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首页> 外文期刊>Chemistry: A European journal >Nitration of Alkanes with Nitric Acid by Vanadium-Substituted Polyoxometalates
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Nitration of Alkanes with Nitric Acid by Vanadium-Substituted Polyoxometalates

机译：钒取代的多金属氧酸盐对硝酸与烷烃的硝化

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摘要

The nitration of alkanes by using nitric acid as a nitrating agent in acetic acid was efficiently promoted by vanadium-substituted Keggin-type phosphomolybdates such as [H_4PVMo_(11)O_(40)],[H_5PV_2Mo_(10)O_(40)],and [H_6PV_3Mo_9O_(40)] as catalyst precursors.A variety of alkanes including alkyl-benzenes were nitrated to the corresponding nitroalkanes as major products in moderate yields with formation of oxygenated products under mild reaction conditions.The carbon-carbon bond cleavage reactions hardly pro-ceeded.ESR,NMR,and IR spectros-copic data show that the vanadium-substituted polyoxometalate,for example,[H_4PVMo_(11)O_(40)],decomposes to form free vanadium species and [PMo_(12)O_(40)]~(3-)Keggin anion.The reaction mechanism involving a radical-chain path is proposed.The polyoxo-metalates initially abstract the hydro- gen of the alkane to form the alkyl radical and the reduced polyoxometalates.The reduced polyoxometalates subsequently react with nitric acid to produce the oxidized form and nitrogen dioxide.This step would be promoted mainly by the phosphomolybdates,[PMo_(12)O_(40)]~(n-),and the vanadium cations efficiently enhance the activity.The nitrogen dioxide promotes the further formation of nitrogen dioxide and an alkyl radical.The alkyl radical is trapped by nitrogen dioxide to form the corresponding nitroalkane.
机译：钒取代的Keggin型磷钼酸盐，例如[H_4PVMo_（11）O_（40）]，[H_5PV_2Mo_（10）O_（40）]，使用硝酸作为乙酸中硝化剂的烷烃的硝化作用得到了有效促进。并以[H_6PV_3Mo_9O_（40）]作为催化剂前体。以中等收率将包括烷基苯在内的多种烷烃硝化成相应的硝基烷烃作为主要产物，并在温和的反应条件下形成了氧化产物。碳-碳键断裂反应难以进行的ESR，NMR和IR光谱数据表明，钒取代的多金属氧酸盐，例如[H_4PVMo_（11）O_（40）]，分解形成游离的钒物质，而[PMo_（12）O_（40 ）]〜（3-）Keggin阴离子。提出了涉及自由基链路径的反应机理。多金属氧酸盐首先提取烷烃的氢，形成烷基和还原的多金属氧酸盐，然后还原的多金属氧酸盐发生反应。用硝酸产生氧化d形式和二氧化氮。该步骤主要由磷钼酸盐[PMo_（12）O_（40）]〜（n-）促进，钒阳离子有效地提高了活性。二氧化氮促进了氮的进一步形成烷基被二氧化氮捕获以形成相应的硝基烷。

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