Abstract: Cyclic ketones of the general formula I ##STR1## where n is an integer from 4 to 6, are prepared by reacting aliphatic dicarbonitriles of the general formula IINC--(CH.sub.2).sub.n --CN (II),where n has the abovementioned meaning, in the gas phase in the presence of water at from 250.degree. to 500.degree. C. on solid oxide catalysts.

Abstract: Muscone of the formula I ##STR1## is prepared by a process in which an open-chain 2,15-diketone of the general formula IICH.sub.3 --CO--X--CO--CH.sub.3 (II)whereX is one of the radicals--(--CH.sub.2 --).sub.12 -- (a)--CH.dbd.CH--(--CH.sub.2 --).sub.8 --CH.dbd.CH-- (b)--CH.sub.2 --CH.dbd.CH--(--CH.sub.2 --).sub.6 --CH.dbd.CH--CH.sub.2 --(c)--CH.sub.2 --CH.sub.2 --CH.dbd.CH--(--CH.sub.2 --).sub.4 --CH.dbd.CH--CH.sub.2 --CH.sub.2 -- (d)or--CH.sub.2 --CH.sub.2 --CH.sub.2 --CH.dbd.CH--(--CH.sub.2 --).sub.2 --CH.dbd.CH--CH.sub.2 --CH.sub.2 --CH.sub.2 -- (e)is brought into contact, at from 300.degree. to 400.degree. C. in the presence of from 5 to 15% by weight, based on the amount of catalyst, of water, in the gas phase, with a fixed-bed catalyst containing TiO.sub.2, CeO.sub.2 or ThO.sub.2 as the catalytically active compound and the unsaturated cyclic ketone formed by intramolecular aldol condensation is subjected to catalytic hydrogenation.

Abstract: Muscone of the formula I ##STR1## is prepared by a process in which an open-chain 2,15-diketone of the general formula IICH.sub.3 --CO--X--CO--CH.sub.3 (II)where X is one of the radicals--(--CH.sub.2 --).sub.12 -- (a)--CH.dbd.CH--(--CH.sub.2 --).sub.8 --CH.dbd.CH-- (b)--CH.sub.2 --CH.dbd.CH--(--CH.sub.2 --).sub.6 --CH.dbd.CH--CH.sub.2 --(c)--CH.sub.2 --CH.sub.2 --CH.dbd.CH--(--CH.sub.2 --).sub.4 --CH.dbd.CH--CH.sub.2 --CH.sub.2 -- (d) or--CH.sub.2 --CH.sub.2 CH.sub.2 --CH.dbd.CH--(--CH.sub.2 --).sub.2 --CH.dbd.CH--CH.sub.2 --CH.sub.2 --CH.sub.2 -- (e)is brought into contact, at from 300.degree. to 400.degree. C. in the presence of from 5 to 15% by weight, based on the amount of catalyst, of water, in the gas phase, with a fixed-bed catalyst containing TiO.sub.2, CeO.sub.2 or the ThO.sub.2 as the catalytically active compound and the unsaturated cyclic ketone formed by intramolecular aldol condensation is subjected to catalytic hydrogenation.

Abstract: Ketones of the general formula (I) ##STR1## where R.sup.1 and R.sup.2 independently of one another are each alkyl, cycyloalkyl, arylalkyl, aryl or hetaryl, and one or more of the radicals R.sup.1 and R.sup.2 carry one or more hydrogen atoms on the .alpha.-carbon atom, are prepared by reacting two carboxylic acids of the general formulae (IIa/IIb), R.sup.1 --COOH (IIa) and R.sup.2 --COOH (IIb) or by reacting a carboxylic acid R.sup.1 --COOH (IIa) and a ketone ##STR2## or by reacting a mixture of IIa, IIb and Ib, in the gas phase in the presence of a catalyst, by a process in which a catalyst is used whose active material contains at least 50% by weight of titanium dioxide having a specific surface area greater than 10 m.sup.2 /g.0.