1. o-nitro toluene , commercial, min 98%
2. Cyclohexane, commercial, 99%
3. Sodium ethoxide, commercial
4. Isoamyl formate, Prepared by refluxing isoamyl alcohol with formic acid and distilling. Purity 98.5%

o-Nitro toluene (550 g, 4.01 mol), cylohexane (2000 mL) and isoamylformate (464 g, 4 mol) are charged to a dry 5 Lt -3 necked flask carrying nitrogen inlet, thermometer pocket and mechanical stirrer at room temperature (whole setup should be in cooling tub to give sufficient cooling for 16-18h). With a slow stream of nitrogen, the reaction mass is cooled to about –2 degree centigrade. At this point, slowly add sodium ethoxide (272 g, 4 mol) in lots (about 10-20 g each lot) slowly over a period of 4 hours keeping the temperature below 3 oC. After complete addition, stir the reaction mixture at the same temperature for additional 8-9 h. T this point, one can observe lots of solid formation in the reaction mixture. Add water ( 2 Lt) and adjust the pH to about 6 and filter the solid. Wash the solid with cyclohexane ( 200-250 mL) to get almost 425-450 g o,o-dinitro bibenzyl. This can be dried at 60-70 oC for 6 h to get about 350-360 g product (64% ). This is almost pure by NMR. If required this can be crystallized by acetone to get light yellow product.

 

1. This reaction works only in cyclohexane and other hydrocarbons like n-hexane/heptane. There is no reaction in solvents like toluene/benzene.
2. Quality of sodium ethoxide is important. One can also use commercially avalable sodium tert butoxide.
3. Reaction should be carried out at about 0 degree . Hiigher temperature gives dark oily mass. One cannot recover starting material from this oily mass.
4. Nitrogen should be purged in such a way that it should not carry away all cyclohexane. If required, one can add additional cyclohexane to makeup for the loss.

Melting pont : 120-123 oC

1H NMR (CDCl3, 300 MHz): δ 7.95 (d,2H ), 7.56-7.52 & 7.43-7.36 (2 m,6H), 3.25 (s, 4H)

13C NMR (CDCl3, 75 MHz): δ 149.17, 135.96, 133.27, 132.44, 127.52, 124.80, 34.38

 

W. Schindler, US Patent, 1956, 2764580