{"id":898,"date":"2017-10-19T15:26:32","date_gmt":"2017-10-19T15:26:32","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/?post_type=chapter&#038;p=898"},"modified":"2018-10-03T18:21:11","modified_gmt":"2018-10-03T18:21:11","slug":"prochirality","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/chapter\/prochirality\/","title":{"raw":"Prochirality","rendered":"Prochirality"},"content":{"raw":"<div class=\"elm-header\">\r\n<div class=\"textbox learning-objectives\">\r\n<h3>Objectives<\/h3>\r\n<div id=\"elm-main-content\" class=\"elm-content-container\">\r\n<div>\r\n<div id=\"skills\">\r\n\r\nAfter completing this section, you should be able to\r\n<ol>\r\n \t<li>identify a compound as being prochiral.<\/li>\r\n \t<li>identify the <em>Re<\/em> and <em>Si<\/em> faces of prochiral <em>sp<\/em><sup>2<\/sup> centre.<\/li>\r\n \t<li>identify atoms (or groups of atoms) as <em>pro<\/em>-<em>R<\/em> or <em>pro<\/em>-<em>S<\/em> on a prochiral <em>sp<\/em><sup>3<\/sup> centre.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div id=\"elm-main-content\" class=\"elm-content-container\">\r\n<div>\r\n<div class=\"textbox key-takeaways\">\r\n<h3>Key TERMS<\/h3>\r\nMake certain that you can define, and use in context, the key terms below.\r\n<ul>\r\n \t<li>prochiral<\/li>\r\n \t<li><em>pro<\/em>-<em>R<\/em><\/li>\r\n \t<li><em>pro<\/em>-<em>S<\/em><\/li>\r\n \t<li><em>Re<\/em><\/li>\r\n \t<li><em>Si<\/em><\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n<div id=\"section_1\">\r\n<h3 class=\"editable\">Prochiral substituents on tetrahedral carbons<\/h3>\r\nWhen a tetrahedral carbon can be converted to a chiral center by changing only one of its attached groups, it is referred to as a \u2018<strong>prochiral<\/strong><strong>'<\/strong> center. The actual example shown below is the reduced form of a molecule called nicotinamide adenine dinucleotide (NADH), an important participant in many biochemical oxidation\/reduction reactions (<a title=\"Organic Chemistry\/Organic Chemistry With a Biological Emphasis\/Chapter 16: Oxidation and reduction reactions\/Section 16.4: Hydrogenation\/\/dehydrogenation reactions of carbonyls, imines, and alcohols\" href=\"https:\/\/chem.libretexts.org\/Textbook_Maps\/Organic_Chemistry_Textbook_Maps\/Map%3A_Organic_Chemistry_with_a_Biological_Emphasis_(Soderberg)\/16%3A_Oxidation_and_reduction_reactions\/16.04%3A_Hydrogenation%2F%2F%2F%2Fdehydrogenation_reactions_of_carbonyls%2C_imines%2C_and_alcohols\" rel=\"internal\">section 16.4A<\/a>).\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133743\/image187.png\" alt=\"image186.png\" width=\"410\" height=\"225\" \/>\r\n\r\nNote that if, in a thought experiment, we changed either one of the indicated hydrogens on NADH to a deuterium (the <sup>2<\/sup>H isotope of hydrogen), the carbon would become a chiral center. Prochirality is an important concept in biological chemistry, because enzymes can distinguish between the two \u2018identical\u2019 groups bound to a prochiral carbon center due to the fact that <em>they occupy different regions in three-dimensional space<\/em>. For example in the following reaction, which is a key step in the oxidation of fatty acids, it is specifically H<sub>A<\/sub> and H<sub>D<\/sub> that are lost, while H<sub>B<\/sub> and H<sub>C<\/sub> remain in the resulting conjugated alkene.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133746\/image189.png\" alt=\"image188.png\" width=\"442\" height=\"93\" \/>\r\n\r\nThe prochiral hydrogens on C<sub>2<\/sub>and C<sub>3<\/sub> of the fatty acid can be designated according to a variation on the <em>R\/S<\/em> system. For the sake of clarity, we'll look at a much simpler molecule (ethanol) to explain this system.