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0 °C

N,N-Dimethylhydrazine (42.0 mL 0.55 mol) was added dropwise to trans-2-pentenal (42.06 g, 0.50 mol) at such a rate that the reaction temperature could be maintained at about 0° C. The mixture was then stirred for 1 h at ambient temperature, and the organic phase separated and dried (K2CO3). Distillation (bp 84°-86° C., 25 mm Hg; lit bp 60° C., 15 mm Hg) through a 10 cm Vigreaux column gave trans-2-pentenal N,N-dimethylhydrazone (12) (51.3 g, 81%): n20 1.5104; IR (neat) 2960, 2870, 2850, 2820, 2780, 1565, 1470, 1460, 1445, 1265, 1135, 1030, 970 cm-1 ; 1H NMR (CDCl3) δ 0.98 (t, 3H, J=7.4 Hz), 2.16-2.05 (m, 2H), 2.76 (s, 6H), 5.82 (dt, 1H, J=15.6, 6.3 Hz), 6.14 (dd, 1H, J=15.6, 8.8 Hz) 6.97 (d, 1H, J=8.8 Hz).

1. customthe organic phase separated
2. dry with materialdried (K2CO3)
3. distillationDistillation (bp 84°-86° C., 25 mm Hg; lit bp 60° C., 15 mm Hg) through a 10 cm Vigreaux column