70401-56-8

Basic information

• Product Name: 2H-1-Benzopyran, 3,4-dihydro-3-methyl-
• CAS NO: 70401-56-8
• Molecular Formula: C10H12O
• Molecular Weight: 148.205
• Mol File: 70401-56-8.mol
• Article Data: 6

Chemical Properties

• CAS DataBase Reference: 2H-1-Benzopyran, 3,4-dihydro-3-methyl-(CAS DataBase Reference)
• NIST Chemistry Reference: 2H-1-Benzopyran, 3,4-dihydro-3-methyl-(70401-56-8)
• EPA Substance Registry System: 2H-1-Benzopyran, 3,4-dihydro-3-methyl-(70401-56-8)

Safety Data

• Hazardous Substances Data: 70401-56-8(Hazardous Substances Data)

Upstream product

• 493-08-3 chromane 
• 187737-37-7 propene 
• 861009-82-7 acetic acid-(2-methallyl-phenyl ester) 
• 6627-85-6 (2-allyl-phenoxy)-acetic acid 
• 27890-67-1 6-methylene-cyclohexa-2,4-dienone 
• 10178-53-7 1-bromo-2-((2-methylallyl)oxy)benzene 
• 493-09-4 benzo-1,4-dioxane 

Relevant articles and documents

Radical Hydrodehalogenation of Aryl Bromides and Chlorides with Sodium Hydride and 1,4-Dioxane

A practical method for radical chain reduction of various aryl bromides and chlorides is introduced. The thermal process uses NaH and 1,4-dioxane as reagents and 1,10-phenanthroline as an initiator. Hydrodehalogenation can be combined with typical cyclization reactions, proving the nature of the radical mechanism. These chain reactions proceed by electron catalysis. DFT calculations and mechanistic studies support the suggested mechanism.

Thermal Decomposition of Chroman. Reactivity of o-Quinone Methide

The gas phase thermal decomposition of 3,4-dihydro-2H-1-benzopyran (chroman, 1) has been studied between 760 and 1110 K in different bath gases and hydrogen donors. In nitrogen, the unimolecular rate parameters are k1 (s-1) = 1015.3 exp(-263 (kJ mol-1)/RT). The activation energy is slightly higher than the bond dissociation energy (BDE) of the phenoxylic C - O bond. The decomposition starts with elimination of ethene and formation of 6-methylene-2,4-cyclohexadien-1-one (o-quinone methide, 2). Quinone methides are important intermediates in the chemistry of lignin. In the high temperature range (860-980 K) 2 decomposes cleanly into CO, benzene, and small amounts of fulvene, obeying k2 (s-1) = 1014.8 exp(-281 (kJ mol-1)/RT. Reverse radical disproportionation of 2 with toluene is mainly responsible for o-cresol formation. In cis-2-butene at 770 K, exclusively cis-2,3-dimethylchroman is formed. This stereospecificity suggests a concerted retro-Diels - Alder mechanism and is not compatible with the high Arrhenius parameters, indicative of a stepwise, biradical mechanism.

Thermal Decomposition of 2,3-Dihydro-1,4-benzodioxin and 1,2-Dimethoxybenzene

Rates and mechanisms of decomposition of 2,3-dihydro-1,4-benzodioxin (1) and 1,2-dimethoxybenzene (27) have been investigated in the gas phase near atmospheric pressure between 750 and 900 K in a tubular flow reactor in a large excess of radical trapping agents.The following rate expressions for decomposition have been determined: log kt/s-1 (1) = 15.7 - (271 kJ mol-1/2.303 RT); log kt/s-1 (27) = 15.7 - (251 kJ mol-1/2.303 RT).The main decomposition routes for 1 are the formation of o-benzoquinone (2) and 2-methyl-1,3-benzodioxole (7) through a biradical intermediate.The measured activation energy is 20 kJ mol-1 above the required C-O bond dissociation energy.Compound 2 rapidly loses CO to form cyclopenta-2,4-dien-1-one (6) which after dimerisation decomposes mainly into 3-phenylprop-2-enal (12) and indenols (14).The main product of the thermolysis of 27 is o-hydroxybenzaldehyde (33).The O-methyl bond is weakened by 16 kJ mol-1 compared to methoxybenzene as a result of the o-methoxy-substitution.