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133749\/image191.png\" alt=\"image190.png\" width=\"490\" height=\"109\" \/>\r\n\r\nTo name the two prochiral hydrogens on ethanol, we again need to engage in a thought experiment. If we, in our imagination, were to arbitrarily change H<sub>B<\/sub> to a deuterium, the molecule would now be chiral and the stereocenter would have the <em>S<\/em> configuration (D has a higher priority than H). For this reason, we can refer to H<sub>B<\/sub> as the <em>pro-S<\/em> hydrogen of ethanol, and label it H<em><sub>S<\/sub><\/em>. Conversely, if we change H<sub>A<\/sub> to D and leave H<sub>B<\/sub> as a hydrogen, the configuration of the molecule becomes <em>R<\/em>, so we can refer to H<sub>A<\/sub> as the <em>pro-R<\/em> hydrogen of ethanol, and label it H<em><sub>R<\/sub><\/em>.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133751\/image193.png\" alt=\"image192.png\" width=\"233\" height=\"74\" \/>\r\n\r\nLooking back at our fatty acid example, we see that it is specifically the <em>pro-R<\/em> hydrogens on carbons 2 and 3 that are lost in the reaction.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133753\/image195.png\" alt=\"image194.png\" width=\"670\" height=\"180\" \/>\r\n\r\nProchiral hydrogens can be designated either enantiotopic or diastereotopic. If either H<sub>R<\/sub> or H<sub>S<\/sub> on ethanol were replaced by a deuterium, the two resulting molecules would be enantiomers (because there are no other stereocenters)\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133756\/image197.png\" alt=\"image196.png\" width=\"470\" height=\"120\" \/>\r\n\r\nThus, these two hydrogens are referred to as <strong>enantiotopic<\/strong>.\r\n\r\nIn glyceraldehyde-3-phosphate (GAP), however, we see something different:\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133759\/image199.png\" alt=\"image198.png\" width=\"513\" height=\"198\" \/>\r\n\r\nIf either H<sub>R<\/sub> or H<sub>S<\/sub> is replaced by a deuterium, the two resulting molecules will be diastereomers - thus, in this molecule, H<sub>R<\/sub> and H<sub>S<\/sub> are referred to as <strong>diastereotopic<\/strong> hydrogens. The importance of the distinction between enantiotopic and diastereotopic groups will become apparent when we learn about the analytical technique called nuclear magnetic resonance.\r\n\r\nTwo hydrogens on the same carbon of a substituted ring structure can be diastereotopic - we determine this by carrying out the same thought experiment as discussed above. In the example below, the diastereotopic hydrogens indicated are either on the same side or on the opposite side of the ring relative to the hydroxyl group.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133801\/image201.png\" alt=\"image200.png\" width=\"362\" height=\"180\" \/>\r\n\r\nFinally, hydrogens that are completely identical and can be designated neither enantiotopic nor diastereotopic are called <strong>homotopic<\/strong>. If a homotopic hydrogen is replaced by deuterium, a chiral center is <em>not<\/em> created. The three hydrogen atoms on the methyl (CH<sub>3<\/sub>) group of ethanol (and on <em>any<\/em> methyl group) are homotopic.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133804\/image203.png\" alt=\"image202.png\" width=\"169\" height=\"112\" \/>\r\n\r\nEven to an enzyme, all three of these hydrogens will look the same.