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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.[2]
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| Names | |
|---|---|
| Preferred IUPAC name
1H-Isoindole-1,3(2H)-dione | |
| Other names
1,3-dioxoisoindoline Phthalimidoyl (deprotonated) | |
| Identifiers | |
3D model (JSmol) |
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| ChEBI | |
| ChEMBL | |
| ChemSpider | |
| ECHA InfoCard | 100.001.458 |
PubChem CID |
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| UNII | |
CompTox Dashboard (EPA) |
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| Properties[1] | |
| C8H5NO2 | |
| Molar mass | 147.133 g·mol−1 |
| Appearance | White solid |
| Melting point | 238 °C (460 °F; 511 K) |
| Boiling point | 336 °C (637 °F; 609 K) sublimes |
| <0.1 g/100 ml (19.5 °C) | |
| Acidity (pKa) | 8.3 |
| Basicity (pKb) | 5.7 |
| −78.4×10−6 cm3/mol | |
| Related compounds | |
Related Amides |
Maleimide |
Related compounds |
Phthalic anhydride |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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.[2]
Phthalimide is used as a precursor to anthranilic acid, a precursor to azo dyes and saccharin.[2]
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".[4] 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.[5]
Some examples of phthalimide drugs include thalidomide, amphotalide, taltrimide, talmetoprim, and apremilast. With a trichloromethylthio substituent, a phthalimide-derived fungicide is Folpet.
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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,[6] is used in the Gabriel synthesis of primary amines, such as glycine.
Kladnoite is a natural mineral analog of phthalimide.[7] It is very rarely found among a few burning coal fire sites.
Phthalimide has low acute toxicity with LD50 (rat, oral) of greater than 5,000 mg/kg.[2]
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