Phthalimide

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
CAS Number	85-41-6 Y
ChEBI	CHEBI:38817 Y
ChEMBL	ChEMBL277294 Y
ChemSpider	6550 Y
Jmol 3D model	Interactive image
PubChem	6809
InChI InChI=1S/C8H5NO2/c10-7-5-3-1-2-4-6(5)8(11)9-7/h1-4H,(H,9,10,11) Y Key: XKJCHHZQLQNZHY-UHFFFAOYSA-N Y InChI=1/C8H5NO2/c10-7-5-3-1-2-4-6(5)8(11)9-7/h1-4H,(H,9,10,11) Key: XKJCHHZQLQNZHY-UHFFFAOYAS
SMILES O=C2c1ccccc1C(=O)N2
Properties
Chemical formula	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
Solubility in water	<0.1 g/100 ml (19.5 °C)
Acidity (pKa)	8.3
Basicity (pKb)	5.7
Vapor pressure	{{{value}}}
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).
Y verify (what is YN ?)
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.

Preparation

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.

Uses

Phthalimide is used as a precursor to anthranilic acid, a precursor to azo dyes and saccharin.

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". 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.

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, is used in the Gabriel synthesis of primary amines, such as glycine.

Natural occurrence

Kladnoite is a natural mineral analog of phthalimide. 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 5000 mg/kg.