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The photoelectrochemical behaviour of several chlorinated nitrobenzenes has been investigated using steady state channel flow cell methods. It has been shown that, in acetonitrile+0.1 M TBAHFP, 4-chloronitrobenzene (p-CNB), 2-chloronitrobenzene (o-CNB), 2,4-dichloronitrobenzene (2,4-DCNB), 2,6-dichloronitrobenzene (2,6-DCNB) and 1,3,5-trichloro-2-nitrobenzene (TCNB) can undergo reversible one-electron reductions to form radical anions that are stable on the timescale of at least tens of seconds under dark conditions. When the electrode surface is irradiated with light of intensity 2 mW cm−2, the electrochemically formed radical anions can absorb light to form an excited state from which dechlorination is favoured. Reactivity orders of o-CNB>p-CNB>2,4-DCNB>2,6-DCNB>TCNB at 330 nm, and o-CNB>2,4-DCNB>2,6-DCNB>p-CNBTCNB at 470 nm have been determined. The relative order is rationalised in terms of radical anion lifetime effects and the role of heavy atom subsituents in reducing the excited state lifetime. 相似文献
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On the basis of competition experiments using a model VNS reaction of chloromethyl phenyl sulfone with halonitrobenzenes it was shown that halogen substituents activate electron-deficient nitroarenes for the addition of carbanions whereas they protect the positions they occupy against the addition. 相似文献
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