\r\n<div style=\"margin: auto\">\r\n<div id=\"example\">\r\n<div class=\"textbox examples\">\r\n<h3>Example<\/h3>\r\nIdentify in the molecules below all pairs\/groups of hydrogens that are homotopic, enantiotopic, or diastereotopic. When appropriate, label prochiral hydrogens as H<em><sub>R<\/sub><\/em> or H<em><sub>S<\/sub><\/em>.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133806\/image205.png\" alt=\"image204.png\" width=\"435\" height=\"309\" \/>\r\n<dl>\r\n \t<dt><strong><strong>Answer<\/strong><\/strong>&nbsp;<\/dt>\r\n \t<dd><img class=\"internal default alignnone\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133809\/5-11-1.png\" alt=\"5-11-1.png\" width=\"434px\" height=\"327px\" \/>\r\n<dl>\r\n \t<dt><\/dt>\r\n \t<dt><\/dt>\r\n<\/dl>\r\n<\/dd>\r\n<\/dl>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div>Groups other than hydrogens can be considered prochiral. The alcohol below has two prochiral methyl groups - methyl A is the <em>pro-R<\/em> methyl, and methyl B is <em>pro-S<\/em>. (How do we make these designations? Simple - just arbitrarily make methyl A higher priority than methyl B, and the compound now has the <em>R<\/em> configuration).<\/div>\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133811\/image207.png\" alt=\"image206.png\" width=\"170\" height=\"162\" \/>\r\n\r\nCitrate provides a more complex example. The central carbon is a prochiral center with two 'arms' that are identical except that one can be designated <em>pro-R<\/em> and the other <em>pro-S<\/em>.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133812\/image209.png\" alt=\"image208.png\" width=\"169\" height=\"138\" \/>\r\n\r\nIn a reaction of the citric acid cycle (Krebs cycle), a water molecule is specifically lost on the <em>pro-R<\/em> arm (we will study this reaction in <a title=\"Organic Chemistry\/Organic Chemistry With a Biological Emphasis\/Chapter 14: Reactions with stabilized carbanion intermediates II\/Section 14.1: Michael additions, \u03b2 eliminations and reactions with electron sink cofactors\" href=\"https:\/\/chem.libretexts.org\/Textbook_Maps\/Organic_Chemistry_Textbook_Maps\/Map%3A_Organic_Chemistry_with_a_Biological_Emphasis_(Soderberg)\/14%3A_Reactions_with_stabilized_carbanion_intermediates%2C_part_II\/14.1%3A_Michael_additions%2C_%CE%B2_eliminations_and_reactions_with_electron_sink_cofactors\" rel=\"internal\">section 14.1B<\/a>).\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133815\/image211.png\" alt=\"image210.png\" width=\"582\" height=\"100\" \/>\r\n\r\nNotice also that it is specifically the <em>pro-R<\/em> hydrogen on the <em>pro-R<\/em> arm of citrate that is lost - one more layer of stereoselectivity!\r\n<div style=\"margin: auto\">\r\n<div class=\"textbox examples\">\r\n<h3>Example<\/h3>\r\n<div>Assign <em>pro-R <\/em>and<em>pro-S<\/em> designations to all prochiral groups in the amino acid leucine. (<em>Hint<\/em>: there are two pairs of prochiral groups!). Are these prochiral groups diastereotopic or enantiotopic?<\/div>\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133817\/image213.png\" alt=\"image212.png\" width=\"116\" height=\"151\" \/>\r\n<dl>\r\n \t<dt><strong>Answer:<\/strong><\/dt>\r\n \t<dd><a class=\"thumb\" title=\"\" href=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/107722\/5-11-2.png?revision=1\" rel=\"internal\"><img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133819\/5-11-2.png\" alt=\"\" width=\"189px\" height=\"197px\" \/><\/a><\/dd>\r\n<\/dl>\r\n<\/div>\r\n<dl><\/dl>\r\n<\/div>\r\n<div>Although an alkene carbon bonded to two identical groups is <em>not<\/em> considered a prochiral center, these two groups <em>can<\/em> be diastereotopic. H<sub>a<\/sub> and H<sub>b<\/sub> on the alkene below, for example, are diastereotopic: if we change one, and then the other, of these hydrogens to deuterium, the resulting compounds are <em>E<\/em> and <em>Z<\/em> diastereomers.