Phthalic anhydride

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Phthalic anhydride
Skeletal formula of phthalic anhydride Phthalic anhydride-2D-Skeletal.png
Skeletal formula of phthalic anhydride
Space-filing model Phthalic-anhydride-3D-spacefill.png
Space-filing model
Sample of phthalic anhydride.jpg
Names
Preferred IUPAC name
2-Benzofuran-1,3-dione [1]
Other names
Isobenzofuran-1,3-dione [1]
Phthalic anhydride [1]
Identifiers
3D model (JSmol)
118515
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.001.461 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 201-607-5
27200
PubChem CID
RTECS number
  • TI3150000
UNII
UN number 2214
  • InChI=1S/C8H4O3/c9-7-5-3-1-2-4-6(5)8(10)11-7/h1-4H Yes check.svgY
    Key: LGRFSURHDFAFJT-UHFFFAOYSA-N Yes check.svgY
  • O=C1OC(=O)c2ccccc12
Properties
C8H4O3
Molar mass 148.1 g/mol
Appearancewhite flakes
Odor characteristic, acrid [2]
Density 1.53 g/cm3, solid; 1.20 g/mL, molten [2]
Melting point 131.6 °C (268.9 °F; 404.8 K)
Boiling point 295 °C (563 °F; 568 K) sublimates
0.62 g/100g (20—25 °C);
19.0 g/100g (100 °C);
reacts slowly
Vapor pressure 0.0015 mmHg (20 °C) [2]
−67.31×10−6 cm3/mol
Hazards
GHS labelling:
GHS-pictogram-acid.svg GHS-pictogram-exclam.svg GHS-pictogram-silhouette.svg
Danger
H302, H315, H317, H318, H334, H335
P261, P264, P270, P271, P272, P280, P285, P301+P312, P302+P352, P304+P340, P304+P341, P305+P351+P338, P310, P312, P321, P330, P332+P313, P333+P313, P342+P311, P362, P363, P403+P233, P405, P501
NFPA 704 (fire diamond)
NFPA 704.svgHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
3
1
0
Flash point 152 °C (306 °F; 425 K)
Explosive limits 1.7%–10.5%
Lethal dose or concentration (LD, LC):
4020 mg/kg (oral, rat)
1520 mg/kg (oral, mouse)
800 mg/kg (oral, cat)
800–1600 mg/kg (oral, rat)
2210 mg/kg (oral, mouse) [3]
NIOSH (US health exposure limits):
PEL (Permissible)
TWA 12 mg/m3 (2 ppm) [2]
REL (Recommended)
TWA 6 mg/m3 (1 ppm) [2]
IDLH (Immediate danger)
60 mg/m3 [2]
Related compounds
Related compounds
 Phthalic acid
Phthalimide
Phthalide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Phthalic anhydride is the organic compound with the formula C6H4(CO)2O. It is the anhydride of phthalic acid. Phthalic anhydride is a principal commercial form of phthalic acid. It was the first anhydride of a dicarboxylic acid to be used commercially. This white solid is an important industrial chemical, especially for the large-scale production of plasticizers for plastics. In 2000, the worldwide production volume was estimated to be about 3 million tonnes per year. [4]

Synthesis and production

Phthalic anhydride was first reported in 1836 by Auguste Laurent. Early procedures involved liquid-phase mercury-catalyzed oxidation of naphthalene. [5] The modern industrial variant process instead uses vanadium pentoxide (V2O5) as the catalyst in a gas-phase reaction with naphthalene using molecular oxygen. [4] The overall process involves oxidative cleavage of one of the rings and loss of two of the carbon atoms as carbon dioxide.

An alternative process involves oxidation of the two methyl groups of o-xylene, a more atom-economical process. This reaction is run at about 320–400 °C and has the following stoichiometry:

C6H4(CH3)2 + 3 O2 → C6H4(CO)2O + 3 H2O

The reaction proceeds with about 70% selectivity. About 10% of maleic anhydride is also produced:

C6H4(CH3)2 + 7+1/2 O2 → C4H2O3 + 4 H2O + 4 CO2

Phthalic anhydride and maleic anhydride are recovered by distillation by a series of switch condensers.

