{"id":1699,"date":"2018-03-21T15:41:54","date_gmt":"2018-03-21T15:41:54","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/suny-orgbiochemistry\/chapter\/physical-properties-of-amides\/"},"modified":"2018-11-09T15:41:51","modified_gmt":"2018-11-09T15:41:51","slug":"physical-properties-of-amides","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/suny-monroecc-orgbiochemistry\/chapter\/physical-properties-of-amides\/","title":{"raw":"15.15 Physical Properties of Amides","rendered":"15.15 Physical Properties of Amides"},"content":{"raw":"
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Learning Objectives<\/h3>\r\n
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  1. Compare the boiling points of amides with alcohols of similar molar mass.<\/li>\r\n \t
  2. Compare the solubilities in water of amides 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

    With the exception of formamide (HCONH2<\/sub>), which is a liquid, all simple amides are solids (Table 15.6 \"Physical Constants of Some Unsubstituted Amides\"<\/a>). The lower members of the series are soluble in water, with borderline solubility occurring in those that have five or six carbon atoms. Like the esters, solutions of amides in water usually are neutral\u2014neither acidic nor basic.<\/p>\r\n\r\n

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    Table 15.6<\/span> Physical Constants of Some Unsubstituted Amides<\/strong><\/h5>\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
    Condensed Structural Formula<\/th>\r\nName<\/th>\r\nMelting Point (\u00b0C)<\/th>\r\nBoiling Point (\u00b0C)<\/th>\r\nSolubility in Water<\/th>\r\n<\/tr>\r\n<\/thead>\r\n
    HCONH2<\/sub><\/td>\r\nformamide<\/td>\r\n2<\/td>\r\n193<\/td>\r\nsoluble<\/td>\r\n<\/tr>\r\n
    CH3<\/sub>CONH2<\/sub><\/td>\r\nacetamide<\/td>\r\n82<\/td>\r\n222<\/td>\r\nsoluble<\/td>\r\n<\/tr>\r\n
    CH3<\/sub>CH2<\/sub>CONH2<\/sub><\/td>\r\npropionamide<\/td>\r\n81<\/td>\r\n213<\/td>\r\nsoluble<\/td>\r\n<\/tr>\r\n
    CH3<\/sub>CH2<\/sub>CH2<\/sub>CONH2<\/sub><\/td>\r\nbutyramide<\/td>\r\n115<\/td>\r\n216<\/td>\r\nsoluble<\/td>\r\n<\/tr>\r\n
    C6<\/sub>H5<\/sub>CONH2<\/sub><\/td>\r\nbenzamide<\/td>\r\n132<\/td>\r\n290<\/td>\r\nslightly soluble<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<\/div>\r\n

    The amides generally have high boiling points and melting points. These characteristics and their solubility in water result from the polar nature of the amide group and hydrogen bonding (Figure 15.7 \"Hydrogen Bonding in Amides\"<\/a>). (Similar hydrogen bonding plays a critical role in determining the structure and properties of proteins, deoxyribonucleic acid [DNA], ribonucleic acid [RNA], and other giant molecules so important to life processes. See Chapter 19 \"Nucleic Acids\"<\/a>.)<\/p>\r\n\r\n

    \r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"1500\"]\"image\" Figure 15.7 Hydrogen Bonding in Amides.<\/em> Amide molecules can engage in hydrogen bonding with water molecules (a). Those amides with a hydrogen atom on the nitrogen atom can also engage in hydrogen bonding (b). Both hydrogen bonding networks extend in all directions.[\/caption]\r\n\r\n<\/div>\r\n
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    Concept Review Exercises<\/h3>\r\n
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    1. \r\n
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      Which compound has the higher boiling point\u2014pentanamide (CH3<\/sub>CH2<\/sub>CH2<\/sub>CH2<\/sub>CONH2<\/sub>) or propyl acetate (CH3<\/sub>COOCH2<\/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\u2014propanamide (CH3<\/sub>CH2<\/sub>CONH2<\/sub>) or 1-pentene (CH2<\/sub>=CHCH2<\/sub>CH2<\/sub>CH3<\/sub>)? Explain.<\/p>\r\n\r\n<\/div><\/li>\r\n<\/ol>\r\n<\/div>\r\n

      \r\n\r\n[reveal-answer q=\"369942\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"369942\"]\r\n\r\n1. pentanamide because the nitrogen-to-hydrogen (N\u2013H) and the carbon-to-oxygen double (C=O) bonds can engage in intermolecular hydrogen bonding; propyl acetate cannot engage in intermolecular hydrogen bonding because it has no bonds between hydrogen atoms and nitrogen or oxygen atoms.\r\n\r\n2. propanamide because the N\u2013H and C=O bonds can engage in hydrogen bonding with water; 1-pentene cannot engage in hydrogen bonding with water. [\/hidden-answer]\r\n\r\n<\/div>\r\n<\/div>\r\n
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      Key Takeaways<\/h3>\r\n<\/div>\r\n
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