{"id":1330,"date":"2018-03-21T14:58:58","date_gmt":"2018-03-21T14:58:58","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/suny-orgbiochemistry\/chapter\/alcohols-nomenclature-and-classification\/"},"modified":"2018-10-25T15:49:27","modified_gmt":"2018-10-25T15:49:27","slug":"alcohols-nomenclature-and-classification","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/suny-monroecc-orgbiochemistry\/chapter\/alcohols-nomenclature-and-classification\/","title":{"raw":"14.2 Alcohols: Nomenclature and Classification","rendered":"14.2 Alcohols: Nomenclature and Classification"},"content":{"raw":"
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Learning Objectives<\/h3>\r\n
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  1. Identify the general structure for an alcohol.<\/li>\r\n \t
  2. Identify the structural feature that classifies alcohols as primary, secondary, or tertiary.<\/li>\r\n \t
  3. Name alcohols with both common names and IUPAC names.<\/li>\r\n<\/ol>\r\n<\/div>\r\nAs noted in <\/span>Chapter 4 \"Covalent Bonding and Simple Molecular Compounds\"<\/a>, an <\/span>alcohol<\/span><\/span>\u00a0is an organic compound with a hydroxyl (OH) functional group on an aliphatic carbon atom. Because OH is the functional group of all alcohols, we often represent alcohols by the general formula ROH, where R is an alkyl group. (For more information about alkyl groups, see <\/span>Chapter 12 \"Organic Chemistry: Alkanes and Halogenated Hydrocarbons\"<\/a>, <\/span>Section 12.5 \"IUPAC Nomenclature\"<\/a>. <\/span>Table 12.4 \"Common Alkyl Groups\"<\/a> presents some common alkyl groups.)<\/span>\r\n\r\n<\/div>\r\n

    Alcohols are common in nature. Most people are familiar with ethyl alcohol (ethanol), the active ingredient in alcoholic beverages, but this compound is only one of a family of organic compounds known as alcohols. The family also includes such familiar substances as cholesterol and the carbohydrates.<\/p>\r\n

    As we noted in Chapter 4 \"Covalent Bonding and Simple Molecular Compounds\"<\/a>, Section 4.6 \"Introduction to Organic Chemistry\"<\/a>, methanol (CH3<\/sub>OH) and ethanol (CH3<\/sub>CH2<\/sub>OH) are the first two members of the homologous series of alcohols.<\/p>\r\n\r\n

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    Nomenclature of Alcohols<\/h2>\r\n

    Alcohols with one to four carbon atoms are frequently called by common names, in which the name of the alkyl group is followed by the word alcohol<\/em>:<\/p>\r\n\r\n

    \"image\"<\/div>\r\n

    According to the International Union of Pure and Applied Chemistry (IUPAC), alcohols are named by changing the ending of the parent alkane name (Chapter 12 \"Organic Chemistry: Alkanes and Halogenated Hydrocarbons\"<\/a>, Section 12.5 \"IUPAC Nomenclature\"<\/a>) to -ol<\/em>. Here are some basic IUPAC rules for naming alcohols:<\/p>\r\n\r\n

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    1. The longest continuous chain (LCC) of carbon atoms containing carbon atom to which the the OH group is attached is considered the parent compound\u2014an alkane with the same number of carbon atoms. The chain is numbered from the end nearest the OH group.<\/li>\r\n \t
    2. The number that indicates the position of the OH group is prefixed to the name of the parent hydrocarbon, and the -e<\/em> ending of the parent alkane is replaced by the suffix -ol.<\/em> (In cyclic alcohols, the carbon atom bearing the OH group is designated C1, but the 1 is not used in the name.) Substituents are named and numbered as in alkanes.<\/li>\r\n \t
    3. If more than one OH group appears in the same molecule (polyhydroxy alcohols), suffixes such as -diol<\/em> and -triol<\/em> are used. In these cases, the -e<\/em> ending of the parent alkane is retained.<\/li>\r\n<\/ol>\r\n

      Figure 14.1 \"IUPAC Rules for Alcohols\"<\/a> shows some examples of the application of these rules.<\/p>\r\n\r\n

