在标准状况下，密度Z小的气体是（　　） A．NO 2 B．SO 2 C．O 2 D．CH

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在标准状况下，密度Z小的气体是（　　） A．NO 2 B．SO 2 C．O 2 D．CH 4

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tenniingqq 2017-11-22 00:00:00

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在标准状况下，密度Z小的气体是（　　） A．NO 2 B．SO 2 C．O 2 D．CH: 在标准状况下，密度Z小的气体是（　　） A．NO 2 B．SO 2 C．O 2 D．CH 4

标准状况下1mol气体的体积为22.4L，那么2mol气体就是2×22.4L=44.8L了？:

难溶于水的非金属氧化物是（　　） A．MnO 2 B．CO 2 C．NO 2 D．SiO: 难溶于水的非金属氧化物是（　　） A．MnO 2 B．CO 2 C．NO 2 D．SiO 2

气体的密度，标准状况下气体的密度: 气体的密度(g/L)= _______即ρ= ________:

战地2就战地2嘛，什么男朋友2:

小时代2什么时候上映: 小时代2什么时候上映... 小时代2什么时候上映展开

下列单质中，Z容易与氢气发生反应的是 A．O 2 B．N 2 C．F 2 D．Cl: 下列单质中，Z容易与氢气发生反应的是 A．O 2 B．N 2 C．F 2 D．Cl 2

狙击精英2提示鼠标按键2探头什么是鼠标按键2:

断路器S263H/C25*2*2什么意思:

同质量的下列气体中，所含原子数Z多的是 A．CH 4 B．CO 2 C．H 2 S D．N: 同质量的下列气体中，所含原子数Z多的是 A．CH 4 B．CO 2 C．H 2 S D．N 2

A H为气体单质且A是标准状况下密度Z小的气体 EF是两种生活中常见的盐

英语翻译(2): Keywords:Epoxides;Amines;2-Aminoalcohols;Yttriumnitratehexahydrate;RegioselectivityAminoalcoholsconstituteanimportantclassofcompoundshavingbothchemicalandbiologicalapplic... Keywords: Epoxides; Amines; 2-Amino alcohols; Yttrium nitrate hexahydrate; Regioselectivity Amino alcohols constitute an important class of compoundshaving both chemical and biological applications. They are important pharmacophores present in various inhibitors and are used as building blocks for the synthesis of biologically active natural products， insecticidal agents and chiral auxillaries for asymmetric reactions.1a–f They act as starting materials for the synthesis of oxazolines which are useful in the polymer industry.1g Owing to their widespread applications， the synthesis of amino alcohols has received much attention in recent years. Traditionally， 2-amino alcohols are prepared by heating an epoxide with an excess of amine at elevated temperature. The use of a high temperature leads to undesired side reactions and also limits the applicability towards temperature sensitive substrates. To overcome these drawbacks various promoters such as ZnCl2，2 ScOTf，3 MgBr2OEt2，4 67 9 bismuth salts，5 CoCl2， CuBF4， DIPAT，8 Ti(OiPr)4， 1011 12TaCl5， ZrCl4， Sm(OTf)3， potassium dodecatungstocobaltate， 13 and aluminosilicate14 have been employed for the above transformation. The use of non-conventional techniques such as microwave irradiation at elevated temperaturehas also been reported.15 Recently， the use of Al(OTf)3 (1 mol %) as catalyst in toluene at reflux has also been reported.16 Although significant advances have been made in this area， low regioselectivity， longer reaction time， use of elevated temperature， high catalyst loading， toxic solvents and lower substrate compatibilitylimit their applications.Thus there is a need to develop an efficient catalytic protocol for ring opening of various epoxides with aliphatic， aromatic andheteroaromatic amines under ambient conditions 展开