The filtrate of Step A, above, is adjusted to pH 8-9
with 2 N sodium hydroxide and is heated at 35-40 °C.
while adding a 3-6% aqueous hydrogen peroxide solu
tion until samples no longer turn dark on treatment with
2N sodium hydroxide. The tan precipitate is suspended
in 1500 ml. of water, adjusted to pH 8-9 and similarly
treated with aqueous hydrogen peroxide. The combined
reaction mixtures are then acidified with concentrated
hydrochloride acid to obtain a precipitate which are re
covered by filtration, washed 3 times with water and
dried in vacuo. The crude product (mp 145-150°C) is
recrystallized from ether to obtain 4-chloro-2-nitro
phenylacetic acid, m.p. 156-159°C.
