In a
1-l. flask equipped with a
mechanical stirrer are placed
200 g. (1.27 moles) of o-chloronitrobenzene and 300 g. of clean dry sand. The mixture is heated in an
oil bath to 215–225°, and then
200 g. of copper bronze (Note
1) is slowly added, the addition requiring about 1.2 hours (Note
2). The temperature is kept at 215–225° for 1.5 hours longer, the stirring being continued throughout. The mixture is poured while hot into a
beaker containing 300–500 g. of sand and is then stirred until small clumps are formed; upon cooling, these are broken up in a
mortar (Note
3). The mixture is boiled 10 minutes with two
1.5-l. portions of ethanol and removed by filtration each time. The filtrates are cooled in an
ice bath, and the
2,2'-dinitrobiphenyl is collected on a filter (Note
4). A second crop is obtained by concentrating the filtrate. The product is dissolved in hot
ethanol (Note
5), and the solution is treated with
Norit, filtered, and cooled in an
ice bath. The solid is recrystallized from hot
ethanol and is obtained as pure, yellow crystals melting at
123.5–124.5° (cor). The yield is
80–95 g. (
52–61%).