Phthalic anhydride

Phthalic anhydride ;
Names:	phthalic anhydride; phthalic acid anhydride; orho-phthalic acid anhydride; benzo[c]furandion; 2-benzofuran-1,3-diol;
Formula:	C8H4O3;
Molar mass:	148.117 g/mol;
Density:	1.527 g/cm3;
Crystal system:	orthorhombic; a=7.859 Å, b=14.173 Å, c=5.911 Åα=90°, β=90°, γ=90°;
Shapes:	https://en.crystalls.info/w/uploads/media/5/52/Needle.json Needle ;
Color:	colorless;
Melting point:	130.95 °C404.1 K <br />267.71 °F <br />727.38 °R <br />;
Boiling point:	284.5 °C557.65 K <br />544.1 °F <br />1,003.77 °R <br />;
Magnetic properties:	diamagnetic; χ=-6.73 · 10-5cm³/mol;
Stability:	stable;
Hardness:	fragile;
Toxicity:	slightly toxic; LD50=1600mg/kg

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Description

Organic compound, anhydride phthalic acid. Doesn't form water hydrates.

Precursors

Distillation of phthalic acid

Chemical equation:

C₈H₆O₄ → C₈H₄O₃ + H₂O↑

For preparation of 100.00g of phthalic anhydride а 112.16g of phthalic acid is required.

Add acid into the beaker placed on oil bath. Cover it with a round flask filled up with ice cold water. Anhydride will form at the bottom of the flask.

Influence of temperature

Boiling water solution lead to converting anhydride back to phthalic acid

Solubility

TableGraph

Temperature	g/`100,00` g water	g/`100,00` g pyridine	g/`100,00` g carbon disulfide	g/`100,00` g formic acid 95%
0°C273.15 K <br />32 °F <br />491.67 °R <br />	`0.00295`		`0.2`
10°C283.15 K <br />50 °F <br />509.67 °R <br />			`0.3`
19.8°C292.95 K <br />67.64 °F <br />527.31 °R <br />				`4.67`
20°C293.15 K <br />68 °F <br />527.67 °R <br />		`83.5`	`0.7`
26.7°C299.85 K <br />80.06 °F <br />539.73 °R <br />	`0.62`
50°C323.15 K <br />122 °F <br />581.67 °R <br />	`1.63`
60°C333.15 K <br />140 °F <br />599.67 °R <br />			`1.7`
100°C373.15 K <br />212 °F <br />671.67 °R <br />	`19.0`

Soluble in ethanol, acetone, benzene and 1,1,2-trichloro-1,2,2-trifluoroethane. Slightly soluble in diethyl ether.

Gallery

Video

Sources

Anhydrides
Phthalic anhydride (С8H₄O₃)

Phthalates
Phthalic acid (C₈H₆O₄) • Phthalic anhydride (C₈H₄O₃) • Potassium hydrogen phthalate (C₈H₆O₄K)

Phthalic anhydride
Names:	phthalic anhydride phthalic acid anhydride orho-phthalic acid anhydride benzo[c]furandion 2-benzofuran-1,3-diol
Formula:	C₈H₄O₃
Molar mass:	148.117 g/mol
Density:	1.527 g/cm³
Crystal system:	orthorhombic a=7.859 Å, b=14.173 Å, c=5.911 Åα=90°, β=90°, γ=90°
Shapes:	Needle
Color:	colorless
Melting point:	130.95 °C404.1 K <br />267.71 °F <br />727.38 °R <br />
Boiling point:	284.5 °C557.65 K <br />544.1 °F <br />1,003.77 °R <br />
Magnetic properties:	diamagnetic χ=-6.73 · 10^-5cm³/mol
Stability:	stable
Hardness:	fragile
Toxicity:	slightly toxic LD₅₀=1600mg/kg