide and quinoline to yield p-dicyanobenzene; chlorobenzene similarly yields benzonitrile; (24) 2 : 4-dibromaniline, cuprous cyanide and pyridine yield 2 : 4-dicyanoaniline; 2 : 4-dibromoacetanilide similarly yields 2 : 4-dicyanoacetanilide; (25) o-chloranisole is heated with cuprous cyanide, cuprous bromide and quinoline to yield o-cyanoanisole; (26) p-bromacetanilide is heated with cuprous cyanide, sodium cyanide and pyridine to yield p-cyanoacetanilide; (27) 2-acetylamino-3-bromanthraquinone, cuprous cyanide and pyridine are heated in nitrobenzene to yield 2-acetylamino-3-cyanoanthraquinone; (28) 31 : 51 : 61-trichloranthraquinonebenzacridone, cuprous cyanide, and pyridine are heated in nitrobenzene to yield a monocyanodichloranthraquinonebenzacridone, useful as an orange vat dye for cotton; 4-cyano-31 : 51-dichloranthraquinonebenzacridone (a red vat dye) is similarly obtainable from 4 : 31 : 51-trichloranthraquinonebenzacridone; (29) 4 - chloro - 3 - nitroanisole, cuprous cyanide and pyridine yield 4-cyano-3-nitroanisole; (30) 4-chloro-3-nitrobenzoic acid is heated with cuprous cyanide, cuprous chloride and quinoline to yield 4-cyano-3-nitrobenzoic acid; 4-cyano-3-nitrobenzamide, 2 - cyano - 1 - nitrobenzene - 5-sulphonamide, and 2-cyano-1-nitro-5-phenylethyl sulphone are similarly obtainable from the corresponding chloro compounds; (31) 2 : 4 : 6-tribromaniline, cuprous cyanide and pyridine yield 2 : 4 : 6-tricyanoaniline; (32) 3 - methoxy - 4 - chlorobenzotrifluoride, cuprous cyanide, cuprous chloride and quinoline yield 3 - methoxy - 4 - cyanobenzotrifluoride; (33) 3-bromo - 4 - chlorobenzotrifluoride, cuprous cyanide and quinoline yield 3-cyano-4-chlorobenzotrifluoride; p - chlorobenzotrifluoride similarly yields p-cyanobenzotrifluoride. The products may be saponified to yield the corresponding carboxylic acids or their amides, and these products, and also the cyano compounds themselves, are useful as intermediates for azo dyes; some of the cyano compounds are useful also for dyeing acetate artificial silk, and others may be polymerized to yield products of high molecular weight.