      \r\n\r\n[caption id=\"\" align=\"alignnone\" width=\"1499\"]\"image\" Figure 14.1 IUPAC Rules for Alcohols. The names and structures of some alcohols demonstrate the use of IUPAC rules. <\/em>[\/caption]\r\n\r\n<\/div>\r\n
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      Example 1<\/h3>\r\n

      Give the IUPAC name for each compound.<\/p>\r\n\r\n

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      1. \r\n
        \"image\"<\/div><\/li>\r\n \t
      2. HOCH2<\/sub>CH2<\/sub>CH2<\/sub>CH2<\/sub>CH2<\/sub>OH<\/li>\r\n<\/ol>\r\n

        Solution<\/p>\r\n\r\n

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        1. \r\n

          Ten carbon atoms in the LCC makes the compound a derivative of decane (rule 1), and the OH on the third carbon atom makes it a 3-decanol (rule 2).<\/p>\r\n\r\n

          \"image\"<\/div>\r\n

          The carbon atoms are numbered from the end closest to the OH group. That fixes the two methyl (CH3<\/sub>) groups at the sixth and eighth positions. The name is 6,8-dimethyl-3-decanol (not 3,5-dimethyl-8-decanol).<\/p>\r\n<\/li>\r\n \t

        2. \r\n

          Five carbon atoms in the LCC make the compound a derivative of pentane. Two OH groups on the first and fifth carbon atoms make the compound a diol and give the name 1,5-pentanediol (rule 3).<\/p>\r\n\r\n

          \"image\"<\/div><\/li>\r\n<\/ol>\r\n<\/div>\r\n
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          Skill-Building Exercise<\/h3>\r\n

          Give the IUPAC name for each compound.<\/p>\r\n\r\n

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          1. \r\n
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            \"image\"<\/div>\r\n<\/div><\/li>\r\n \t
          2. \r\n
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            \"image\"<\/div>\r\n<\/div><\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
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            Example 2<\/h3>\r\n

            Draw the structure for each compound.<\/p>\r\n\r\n

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            1. 2-hexanol<\/li>\r\n \t
            2. 3-methyl-2-pentanol<\/li>\r\n<\/ol>\r\n

              Solution<\/p>\r\n\r\n

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              1. \r\n

                The ending -ol<\/em> indicates an alcohol (the OH functional group), and the hex<\/em>- stem tells us that there are six carbon atoms in the LCC. We start by drawing a chain of six carbon atoms: \u2013C\u2013C\u2013C\u2013C\u2013C\u2013C\u2013.<\/p>\r\n

                The 2 indicates that the OH group is attached to the second carbon atom.<\/p>\r\n\r\n

                \"image\"<\/div>\r\n

                Finally, we add enough hydrogen atoms to give each carbon atom four bonds.<\/p>\r\n\r\n

                \"image\"<\/div><\/li>\r\n \t
              2. \r\n

                The ending -ol<\/em> indicates an OH functional group, and the pent<\/em>- stem tells us that there are five carbon atoms in the LCC. We start by drawing a chain of five carbon atoms:<\/p>\r\n\u2013C\u2013C\u2013C\u2013C\u2013C\u2013<\/strong><\/span><\/span>\r\n

                The numbers indicate that there is a methyl (CH3<\/sub>) group on the third carbon atom and an OH group on the second carbon atom.<\/p>\r\n\r\n

                \"image\"<\/div><\/li>\r\n<\/ol>\r\n<\/div>\r\n
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                Skill-Building Exercise<\/h3>\r\n

                Draw the structure for each compound.<\/p>\r\n\r\n

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                1. \r\n
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                  3-heptanol<\/p>\r\n\r\n<\/div><\/li>\r\n \t

                2. \r\n
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                  2-methyl-3-hexanol\u00a0<\/span><\/p>\r\n\r\n<\/div><\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n

                  Classification of Alcohols<\/h2>\r\n<\/div>\r\n<\/div>\r\n
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                  Some of the properties of alcohols depend on the number of carbon atoms attached to the specific carbon atom that is attached to the OH group. Alcohols can be grouped into three classes on this basis.<\/p>\r\n\r\n