Phthalic anhydride

Phthalic anhydride  | Skeletal formula of phthalic anhydride | Space-filing model

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Names
Preferred IUPAC name

2-Benzofuran-1,3-dione[1]

Other names

Isobenzofuran-1,3-dione[1]
Phthalic anhydride[1]

Identifiers

CAS Number

* 85-44-9 Y

3D model (JSmol)

* Interactive image

Beilstein Reference

| 118515
ChEBI |

* CHEBI:36605 Y

ChEMBL |

* ChEMBL1371297 N

ChemSpider |

* 6552 Y

EC Number |

* 201-607-5

Gmelin Reference

| 27200

PubChem CID

* 6811

RTECS number |

* TI3150000

UNII |

* UVL263I5BJ Y

UN number | 2214

InChI

* InChI=1S/C8H4O3/c9-7-5-3-1-2-4-6(5)8(10)11-7/h1-4H Y

Key: LGRFSURHDFAFJT-UHFFFAOYSA-N Y

SMILES

* O=C1OC(=O)c2ccccc12

Properties

Chemical formula

| C8H4O3
Molar mass | 148.1 g/mol
Appearance  | white 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

Solubility in water

| 0.62 g/100g (20—25 °C);
19.0 g/100g (100 °C);
reacts slowly
Vapor pressure | 0.0015 mmHg (20 °C)[2]

Magnetic susceptibility (χ)

| −67.31×10−6 cm3/mol
Hazards
GHS pictograms |
GHS Signal word | Danger

GHS hazard statements

| H302, H315, H317, H318, H334, H335

GHS precautionary statements

| P261, P264, P270, P271, P272, P280, P285, P301+312, P302+352, P304+340, P304+341, P305+351+338, P310, P312, P321, P330, P332+313, P333+313, P342+311, P362, P363, P403+233, P405, P501
NFPA 704 (fire diamond)  |

Flash point |  152 °C (306 °F; 425 K)
Explosive limits | 1.7%–10.5%
Lethal dose or concentration (LD, LC):

LD50 (median dose)

| 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).

N verify (what is YN ?)
Infobox references

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]

## Contents

* 1 Synthesis and production
* 2 Uses
* 2.1 Phthalate esters plasticizers
* 2.2 Precursor to dyestuffs
* 2.3 Pharmaceuticals
* 3 Reactions
* 3.1 Hydrolysis, alcoholysis, ammonolysis
* 3.2 Preparation of aliphatic nitroalkenes
* 4 Safety
* 5 References
* 6 External links

## 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 Gibbs phthalic anhydride process (the Gibbs–Wohl naphthalene oxidation) uses vanadium pentoxide (V2O5) to catalyze gas-phase reaction between naphthalene and molecular oxygen.[4] The reaction involves oxidative cleavage of a ring and loss of two carbon atoms as carbon dioxide:

Proposed early steps in vanadium-catalyzed oxidation of naphthalene to phthalic anhydride, with V2O5 represented as a molecule versus its true extended structure.[6] An alternative mechanistic proposal is similar, but proceeds through a naphthoquinone intermediate.[7]

ortho-Xylene oxidation, a more atom-economical process, has slowly displaced the naphthalene route, in part because ortho-xylene is more easily transported than napthalene.[7] Run at about 320–400 °C, the reaction has the following stoichiometry:

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

Ideally only benzylic hydrogens oxidize, but the reaction proceeds with only about 70% selectivity. About 10% goes to maleic anhydride instead:

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

Distillation in a series of switch condensers recovers both products.

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.

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.[8] 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.[9][10][11]

Synthesis of phenolphthalein[12]

### 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.[13] Phthalic anhydride is a degradation product of CAP.[14]

## 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:[15]

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.[16] A related ring-opening reaction involves peroxides to give the useful peroxy acid:[17]

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.[18]

### Preparation of aliphatic nitroalkenes

Phthalic anhydride is used to dehydrate short-chain nitro-alcohols to yield nitroalkenes, compounds with a high tendency to polymerize.[19]

