{"id":1660,"date":"2018-03-21T15:38:18","date_gmt":"2018-03-21T15:38:18","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/suny-orgbiochemistry\/chapter\/physical-properties-of-amines\/"},"modified":"2018-11-09T15:15:40","modified_gmt":"2018-11-09T15:15:40","slug":"physical-properties-of-amines","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/suny-monroecc-orgbiochemistry\/chapter\/physical-properties-of-amines\/","title":{"raw":"15.12 Physical Properties of Amines","rendered":"15.12 Physical Properties of Amines"},"content":{"raw":"
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Learning Objectives<\/h3>\r\n
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  1. Explain why the boiling points of primary and secondary amines are higher than those of alkanes or ethers of similar molar mass but are lower than those of alcohols.<\/li>\r\n \t
  2. Compare the boiling points of tertiary amines with alcohols, alkanes, and ethers of similar molar mass.<\/li>\r\n \t
  3. Compare the solubilities in water of amines of five or fewer carbon atoms with the solubilities of comparable alkanes and alcohols in water.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
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    Primary and secondary amines have hydrogen atoms bonded to an nitrogen atom and are therefore capable of intermolecular hydrogen bonding as shown in Part (a) of Figure 15.6 \"Hydrogen Bonding.<\/a>\u00a0 The hydrogen bonding between amine molecules is not as strong as hydrogen bonding between alcohol molecules because nitrogen is less electronegative than oxygen, resulting in smaller partial charges. \u00a0 Thus primary and secondary amines boil at higher temperatures than alkanes but at lower temperatures than alcohols of similar molar masses. For example, compare the boiling point of methylamine (CH3<\/sub>NH2<\/sub>; \u22126\u00b0C) with those of ethane (CH3<\/sub>CH3<\/sub>; \u221289\u00b0C) and methanol (CH3<\/sub>OH; 65\u00b0C).<\/p>\r\n

    Tertiary amines have no hydrogen atom bonded to the nitrogen atom and so cannot participate in intermolecular hydrogen bonding. They have boiling points comparable to those of ethers, reflecting dipole\/dipole intermolecular attractions. (Table 15.5 \"Physical Properties of Some Amines and Comparable Oxygen-Containing Compounds\"<\/a>).<\/p>\r\n\r\n

    \r\n\r\n[caption id=\"\" align=\"alignnone\" width=\"1545\"]\"image\" Figure 15.6 Hydrogen Bonding.\u00a0(a) Amine molecules are associated through hydrogen bonding. (b) An amine molecule can form a hydrogen bond with water molecules.\u00a0 Note color scheme:\u00a0 pink = C, blue = H, orange = O, purple = N.[\/caption]\r\n\r\n \r\n\r\n<\/div>\r\n
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    Table 15.5<\/span> Physical Properties of Some Amines and Comparable Oxygen-Containing Compounds<\/th>\r\n<\/tr>\r\n
    Name<\/th>\r\nCondensed Structural Formula<\/th>\r\nClass<\/th>\r\nMolar Mass<\/th>\r\nBoiling Point (\u00b0C)<\/th>\r\nSolubility at 25\u00b0C (g\/100 g Water)<\/th>\r\n<\/tr>\r\n<\/thead>\r\n
    butylamine<\/td>\r\nCH3<\/sub>CH2<\/sub>CH2<\/sub>CH2<\/sub>NH2<\/sub><\/td>\r\n1\u00b0<\/td>\r\n73<\/td>\r\n78<\/td>\r\nmiscible<\/td>\r\n<\/tr>\r\n
    diethylamine<\/td>\r\n(CH3<\/sub>CH2<\/sub>)2<\/sub>NH<\/td>\r\n2\u00b0<\/td>\r\n73<\/td>\r\n55<\/td>\r\nmiscible<\/td>\r\n<\/tr>\r\n
    butyl alcohol<\/td>\r\nCH3<\/sub>CH2<\/sub>CH2<\/sub>CH2<\/sub>OH<\/td>\r\n\u2014<\/td>\r\n74<\/td>\r\n118<\/td>\r\n8<\/td>\r\n<\/tr>\r\n
    dipropylamine<\/td>\r\n(CH3<\/sub>CH2<\/sub>CH2<\/sub>)2<\/sub>NH<\/td>\r\n2\u00b0<\/td>\r\n101<\/td>\r\n111<\/td>\r\n4<\/td>\r\n<\/tr>\r\n
    triethylamine<\/td>\r\n(CH3<\/sub>CH2<\/sub>)3<\/sub>N<\/td>\r\n3\u00b0<\/td>\r\n101<\/td>\r\n90<\/td>\r\n14<\/td>\r\n<\/tr>\r\n
    dipropyl ether<\/td>\r\n(CH3<\/sub>CH2<\/sub>CH2<\/sub>)2<\/sub>O<\/td>\r\n\u2014<\/td>\r\n102<\/td>\r\n91<\/td>\r\n0.25<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<\/div>\r\n

