{"id":7894,"date":"2021-06-08T21:58:03","date_gmt":"2021-06-08T21:58:03","guid":{"rendered":"https:\/\/opentextbc.ca\/introductorychemistry\/chapter\/other-functional-groups\/"},"modified":"2021-10-13T18:28:02","modified_gmt":"2021-10-13T18:28:02","slug":"other-functional-groups","status":"publish","type":"chapter","link":"https:\/\/opentextbc.ca\/introductorychemistry\/chapter\/other-functional-groups\/","title":{"raw":"Other Functional Groups","rendered":"Other Functional Groups"},"content":{"raw":"[latexpage]\r\n
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Learning Objectives<\/p>\r\n\r\n<\/header>\r\n

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  1. Identify the amine, amide, and thiol functional groups.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\nThere are some common \u2014 and important \u2014 functional groups that contain elements other than oxygen. In this section, we will consider three of them.\r\n

    Nitrogen-Containing Compounds<\/h1>\r\nAn amine<\/strong> is an organic derivative of ammonia (NH3<\/sub>). In amines, one or more of the H atoms in NH3<\/sub> is substituted with an organic group. A primary<\/em> amine has one H atom substituted with an R group:\r\n

    [latex]\\chemname[1em]{\\chemfig{CH_3-NH_2}}{methylamine}[\/latex]<\/p>\r\nA secondary<\/em> amine has two H atoms substituted with R groups:\r\n

    [latex]\\chemname[1em]{\\chemfig{\\ce{NH}(-[:-150]\\ce{CH3})-[:-30]\\ce{CH3}}}{dimethylamine}[\/latex]<\/p>\r\nA tertiary<\/em> amine has all three H atoms substituted with R groups:\r\n

    [latex]\\chemname[1em]{\\chemfig{N(-[:120]\\ce{H3C})(-[:-120]\\ce{H3C})-\\ce{CH3}}}{trimethylamine}[\/latex]<\/p>\r\nNaming simple amines is straightforward: name the R groups as substituents and then add the suffix -amine<\/em>, using numerical suffixes on the substituent names as necessary. This amine is diethylamine:\r\n

    [latex]\\chemfig{-[:30]-[:-30]\\ce{NH}-[:30]-[:-30]}[\/latex]<\/p>\r\nThis amine is ethyldipropylamine:\r\n

    [latex]\\chemfig{-[:30]-[:-30]-[:30]N(-[:90]-[:150])-[:-30]-[:30]-[:-30]}[\/latex]<\/p>\r\n\r\n

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    Example 16.11<\/p>\r\n\r\n<\/header>\r\n

    \r\n\r\nName this amine.\r\n

    [latex]\\chemfig{N(-[:120]-[:180])(-[:-120])--[:60]-}[\/latex]<\/p>\r\nSolution<\/em>\r\nThis amine has a methyl group, an ethyl group, and a propyl group. Listing the names in alphabetical order, this amine is ethylmethylpropylamine.\r\n\r\nTest Yourself<\/em>\r\nName this amine.\r\n

    [latex]\\chemfig{-[:-30]-[:30]N(-[:90]-[:30])-[:-30]-[:30]}[\/latex]<\/p>\r\nAnswer<\/em>\r\ntriethylamine\r\n\r\n<\/div>\r\n<\/div>\r\nAs with NH3<\/sub>, the N atom in amines can accept a proton onto the lone electron pair on the N atom. That is, amines act as Br\u00f8nsted-Lowry bases (i.e., proton acceptors):\r\n

    [latex]\\begin{array}{ccccccc}\r\n\\chemfig{\\ce{CH3}-\\Lewis{0:,N}(-[:90]\\ce{CH3})(-[:-90]\\ce{CH3})}&+&\\ce{H2O}&\\rightarrow&\\chemfig{\\ce{CH3}-\\ce{N+}(-[:90]\\ce{CH3})(-[:-90]\\ce{CH3})-H}&+&\\ce{OH-}\r\n\\end{array}[\/latex]<\/p>\r\n(For more information on Br\u00f8nsted-Lowry bases, see the section \"Br\u00f8nsted-Lowry Acids and Bases\"<\/a>.) The amine becomes an ion, the organic counterpart of the ammonium (NH4<\/sub>+<\/sup>) ion.\r\n\r\nBecause no amine is presented in Table 12.1 \"Strong Acids and Bases,\"<\/a> all amines are weak bases. The weakness of amines is about the same as that of carboxylic acids. N-containing organic compounds are very common in nature, and they all act as weak bases. Some of these compounds have rather complicated structures. Below are some N-containing substances that you may recognize.\r\n

