Laser flash photolysis study of the reactions of carbonyl triplets with phenols and photochemistry of p-hydroxypropiophenone
作者:P. K. Das、M. V. Encinas、J. C. Scaiano
DOI:10.1021/ja00404a029
日期:1981.7
process involves electronic energy transfer. The temperature dependence of a few representative systems, as well as the quenching by methyl ethers of similar structure, has also been examined. The photochemistry of p-hydroxypropiophenone is characterized by efficient self-quenching involving a head-to-tail hydrogen-transfer reaction.
对于 n,..pi..* 和..pi..,..pi..* 状态,苯酚对芳香族羰基三联体的猝灭是一个非常快的过程。苯中二苯甲酮三联体的代表性速率常数为 1.3 x 10/sup 9/(苯酚)和 8.1 x 10/sup 8/(间氟苯酚)M/sup -1/ s/sup -1/,而对甲氧基苯甲酮对于同一对底物,该值为 4.9 x 10/sup 9/ 和 5.0 x 10/sup 9/ M/sup -1/ s/sup -1/;检查了 18 种不同的酚。由于氢键,湿乙腈中的速率常数较小;例如,对于二苯甲酮-苯酚系统,我们测得 8.0 x 10/sup 7/ M/sup -1/ s/sup -1/。对甲氧基苯丙酮的同位素效应大于二苯甲酮:例如,在苯酚的情况下,k/sub H//k/sub D/ 的值分别为 3.9 和 1.2(在湿乙腈中)。淬灭反应导致苯氧基和羰基自由基的有效但非定量形成,唯一的例外是
The hydrogen atom transfer reactivity of sulfinic acids
作者:Markus Griesser、Jean-Philippe R. Chauvin、Derek A. Pratt
DOI:10.1039/c8sc02400f
日期:——
thiols (∼107 M−1 s−1) and sulfenic acids (∼109 M−1 s−1). Importantly, since sulfinic and sulfenic acids are very strong H-bond donors (αH2 ∼ 0.63 and 0.55, respectively), their reactivity is greatly attenuated in H-bond accepting solvents, whereas the reactivity of thiols is largely solvent-independent. Efforts to measure rate constants for the reactions of sulfinic acids with alkylperoxyl radicals were
亚磺酸(RSO 2 H)因其容易自氧化而成为困难的试剂而闻名。然而,近来它们已在各种有用的自由基链反应中用作关键试剂。为了解决这一矛盾,并使使用亚磺酸的自由基反应得以进一步发展,我们首次表征了其H原子转移反应的热力学和动力学。通过自由基平衡确定亚磺酸的OH键离解焓(BDE)为〜78 kcal mol -1;大致中途的RS-H BDE在硫醇(~87千卡mol之间-1)和RSO-H BDE在次磺酸(约70千卡摩尔-1)。无论如何,RSH,RSOH和RSO 2H与烷基具有相对相似的固有H原子转移反应性(〜10 6 M -1 s -1)。与直觉相反,具有更多反应性烷氧基的速率常数趋势遵循反应能量:RSO 2 H约为10 8 M -1 s -1,硫醇(约10 7 M -1 s -1)和亚硫酸之间(〜10 9 M -1 s -1)。重要的是,由于亚和次磺酸都非常强的氢键供体(α ħ 2分别为约0.63和0
The reactivity of ketyl and alkyl radicals in reactions with carbonyl compounds
作者:E. T. Denisov
DOI:10.1007/bf02494263
日期:1998.11
parabolic model of bimolecular radical reactions was used for analysis of the hydrogen transfer reactions of ketyl radicals: >C·OH+R1COR2→>C=O+R1R2C·OH. The parameters describing the reactivity of the reagents were calculated from the experimental data. The parameters that characterize the reactions of ketyl and alkyl radicals as hydrogen donors with olefins and with carbonyl compounds were obtained: >C·OH
Nanosecond flash studies of reduction of benzophenone by aliphatic amines. Quantum yields and kinetic isotope effects
作者:Shai Inbar、Henry Linschitz、Saul G. Cohen
DOI:10.1021/ja00395a009
日期:1981.3
.cap alpha..-C, does not occur with common aliphaticamines but does with Dabco (VIII). The latter quenching is markedly increased by small additions of acetonitrile; the flash spectrum from this compound indicates formation of a triplet amine CT complex or radical ion pair. Triplet-reductant interaction rate constants, k/sur ir/, are high for the amines (approx. 10/sup 8/-10/sup 9/ M/sup -1/ s/sup
Laser photolysis investigation of induced quenching in photoreduction of benzophenone by alkylbenzenes and anisoles
作者:Katsuji Okada、Minoru Yamaji、and Haruo Shizuka
DOI:10.1039/a707900a
日期:——
by electron transfer (ET) to produce the benzophenone anion (BP-) and corresponding cation (AD+) radicals with efficiencies, αET<1 whereas no chemical species were formed in Bz; and (2) photoreduction of 3BP* by ABs resulted in benzophenone ketyl radical (BPK) formation by benzylic hydrogen abstraction (HA) with efficiencies αHA<1 in Bz and ACN–H2O (4:1 v/v). The residual efficiency (αIQ: 1-αET or
研究了在苯(Bz)和乙腈(ACN)与水(4:1 v / v)的混合物中烷基苯(AB)和苯甲醚衍生物(AD)淬灭三联体二苯甲酮(3 BP *)的过程。速率常数和效率由295 K处355 nm的纳秒激光闪光光解所确定。我们发现(1)可以控制ACN–H 2 O(4:1 v / v)中的AD使3 BP *失活通过电子转移(ET),以产生二苯甲酮阴离子(BP - )和相应的阳离子(AD +)与效率自由基,α ET <1,而在的Bz未形成化学物种; 和(2)3的光还原ABs的BP *通过苄基氢提取(HA)导致二苯甲酮酮基(BPK)形成,在Bz和ACN–H 2 O中效率αHA <1 (4:1 v / v)。残留效率(αIQ:1- αET或1- αHA)归因于没有光化学产物的双分子过程,被称为“诱导猝灭(IQ)”。AD和AB的3 BP *的猝灭速率常数(k q)小于Bz和ACN–H 2 O的扩散极限(4:1