To a 2-L flask equipped with a condenser were added 137 g anthranilic acid (1 mol),94.5 g chloroacetic acid (1 mol), and 1 L water; the mixture was
heated for 3 h. On cooling,crystals of phenylglycine-o-carboxylic acid were separated out. These were filtered off and recrystallized from hot water
to give∼1000 g of such acid.The mixture of 1 eq. phenylglycine-o-carboxylic acid, 3 eq. NaOH, and 1 eq. water was heated at 235–265◦C in the
absence of air until the alkaline mass assumed an intense orange color, whereupon it was allowed to cool and subsequently dissolved in water. Passing
a stream of air through the aqueous solution resulted in the precipitation of indigo. No yield was given |
