Vibrational Excitation of Both Products of the Reaction of CN Radicals with Acetone in Solution.
Vibrational Excitation of Both Products of the Reaction of CN Radicals with Acetone in Solution.
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DOI：
10.1021/acs.jpca.5b05624
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发表时间：
2015-12-17
期刊：
影响因子：
--
通讯作者：
Orr-Ewing AJ
中科院分区：
文献类型：
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作者：
Dunning GT;Preston TJ;Greaves SJ;Greetham GM;Clark IP;Orr-Ewing AJ
瞬态电子和振动吸收光谱揭示了氘代氯仿溶液中 CN 自由基与丙酮的双分子反应的机制和动力学。 CN 自由基是通过溶解的 ICN 的超快紫外光解产生的。 CN自由基的两种反应形式通过其电子吸收带来区分：“游离”（未络合的）CN自由基和与溶剂分子络合的“溶剂化”CN自由基。由于与 ICN 和 INC 的成对重组、与 CDCl3 分子的络合以及与丙酮的反应，CN 自由基在光解产生后的寿命仅限于几皮秒。丙酮反应的速率系数为 (8.0 ± 0.5) × 1010 M–1 s–1，C=N 和 C=O 拉伸区域的瞬态振动光谱表明，新生的 HCN 和 2-氧代丙基 (CH3C(O)CH2) 自由基产物均受到振动激发。溶剂化 CN 与丙酮的反应速率系数比游离 CN 慢 40 倍，速率系数为 (2.0 ± 0.9) × 109 M–1 s–1，由 HCN 产物 v1(C=N 拉伸) IR 吸收带的上升得到。还提供了 CN 与丙酮的配合物的证据，由于 CN 与羰基的相互作用，其结合力比 CN-CDCl3 配合物更强。这些关联性更强的自由基的反应速率更慢。
Transient electronic and vibrational absorption spectroscopy unravel the mechanisms and dynamics of bimolecular reactions of CN radicals with acetone in deuterated chloroform solutions. The CN radicals are produced by ultrafast ultraviolet photolysis of dissolved ICN. Two reactive forms of CN radicals are distinguished by their electronic absorption bands: “free” (uncomplexed) CN radicals, and “solvated” CN radicals that are complexed with solvent molecules. The lifetimes of the free CN radicals are limited to a few picoseconds following their photolytic production because of geminate recombination to ICN and INC, complexation with CDCl3 molecules, and reaction with acetone. The acetone reaction occurs with a rate coefficient of (8.0 ± 0.5) × 1010 M–1 s–1 and transient vibrational spectra in the C=N and C=O stretching regions reveal that both the nascent HCN and 2-oxopropyl (CH3C(O)CH2) radical products are vibrationally excited. The rate coefficient for the reaction of solvated CN with acetone is 40 times slower than for free CN, with a rate coefficient of (2.0 ± 0.9) × 109 M–1 s–1 obtained from the rise in the HCN product v1(C=N stretch) IR absorption band. Evidence is also presented for CN complexes with acetone that are more strongly bound than the CN–CDCl3 complexes because of CN interactions with the carbonyl group. The rates of reactions of these more strongly associated radicals are slower still.