phthalic anhydride
1 Phthalic anhydride is the organic compound with the formula C8H4O3. This anhydride of phthalic acid, a colourless solid, is an important industrial chemical, especially for the large-scale production of plasticizers for plastics. In 2002, approximately 4.6 billion kilograms were produced
2 Applications in industry and organic synthesis
Phthalic anhydride is a versatile intermediate in organic chemistry, in part because it is bifunctional and cheaply available. It undergoes hydrolysis and alcoholysis. Hydrolysis by hot water forms ortho-phthalic acid. This process is reversible: Phthalic anhydride re-forms upon heating the acid above 180 °C.
3 Hydrolysis of anhydrides is not typically a reversible process. However, phthalic acid is easily dehydrated to form phthalic anhydride due to the creation of a thermodynamically favorable 5-membered ring.
Organic synthesis
4 Phthalic anhydride is a precursor to a variety of reagents useful in organic synthesis. Important derivatives include phthalimide and its many derivatives. Chiral alcohols form half-esters (see above), and these derivatives are often resolvable because they form diastereomeric salts with chiral amines such as brucine. A related ring-opening reaction involves peroxides to give the useful peroxy acid:
C6H4(CO)2O + H2O2 → C6H4(CO3H)CO2H5 Precursor to dyestuffs
6 Phthalic anhydride is widely used in industry for the production of certain dyes. A well-known application of this reactivity is the preparation of the anthroquinone dye quinizarin by reaction with para-chlorophenol followed by hydrolysis of the chloride.
Item | Index | ||
Top grade | First grade | Qualified product | |
Appearance | white scaly or crystalline powder | white scaly or crystalline powder with slight colors | |
molten Chroma(Chroma no. )≤ | 20 | 50 | 100 |
thermostable Chroma(Chroma no. )≤ | 50 | 150 | - |
Chroma of vitriol(Chroma no. )≤ | 60 | 100 | 150 |
crystallization point°C≥ | 130.5 | 130.3 | 130.0 |
Purity(mass fraction)%≥ | 99.50 | 99.50 | 99.00 |
Free acid(mass fraction)≤ % | 0.20 | 0.30 | 0.50 |
Ash(mass fraction)%≤ | 0.05 | - | - |
Phthalic anhydride 99.5% 85-44-9 best price