3225-37-4

Upstream product

• 89713-14-4 4-diazo-2,5-cyclohexadienone 
• 133985-05-4 1H-bicyclo<3.1.0>hexa-3,5-dien-2-one 

Downstream Products

• 94324-06-8 4-Oxomethylene-cyclohexa-2,5-dienone 
• 89713-14-4 4-diazo-2,5-cyclohexadienone 
• 118949-77-2 p-benzoquinone oxide 
• 150-76-5 4-methoxy-phenol 
• 106-41-2 4-bromo-phenol 
• 106-48-9 4-chloro-phenol 
• 123-31-9 hydroquinone 
• 106-51-4 p-benzoquinone 
• 133985-08-7 C₆⁽²⁾H₄O 

Relevant academic research and scientific papers

Heavy-atom tunneling in the ring opening of a strained cyclopropene at very low temperatures

The highly strained 1H-bicyclo[3.1.0]-hexa-3,5-dien-2-one 1 is metastable, and rearranges to 4-oxacyclohexa-2,5-dienylidene 2 in inert gas matrices (neon, argon, krypton, xenon, and nitrogen) at temperatures as low as 3 K. The kinetics for this rearrangement show pronounced matrix effects, but in a given matrix, the reaction rate is independent of temperature between 3 and 20 K. This temperature independence means that the activation energy is zero in this temperature range, indicating that the reaction proceeds through quantum mechanical tunneling from the lowest vibrational level of the reactant. At temperatures above 20 K, the rate increases, resulting in curved Arrhenius plots that are also indicative of thermally activated tunneling. These experimental findings are supported by calculations performed at the CASSCF and CASPT2 levels by using the small-curvature tunneling (SCT) approximation. Quantum mechanical tunneling: Despite an estimated activation barrier of more than 6 kcal mol -1, the strained cyclopropene 1 rearranges at temperatures as low as 3 K to the carbene 2 in its triplet ground state (see figure). Experiments and theory provide clear evidence that the rearrangement proceeds through heavy-atom tunneling.

Deuterium and hydrogen tunneling in the hydrogenation of 4-oxocyclohexa-2,5-dienylidene

4-Oxocyclohexa-2,5-dienylidene is a highly reactive triplet ground state carbene that is hydrogenated in solid H2, HD, and D2 at temperatures as low as 3 K. The mechanism of the insertion of the carbene into dihydrogen was investigated by IR and EPR spectroscopy and by kinetic studies. H or D atoms were observed as products of the reaction with H2 and D2, respectively, whereas HD produces exclusively D atoms. The hydrogenation shows a very large kinetic isotope effect and remarkable isotope selectivity, as was expected for a tunneling reaction. The experiments, therefore, provide clear evidence for both hydrogen tunneling and the rare deuterium tunneling in an intermolecular reaction. Tunnel beats mountain pass: Triplet oxocyclohexadienylidene readily reacts with H2, HD, and even D2 at 3 K by a tunneling reaction. The experiments provided clear evidence for both hydrogen tunneling and the rare deuterium tunneling in an intermolecular reaction (see figure).

α,2-, α,3-, and α,4-dehydrophenol radical anions: Formation, reactivity, and energetics leading to the heats of formation of α,2-, α,3-, and α,4-oxocyclohexadienylidene

We have regiospecifically generated the α2-, α3-, and α4-dehydrophenoxide anions by collisional activation of o-, m-, and p-nitrobenzoate. The α,2 and α,4 isomers also were synthesized by reacting o-benzyne radical anion with carbon dioxide and electron i

Photochemistry of p-benzoquinone diazide carboxylic acids: Formation of 2,4-didehydrophenols

The photochemistry of p-benzoquinone diazide carboxylic acids (7) was studied using matrix isolation spectroscopy, product analysis, and high-level ab initio molecular orbital theory. The general photochemical pathway observed includes primary carbene formation, followed by secondary photodecarboxylation to yield derivatives of 2,4-didehydrophenol 9. CCSD(T) calculations on the parent 2,4-didehydrophenol (9a) lead to an infrared spectrum which is in excellent agreement with the experiment alone. Furthermore; calculations predict 9a to be characterized by a distorted benzene ring with the hydroxy group pointing toward the radical center in ortho position. The heat of formation of 9a is predicted to be 85 kcal/mol. Its formation from 1-oxo-2,5-cyclohexadien-4-ylidene-2-carboxylic acid (8a) by decarboxylation is exothermic by 30 kcal/mol where strong H-bonding in 8a can be considered to facilitate the formation of 9a.

1H-bicyclo[3.1.0]hexa-3,5-dien-2-one. A strained 1,3-bridged cyclopropene

Triplet 4-oxocyclohexa-2,5-dienylidene (5) gives 1H-bicyclo[3.1.0]hexa-3,5-dien-2-one (4) on irradiation into its long-wavelength triplet-triplet absorption band (λ = 508-566 nm). Bicyclus 4 was characterized by IR spectroscopy in partially oriented matrices, by deuterium and oxygen-18 isotopic labeling and by comparison of experimental data with ab initio calculations. 4 is highly labile and readily rearranges back to carbene 5 thermally or on visible light (λ = 470 nm) or infrared irradiation. The rates of the thermal 4→5 rearrangement have been measured in argon, krypton, xenon, and nitrogen matrices, and deuterium kinetic isotope effects have been determined. The data show that 4 is directly transformed into 5, with intersystem crossing being rate determining. At low temperatures (20 K), the rates are independent of temperature, which indicates that the rearrangement occurs via quantum mechanical tunneling. MP2/6-31G(d) calculations show that the cyclopropene ring in 4 is tilted by 129.6° with regard to the cyclopentene ring. The torsional angle between the two carbon 2pπ-orbitals in the cyclopropene ring is 9°, and the pyramidalization angles at C5 are 19.2°. The extra strain energy caused by distortion of the cyclopropene double bond is compensated by the π-stabilization energy of the dienone system. Thus, the total strain energy is only 54 ±1 kcal/mol - comparable to the strain energy of cyclopropene.