1,1-Diisopropylethylene

Synthesis

Triphenylmethylphosphonium iodide (8.55 g, 21.2 mmoles) was weighed into a dry 100 mL round bottom flask, and 40 mL of dry tetrahydrofuran were cannulated into the reaction vessel. Phenyllithium in cyclohexane (11.8 mL of a 1.8 M solution, 21.2 mmoles) was added dropwise using an addition funnel. A color change from yellow to dark brown was observed. The mixture was stirred for 3 hrs at room temperature. 2,4-Dimethyl-3-pentanone (8) (2.4 g, 21.2 mmoles) was added slowly to the reaction mixture resulting in a color change from brown to gray. After stirring for an additional hour, a condenser was connected to the reaction vessel, and the mixture was heated at reflux for 24 hours.
The mixture was allowed to cool to room temperature and extracted successively with aqueuos of 5% HCI, 10% NaHCO3, and distilled water. The organic layer was separated and dried over anhydrous MgSO4, and the drying agent was removed by gravity filtration. The solvent was removed by fractional distillation. Gas 61 chromatographic analysis indicated the presence of 1,- diisopropylethylene (-70%) (9), unreacted ketone (-20%) . The distillate was purified by column chromatography on silica gel (60-100 mesh, 2 in height and 2 in i.d.), using hexane as the eluant. The 1,1-diisopropylethylene was identified and characterized by 1 H and 13C-NMR spectroscopy.