<\/div>\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133821\/image215.png\" alt=\"image214.png\" width=\"579\" height=\"170\" \/>\r\n\r\n<\/div>\r\n<div id=\"section_2\">\r\n<h3 class=\"editable\">Carbonyl and imine carbons as prochiral centers<\/h3>\r\nTrigonal planar, sp<sup>2<\/sup>-hybridized carbons are not, as we well know, chiral centers\u2013 but they are referred to as prochiral centers if they are bonded to three different substitutuents. As you might expect, we (and the enzymes that catalyze their reactions) can distinguish between the two planar \u2018faces\u2019 of a prochiral sp<sup>2<\/sup> - hybridized group. These faces are designated by the terms <strong><em>re<\/em><\/strong> and <strong><em>si<\/em><\/strong>. To determine which is the <em>re<\/em> and which is the <em>si<\/em> face of a planar organic group, we simply use the same priority rankings that we are familiar with from the R\/S system, and trace a circle: <em>re<\/em> is clockwise and <em>si<\/em> is counterclockwise.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133824\/image217.png\" alt=\"image216.png\" width=\"413\" height=\"176\" \/>\r\n\r\nBelow, for example, we are looking down on the <em>re<\/em> face of the ketone group in pyruvate:\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133827\/image219.png\" alt=\"image218.png\" width=\"358\" height=\"168\" \/>\r\n\r\nIf we flipped the molecule over, we would be looking at the <em>si<\/em> face of the ketone group. Note that the carboxylate group does not have <em>re<\/em> and <em>si<\/em> faces, because two of the three substituents on that carbon are identical (when the two resonance forms of carboxylate are taken into account).\r\n\r\nAs we will see beginning in chapter 11, enzymes which catalyze reactions at carbonyl carbons act specifically from one side or the other.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133829\/image221.png\" alt=\"image220.png\" width=\"626\" height=\"163\" \/>\r\n\r\nNotice that the 'hydrogenation' reaction above is specific not only in terms of which face of the carbonyl group is affected, but also in terms of which of the two diastereotopic hydrogens on NADH is transferred (we will study this type of reaction in more detail in <a title=\"Organic Chemistry\/Organic Chemistry With a Biological Emphasis\/Chapter 16: Oxidation and reduction reactions\/Section 16.4: Hydrogenation\/\/dehydrogenation reactions of carbonyls, imines, and alcohols\" href=\"https:\/\/chem.libretexts.org\/Textbook_Maps\/Organic_Chemistry_Textbook_Maps\/Map%3A_Organic_Chemistry_with_a_Biological_Emphasis_(Soderberg)\/16%3A_Oxidation_and_reduction_reactions\/16.04%3A_Hydrogenation%2F%2F%2F%2Fdehydrogenation_reactions_of_carbonyls%2C_imines%2C_and_alcohols\" rel=\"internal\">section 16.4<\/a>).\r\n<div>\r\n<div class=\"textbox examples\">\r\n<h3>Example<\/h3>\r\n<div id=\"section_2\">\r\n<div>\r\n<div>\r\n<div>\r\n\r\nFor each of the carbonyl groups in uracil, state whether we are looking at the <em>re<\/em> or the <em>si<\/em> face in the structural drawing below.