General Description
White crystals or fine white powder.
Reactivity Profile
PHTHALIC ACID(88-99-3) is a carboxylic acid. This chemical is sensitive to exposure to extreme heat. This compound reacts violently with nitric acid. PHTHALIC ACID(88-99-3) is incompatible with sodium nitrite. PHTHALIC ACID(88-99-3) is also incompatible with oxidizers. .
Air & Water Reactions
Insoluble in water.
Fire Hazard
This chemical is combustible.
Description
Phthalic acid is an aromatic dicarboxylic acid, with formula C6H4(CO2H)2. It is an isomer of isophthalic acid and terephthalic acid. Although phthalic acid is of modest commercial importance, the closely related derivative phthalic anhydride is a commodity chemical produced on a large scale.
Chemical Properties
PHTHALIC ACID,C6H4(COOH)2, mp 208 °C (ortho), 330 °C (meta and iso), the ortho form sublimes and the meta and iso forms decompose with heat, sp gr 1.593 (ortho). Phthalic acid is very slightly soluble in H2O, soluble in alcohol, and slightly soluble in ether. The solid form is colorless, crystalline
Uses
It is a dibasic acid, with pKa's of 2.89 and 5.51. The mono potassium salt, potassium hydrogen phthalate is a standard acid in analytical chemistry. Typically phthalate esters are prepared from the widely available phthalic anhydride. Reduction of phthalic acid with sodium amalgam in the presence of water gives the 1,3- cyclohexadiene derivative.
Uses
Organic reagent used to synthesize phthalates.
Definition
ChEBI: A benzenedicarboxylic acid cosisting of two carboxy groups at ortho positions.
Definition
phthalic acid: colourlesscrystalline dicarboxylic acid,C6H4(COOH)2; r.d. 1.6; m.p. 207°C.The two –COOH groups are substitutedon adjacent carbon atoms ofthe ring, the technical name beingbenzene-1,2-dicarboxylic acid. Theacid is made from phthalic anhydride(benzene-1,2-dicarboxylic anhydride,C8H4O3), which is made by the catalyticoxidation of naphthalene. Theanhydride is used in making plasticizersand polyester resins.
Production Methods
Phthalic acid is produced by the catalytic oxidation of naphthalene directly to phthalic anhydride and a subsequent hydrolysis of the anhydride.
Phthalic acid was first obtained by French chemist Auguste Laurent in 1836 by oxidizing naphthalene tetrachloride. Believing the resulting substance to be a naphthalene derivative, he named it "naphthalic acid". After the Swiss chemist Jean Charles Galissard de Marignac determined its correct formula, Laurent gave it its present name. Manufacturing methods in the nineteenth century included oxidation of naphthalene tetrachloride with nitric acid, or, better, oxidation of the hydrocarbon with fuming sulfuric acid, using mercury or mercury(II) sulfate as a catalyst.
Flammability and Explosibility
Notclassified
Safety
The toxicity of phthalic acid is low with LD50 (mouse) of 550 mg/kg. However, many phthalate esters have been implicated as endocrine disruptors.
Synthesis
Add 97.2 kg of water to the reactor, add an equal mass of 65% concentrated nitric acid under stirring, and heat to 95℃ for reflux to prepare a nitric acid solution; dissolve 48.6 kg of phthalhydrazide in 280 kg of water, slowly add the solution dropwise to the nitric acid solution at 90–110℃ over 2–3 hours, feed the generated reaction gas into a spray absorption tower, reflux for 1 hour after the completion of dropwise addition, continue refluxing for another 35 minutes after the reaction solution becomes clear, then cool to 5–10℃ and filter; wash the solid with 50 kg of water, drain the water, and dry at 80℃ to obtain 45.8 kg of crude phthalic acid; add the crude product to 350 kg of water, heat to 90–105℃ for reflux for 50–60 minutes until complete dissolution, cool to 5–10℃ for crystallization for 2 hours, filter, wash the solid with 50 kg of water, drain the water, and dry at 80℃ to obtain 43.1 kg of refined phthalic acid product.
Purification Methods
Crystallise phthalic acid from water. [Beilstein 9 IV 3167.]
Isomers
Phthalic acid is one of three isomers of benzene dicarboxylic acid, the others being iso phthalic acid and terephthalic acid. Sometimes the term "phthalic acids" is used to refer to this family of isomers, but in the singular, "phthalic acid", refers exclusively to the ortho- isomer.
