Benzaldehyde → 2-[(E)-Benzylidene]cyclohexanone

Participants

Reaction Conditions

Reaction Steps

Into an inert 100 gallon reactor, there is drawn 29.3 kg of cyclohexanone from a grounded drum on a weight scale. The reactor is vented with nitrogen and then 28.5 kg of benzaldehyde is added. Then 125 liters of deionized water is metered into the above mixture. The vessel is closed and `reinerted` with nitrogen. To the resulting reactor contents there is added, from a grounded drum on a weight scale, a 50 percent (w/v) solution of sodium hydroxide in water solution, (10.6 kg), while stirring the mixture. The resulting mixture is stirred and heated to reflux (about 98° C.). under an atmosphere of nitrogen. The mixture is held at reflux temperature for about three hours and then stirred and cooled overnight. The resulting cooled reaction mixture is extracted once with a 198 liter batch of methylene chloride, separating the aqueous layer, and then again with 132 liters of methylene chloride, neutralizing and discarding the aqueous layer. The combined methylene chloride liquid layers are washed with 284 liters of water and then with 284 liters of water containing 50 ml of acetic acid. After aqueous layer separation, the methylene chloride liquid layer is dried over sodium sulfate with stirring. The resulting dried methylene chloride layer is concentrated to an oil using 35° C. jacket water temperature and jet vacuum procedures. The (E)-2-(benzylidene)cyclohexanone is crystallized by dissolving the oily residue in 60 liters of Skellysolve® B and seeding with authentic material and cooling the vessel overnight by circulating a cooled water/methanol mixture through the reactor jacket. The pale yellow crystals are collected on a 24-inch filter, washed with Skellysolve® B, and recrystallized from 75 gallons of Skellysolve® B by heating to 50° C. to effect dissolution and then cooling the tank contents to 0° C. Alternatively, we have used isopropanol in this crystallization step with approximately equal effectiveness in terms of quality of the crystalline intermediate (E)-2-(benzylidene)cyclohexanone. The crystalline intermediate is dried in a vacuum oven at room temperature to give about 16.4 kg (33 percent yield) of the (E)-2-(benzylidene)cyclohexanone, m.p. 47°-54° C. (Lit. m.p. 54° C.). TLC analysis (silica gel GF; 5 percent ethyl acetate in Skellysolve® B developer) indicates the presence of a small amount of a less polar impurity, identified as ##STR10## on the basis of isolation and melting point.

Provenance & Evidence