Pyromellitic dianhydride

Pyromellitic dianhydride

Names
Preferred IUPAC name 1H,3H-Benzo[1,2-c:4,5-c′]difuran-1,3,5,7-tetrone
Identifiers
CAS Number	89-32-7^Y
3D model (JSmol)	Interactive image
ChemSpider	21106533
ECHA InfoCard	100.001.726
EC Number	201-898-9
PubChem CID	6966
RTECS number	DB9300000
UNII	2Z22T30QZQ^Y
CompTox Dashboard (EPA)	DTXSID1026536
InChI InChI=1S/C10H2O6/c11-7-3-1-4-6(10(14)16-8(4)12)2-5(3)9(13)15-7/h1-2H Key: ANSXAPJVJOKRDJ-UHFFFAOYSA-N
SMILES C1=C2C(=CC3=C1C(=O)OC3=O)C(=O)OC2=O
Properties
Chemical formula	C10H2O6
Molar mass	218.120 g·mol^−1
Appearance	White solid
Density	1.68 g/cm^3
Melting point	283 to 286 °C (541 to 547 °F; 556 to 559 K)
Boiling point	397 to 400 °C (747 to 752 °F; 670 to 673 K)
Solubility in water	Hygroscopic
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H317, H318, H334
Precautionary statements	P261, P272, P280, P285, P302+P352, P304+P341, P305+P351+P338, P310, P321, P333+P313, P342+P311, P363, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Pyromellitic dianhydride (PMDA) is an organic compound with the formula C₆H₂(C₂O₃)₂. It is the double carboxylic acid anhydride that is used in the preparation of polyimide polymers such as Kapton. It is a white, hygroscopic solid. It forms a hydrate.

Preparation

It is prepared by gas-phase oxidation of 1,2,4,5-tetramethylbenzene (or related tetrasubstituted benzene derivatives). An idealized equation is:[1]

C₆H₂(CH₃)₄ + 6 O₂ → C₆H₂(C₂O₃)₂ + 6 H₂O

In the laboratory, it can be prepared by dehydration of pyromellitic acid using acetic anhydride.[2]

Reactions

Structure of the complex formed upon co-crystallization of pyromellitic anhydride (molecules terminated in red) and anthracene.[3]

PMDA is an electron-acceptor, forming a variety of charge-transfer complexes. It reacts with amines to diimides, C₆H₂[(CO)₂NR]₂ which also have acceptor properties.[4]

Applications

PMDA is used in PET bottle recycling as a chain extender. It increases the molecular weight of the polymer by linking-together alcohol and carboxylic acid groups formed by hydrolysis of the PET. This improves the rheological properties and overall quality of the recycled plastic.[5]

Safety

Evidence suggests that PMDA causes occupational asthma.[6]

References

1. F. Röhrscheid (2012). "Carboxylic Acids, Aromatic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a05_249. ISBN 978-3-527-30673-2.
2. E. Philippi; R. Thelen (1930). "Pyromellitic Acid". Organic Syntheses. 10: 90. doi:10.15227/orgsyn.010.0090.
3. Robertson, B. E.; Stezowski, J. J. (1978). "The crystal structure of the π-molecular complex of anthracene with pyromellitic dianhydride at –120°C". Acta Crystallographica Section B. 34 (10): 3005–3011. doi:10.1107/S0567740878009929.
4. Song, Zhiping; Zhan, Hui; Zhou, Yunhong (2010). "Polyimides: Promising Energy-Storage Materials". Angewandte Chemie International Edition. 49 (45): 8444–8448. doi:10.1002/anie.201002439. PMID 20862664.
5. Incarnato, L; Scarfato, P; Di Maio, L; Acierno, D (August 2000). "Structure and rheology of recycled PET modified by reactive extrusion". Polymer. 41 (18): 6825–6831. doi:10.1016/S0032-3861(00)00032-X.
6. Madsen, Milene Torp; Skadhauge, Lars Rauff; Nielsen, Anders Daldorph; Baelum, Jesper; Sherson, David Lee (2019). "Pyromellitic dianhydride (PMDA) may cause occupational asthma". Occupational and Environmental Medicine. 76 (3): 175–177. doi:10.1136/oemed-2018-105295. PMC 6581108. PMID 30635433.