Methylcyclopentadiene dimer
[CAS# 26472-00-4]

Identification

• Classification: Chemical reagent >> Organic reagent >> Olefins (cyclic and non-cyclic)
• Name: Methylcyclopentadiene dimer
• Synonyms: Bis(methylcyclopentadiene); 3a,4,7,7a-Tetrahydrodimethyl-4,7-methano-1H-indene
• Molecular Formula: C₁₂H₁₆
• Molecular Weight: 160.26
• CAS Registry Number: 26472-00-4
• EC Number: 247-724-5
• SMILES: CC1=CC2C3CC(C2C1)C=C3C

Properties

• Solubility: 4.566 mg/L (25 °C water)
• Density: 1.0±0.1 g/cm³, Calc.^*
• Index of Refraction: 1.540, Calc.^*
• Melting point: 17.75 °C
• Boiling Point: 223.4±30.0 °C (760 mmHg), Calc.^*, 213.55 °C
• Flash Point: 26.7±0.0 °C, Calc.^*

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS02;GHS08;GHS09 Danger
• Risk Statements: H226-H304-H400-H410
• Safety Statements: P210-P233-P240-P241-P242-P243-P273-P280-P301+P316-P303+P361+P353-P331-P370+P378-P391-P403+P235-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Flammable liquids	Flam. Liq.	3	H226
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400
Chronic hazardous to the aquatic environment	Aquatic Chronic	1	H410
Aspiration hazard	Asp. Tox.	1	H304
Carcinogenicity	Carc.	1A	H350
Germ cell mutagenicity	Muta.	1B	H340
Skin irritation	Skin Irrit.	2	H315
Acute toxicity	Acute Tox.	4	H332
Eye irritation	Eye Irrit.	2	H319
Carcinogenicity	Carc.	2	H351

Discovery and Applications

Methylcyclopentadiene dimer is an organic compound derived from methylcyclopentadiene, a cyclic hydrocarbon. The dimerization process involves the chemical combination of two methylcyclopentadiene molecules to form a more stable dimer. This substance has found extensive application in various industries, particularly in polymer chemistry and as a precursor for the synthesis of other complex compounds.

The discovery of methylcyclopentadiene dimer can be traced to research aimed at improving the stability of reactive monomers like cyclopentadienes. Cyclopentadienes are known for their high reactivity, making them useful in a range of chemical applications, but their instability can pose challenges during storage and handling. Dimerization was discovered as an effective way to stabilize these compounds, allowing them to be stored safely and easily converted back to their monomeric forms when needed. This reaction typically occurs through a Diels-Alder mechanism, a classic method in organic chemistry where a diene and a dienophile react to form a more complex molecule.

Methylcyclopentadiene dimer is especially valuable because, under certain conditions, it can revert to its monomeric form, which makes it useful in the production of specialty polymers. This reversion process occurs when the dimer is heated, releasing the reactive monomer for further polymerization reactions. This feature is particularly advantageous in industries such as rubber manufacturing, where methylcyclopentadiene monomer can be used as a building block for synthetic rubbers with enhanced properties such as improved flexibility, resilience, and chemical resistance.

Another significant application of methylcyclopentadiene dimer is in the production of metallocene catalysts. Metallocenes are a class of organometallic compounds that play a crucial role in the polymerization of olefins, such as polyethylene and polypropylene. These catalysts rely on cyclopentadiene derivatives like methylcyclopentadiene to create stable complexes with transition metals. These complexes improve the efficiency and selectivity of the polymerization process, leading to the production of high-performance polymers with controlled molecular weight and architecture.

Beyond its role in polymer chemistry, methylcyclopentadiene dimer is also used in the synthesis of pharmaceuticals and fine chemicals. It can serve as an intermediate in the production of biologically active compounds, contributing to the development of new drugs and therapeutic agents. The ability to decompose into reactive monomers provides versatility in creating a wide range of chemical structures, making it a valuable tool in organic synthesis.

In summary, the discovery of methylcyclopentadiene dimer as a stable, dimerized form of methylcyclopentadiene has expanded its applications in polymer chemistry, metallocene catalyst production, and fine chemical synthesis. Its unique ability to revert to a reactive monomer under heat makes it an essential compound for industrial processes requiring precise control over reactivity and stability.

References

2024. Emergency Response Guidebook.
https://www.phmsa.dot.gov/training/hazmat/erg/emergency-response-guidebook-erg

U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.

1981. Gigiena Truda i Professional'nye Zabolevaniya. Labor Hygiene and Occupational Diseases. 25(5)(45).