how can anthranilic acid be prepared from pthalimide?

how can anthranilic acid be prepared from pthalimide?


1 Answers

askIITians Faculty 747 Points
8 years ago
When it comes to Quaalude chemistry we still have one major victory left: An useful/simple/OTC anthranilic acid from naphthalene synthesis. Rhodium has a long time ago pointed out that phthalimide could probably be converted to anthranilic acid using a commercial NaOCl solution such as "Clorox".

Test #1

225ml Alclorite and 10.0g NaOH were mixed in a 500ml Erlenmeyer. 8.0g NaOH and 80ml H2O were mixed in another 250ml Erlenmeyer. 15.0g phthalimide was grinded to a very fine powder. The Alcorite solution was cooled to about 0°C, perhaps a bit cooler. Half of the phthalimide was added in portions, the solution was again cooled in the freezer before the rest was added, in portions. When it was all dissolved the solution was a bit yellow-orange.

The 80ml NaOH solution from above was added and the temperature was raised to 80°C and held there for two minutes. Brought it back to room temperature using cold water.

Transferred the mixture to a 1000ml beaker and neutralized it with about 110ml of 10% hydrochloric acid. The pH was 7.0-7.5. A precipitate formed and it was removed by filtration. (After drying in an oven the amount was 1.93g). Now glacial acetic acid was added to the solution, a total of 22ml was used. A lot of CO2 was formed. A mess precipitated and the solution was filtered. Rather dirty but not hopelessly dirty "crystals" were collected. They were dried in an oven at 100°C (darkened a little bit) and before further purification the yield was 8.48g (60,6%).

Test #2

260ml Alclorite (15-2/15 = 225/260, just a thought) and 12.0g NaOH were mixed as above and cooled to -10°C. A NaOH solution in water was prepared just as above and cooled to +4°C. 15.0g Phthalimid was grinded into a very fine powder and added in portions, while stirring fast, to the Alclorite solution. When it had all dissolved the solution was not more (Alclorite is slightly yellow) colored at all, quite the opposite in fact. The temperature of the solution was now +5°C. Added the 80mls of NaOH solution and begun to heat the mixture. At 30°C it quickly turned rather deep orange/red/brown. Heated it up to 90°C let it cool to 80°C over 5 minutes and then cooled it actively. The solution was much more colored then in Test #1. Neutralized the solution in a 1000ml beaker with a little less then 50ml 30% hydrochloric acid. A precipitate was formed, proceed as above and got 2.34g dirty phthalimide back (It "must" be phthalimide, it will not dissolve in water, has no taste at all (slightly salty but that is because of the NaCl solution it came from), and it look like phthalimide).

Now GAA was added as above, 20ml, which was more than enough. Filtered, dried, and ended up with 11.83g of very, very dirty crystals. 11.83g was more then possible if we consider the >2g phtalimide we got back, and the fact that the solution was colored as hell. Well, the yield of PURE crystals from this will be much lower.

Test #3

210ml cold Alclorite and 8.0g was mixed in a 500ml Erlenmeyer and we cooled it to -10°C. 80ml ~10% NaOH solution was prepared as before and cooled to +5°C. 15.0g Phthalimide as a very, very fine powder was added, all at once, and the flask was plugged and stirred at 1600rpm. The solution became as above not more colored then before, rather less colored. Cooled it again to +3°C. Added the NaOH solution and put the solution in the cold fridge (+3°C). I stood there overnight (yes, even Dr Dream sleeps). Now it was placed in room temperature and left there for 3.5 hours. At ~20°C it was just as achromatic as before. Heated it to 85°C and kept it there for 5 minutes, the solution hardly darkened at all! (2 minutes at 80°C would possibly not be noticeable!). Cooled fast to room temp, then further to +5°C. Neutralized with 31.5ml 30% hydrochloric acid (this made the solution yet a bit more colored, but not much compared to Test #1). Solution got cloudy, filtered, 2.07g when dry. Now GAA was added (solution in 1000ml beaker!), 15ml was probably enough, but we added 20ml. Nice crystals formed! filtered and dried. Only very slightly yellow/brown, maybe pure enough for whatever uses. The yield was a fair 9.42g (67.4%). When we subtracted for the 2g phthalimide we got back, the effective yield of almost pure crystals was 77.7%!

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