Haruhisa Handa

Superbase character of alumina loaded with potassium by impregnation from ammoniacal solution

Al2O3 has been loaded with potassium by impregnation from an ammoniacal solution and heated under vacuum at 573 K. The resulting catalyst [K(NH3)/Al2O3] showed extremely high catalytic activity for the isomerization of alkenes. These catalysts had much greater activity than that of Al2O3 loaded with alkali metals by vapour deposition. The isomerization, over K(NH3)/Al2O3, of pent-1-ene to pent-2-ene gave a 98% yield in 6 min at 201 K. The temperature-programmed desorption and IR spectra of Al2O3 after impregnation indicated that the metal amide-like species formed on the alumina is a catalytically active species.Al2O3 loaded with KNH2 was found to be more active than K(NH3)/Al2O3 for the isomerization of 2,3-dimethylbut-1-ene. The basic strength of these catalysts was estimated to be at least H–= 37.

Highly efficient self-condensation of benzaldehyde to benzyl benzoate over KF-loaded alumina

The self-condensation of benzaldehyde to benzyl benzoate was carried out over KF-loaded alumina. The catalytic activity strongly depends on the loading amount of KF. The pretreatment of the catalyst at high temperature under vacuum is essential for the high catalytic activity. When KF (5 mmol/g-alumina) loaded alumina was evacuated at 673 K, the catalyst gave selectively benzyl benzoate, whose yield was 94.2% in 3 h at 323 K.

Characterization of strong solid bases by test reactions

The isomerization of 2,3-dimethylbut-1-ene and the decomposition of 2-methyl-3-butyn-2-ol were carried out over a number of solid base catalysts. Rubidium amide supported on alumina was the most active for the isomerization, which proceeds almost to the equilibrium in 10 min at 201 K. The isomerization is a very useful test reaction for determining the relative activities of very strong solid bases. However, weak solid bases such as K+-exchanged Y zeolite are totally inactive for the isomerization. The decomposition of 2-methyl-3-butyn-2-ol is a suitable reaction to discriminate acidic and basic catalysts. It can be also used for estimating the basic property of weak bases such as lithium hydroxide supported on alumina. However, caution is necessary for strongly basic catalysts because of strong adsorption of the products, acetylene and acetone.

Calcium oxide as a catalyst for the isomerization of 5-vinylbicyclo[2.2.1]hept-2-ene to 5-ethylidenebicyclo[2.2.1]hept-2-ene in the liquid phase

Abstract Calcium oxide prepared by decomposing CaCO 3 in vacuo shows a very high catalytic activity for the isomerization of 5-vinylbicyclo[2.2.1]hept-2-ene (VBH) to 5-ethylidenebicyclo[2.2.1]hept-2-ene (ENB), the yield of which reached 99.8% at 273 K in 10 min.

Double-bond isomerization of olefinic amines over potassium amide loaded on alumina

Potassium amine loaded on alumina heated under vacuum at 573 K (KNH2/Al2O3) readily isomerizes N,N-diethyl-3,7-dimethyl-octa-2(Z),6-dienylamine to N,N-diethyl-3,7-dimethyl-octa-1(E),3-dienylamine, which was obtained in 99% yield at 313 K for 1 h with or without solvent. The double bond at the 1 position was 100% E. The ratio of E/Z of the double bond at the 3 position was almost 1/1.

Regio- and stereoselective dimerization of phenylacetylene to (Z)-1,4-diphenylbut-1-en-3-yne over potassium amide loaded on alumina

Potassium amide loaded on alumina catalyzes the regio- and stereoselective dimerization of phenylacetylene to (Z)-1,4-diphenylbut-1-en-3-yne, the selectivity being 96% at 98% conversion of phenylacetylene.

H–D Exchange between methane and deuteriated potassium amide supported on alumina

The H–D exchange reaction between methane and deuteriated potassium amide supported on alumina (KND2/Al2O3), a strongly basic catalyst, has been investigated by FTIR spectroscopy. KND2/Al2O3 was prepared by contacting KNH2/Al2O3 with D2 at 373 K for 30 min. The N–D asymmetric and symmetric bands in KND2 were observed at 2411 and 2343 cm−1. The ND2 bending bands were observed at 1132 cm−1. The H–D exchange reaction between CH4 and KND2 proceeded at room temperature. First, the N–H bands in KNDH were observed at 3210 cm−1. and then KNDH was further converted to KNH2, whose N–H stretching bands were observed at 3238 and 3190 cm−1. The H–D exchange reaction between ethane and KND2/Al2O3 also proceeded at room temperature, but the rate was slower than that between methane and KND2/Al2O3. The lower reactivity of ethane indicates a carbanion mechanism since the acidity (pKa) of ethane (42) is lower than that of methane (40).

Catalytic Si-C bond formation by nucleophilic substitution at silicon by benzyl anions generated over KNH2 loaded on alumina

The catalytic substitution at silicon occurs in the reaction of toluene and diethylsilane in the presence of KNH2 loaded on alumina, the yield of benzyldiethylsilane being 85% in 40 h at 329 K. Benzene also reacted with diethylsilane in the presence of the catalyst to afford a 7.5% yield of benzyl diethylsilane in 20 h at 329 K.

Catalytic property of Europium supported on alumina from its ammoniacal solution

Europium supported on alumina (Eu/Al2O3) was prepared by impregnation from an ammoniacal solution of the metal. The catalytic activity of Eu/Al2O3 for the isomerization of 2,3-dimethylbut-1-ene to 2,3-dimethylbut-2-ene was examined. Eu/Al2O3 showed the highest catalytic activity for the isomerization when heated under a vacuum at 523 K, the yield of 2,3-dimethylbut-2-ene in 20 min being 81.6% at 314 K. IR spectrum shows the presence of two kinds of Eu amides. The change of the IR spectra and the catalytic activities with evacuation temperature suggest that only one of the two Eu amides is catalytically active for this base-catalyzed isomerization.