《有机化学精品教学》（汕头大学）Chap.02 Alkane.pptVIP

* * * * * * * * * * * 碘不能与甲烷发生取代反应生成碘甲烷，但其逆反应很容易进行 * * * * 甲烷是天然气的最主要成分，约占了87%，是一种很重要的燃料。同时它也是一种温室气体：其全球变暖潜能为21（即它的暖化能力比二氧化碳高二十一倍）。它主要的来源有： 有机废物的分解 天然源头（如沼泽）：23%；从化石燃料中提取：20%；动物（如牛）的消化过程：17%；稻田之中的细菌：12%；生物物质缺氧加热或燃烧。 甲烷同时也是一种窒息剂，在密闭空间内可能会取代氧气。若氧气被甲烷取代后含量低于19.5%时可能导致窒息。 * * * * * * * * 汽油C4-8，煤油C10-16,柴油C15-20。异辛烷用作抗爆性优良的标准，辛烷值定为100；正庚烷用作抗爆性低劣的标准，辛烷值为0 * * * * * * * * * * * * * * * * * * * * * * * √ × 1 2 3 4 5 6 7 1 2 3 4 5 6 7 * * * D 2,2-dimethylbutane E 2,3-dimethylbutane C6H14: * 1 2 3 4 5 6 1 2 3 4 5 3-methylhexane √ × * 1 2 3 4 5 6 7 1 2 3 4 5 6 7 3-ethyl-2-methylheptane √ × * 3-chlorohexane Cl 1 2 3 4 5 6 Cl 1 2 3 4 5 6 Cl * 3-methylhexane 1 2 3 4 5 6 2 3 4 5 1 5 6 1 2 3 4 * 2,3,6-trimethylheptane 1 2 3 4 5 6 7 1 2 3 4 5 6 7 √ × * F F 3,3-difluorohexane 2-chloro-3-fluorobutane Cl F 1 2 3 4 not 3-chloro-2-fluorobutane not 2-fluoro-3-chlorobutane * 4-bromo-3-methylhexane 4-tert-butyl-5-chlorooctane Br 6 5 4 3 2 1 Cl C(CH3)3 1 2 3 4 5 6 7 8 not 3-bromo-4-methylhexane not 3-methyl-4-bromohexane not 4-chloro-5-tert-butyloctane * 1 2 3 4 5 6 1 2 3 4 5 6 7 3-ethyl-2,2,5-trimethylhexane 3,4-dichloro-4-ethyl-5-methylheptane * Section 3 Isomerism of Alkane Ⅰ. carbon-chain isomer Isomers: Molecules have the same formula but different structures. carbon-chain isomers: Molecules have the same formula but different structure of carbon-chains. * C4H10 n-butane iso-butane or 2-methylpropane C5H10 n-pentane neo-pentane or 2,2-dimethylpropane iso-pentane or 2-methylbutane * Ⅱ.conformational isomer （构象异构） Conformation:The three-dimensional structure of a molecule. Conformational isomers are interconverted by rotations about ? bonds. * Because rotations of bond ?C-C , countless conforma- tional isomer would be formed. The conformations are expressed by sawhorse formula（锯架式） or Newman projection formula（纽曼投影式）. H H H H H H H H H H H H sawhorse formula Newman projection formula * ethane * Extreme Conformations of Ethane (CH3CH3) Name of Conform