502-86-3

Basic information

• Product Name: 3,6-dimethylidenecyclohexa-1,4-diene
• Synonyms: NISTC502863;Quinodimethane;p-Quinodimethan;p-Quinodimethane;p-Benzoquinodimethane;p-Benzoquinonedimethane
• CAS NO: 502-86-3
• Molecular Formula: C₈H₈
• Molecular Weight: 104.1491
• Mol File: 502-86-3.mol
• Article Data: 5

Chemical Properties

• Boiling Point: 156.8°C at 760 mmHg
• Flash Point: 25.9°C
• Density: 0.87g/cm³
• Vapor Pressure: 3.67mmHg at 25°C
• Refractive Index: 1.516
• CAS DataBase Reference: 3,6-dimethylidenecyclohexa-1,4-diene(CAS DataBase Reference)
• NIST Chemistry Reference: 3,6-dimethylidenecyclohexa-1,4-diene(502-86-3)
• EPA Substance Registry System: 3,6-dimethylidenecyclohexa-1,4-diene(502-86-3)

Safety Data

• Hazardous Substances Data: 502-86-3(Hazardous Substances Data)

Upstream product

• 106-42-3 para-xylene 
• 2348-52-9 4-methylbenzyl radical 
• 7567-83-1 <2.2>Paracyclophane-1,10-dione 
• 22176-80-3 <2.2>Metaparacyclophan-2,9-dion 
• 875556-32-4 (4-[(trimethylsilyl)methyl]phenyl)methyl acetate 
• 17993-96-3 p-<(Trimethylsilyl)methyl>benzyl alcohol 
• 17095-21-5 4-<(trimethylsilyl)methyl>benzoic acid 
• 623-25-6 p-Xylylene dichloride 

Downstream Products

• 623-27-8 terephthalaldehyde, 
• 62855-80-5 1,4-bis(thiocyanatomethyl)benzene 
• 623-24-5 1,4-bis(bromomethyl)benzene 
• 69386-99-8 terephthalaldehyde oxime 
• 30362-89-1 p-bis(iodomethyl)benzene 
• 99848-46-1 4-(chloromethyl)benzaldehyde oxime 
• 1524-14-7 4-methylbenzyl trifluoroacetate 
• 1633-22-3 [2.2]Paracyclophan 
• 107171-17-5 4,8-dimethyl<2.2>paracyclophane 
• 283-80-7 [2.2.2]paracyclophane 

Relevant articles and documents

Formation of p-xylylene from p-xylene by a two-photon process and hexamethyl Dewar benzene from hexamethylbenzene by a one-photon process at 193 nm

While studying a series of methyl-substituted benzenes, C6H 6-n(CH3)n with n = 2, 3, 4, 6, and perfluorobenzene in the gas phase using 193-nm laser flash photolysis, we observed the formation of p-xylylene (benzoquinodimethane) due to the elimination of two hydrogen atoms as a result of a two-photon process. The results were explained in terms of an intermediate hot molecule formed by internal conversion which finally led to the ground electronic state. Quadratical dependencies on the photoproducts were observed for toluene, xylene, mesitylene, and perfluorobenzene in the presence of a foreign gas, while linear dependencies were observed for durene and hexamethylbenzene. Dewar-type benzene was detected from photolysis of hexamethylbenzene.

Mechanistic studies on the photogeneration of o-and p-xylylenes from aαα′-dichloroxylenes

Two-colour two-laser techniques have unambiguously proved that photolysis of the o-/p-(chloromethyl)benzyl radical leads to the sequential two-photon generation of o-/p-xylylene from α,α′-dichloro-o-/p-xylene.

1,4-Dicarbonyl-2,5-cyclohexadiene

The mechanism of the photolysis of paracyclophane-1,10-dione (9) was investigated in solution and in argon matrices.The first step of the photolysis involves α-cleavage of the cyclophane yielding a diradical 11 which could be trapped by ethanol.In argon at 10 K the diradical rapidly splits into p-xylylene (10) and 1,4-dicarbonyl-2,5-cyclohexadiene (7) and therefore was not directly observed by spectroscopic methods.The bisketene 7 was characterized by comparison of the experimantal and calculated IR spectrum. - Keywords: Ketenes / Matrix isolation / Calculations, ab initio