4-oxocyclohexa-2,5-dienylidene carbene | 42766-45-0

• 分子结构分类: 有机化合物 - 有机氧化合物
• 英文名称: 4-oxocyclohexa-2,5-dienylidene carbene
• 英文别名: α,4-oxocyclohexadienylidene；4-oxacyclohexa-2,5-dienylidene；4-oxocyclohexa-2,5-dienylidene；4-Oxo-2,5-cyclohexadienyliden；cyclohexadienone carbene；4-ylo-phenyloxyl
• CAS: 42766-45-0；3225-37-4；162827-89-6
• 化学式: C₆H₄O
• 分子量: 92.0972
• InChiKey: GVNCFPLWSTWGBZ-UHFFFAOYSA-N

计算性质

• 辛醇/水分配系数(LogP)：
  1.5
• 重原子数：
  7
• 可旋转键数：
  0
• 环数：
  1.0
• sp3杂化的碳原子比例：
  0.0
• 拓扑面积：
  23.1
• 氢给体数：
  0
• 氢受体数：
  1

反应信息

• 作为反应物：
  描述：

  4-oxocyclohexa-2,5-dienylidene carbene 在 氢溴酸 作用下， 以 水 为溶剂， 生成 4-溴苯酚
  参考文献：
  名称：

  Formation and Reactivity of 4-Oxocyclohexa-2,5-dienylidene in the Photolysis of 4-Chlorophenol in Aqueous Solution at Ambient Temperature

  摘要：

  Nanosecond laser flash photolysis of an aqueous solution of 4-chlorophenol (lambda(exc) = 266 nm) produces, at pulse end, a transient with absorption maxima at 384, 370, and ca. 250 nm; upon addition of an H-donor such as 2-propanol, this spectrum is converted into that of the phenoxyl radical (lambda(max) = 400 and 385 nm), and in presence of O-2, it is converted into a transient with a broad absorption band peaking at 460 nm. This reaction behavior can be understood by assuming formation of the carbene, 4-oxocyclohexa-2,5-dienylidene, by elimination of HCl from excited 4-chlorophenol; the pulse end transient spectrum is assigned to this species, while the 460 nm band is assigned to benzoquinone O-oxide formed by addition of O-2 to the carbene. Both phenoxyl radical and benzoquinone O-oxide are produced upon photolysis of 4-chlorophenol in neat alkanols as well. On the other hand, photolysis in n-hexane yields the triplet-triplet absorption, which is absent in polar solvents, and no indication of carbene formation. It can be concluded that the primary step of 4-chlorophenol photolysis in aqueous or alcoholic solution is heterolytic C-Cl bond scission; a quantum yield of 0.75 is determined for it in neutral or acid aqueous medium upon excitation at 266 nm. Photolysis of chlorophenolate produces the same transients, but with a markedly lower yield, and, in addition, e(aq)(-) and 4-chlorophenoxyl radicals. The proposed reaction mechanism provides a straightforward explanation of the results of photoproduct analysis, published by previous authors as well as contributed in the present work. In particular, formation of p-benzoquinone in the presence of O-2 can be accounted for by intermediate formation of benzoquinone O-oxide. Production of 4-oxocyclohexa-2,5-dienylidene with high yield allows, for the first time, extensive investigation of the kinetics and mechanism of the reactions of a carbene in an aqueous environment. In the present work, we have studied (a) the addition reaction with O-2 on the one hand and with halides on the other; (b) H abstraction reactions with alkanols; (c) reaction with 4-chlorophenol itself; and (d) reaction with H2O. The rate constants for reaction with O-2 (3.5 x 10(9) M(-1) s(-1)) and with I- (4.6 x 10(9) M(-1) s(-1)) are close to the diffusion-controlled limit, whereas reactions with Br- (6.8 x 10(7) M(-1) s(-1)) and Cl- (<3 x 10(5) M(-1) s(-1)) are slower. Rate constants for reaction with alkanols follow the pattern known for their reactions with radicals, with values ranging from 5 x 10(5) M(-1) s(-1) for tert-butyl alcohol to 1.9 x 10(7) M(-1) s(-1) for 2-butanol. All these observations are consistent with the triplet character of the carbene. A rate constant of 1.5 x 10(3) M(-1) s(-1) has been determined for reaction with H2O. This reaction is not accompanied by formation of OH radicals; it is concluded that it proceeds by insertion into the O-H bond rather than by O-H cleavage. The exceptional stability of the carbene in aqueous solution is thus mainly attributed to the high barrier for O-H rupture in the water molecule. Additionally, a specific carbene-H2O interaction is revealed by semiempirical calculations, which could contribute to energetic and orientational hindrance of the reaction. Further theoretical results support the interpretation of both spectroscopic and kinetic properties of the carbene.

