The invention comprises selenium compounds of the formula A-Se-R, in which A represents an aromatic residue and R one of the radicals <FORM:0788725/IV (b)/1> in which both X1's, together with the -C-C-group, represent a cycloalkyl radical, X2 represents a phenyl radical or an alkyl group, X3 and X4 each represents an alkyl group, both X5's, together with the -C-C-group, represent a pyrane radical, and Y represents an acyl group or a hydroxyl group, and also a method of making such compounds by reacting a compound of the formula: A-Se-O-Acyl with an unsaturated organic compound and, if desired, a resulting compound containing an O-acyl group is reacted with a hydrolysing agent, or carboxylic acid may be split off to give an unsaturated compound. A may be a vattable residue, e.g. an anthraquinone residue, attached to selenium in a -position, and may contain alkoxy groups. The products dye or print cellulose acetate, or nylon. Unsaturated compounds specified are ethylene, vinyl acetate, allyl bromide, isobutylene, butadiene, styrene, 1 - methyl - 2 - phenylethylene, 1 - methyl - 1-phenyl-ethylene, cyclohexene, dihydropyrane. The compounds of the formula A-Se-O-Acyl may be prepared (1) from compounds of the formula A-Se-O-Alkyl by reaction with the acid from which the acyl residue is derived, or (2) from a compound A-Se-Halogen and a salt of said acid. In examples, anthraquinone - 1 - selenenic acid methyl ester is boiled with glacial acetic acid to give anthraquinone-1-selenenyl acetate which is reacted with (1) cyclohexene, to give 1-(21-acetoxy - cyclohexylselenyl) - anthraquinone, which is hydrolysed with alcoholic potash to remove the hydroxy group, (2) styrene, to give 21 - acetoxy - 21 - phenyl - ethylselenyl - anthraquinone, (3) vinyl acetate, to give an ethylidene diacetate, (4) 1-methyl-1-phenylethylene, (5) isobutylene, (6) ethylene, (7) dihydropyrane, (8) butadiene-1,3. Also in examples, (9) 1-methoxyanthraquinone - 4 - selenenyl bromide is reacted with acetic acid to give 1-methoxyanthraquinone - 4 - selenenyl acetate which is reacted with cyclohexene, (10) 1-hydroxyanthraquinone-4-selenenyl acetate is reacted with vinyl acetate, (11) 1-nitrobenzene-2-selenenyl acetate is reacted with vinyl acetate to give a compound of the formula: <FORM:0788725/IV (b)/2> A dyeing example is given.ALSO:The invention comprises selenium compounds of the formula A-Se-R, in which A represents an aromatic residue and R one of the radicals: <FORM:0788725/IV (b)/1> in which both X1's, together with the -C-C-group, represent a cycloalkyl radical, X2 represents a phenyl radical or an alkyl group, X3 and X4 each represents an alkyl group, both X'5s, together with the -C=C- group represent a pyrane radical, and Y represents an acyl group or an hydroxyl group, and also a method of making such compounds by reacting a compound of the formula: A-Se-O-Acyl with an unsaturated organic compound and, if desired, a resulting compound containing an O-acyl group is reacted with a hydrolysing agent, or carboxylic acid may be split off to give an unsaturated compound. A may be a vattable residue, e.g. an anthraquinone residue, attached to selenium in a -position and may contain alkoxy groups. The products dye or print cellulose acetate, or nylon. Unsaturated compounds specified are ethylene, vinyl acetate, allyl bromide, isobutylene, butadiene, styrene, 1 - methyl - 2 - phenylethylene, 1 - methyl - 1-phenyl-ethylene, cyclohexene, dihydropyrane. The compounds of the formula A-Se-O-Acyl may be prepared (1) from compounds of the formula A-Se-O-Alkyl by reaction with the acid from which the acyl residue is derived, or (2) from a compound A-Se-Halogen and a salt of said acid. In examples, anthraquinone-1-selenenic acid methyl ester is boiled with glacial acetic acid to give anthraquinone-1-selenenyl acetate which is reacted with (1) cyclohexene, to give 1 - (21 - acetoxycyclohexylselenyl) - anthraquinone, which is hydrolysed with alcoholic potash to remove the hydroxy group; (2) styrene, to give 21-acetoxy-21 - phenyl - ethylselenyl - anthraquinone; (3) vinyl acetate, to give an ethylidene diacetate; (4) 1 - methyl - 1 - phenylethylene; (5) isobutylene; (6) ethylene; (7) dihydropyrane; (8) butadiene-1.3. Also in examples: (9) 1-methoxyanthraquinone - 4 - selenenyl bromide is reacted with acetic acid to give 1-methoxy-anthraquinone - 4 - selenenyl acetate which is reacted with cyclohexene; (10) 1-hydroxy-anthraquinone - 4 - selenenyl acetate is reacted with vinyl acetate; (11) 1-nitrobenzene-2-selenenyl acetate is reacted with vinyl acetate to give a compound of the formula: <FORM:0788725/IV (b)/2> A dyeing example is given.