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133831\/image223.png\" alt=\"image222.png\" width=\"72\" height=\"135\" \/>\r\n<div><\/div>\r\n<div>\r\n<dl>\r\n \t<dt><strong class=\"emphasis bold\">Answer:<\/strong><\/dt>\r\n \t<dd><a class=\"thumb\" title=\"\" href=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/107723\/5-11-3.png?revision=1\" rel=\"internal\"><img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133833\/5-11-3.png\" alt=\"\" width=\"350px\" height=\"256px\" \/><\/a><\/dd>\r\n<\/dl>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div class=\"textbox exercises\">\r\n<h3>Exercises<\/h3>\r\n<div id=\"section_3\">\r\n<div id=\"s61692\">\r\n\r\n<strong>1.<\/strong>\r\n\r\nState which of the following hydrogen atoms are<em> pro-R<\/em> or <em>pro-S<\/em>.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133835\/5.11.png\" alt=\"\" width=\"593\" height=\"150\" \/>\r\n\r\n<strong>2.<\/strong>\r\n\r\nIdentify which side is Re or Si\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133837\/5.112.png\" alt=\"\" width=\"448\" height=\"194\" \/>\r\n\r\n<\/div>\r\n<div>\r\n<dl>\r\n \t<dt><strong class=\"emphasis bold\">Answer:<\/strong><\/dt>\r\n \t<dd>\r\n<div>\r\n\r\n<strong>1.<\/strong>\r\n\r\n[reveal-answer q=\"497360\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"497360\"]Left compound: Ha = pro-S and Hb = pro-R Right compound: Ha = pro-R\u00a0 and Hb = pro-S[\/hidden-answer]\r\n\r\n<strong>2.<\/strong>\r\n\r\n[reveal-answer q=\"586755\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"586755\"]A \u2013 Re; B \u2013 Si; C \u2013 Si; D \u2013 Re[\/hidden-answer]\r\n\r\n<\/div><\/dd>\r\n<\/dl>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div id=\"section_3\">\r\n<div>\r\n<div>\r\n<h3 class=\"editable\">Contributors<\/h3>\r\n<ul>\r\n \t<li><a title=\"http:\/\/chemwiki.ucdavis.edu\/Organic_Chemistry\/Organic_Chemistry_With_a_Biological_Emphasis\" href=\"https:\/\/chem.libretexts.org\/Textbook_Maps\/Organic_Chemistry_Textbook_Maps\/Map%3A_Organic_Chemistry_with_a_Biological_Emphasis_(Soderberg)\" rel=\"internal\"><strong>Organic Chemistry With a Biological Emphasis <\/strong><\/a>by\u00a0<a class=\"external\" title=\"http:\/\/facultypages.morris.umn.edu\/~soderbt\/\" href=\"http:\/\/facultypages.morris.umn.edu\/%7Esoderbt\/\" target=\"_blank\" rel=\"external nofollow noopener\">Tim Soderberg<\/a>\u00a0(University of Minnesota, Morris)<\/li>\r\n<\/ul>\r\n<\/div>\r\n<ul>\r\n \t<li><a class=\"external\" title=\"http:\/\/science.athabascau.ca\/staff-pages\/dietmark\" href=\"http:\/\/science.athabascau.ca\/staff-pages\/dietmark\" target=\"_blank\" rel=\"external nofollow noopener\">Dr. Dietmar Kennepohl<\/a> FCIC (Professor of Chemistry, <a class=\"external\" title=\"http:\/\/www.athabascau.ca\/\" href=\"http:\/\/www.athabascau.ca\/\" target=\"_blank\" rel=\"external nofollow noopener\">Athabasca University<\/a>)<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n<\/div>","rendered":"<div class=\"elm-header\">\n<div class=\"textbox learning-objectives\">\n<h3>Objectives<\/h3>\n<div id=\"elm-main-content\" class=\"elm-content-container\">\n<div>\n<div id=\"skills\">\n<p>After completing this section, you should be able to<\/p>\n<ol>\n<li>identify a compound as being prochiral.<\/li>\n<li>identify the <em>Re<\/em> and <em>Si<\/em> faces of prochiral <em>sp<\/em><sup>2<\/sup> centre.<\/li>\n<li>identify atoms (or groups of atoms) as <em>pro<\/em>&#8211;<em>R<\/em> or <em>pro<\/em>&#8211;<em>S<\/em> on a prochiral <em>sp<\/em><sup>3<\/sup> centre.<\/li>\n<\/ol>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"elm-main-content\" class=\"elm-content-container\">\n<div>\n<div class=\"textbox key-takeaways\">\n<h3>Key TERMS<\/h3>\n<p>Make certain that you can define, and use in context, the key terms below.