The naphthalene route (the Gibbs phthalic anhydride process or the Gibbs–Wohl naphthalene oxidation reaction) has declined relative to the o-xylene route.

Proposed early steps in vanadium-catalyzed oxidation of naphthalene to phthalic anhydride, with V2O5 represented as a molecule versus its true extended structure. V2O5OxNaphth.svg
Proposed early steps in vanadium-catalyzed oxidation of naphthalene to phthalic anhydride, with V2O5 represented as a molecule versus its true extended structure.

Phthalic anhydride can also be prepared from phthalic acid by simple thermal dehydration above 210°C. [4]

Uses

Phthalate esters plasticizers

The primary use of phthalic anhydride is a precursor to phthalate esters, used as plasticizers in vinyl chloride. Phthalate esters are derived from phthalic anhydride by the alcoholysis reaction. [4] In the 1980s, approximately 6.5 million tonnes of these esters were produced annually, and the scale of production was increasing each year, all from phthalic anhydride. The process begins with the reaction of phthalic anhydride with alcohols, giving the monoesters:

C6H4(CO)2O + ROH → C6H4(CO2H)CO2R

The second esterification is more difficult and requires removal of water:

C6H4(CO2H)CO2R + ROH ⇌ C6H4(CO2R)2 + H2O

The most important diester is bis(2-ethylhexyl) phthalate ("DEHP"), used in the manufacture of polyvinyl chloride compounds.

Precursor to dyestuffs

Quinoline Yellow SS is a popular dye derived from the condensation of phthalic anhydride and 2-methylquinoline. Quinoline Yellow SS.svg
Quinoline Yellow SS is a popular dye derived from the condensation of phthalic anhydride and 2-methylquinoline.

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 anthraquinone dye quinizarin by reaction with para-chlorophenol followed by hydrolysis of the chloride. [7] Phenolphthalein can be synthesized by the condensation of phthalic anhydride with two equivalents of phenol under acidic conditions (hence the name). It was discovered in 1871 by Adolf von Baeyer. [8] [9] [10]

Synthesis of phenolphthalein Phenolphthalein Synthesis.svg
Synthesis of phenolphthalein

Pharmaceuticals

Phthalic anhydride treated with cellulose acetate gives cellulose acetate phthalate (CAP), a common enteric coating excipient that has also been shown to have antiviral activity. [12] Phthalic anhydride is a degradation product of CAP. [13]

Reactions

Phthalic anhydride is a versatile intermediate in organic chemistry, in part because it is bifunctional and cheaply available.

Hydrolysis, alcoholysis, ammonolysis

Hydrolysis by hot water forms ortho-phthalic acid: [14]

C6H4(CO)2O + H2O → C6H4(CO2H)2

Hydrolysis of anhydrides is not typically a reversible process. Phthalic acid is however easily dehydrated to form phthalic anhydride. Above 180 °C, phthalic anhydride re-forms.

Chiral alcohols form half-esters (see above), and these derivatives are often resolvable because they form diastereomeric salts with chiral amines such as brucine. [15] A related ring-opening reaction involves peroxides to give the useful peroxy acid: [16]

C6H4(CO)2O + H2O2 → C6H4(CO3H)CO2H

Phthalimide can be prepared by heating phthalic anhydride with aqueous ammonia giving a 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 o-xylene. [4] Potassium phthalimide is commercially available and is the potassium salt of phthalimide. It may be prepared by adding a hot solution of phthalimide to a solution of potassium hydroxide; the desired product precipitates. [17]

Preparation of aliphatic nitroalkenes

Phthalic anhydride is used to dehydrate short-chain nitro-alcohols to yield nitroalkenes, compounds with a high tendency to polymerize. [18]

Safety

The most probable human exposure to phthalic anhydride is through skin contact or inhalation during manufacture or use. Studies show that exposure to phthalic anhydride can cause rhinitis, chronic bronchitis, and asthma. Phthalic anhydride's reaction on human health is generally an asthma–rhinitis–conjunctivitis syndrome or a delayed reaction and influenza-like symptoms and with increased immunoglobulin (E and G) levels in the blood.