    [latex]\\chemname[1.5em]{\\chemfig{[:-54]*5(---(<:*6(=-N=-=-))-N(-)-)}}{Nicotine (Compound found in tobacco)}[\/latex]<\/p>\r\n

    [latex]\\chemname[1.5em]{\\chemfig{*6((-\\ce{HO})-=-(-[:30]-[:-30]-[:30]\\ce{NH2})=-(-\\ce{HO})=)}}{Dopamine (Associated with motor skills and emotions)}[\/latex]<\/p>\r\n

    [latex]\\chemname[1.5em]{\\chemfig{*6((=O)-N(-)-*5(-N=-N(-)-)=-(=O)-N(-)-)}}{Caffeine (Stimulant found in coffee and tea)}[\/latex]<\/p>\r\nAn amide<\/strong>\u00a0functional group is a combination of an amine group and a carbonyl group:\r\n

    [latex]\\chemname[1em]{\\chemfig{R-N(-[:90]H)-C(=[:90]O)-R'}}{amide}[\/latex]<\/p>\r\nAmides are actually formed by bringing together an amine-containing molecule and a carboxylic acid-containing molecule. A molecule of H2<\/sub>O is lost, much like when an ester forms:\r\n

    [latex]\\chemfig{R-N(-[:90]H)-H}+\\chemfig{\\ce{HO}-C(=[:90]O)-R'}\\longrightarrow\\chemfig{R-N(-[:90]H)-C(=[:90]O)-R'}+\\ce{H2O}[\/latex]<\/p>\r\nThe bond between the N of the amine group and the C of the carbonyl group is called an amide bond<\/strong>. Amide bonds are particularly important in biological molecules called proteins<\/em>, which are composed of strings of amino acids \u2014 molecules that have an amine group and a carboxylic acid group in them. The amine group on one amino acid reacts with the carboxylic acid group of another amino acid, making a chain held together by amide bonds. We will consider proteins later in this chapter.\r\n

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    Example 16.12<\/p>\r\n\r\n<\/header>\r\n

    \r\n\r\nDraw the structure of the amide formed by the combination of ethylamine and butanoic acid.\r\n\r\nSolution<\/em>\r\nThe structures of ethylamine and butanoic acid are:\r\n

    [latex]\\chemfig{-[:30]-[:-30]\\ce{NH2}}\\hspace{5em}\\chemfig{-[:30]-[:-30]-[:30](=[:90]O)-[:-30]\\ce{OH}}[\/latex]<\/p>\r\nWhen they come together to make an amide, an H2<\/sub>O molecule is lost, and the N of the amine group bonds to the C of the carboxyl group. The resulting molecule is:\r\n

    [latex]\\chemfig{-[:30]-[:-30]N(-[:-90]H)-[:30](=[:90]O)-[:-30]-[:30]-[:-30]}[\/latex]<\/p>\r\nTest Yourself<\/em>\r\nDraw the structure of the amide formed by the combination of methylamine and formic acid.\r\n\r\nAnswer<\/em>\r\n[latex]\\chemfig{H-[:30](=[:90]O)-[:-30]N(-[:-90]H)-[:30]}[\/latex]\r\n\r\n<\/div>\r\n<\/div>\r\n

    Sulfur-Containing Compounds<\/h1>\r\nSulfur is below oxygen on the periodic table, and it occasionally shows some similar chemistry. One similarity is that an S atom can take the place of an O atom in an alcohol, to make a molecule that looks like this:\r\n

    [latex]\\chemfig{R-SH}[\/latex]<\/p>\r\nThe sulfur analog of an alcohol is called a thiol<\/strong>. The formal way of naming a thiol is similar to that of alcohols, except that instead of using the suffix -ol<\/em>, you use the suffix -thiol<\/em>. The following illustrates thiol nomenclature:\r\n

