Phthalimide

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Not to be confused with Thalidomide.
Phthalimide
skeletal formula of the phthalimide molecule
ball-and-stick model of the phthalimide molecule
Names
IUPAC name
Isoindole-1,3-dione
Other names
1,3-dioxoisoindoline
Phthalimidoyl (deprotonated)
Identifiers
85-41-6 YesY
ChEBI CHEBI:38817 YesY
ChEMBL ChEMBL277294 YesY
ChemSpider 6550 YesY
Jmol-3D images Image
PubChem 6809
Properties[1]
C8H5NO2
Molar mass 147.13 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
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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Infobox references

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]

Preparation[edit]

Phthalimide can be prepared by heating phthalic anhydride with aqueous 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 ortho-xylene.[2]

Uses[edit]

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".[3] Alkyl halides can be converted to the N-alkylphthalimide:

C6H4(CO)2NH + RX + NaOH → C6H4(CO)2N-R + NaX + H2O

The amine is commonly liberated using hydrazine:

C6H4(CO)2NR + N2H4 → C6H4(CO)2N2H2 + RNH2

Dimethylamine can also be used.[4]

Reactivity[edit]

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.

Natural occurrence[edit]

Kladnoite is a natural mineral analog of phthalimide.[6] It is very rarely found among a few burning coal fire sites.

Safety[edit]

Phthalimide has low acute toxicity with LD50 (rat, oral) of greater than 5000 mg/kg.[2]

References[edit]

  1. ^ "Phthalimide". Chemicalland21. Retrieved 15 November 2011. 
  2. ^ a b c d Peter M. Lorz; Friedrich K. Towae; Walter Enke; Rudolf Jäckh; Naresh Bhargava; Wolfgang Hillesheim (2005), "Phthalic Acid and Derivatives", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a20_181.pub2 
  3. ^ "Phthalimides". Retrieved 2013-02-07. 
  4. ^ "DEPROTECTION – REMOVAL OF AMINE PROTECTING GROUPS (PHTHALIMIDE AND DIMETHYLAMINOSULPHONYL)". Retrieved 2013-02-07. 
  5. ^ "β-Bromoethylphthalimide". Organic Syntheses. Retrieved 15 November 2011. 
  6. ^ "Kladnoite". mindat.org. Retrieved 15 November 2011. 

General reading (textbooks)[edit]

  • Vollhardt, K. Peter C.; Schore, Neil Eric (2002). Organic Chemistry: Structure and Function (4th ed.). New York: W.H. Freeman. ISBN 978-0-7167-4374-3. 
  • Finar, Ivor Lionel (1973). Organic Chemistry 1 (6th ed.). London: Longman. ISBN 0-582-44221-4.