Related Research Articles

<span class="mw-page-title-main">Carboxylic acid</span> Organic compound containing a –C(=O)OH group

In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group attached to an R-group. The general formula of a carboxylic acid is often written as R−COOH or R−CO2H, sometimes as R−C(O)OH with R referring to an organyl group, or hydrogen, or other groups. Carboxylic acids occur widely. Important examples include the amino acids and fatty acids. Deprotonation of a carboxylic acid gives a carboxylate anion.

<span class="mw-page-title-main">Naphthalene</span> Chemical compound

Naphthalene is an organic compound with formula C
10H
8. It is the simplest polycyclic aromatic hydrocarbon, and is a white crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass. As an aromatic hydrocarbon, naphthalene's structure consists of a fused pair of benzene rings. It is the main ingredient of traditional mothballs.

Mesitylene or 1,3,5-trimethylbenzene is a derivative of benzene with three methyl substituents positioned symmetrically around the ring. The other two isomeric trimethylbenzenes are 1,2,4-trimethylbenzene (pseudocumene) and 1,2,3-trimethylbenzene (hemimellitene). All three compounds have the formula C6H3(CH3)3, which is commonly abbreviated C6H3Me3. Mesitylene is a colorless liquid with sweet aromatic odor. It is a component of coal tar, which is its traditional source. It is a precursor to diverse fine chemicals. The mesityl group (Mes) is a substituent with the formula C6H2Me3 and is found in various other compounds.

<span class="mw-page-title-main">Phthalic acid</span> Aromatic organic compound with formula C6H4(COOH)2

In organic chemistry, phthalic acid is an aromatic dicarboxylic acid, with formula C6H4(CO2H)2 and structure HO(O)C−C6H4−C(O)OH. Although phthalic acid is of modest commercial importance, the closely related derivative phthalic anhydride is a commodity chemical produced on a large scale. Phthalic acid is one of three isomers of benzenedicarboxylic acid, the others being isophthalic acid and terephthalic acid.

The Friedel–Crafts reactions are a set of reactions developed by Charles Friedel and James Crafts in 1877 to attach substituents to an aromatic ring. Friedel–Crafts reactions are of two main types: alkylation reactions and acylation reactions. Both proceed by electrophilic aromatic substitution.

In organic chemistry, an acyl chloride is an organic compound with the functional group −C(=O)Cl. Their formula is usually written R−COCl, where R is a side chain. They are reactive derivatives of carboxylic acids. A specific example of an acyl chloride is acetyl chloride, CH3COCl. Acyl chlorides are the most important subset of acyl halides.

In chemistry, acetylation is an organic esterification reaction with acetic acid. It introduces an acetyl group into a chemical compound. Such compounds are termed acetate esters or simply acetates. Deacetylation is the opposite reaction, the removal of an acetyl group from a chemical compound.

<span class="mw-page-title-main">Imide</span> Class of chemical compounds

In organic chemistry, an imide is a functional group consisting of two acyl groups bound to nitrogen. The compounds are structurally related to acid anhydrides, although imides are more resistant to hydrolysis. In terms of commercial applications, imides are best known as components of high-strength polymers, called polyimides. Inorganic imides are also known as solid state or gaseous compounds, and the imido group (=NH) can also act as a ligand.