<\/p>\n<ul>\n<li>prochiral<\/li>\n<li><em>pro<\/em>&#8211;<em>R<\/em><\/li>\n<li><em>pro<\/em>&#8211;<em>S<\/em><\/li>\n<li><em>Re<\/em><\/li>\n<li><em>Si<\/em><\/li>\n<\/ul>\n<\/div>\n<\/div>\n<div id=\"section_1\">\n<h3 class=\"editable\">Prochiral substituents on tetrahedral carbons<\/h3>\n<p>When a tetrahedral carbon can be converted to a chiral center by changing only one of its attached groups, it is referred to as a \u2018<strong>prochiral<\/strong><strong>&#8216;<\/strong> center. The actual example shown below is the reduced form of a molecule called nicotinamide adenine dinucleotide (NADH), an important participant in many biochemical oxidation\/reduction reactions (<a title=\"Organic Chemistry\/Organic Chemistry With a Biological Emphasis\/Chapter 16: Oxidation and reduction reactions\/Section 16.4: Hydrogenation\/\/dehydrogenation reactions of carbonyls, imines, and alcohols\" href=\"https:\/\/chem.libretexts.org\/Textbook_Maps\/Organic_Chemistry_Textbook_Maps\/Map%3A_Organic_Chemistry_with_a_Biological_Emphasis_(Soderberg)\/16%3A_Oxidation_and_reduction_reactions\/16.04%3A_Hydrogenation%2F%2F%2F%2Fdehydrogenation_reactions_of_carbonyls%2C_imines%2C_and_alcohols\" rel=\"internal\">section 16.4A<\/a>).<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133743\/image187.png\" alt=\"image186.png\" width=\"410\" height=\"225\" \/><\/p>\n<p>Note that if, in a thought experiment, we changed either one of the indicated hydrogens on NADH to a deuterium (the <sup>2<\/sup>H isotope of hydrogen), the carbon would become a chiral center. Prochirality is an important concept in biological chemistry, because enzymes can distinguish between the two \u2018identical\u2019 groups bound to a prochiral carbon center due to the fact that <em>they occupy different regions in three-dimensional space<\/em>. For example in the following reaction, which is a key step in the oxidation of fatty acids, it is specifically H<sub>A<\/sub> and H<sub>D<\/sub> that are lost, while H<sub>B<\/sub> and H<sub>C<\/sub> remain in the resulting conjugated alkene.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133746\/image189.png\" alt=\"image188.png\" width=\"442\" height=\"93\" \/><\/p>\n<p>The prochiral hydrogens on C<sub>2<\/sub>and C<sub>3<\/sub> of the fatty acid can be designated according to a variation on the <em>R\/S<\/em> system. For the sake of clarity, we&#8217;ll look at a much simpler molecule (ethanol) to explain this system.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133749\/image191.png\" alt=\"image190.png\" width=\"490\" height=\"109\" \/><\/p>\n<p>To name the two prochiral hydrogens on ethanol, we again need to engage in a thought experiment. If we, in our imagination, were to arbitrarily change H<sub>B<\/sub> to a deuterium, the molecule would now be chiral and the stereocenter would have the <em>S<\/em> configuration (D has a higher priority than H). For this reason, we can refer to H<sub>B<\/sub> as the <em>pro-S<\/em> hydrogen of ethanol, and label it H<em><sub>S<\/sub><\/em>. Conversely, if we change H<sub>A<\/sub> to D and leave H<sub>B<\/sub> as a hydrogen, the configuration of the molecule becomes <em>R<\/em>, so we can refer to H<sub>A<\/sub> as the <em>pro-R<\/em> hydrogen of ethanol, and label it H<em><sub>R<\/sub><\/em>.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133751\/image193.png\" alt=\"image192.png\" width=\"233\" height=\"74\" \/><\/p>\n<p>Looking back at our fatty acid example, we see that it is specifically the <em>pro-R<\/em> hydrogens on carbons 2 and 3 that are lost in the reaction.