The reduction of alkyl‐substituted benzoic acids with lithium in liquid ammonia has been investigated. Without added proton donor the aromatic acid yields a dianion which can either be protonated with ammonium chloride or alkylated to give the corresponding 1,4‐dihydrobenzoic acid and 1‐alkyl 2,5‐cyclohexadiene‐1‐carboxylic acid, respectively. In the presence of ethanol, 3‐ and 4‐alkylbenzoic acids yield either 1,4‐dihydro or 4,5‐dihydro products depending on the working up procedure Benzoic acid behaves similarly. Water is shown to be a useful proton donor in the reduction of 3‐ and 4‐alkylbenzoic acids to 1,4‐dihydro products. 2‐Alkylbenzoic acids yield 1,4‐dihydro products, irrespective of the experimental procedure. Experiments with 4‐deuterobenzoic acid show the first proton addition to be irreversible in ammonia as well as in ammonia‐ethanol. Some thirty new alkyl‐ and dialkyl‐cyclohexadienecarboxylic acids are described.

The heterogeneous hydrogenation of hexamethyl-Dewar-benzene (1) over various transition metal catalysts has been studied. At 25 selective (> 95 %)cis ,ex0 addition of hydrogen was observed yielding 1 ,2,3,4,5 endo ,6endo-hexamethylbicyclo[2.2.0]hex-2-ene (2). Hydrogenation at 50°, of 2 and of 1,2,3,4,5endo,6exo-hexamethylbicyclo[2.2.0]hex-2-ene (3) was found to be less stereospecific; the extent of trans addition increased in the order Ru < Rh < Pd < Pt.Homogeneous hydrogenation of 1 has been accomplished using platinum-tin complexes; a 3 : 1 mixture of 3 and 2 was formed. The mechanism of this homogeneous hydrogenation is discussed on the basis of deuteration experiments.The

Die Umsetzung von Cyclohexanon (I) zum Diäthylacetal (II) wird als Testreaktion benutzt zur Untersuchung verschiedener Katalysatoren: sulfonierte Polystyrolharze (A), SiO2 ‐AI2O3 ‐Krackkatalysatoren (B), Molekularsiebe Typ Y (ausgetauscht mit multivalenten Kationen, besonders Kationen Seltener Erden) (C).

Sowohl aus den Cyclohexanolen (I) als auch aus dem Propanol (IV) wird durch Koch‐Haaf‐Carboxylierung die Carbonsäure (II) im Gemisch mit der Propionsäure (III) dargestellt.

Die Reduktion erfolgt nach Methode A, B, C und D. Bei Methode A wird Li zur Benzoesäure in flüssigem Ammoniak und Äthanol gegeben und nachfolgend mit Ammoniumchlorid behandelt.