<span class="mw-page-title-main">Acetic anhydride</span> Organic compound with formula (CH₃CO)₂O

Acetic anhydride, or ethanoic anhydride, is the chemical compound with the formula (CH3CO)2O. Commonly abbreviated Ac2O, it is the simplest isolable anhydride of a carboxylic acid and is widely used as a reagent in organic synthesis. It is a colorless liquid that smells strongly of acetic acid, which is formed by its reaction with moisture in the air.

<span class="mw-page-title-main">Terephthalic acid</span> Chemical compound

Terephthalic acid is an organic compound with formula C6H4(CO2H)2. This white solid is a commodity chemical, used principally as a precursor to the polyester PET, used to make clothing and plastic bottles. Several million tons are produced annually. The common name is derived from the turpentine-producing tree Pistacia terebinthus and phthalic acid.

<span class="mw-page-title-main">Vanadium(V) oxide</span> Precursor to vanadium alloys and industrial catalyst

Vanadium(V) oxide (vanadia) is the inorganic compound with the formula V2O5. Commonly known as vanadium pentoxide, it is a brown/yellow solid, although when freshly precipitated from aqueous solution, its colour is deep orange. Because of its high oxidation state, it is both an amphoteric oxide and an oxidizing agent. From the industrial perspective, it is the most important compound of vanadium, being the principal precursor to alloys of vanadium and is a widely used industrial catalyst.

<span class="mw-page-title-main">Maleic anhydride</span> Chemical compound

Maleic anhydride is an organic compound with the formula C2H2(CO)2O. It is the acid anhydride of maleic acid. It is a colorless or white solid with an acrid odor. It is produced industrially on a large scale for applications in coatings and polymers.

<i>o</i>-Xylene Chemical compound

o-Xylene (ortho-xylene) is an aromatic hydrocarbon with the formula C6H4(CH3)2, with two methyl substituents bonded to adjacent carbon atoms of a benzene ring (the ortho configuration). It is a constitutional isomer of m-xylene and p-xylene, the mixture being called xylene or xylenes. o-Xylene is a colourless slightly oily flammable liquid.

<span class="mw-page-title-main">Succinic anhydride</span> Chemical compound

Succinic anhydride, is an organic compound with the molecular formula (CH2CO)2O. This colorless solid is the acid anhydride of succinic acid.

<span class="mw-page-title-main">Anthranilic acid</span> Chemical compound

Anthranilic acid is an aromatic acid with the formula C6H4(NH2)(CO2H) and has a sweetish taste. The molecule consists of a benzene ring, ortho-substituted with a carboxylic acid and an amine. As a result of containing both acidic and basic functional groups, the compound is amphoteric. Anthranilic acid is a white solid when pure, although commercial samples may appear yellow. The anion [C6H4(NH2)(CO2)]−, obtained by the deprotonation of anthranilic acid, is called anthranilate. Anthranilic acid was once thought to be a vitamin and was referred to as vitamin L1 in that context, but it is now known to be non-essential in human nutrition.

<span class="mw-page-title-main">Phthalimide</span> Organic Compound

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.

<span class="mw-page-title-main">Dibutyl phthalate</span> Chemical compound

Dibutyl phthalate (DBP) is an organic compound which is commonly used as a plasticizer because of its low toxicity and wide liquid range. With the chemical formula C6H4(CO2C4H9)2, it is a colorless oil, although impurities often render commercial samples yellow.

<span class="mw-page-title-main">2-Ethylanthraquinone</span> Intermediate Chemical in H2O2 Synthesis

2-Ethylanthraquinone is an organic compound that is a derivative of anthraquinone. This pale yellow solid is used in the industrial production of hydrogen peroxide (H2O2).

<span class="mw-page-title-main">Phthalonitrile</span> Chemical compound

Phthalonitrile is an organic compound with the formula C6H4(CN)2, which is an off-white crystal solid at room temperature. It is a derivative of benzene, containing two adjacent nitrile groups. The compound has low solubility in water but is soluble in common organic solvents. The compound is used as a precursor to phthalocyanine and other pigments, fluorescent brighteners, and photographic sensitizers.