    [latex]\\begin{array}{ccc}\r\n\\chemname[1em]{\\chemfig{\\ce{CH3}-\\ce{SH}}}{Methanethiol}&\\hspace{3em}\\chemname[1em]{\\chemfig{\\ce{C2H5}-\\ce{SH}}}{Ethanethiol}&\\hspace{3em}\\chemname[1em]{\\chemfig{\\ce{C3H7}-\\ce{SH}}}{Propanethiol}\r\n\\end{array}[\/latex]<\/p>\r\nAn older system uses the word mercaptan<\/em> in naming simple thiols, much like the word alcohol<\/em> is used with small alcohols. These thiols can also be named like this:\r\n

    [latex]\\begin{array}{ccc}\r\n\\chemname[1em]{\\chemfig{\\ce{CH3}-\\ce{SH}}}{Methyl mercaptan}&\\hspace{5em}\\chemname[1em]{\\chemfig{\\ce{C2H5}-\\ce{SH}}}{Ethyl mercaptan}&\\hspace{5em}\\chemname[1em]{\\chemfig{\\ce{C3H7}-\\ce{SH}}}{Propyl mercaptan}\r\n\\end{array}[\/latex]<\/p>\r\nMany thiols have strong, objectionable odours; indeed, the spray from skunks is composed of thiols and is detectable by the human nose at concentrations of less than 10 ppb. Because natural gas is odourless, thiols are intentionally added \u2014 at very low levels, of course \u2014 so that gas leaks can be more easily detected. Not all thiols have objectionable odours; this thiol, grapefruit mercaptan, is responsible for the odour of grapefruit:\r\n

    [latex]\\chemfig{*6(-(-[:-90](-[:-15]\\ce{SH})(-[:-165])-)---(-)=-)}[\/latex]<\/p>\r\nCysteine is an amino acid that is a thiol:\r\n

    [latex]\\chemfig{\\ce{SH}-[:150]-[:90](-[:150]\\ce{H2N})-[:30](=[:90]O)-[:-30]\\ce{OH}}[\/latex]<\/p>\r\nCysteine plays an important role in protein structure. If two cysteine amino acids in a protein chain approach each other, they can be oxidized, and an S\u2013S bond (also known as a disulfide bond<\/em>) is formed:\r\n

    [latex]\\chemfig{R-SH+HS-R}\\longrightarrow \\chemfig{R-S-S-R}[\/latex]<\/p>\r\nwhere the R group is the rest of the cysteine molecule. The disulfide bond is strong enough to fix the position of the two cysteine groups, thus imposing a structure on the protein. Hair is composed of about 5% cysteine, and the breaking and remaking of disulfide bonds between cysteine units is the primary mechanism behind straightening and curling hair (hair \u201cperms\u201d).\r\n

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    Food and Drink App: Amino Acids \u2014 Essential and Otherwise<\/h1>\r\nThe description of\u00a0cysteine mentioned that it is an amino acid. Amino acids are the fundamental building blocks of proteins, a major biological component. Proteins are a necessary part of the diet; meat, eggs, and certain vegetables such as beans and soy are good sources of protein and amino acids.\r\n\r\nAll life on earth \u2014 from the lowliest single-celled organism to humans to blue whales \u2014 relies on proteins for life, so all life on earth is dependent on amino acids. The human body contains 20 different amino acids (curiously, other organisms may have a different number of amino acids). However, not all of them must be obtained from the diet. The body can synthesize 12 amino acids. The other 8 must<\/em> be obtained from the diet. These 8 amino acids are called the essential amino acids<\/em>. Daily requirements range from 4 mg per kilogram of body weight for tryptophan to 40 mg per kilogram of body weight for leucine. Infants and children need a greater mass per kg of body weight to support their growing bodies; also, the number of amino acids that are considered essential for infants and children is greater than for adults due to the greater protein synthesis associated with growth.\r\n\r\nBecause of the existence of essential amino acids, a diet that is properly balanced in protein is necessary. Rice and beans, a very popular food dish in Latin cuisines, actually provides all the essential amino acids in one dish; without one component, the dish would be nutritionally incomplete. Corn (maize) is the most-grown grain crop in the world, but an overreliance on it as a primary food source deprives people of lysine and tryptophan, which are two essential amino acids. People on restricted diets \u2014 whether out of necessity or by choice (e.g., vegetarians) \u2014 may be missing the proper amount of an essential amino acid, so it is important to vary the diet when possible to ensure ingestion of a wide range of protein sources.\r\n\r\n<\/div>\r\n
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    Key Takeaways<\/p>\r\n\r\n<\/header>\r\n

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