    All three classes of amines can engage in hydrogen bonding with water as shown in part (b) of Figure 15.6 \"Hydrogen Bonding\"<\/a>. Amines of low molar mass are quite soluble in water; the borderline of solubility in water is at five or six carbon atoms per nitrogen atom.<\/p>\r\n\r\n

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    To Your Health: Amines in Death and Life<\/h3>\r\n

    Amines have \u201cinteresting\u201d odors. The simple ones smell very much like ammonia. Higher aliphatic amines smell like decaying fish. Or perhaps we should put it the other way around: Decaying fish give off odorous amines. The stench of rotting fish is due in part to two diamines: putrescine and cadaverine. They arise from the decarboxylation of ornithine and lysine, respectively, amino acids that are found in animal cells. (For more information about lysine, see Chapter 18 \"Amino Acids, Proteins, and Enzymes\"<\/a>, Section 18.1 \"Properties of Amino Acids\"<\/a>.)<\/p>\r\n\r\n

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    Aromatic amines generally are quite toxic. They are readily absorbed through the skin, and workers must exercise caution when handling these compounds. Several aromatic amines, including \u03b2-naphthylamine, are potent carcinogens.<\/p>\r\n\r\n

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    Concept Review Exercises<\/h3>\r\n
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      Which compound has the higher boiling point, CH3<\/sub>CH2<\/sub>CH2<\/sub>CH2<\/sub>CH2<\/sub>NH2<\/sub> or CH3<\/sub>CH2<\/sub>CH2<\/sub>CH2<\/sub>CH2<\/sub>CH3<\/sub>? Explain.<\/p>\r\n\r\n<\/div><\/li>\r\n \t

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      Which compound is more soluble in water, CH3<\/sub>CH2<\/sub>CH2<\/sub>CH2<\/sub>CH3<\/sub> or CH3<\/sub>CH2<\/sub>NHCH2<\/sub>CH3<\/sub>? Explain.<\/p>\r\n\r\n<\/div><\/li>\r\n<\/ol>\r\n<\/div>\r\n

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      [reveal-answer q=\"652399\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"652399\"]<\/p>\r\n\r\n

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      1. CH3<\/sub>CH2<\/sub>CH2<\/sub>CH2<\/sub>CH2<\/sub>NH2<\/sub> :\u00a0 the nitrogen-to-hydrogen (N\u2013H) bonds can engage in hydrogen bonding between molecules; CH3<\/sub>CH2<\/sub>CH2<\/sub>CH2<\/sub>CH2<\/sub>CH3<\/sub>\u00a0 has only Van Der Waal's forces acting between molecules.<\/li>\r\n \t
      2. CH3<\/sub>CH2<\/sub>NHCH2<\/sub>CH3<\/sub> because amines can engage in hydrogen bonding with water; alkanes cannot engage in hydrogen bonding with water.\u00a0 [\/hidden-answer]<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
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        Key Takeaways<\/h3>\r\n<\/div>\r\n
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