<i>N</i>-Hydroxyphthalimide Chemical compound

N-Hydroxyphthalimide is the organic compound with the formula C6H4(CO)2NOH. A white or yellow solid, it is a derivative of phthalimide. The compound is as a catalyst in the synthesis of other organic compounds. It is soluble in water and organic solvents such as acetic acid, ethyl acetate and acetonitrile.

References

  1. 1 2 3 "Front Matter". Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 835. doi:10.1039/9781849733069-FP001. ISBN   978-0-85404-182-4.
  2. 1 2 3 4 5 6 NIOSH Pocket Guide to Chemical Hazards. "#0512". National Institute for Occupational Safety and Health (NIOSH).
  3. ↑ "Phthalic anhydride". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  4. 1 2 3 4 5 Lorz, Peter M.; Towae, Friedrich K.; Enke, Walter; et al. (2007). "Phthalic Acid and Derivatives". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a20_181.pub2. ISBN   978-3527306732.
  5. ↑ Laurent, Aug. (1836). "Sur l'acide naphtalique et ses combinaisons" [On naphthalic acid and its compounds]. Annales de Chimie et de Physique. 2nd series (in French). 61: 113–125.
  6. ↑ "Gibbs-Wohl Naphthalene Oxidation". Comprehensive Organic Name Reactions and Reagents. 2010. doi:10.1002/9780470638859.conrr270. ISBN   9780470638859.
  7. ↑ L. A. Bigelow and H. H. Reynolds (1941). "Quinizarin". Organic Syntheses ; Collected Volumes, vol. 1, p. 476.
  8. ↑ Baeyer, A. (1871). "Ueber eine neue Klasse von Farbstoffen". Berichte der Deutschen Chemischen Gesellschaft. 4 (2): 555–558. doi:10.1002/cber.18710040209.
  9. ↑ Baeyer, A. (1871). "Ueber die Phenolfarbstoffe". Berichte der Deutschen Chemischen Gesellschaft. 4 (2): 658–665. doi:10.1002/cber.18710040247.
  10. ↑ Baeyer, A. (1871). "Ueber die Phenolfarbstoffe". Polytechnisches Journal. 201 (89): 358–362.
  11. ↑ Max Hubacher, U.S. patent 2,192,485 (1940 to Ex Lax Inc)
  12. ↑ Neurath AR (2000). "Microbicide for prevention of sexually transmitted diseases using a pharmaceutical excipient". AIDS Patient Care STDs. 14 (4): 215–9. doi:10.1089/108729100317830. PMID   10806641.
  13. ↑ Mayhew JW, Gideon LT, Ericksen B, et al. (2009). "Development of a gel permeation chromatographic assay to achieve mass balance in cellulose acetate phthalate stability studies". J Pharm Biomed Anal. 49 (2): 240–6. doi:10.1016/j.jpba.2008.10.039. PMC   2859192 . PMID   19070984.
  14. ↑ Noller, Carl R. (1965). Chemistry of Organic Compounds (3rd ed.). Philadelphia: W. B. Saunders. p. 602.
  15. ↑ Joseph Kenyon (1941). "d- and l-Octanol-2". Organic Syntheses ; Collected Volumes, vol. 1, p. 418.
  16. ↑ George B. Payne (1973). "Monoperphthalic acid". Organic Syntheses ; Collected Volumes, vol. 5, p. 805.
  17. ↑ P. L. Salzberg and J. V. Supniewski (1941). "β-Bromoethylphthalimide". Organic Syntheses ; Collected Volumes, vol. 1, p. 119.
  18. ↑ Ranganathan, Darshan; Rao, Bhushan; Ranganathan, Subramania; et al. (1980). "Nitroethylene: a stable, clean, and reactive agent for organic synthesis". The Journal of Organic Chemistry. 45 (7): 1185–1189. doi:10.1021/jo01295a003.
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