Phthalimide
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Phthalimide is the organic compound with the formula C6H4(CO)2NH. It is the imide derivative of phthalic anhydride. It is a sublimable white solid that is slightly soluble in water but more so upon addition of base. It is used as a precursor to other organic compounds as a masked source of ammonia.[1]
Uses
File:Folpet.png Folpet, a phthalimide, is a commercial fungicide.[2]
Phthalimide is used as a precursor to anthranilic acid, a precursor to azo dyes and saccharin.[1]
Alkyl phthalimides are useful precursors to amines in chemical synthesis, especially in peptide synthesis where they are used "to block both hydrogens and avoid racemization of the substrates".[3] Alkyl halides can be converted to the N-alkylphthalimide:
- C6H4(CO)2NH + RX + NaOH → C6H4(CO)2NR + NaX + H2O
The amine is commonly liberated using hydrazine:
- C6H4(CO)2NR + N2H4 → C6H4(CO)2N2H2 + RNH2
Dimethylamine can also be used.[4]
Some examples of phthalimide drugs include thalidomide, amphotalide, taltrimide, talmetoprim, and apremilast. With a trichloromethylthio substituent, a phthalimide-derived fungicide is Folpet.
Reactivity
It forms salts upon treatment with bases such as sodium hydroxide. The high acidity of the imido N-H is the result of the pair of flanking electrophilic carbonyl groups. Potassium phthalimide, made by reacting phthalimide with potassium carbonate in water at 100 °C or with potassium hydroxide in absolute ethanol,[5] is used in the Gabriel synthesis of primary amines, such as glycine.
Preparation
Phthalimide can be prepared by heating phthalic anhydride with alcoholic ammonia giving 95–97% yield. Alternatively, it may be prepared by treating the anhydride with ammonium carbonate or urea. It can also be produced by ammoxidation of o-xylene.[1]
File:Phthalimide from phthalic anhydride.svg Synthesis of phthalimide from phthalic anhydride
Phthalimide can also be prepared from phthalic acid by the following process:
File:Phthalimide synthesis.svg Synthesis of phthalimide from phthalic acid
Carboxylic acids when reacted with ammonia give ammonium salts, which in turn give amides when strongly heated.
Natural occurrence
Kladnoite is a natural mineral analog of phthalimide.[6] It is very rarely found among a few burning coal fire sites.
Safety
Phthalimide has low acute toxicity with LD50 (rat, oral) of greater than 5,000 mg/kg.[1]
References
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- ↑ a b c d Template:Ullmann
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General reading
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