  DOI：

  10.1021/ja00104a029
• 作为产物：
  描述：

  α,4-dehydrophenol radical anion 在 对二硝基苯 作用下， 生成 4-oxocyclohexa-2,5-dienylidene carbene
  参考文献：
  名称：

  α,2-、α,3- 和 α,4-脱氢苯酚自由基阴离子：导致 α,2-、α,3- 和 α,4-氧代环己二亚基形成热的形成、反应性和能量学

  摘要：

  我们通过邻、间和对硝基苯甲酸盐的碰撞活化，区域特异性地生成了 α,2-、α,3- 和 α,4- 脱氢苯氧阴离子。α,2 和 α,4 异构体也是通过邻苄基阴离子与二氧化碳反应和对重氮苯酚的电子电离合成的。所有三种脱氢酚自由基阴离子都相互区分，并通过探测它们与几种试剂的化学反应性来鉴定。每种异构体也被转化为酚盐及其相应的醌。对所有三种自由基阴离子进行了热化学测量，并报告了它们的氢原子亲和力、质子亲和力和电子结合能。这些测量的量在热力学循环中组合以推导出每个自由基阴离子及其相应的卡宾（即 α,2-、α、3-, 和 α,4- 脱氢苯酚)。这些结果与适当参考化合物的 MCQDPT2、G3、G2+(MP2) 和 B3LYP 计算和实验数据进行了比较。

  DOI：

  10.1021/ja029571c

文献信息

• Heavy-Atom Tunneling in the Ring Opening of a Strained Cyclopropene at Very Low Temperatures
  作者：Melanie Ertelt、David A. Hrovat、Weston Thatcher Borden、Wolfram Sander

  DOI：10.1002/chem.201303792

  日期：2014.4.14

  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

  高度应变的1H-双环[3.1.0] -hexa-3,5-dien-2-one 1是亚稳态的，并重排为4-oxacyclohexa-2,5-dienylidene 2在惰性气体基质（氖气，氩气，k气，氙气和氮气）中的温度低至3K。这种重排的动力学表现出明显的基质效应，但是在给定的基质中，反应速率与温度在3至30之间无关。 20K。这种温度无关性意味着在此温度范围内活化能为零，这表明反应是通过从反应物的最低振动能级进行的量子力学隧穿来进行的。在高于20 K的温度下，速率增加，导致弯曲的Arrhenius曲线也表明热激活隧穿。这些实验结果得到了使用小曲率隧穿（SCT）近似在CASSCF和CASPT2级别进行的计算的支持。
• Photochemistry of <i>p</i>-Benzoquinone Diazide Carboxylic Acids:  Formation of 2,4-Didehydrophenols
  作者：Wolfram Sander、Götz Bucher、Holger Wandel、Elfi Kraka、Dieter Cremer、William S. Sheldrick

  DOI：10.1021/ja971731a

  日期：1997.11.1

  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

  使用基质分离光谱、产物分析和高级从头分子轨道理论研究了对苯醌二叠氮羧酸 (7) 的光化学。观察到的一般光化学途径包括初级卡宾的形成，然后是二级光脱羧以产生 2,4-二脱氢苯酚 9 的衍生物。母体 2,4-二脱氢苯酚 (9a) 的 CCSD(T) 计算导致红外光谱非常好与实验一致。此外，计算预测 9a 的特征在于一个扭曲的苯环，其中羟基指向邻位的自由基中心。9a 的生成热预计为 85 kcal/mol。它由 1-oxo-2 形成，
• Deuterium and Hydrogen Tunneling in the Hydrogenation of 4‐Oxocyclohexa‐2,5‐dienylidene
  作者：Stefan Henkel、Melanie Ertelt、Wolfram Sander

  DOI：10.1002/chem.201402064

  日期：2014.6.16

  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

  4-氧代环己基-2,5-二烯亚基是一种高反应性三重态基态卡宾，其在低至3 K的温度下在固体H 2，HD和D 2中氢化。研究了卡宾插入二氢的机理通过IR和EPR光谱学和动力学研究。观察到H或D原子分别是与H 2和D 2反应的产物，而HD仅产生D原子。如隧穿反应所预期的，氢化显示出非常大的动力学同位素效应和显着的同位素选择性。因此，实验为分子间反应中的氢隧穿和稀有氘核隧穿提供了清晰的证据。
• 1H-Bicyclo[3.1.0]hexa-3,5-dien-2-one. A strained 1,3-bridged cyclopropene
  作者：Wolfram Sander、Goetz Bucher、Felix Reichel、Dieter Cremer

  DOI：10.1021/ja00014a026

  日期：1991.7

  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 (lambda = 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 (lambda = 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-degrees with regard to the cyclopentene ring. The torsional angle between the two carbon 2p-pi-orbitals in the cyclopropene ring is 9-degrees, and the pyramidalization angles at C5 are 19.2-degrees. The extra strain energy caused by distortion of the cyclopropene double bond is compensated by the pi-stabilization energy of the dienone system. Thus, the total strain energy is only 54 +/- 1 kcal/mol-comparable to the strain energy of cyclopropene.
• Sander, Wolfram; Mueller, Wolfgang; Sustmann, Reiner, Angewandte Chemie, 1988, vol. 100, # 4, p. 577 - 579
  作者：Sander, Wolfram、Mueller, Wolfgang、Sustmann, Reiner

  DOI：——

  日期：——