Here I made some aluminium isopropoxide, which is a useful catalyst for both reductions of ketones and aldehydes to alcohols and vice versa. The selectivity for ketones and aldehydes in reductions, as well as the lacking overoxidation make this a great substance to have around in both hobby and professional labs. This procedure is mostly adapted from a video by NileRed and a modification thereof by Abromination on the Explosions&Fire Discord server, who used gallium instead of toxic mercury chloride, which worked quite well. The iodine is not necessary if your aluminium is fresh enough, but it is a good idea to have some around when doing this reaction regardless in case it doesn’t want to start.
| Substance | M [g/mol] | n [mmol] | m [g] | V [ml] | Eq. |
|---|---|---|---|---|---|
| Aluminium shavings | 26.98 | 371.0 | 10.00 | – | 1.0 |
| Gallium | 69.72 | 14.9 | 1.04 | – | 0.04 |
| Iodine | 253.80 | 0.6 | 0.15 | – | 0.002 |
| Isopropanol (dry) | 60.10 | 1400 | 86.00 | 110 | 3.9 |
Experimental:
To a dried 250 ml three neck flask was added Aluminium (10.00 g, 0.371 mol, 1.0 Eq.) in the form of shavings and Gallium (1.04 g, 0.17 ml, 14.9 mmol, 4 mol%). The flask was sealed and evacuated, after which a solution of Iodine (0.15 g, 0.6 mmol, 0.2 mol%) in dry Isopropanol (110 ml, 3.9 Eq.) was added. A previously dried reflux condenser, fitted with a drying tube containing anhydrous Magnesium sulfate, was attached and the mixture was refluxed for a total of 8 hours. Distillation of excess Isopropanol followed by short path distillation yielded Aluminium isopropoxide (54.91g, 269 mmol, 73%) as a viscous, colourless liquid which solidified over time (fraction: 10 mBar, 120 – 130 °C).
