pHarmacist
(Hive Addict)
03-03-03 16:21
No 413466
      Two Methods for the Preparation of Phthalimide
(Rated as: excellent)
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pHarmacist's voice: A very neet way of preparing primary amines is by using Gabriel Synthesis. Most of you are familiar with Gabriel synthesis. For you that are not; it's basicly conversion of alkyl halides to corresponding primary amines by treatment with potassium phthalimide, followed by hydrolysis. In my opinion Gabriel Synthesis is a great route to phenetylamines. Below I introduce to you two methods for production of phthalimide - a reagent that is universaly used for Gabriel synthesis.

Mechanism for Gabriel synthesis:


Phthalimide:

Method 1.    Place 100 g (0.675 mol) of phthalic anhydride and 105 mL of concentrated ammonia solution in a 1-litre round-bottomed flask fitted with a wide air condenser (10 mm in diameter). Heat on a sand bath, gradually at first until the mixture is in a state of quiet fusion and forms a homogeneous melt (the temperature reaches 300C in about 1.5-2 hours; all the water is evaporatedduring the first hour). Shake the flask occasionally during the heating and push down any material whicj sublimes into the condenser with a glass rod. Pour the contents of the flask while still hot into a porcelain basin, allow to cool and grind to a fine powder in a mortar.

The phthalimide (95 g, 96%) is practically pure and melts at 233-234C. It may be recrystallised from EtOH, but the solubility is only slight (about 5%).


Method 2.    Intimately mix 99 g (0.67 mol) of pure phthalic anhydride and 20 g (0.33 mol) of urea, and placethe mixture in a 1-litre, long-necked, round-bottomed flask. Heat the flask in an oil bath at 130-135C. When the contents have melte, effervescence commences and gradually increases in vigour; after 10-20 minutes, the mixture suddenly froths up to about three times the original volume (this is accompanied by rise in temperature to 150-160C) and becomes almost solid. Remove the heat from beneath the bath and allow to cool. Add about 80 mL of water to disintegrate the solid in the flask, filter at the pump, wash with a little water and then dry at 100C.

The yield of phthalimide, m.p. 233C (i.e practically pure), is 86 g (87%). If desired, the phthalimide may be recrystallised from 1200 mL of industrial spirit; the first crop consists of 34 g of m.p 234C, but further quantities may be recovered from mother-liquor.

Reference:  VOGEL'S Textbook of Practical Organic Chemistry (5:th edition), page 1065-1066

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    Aurelius
(Hive Addict)
03-03-03 16:38
No 413473
      Anthranilic Acid  Bookmark   

Don't know if this has been posted here before, but it's relevant to the use of the Imide:

Take the phthalimide and stir it in 25% aqueous KOH for 1-2 hours at 0*C and then acidify with HCl to give Phthalamidic acid. 

This acid reacted with NaOCl gives anthranilic acid.

OR

The Imide can be reacted with basic (NaOH) NaOCl in water at 80*C  and then acidified to give Anthranilic acid. 

The more anthranilic acid can recovered from solution after initial separation by the use of its Cu salt.

(p 660-661 Org. Chem. 3rd ed. Fieser&Fieser)

 
 
 
 
    Rhodium
(Chief Bee)
03-03-03 16:47
No 413477
      Copper anthranilate  Bookmark   

Aurelius: It has been detailed at my page in the Quaalude FAQ, but that tidbit about copper anthranilate was new to me. I suppose it is the Cu2+ salt?
 
 
 
 
    Aurelius
(Hive Addict)
03-03-03 16:57
No 413487
      copper salt  Bookmark   

I dont' know.  the book didn't state which form was used. I would suppose Cupric as it is available more cheaply in the form of CuSO4
 
 
 
 
    Aurelius
(Hive Addict)
03-03-03 18:49
No 413518
      Another Anthranilic synthesis  Bookmark   

Anthranilic acid can be synthesized by the fusion of leucoindigo with KOH at lower temperatures. 
 
 
 
 
    Aurelius
(Hive Addict)
03-03-03 19:34
No 413531
      Anthranilic acid by hypochlorite  Bookmark   

Post 108807 (dormouse: "Anthranilic acid from phthalimide using OTC sodiumhypochlorite solution  -Methaco(s)m", Novel Discourse)