Synthesis
In a 100?mL round bottom flask, isophorone 3.45 g (25 mmol) and malononitrile 1.65 g (25 mmol) were dissolved in anhydrous ethanol 50 mL. Then sodium acetate trihydrate (1g, 12.5mmol) was added. The mixture was heated to 80°C and stirred for about 12h. The reaction progress was monitored by TLC. Once the starting isophorone disappeared on TLC and the target spot formed regularly, the reaction mixture was cooled to room temperature. The solid sodium acetate trihydrate was removed by filtration. 25mL Ethanol was removed in a vacuum. The left mixture stood still at 27°C overnight. The crystals were collected by filtration and washed carefully with cooled anhydrous ethanol. 2-(3,5,5-trimethylcyclohex-2-en-1-ylidene)malononitrile can be obtained by recrystallization one more time from ethanol.
Structure and conformation
2-(3,5,5-trimethylcyclohex-2-en-1-ylidene)malononitrile (C12H14N2), monoclinic, P21/c (no. 14), a = 10.16290(10)Å, b = 8.25800(10)Å, c = 13.4328(2), β = 95.910(1)°, V = 1121.36(2)Å3, Z = 4, R gt (F) = 0.0380, wR ref (F2) = 0.1126, T = 294 K.
