[7440-23-5]  · Na  · Sodium-Alumina  · (MW 22.99) (Al2O3)

[1344-28-1]  · Al2O3  · Sodium-Alumina  · (MW 101.96)

(isomerization of alkenes;1 isomerization of amines;2 a form of high surface area sodium metal3)

Physical Data: sodium: mp 97.8 °C; d 0.968 g cm-3. Alumina: d 3.97 g cm-3.

Preparative Method: basic Alumina is dried at 150-200 °C and vigorously stirred with Sodium metal under an inert atmosphere until cool. The 2-10% sodium on alumina mixtures (as typically used for alkene isomerization) are free flowing, nonpyrophoric solids ranging from bright to dark gray; the color intensity markedly increases with increasing metal content.1,4-6

Handling, Storage, and Precautions: sodium metal reacts violently with water to produce flammable H2 gas. High sodium-containing Na/Al2O3 catalysts may be pyrophoric. In case of fire, do not expose to water, CO2, or vaporizable liquids. The activity of the catalyst is lost upon exposure to air or moisture.

Alkene Isomerization.

Isomerization of alkenes may be accomplished under mild conditions. Thus methylenecyclobutane is converted to methylcyclobutene in nearly quantitative yield, avoiding the formation of isoprene, common with higher temperature routes (eq 1).4 Both 1-butene and 1-pentene have been isomerized to the internal alkene with this catalyst.5,7 The system operates under kinetic control, favoring the initial formation of the cis-isomer over the trans-isomer (eq 2). When cyclic dialkenes are treated with Na/Al2O3, dehydrogenation can follow the reversible C=C bond shift (eq 3).1 More forcing conditions can cause skeletal rearrangement (eq 4).1

Miscellaneous Uses.

This catalyst has also been used to racemize optically active benzyl amines.2 Na/Al2O3 has also been used as a sodium metal source in the large scale preparation of sodium cyclopentadienide.3 Recently, this method has been abandoned for the use of oil-free Sodium Hydride, avoiding the need to filter Al2O3 from the product.8

1. Rienacker, R.; Graefe, J. AG(E) 1985, 24, 320.
2. U.S. Patent 3 970 700, 1976 (CA 1975, 83, 78 820a).
3. Paquette, L. A.; Wyvratt, M. J. JACS 1974, 96, 4671.
4. Shabtai, J.; Gil-Av, E. JOC 1963, 28, 2893.
5. Haag, W. D.; Pines, H. JACS 1960, 82, 387.
6. This catalyst has also been prepared by the sodium metal deposition on alumina; see: Wozniewski, T.; Malinowski, S. Bull. Acad. Pol. Sci., Ser. Sci. Chim. 1978, 26, 829 (CA 1979, 90, 210 719a).
7. Pines, H.; Haag, W. JOC 1958, 23, 328.
8. Taylor, R. T.; Pelter, M. W.; Paquette, L. A. OS 1989, 68, 198.

Dean R. Lagerwall

Occidental Chemical Corp., Grand Island, NY, USA

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