Anthranilic Acid
Dissolve 8.0g of sodium hydroxide in 30ml of distilled water in a 100ml erlenmeyer flask containing a magnetic stirrer bar and cool the solution with
stirring in an ice bath. Add the bromine [2.1ml, 6.5g, 41mmol] (CARE!) in one portion and stir the mixture vigorously until all of the bromine has
reacted [look for the disappearance of the brown colouration] and the mixture has cooled to ca. 0*C. Continue vigorous stirring and add all of the
finely powdered phthalimide [5.9g, 40mmol] to the solution, followed by a solution of a further 5.5g of sodium hydroxide in 20ml of water. Remove the
ice bath, allow the temperature of the mixture to rise spontaneously to ca. 70*C and continue stirring for a further 10 min. Cool the clear solution
in an ice bath with stirring (if the mixture is cloudy, filter under gravity before cooling), and add concentrated hydrochloric acid dropwise with a
pipette until the solution is just neutral when a drop is spotted onto universal indicator paper (ca. 15ml should be necessary). If too much acid is
added, the mixture may be brought back to neutrality by adding further quantities of sodium hydroxide solution, but it is better to avoid this by
careful addition of acid in the first instance. Transfer the mixture to a 500ml beaker (foaming occurs in the next stage) and precipitate the
2-aminobenzoic acid by addition of glacial acetic acid (ca. 5ml). Filter off the precipitate with suction, wash the residue with 10ml of cold water
and dissolve it in the minimum quantity of boiling water containing a little activated charcoal. Filter the hot solution to remove the charcoal and
cool the filtrate with ice. Filter off the pure acid with suction, dry the residue with suction on the filter for 5 min and complete the drying to
constant weight in an oven at 100-120*C
Vogel 5th
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