Abstract: A process for the preparation of tetrahydrofuran or tetrahydrofuran and .gamma.-butyrolactone from the product of the hydrogenation of maleic acid, succinic acid, maleic anhydride, succinic anhydride and/or fumaric acid, by treating the crude hydrogenation product, without prior work-up, at from 100.degree. to 300.degree. C. with a protic acid, and isolating pure tetrahydrofuran and .gamma.-butyrolactone from the resultant reaction mixture by distillation.

Abstract: In a tube bundle reactor for carrying out catalytic organic reactions in the gas phase, comprising reaction tubes (A) arranged between tubesheets (B), the reaction tubes have an inside diameter ranging from 0.5 to 3 cm, the ratio of reaction tube length to inside diameter ranges from 2 to 10, and the reaction tubes (A) are surrounded by a fluid heat transport medium flowing in the crosswise direction; said tube bundle reactor is useful in particular in exothermic organic reactions.

Abstract: Process for the preparation of 1,4-butanediol or tetrahydrofuran or both by the catalytic hydrogenation of maleic anhydride, succinic anhydride, maleic acid, succinic acid, fumaric acid, or the alkyl esters of these acids at temperatures of from 100.degree. C. to 350.degree. C. and pressures of from 50 bar to 350 bar over a catalyst containing cobalt as the active metal and one or both of the elements copper and phosphorus, if necessary in the presence of an aliphatic alcohol.

Abstract: An improved process for the preparation of unsaturated ketones of the general formula I ##STR1## where R.sup.1 is --CH.sub.3, ##STR2## and R.sup.2 and R.sup.3 are different and each is H or --CH.sub.3, by reacting an aldehyde of the general formula II ##STR3## with a molar excess of acetone or methyl ethyl ketone at an elevated temperature in the presence of an aqueous alkali metal hydroxide solution, wherein (a) all the reactants are mixed thoroughly, (b) the temperature is kept at from 10 to 120.degree. C. above the boiling point of the lowest-boiling component and (c) the pressure is kept at from p to 100 bar, where p is the vapor pressure of the mixture at the reaction temperature.The products methylpseudoionone, dimethylpseudoionone, pseudoirone, methylpseudoirone and dimethylpseudoirone are useful scents and scent intermediates. In addition, pseudoionone is an important intermediate for the industrial preparation of vitamin A, and 6-methyl-hepta-3,5-dien-2-one is a sought-after aromatic.