## 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.

## References

1. ↑ 1.0 1.1 1.2 "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. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 NIOSH Pocket Guide to Chemical Hazards. "#0512". National Institute for Occupational Safety and Health (NIOSH). https://www.cdc.gov/niosh/npg/npgd0512.html.
3. ↑ "Phthalic anhydride". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH). https://www.cdc.gov/niosh/idlh/85449.html.
4. ↑ 4.0 4.1 4.2 4.3 4.4 Lorz, Peter M.; Towae, Friedrich K.; Enke, Walter; Jäckh, Rudolf; Bhargava, Naresh; Hillesheim, Wolfgang (2007). "Ullmann's Encyclopedia of Industrial Chemistry". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a20_181.pub2.
5. ↑ Laurent, Aug. (1836). "Sur l'acide naphtalique et ses combinaisons" (in French). Annales de Chimie et de Physique. 2nd series 61: 113–125. https://babel.hathitrust.org/cgi/pt?id=hvd.hx3dwy&view=1up&seq=119.
6. ↑ "Gibbs-Wohl Naphthalene Oxidation". Comprehensive Organic Name Reactions and Reagents. 2010. pp. 1227–1229. doi:10.1002/9780470638859.conrr270. ISBN 9780470638859.
7. ↑ 7.0 7.1 Montoya Sánchez, Natalia; de Klerk, Arno (28 March 2018). "Autoxidation of aromatics". Applied Petrochemical Research 8. doi:10.1007/s13203-018-0199-4.
8. ↑ L. A. Bigelow and H. H. Reynolds (1941). "Quinizarin". Organic Syntheses. http://www.orgsyn.org/demo.aspx?prep=CV1P0476. ;  Collective Volume, 1, pp. 476
9. ↑ Baeyer, A. (1871). "Ueber eine neue Klasse von Farbstoffen". Berichte der Deutschen Chemischen Gesellschaft 4 (2): 555–558. doi:10.1002/cber.18710040209. https://zenodo.org/record/1425008.
10. ↑ Baeyer, A. (1871). "Ueber die Phenolfarbstoffe". Berichte der Deutschen Chemischen Gesellschaft 4 (2): 658–665. doi:10.1002/cber.18710040247. https://zenodo.org/record/1425010.
11. ↑ Baeyer, A. (1871). "Ueber die Phenolfarbstoffe". Polytechnisches Journal 201 (89): 358–362. http://dingler.culture.hu-berlin.de/article/pj201/ar201089. Retrieved 3 January 2018.
12. ↑ Max Hubacher, U.S. Patent 2,192,485 (1940 to Ex Lax Inc)
13. ↑ "Microbicide for prevention of sexually transmitted diseases using a pharmaceutical excipient.". AIDS Patient Care STDs 14 (4): 215–9. 2000. doi:10.1089/108729100317830. PMID 10806641.
14. ↑ "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. 2009. doi:10.1016/j.jpba.2008.10.039. PMID 19070984.
15. ↑ Noller, Carl R. (1965). Chemistry of Organic Compounds (3rd ed.). Philadelphia: W. B. Saunders. pp. 602.
16. ↑ Joseph Kenyon (1941). "d\- and l-Octanol-2". Organic Syntheses. http://www.orgsyn.org/demo.aspx?prep=CV1P0418. ;  Collective Volume, 1, pp. 418
17. ↑ George B. Payne (1973). "Monoperphthalic acid". Organic Syntheses. http://www.orgsyn.org/demo.aspx?prep=CV5P0805. ;  Collective Volume, 5, pp. 805
18. ↑ P. L. Salzberg and J. V. Supniewski (1941). "β-Bromoethylphthalimide". Organic Syntheses. http://www.orgsyn.org/demo.aspx?prep=cv1p0119. ;  Collective Volume, 1, pp. 119
19. ↑ 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.

## External links

* International Chemical Safety Card 0315
* NIOSH Pocket Guide to Chemical Hazards

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Retrieved from "https://handwiki.org/wiki/index.php?title=Chemistry:Phthalic_anhydride&oldid=4310138"
*[CID]: Compound ID
*[H302]: Harmful if swallowed
*[H315]: Causes skin irritation
*[H317]: May cause an allergic skin reaction
*[H318]: Causes serious eye damage
*[H334]: May cause allergy or asthma symptoms of breathing difficulties if inhaled
*[H335]: May cause respiratory irritation
*[P261]: Avoid breathing dust/fume/gas/mist/vapours/spray
*[P264]: Wash … thoroughly after handling
*[P270]: Do not eat, drink or smoke when using this product
*[P271]: Use only outdoors or in a well-ventilated area
*[P272]: Contaminated work clothing should not be allowed out of the workplace
*[P280]: Wear protective gloves/protective clothing/eye protection/face protection
*[P285]: In case of inadequate ventilation wear respiratory protection
*[P301+312]: IF SWALLOWED: Call a POISON CENTER or doctor/physician if you feel unwell
*[P302+352]: IF ON SKIN: Wash with soap and water
*[P304+340]: IF INHALED: Remove victim to fresh air and keep at rest in a position comfortable for breathing
*[P304+341]: IF INHALED: If breathing is difficult, remove victim to fresh air and keep at rest in a position comfortable for breathing
*[P305+351+338]: IF IN EYES: Rinse continuously with water for several minutes. Remove contact lenses if present and easy to do – continue rinsing
*[P310]: Immediately call a POISON CENTER or doctor/physician
*[P312]: Call a POISON CENTER or doctor/physician if you feel unwell
*[P321]: Specific treatment (see … on this label)
*[P330]: Rinse mouth
*[P332+313]: If skin irritation occurs: Get medical advice/attention
*[P333+313]: If skin irritation or a rash occurs: Get medical advice/attention
*[P342+311]: Call a POISON CENTER or doctor/physician
*[P362]: Take off contaminated clothing and wash before reuse
*[P363]: Wash contaminated clothing before reuse
*[P403+233]: Store in a well ventilated place. Keep container tightly closed
*[P405]: Store locked up
*[P501]: Dispose of contents/container to …