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133753\/image195.png\" alt=\"image194.png\" width=\"670\" height=\"180\" \/><\/p>\n<p>Prochiral hydrogens can be designated either enantiotopic or diastereotopic. If either H<sub>R<\/sub> or H<sub>S<\/sub> on ethanol were replaced by a deuterium, the two resulting molecules would be enantiomers (because there are no other stereocenters)<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133756\/image197.png\" alt=\"image196.png\" width=\"470\" height=\"120\" \/><\/p>\n<p>Thus, these two hydrogens are referred to as <strong>enantiotopic<\/strong>.<\/p>\n<p>In glyceraldehyde-3-phosphate (GAP), however, we see something different:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133759\/image199.png\" alt=\"image198.png\" width=\"513\" height=\"198\" \/><\/p>\n<p>If either H<sub>R<\/sub> or H<sub>S<\/sub> is replaced by a deuterium, the two resulting molecules will be diastereomers &#8211; thus, in this molecule, H<sub>R<\/sub> and H<sub>S<\/sub> are referred to as <strong>diastereotopic<\/strong> hydrogens. The importance of the distinction between enantiotopic and diastereotopic groups will become apparent when we learn about the analytical technique called nuclear magnetic resonance.<\/p>\n<p>Two hydrogens on the same carbon of a substituted ring structure can be diastereotopic &#8211; we determine this by carrying out the same thought experiment as discussed above. In the example below, the diastereotopic hydrogens indicated are either on the same side or on the opposite side of the ring relative to the hydroxyl group.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133801\/image201.png\" alt=\"image200.png\" width=\"362\" height=\"180\" \/><\/p>\n<p>Finally, hydrogens that are completely identical and can be designated neither enantiotopic nor diastereotopic are called <strong>homotopic<\/strong>. If a homotopic hydrogen is replaced by deuterium, a chiral center is <em>not<\/em> created. The three hydrogen atoms on the methyl (CH<sub>3<\/sub>) group of ethanol (and on <em>any<\/em> methyl group) are homotopic.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133804\/image203.png\" alt=\"image202.png\" width=\"169\" height=\"112\" \/><\/p>\n<p>Even to an enzyme, all three of these hydrogens will look the same.<\/p>\n<div style=\"margin: auto\">\n<div id=\"example\">\n<div class=\"textbox examples\">\n<h3>Example<\/h3>\n<p>Identify in the molecules below all pairs\/groups of hydrogens that are homotopic, enantiotopic, or diastereotopic. When appropriate, label prochiral hydrogens as H<em><sub>R<\/sub><\/em> or H<em><sub>S<\/sub><\/em>.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133806\/image205.png\" alt=\"image204.png\" width=\"435\" height=\"309\" \/><\/p>\n<dl>\n<dt><strong><strong>Answer<\/strong><\/strong>&nbsp;<\/dt>\n<dd><img decoding=\"async\" class=\"internal default alignnone\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133809\/5-11-1.png\" alt=\"5-11-1.png\" width=\"434px\" height=\"327px\" \/><\/p>\n<dl>\n<dt><\/dt>\n<dt><\/dt>\n<\/dl>\n<\/dd>\n<\/dl>\n<\/div>\n<\/div>\n<\/div>\n<div>Groups other than hydrogens can be considered prochiral. The alcohol below has two prochiral methyl groups &#8211; methyl A is the <em>pro-R<\/em> methyl, and methyl B is <em>pro-S<\/em>. (How do we make these designations? Simple &#8211; just arbitrarily make methyl A higher priority than methyl B, and the compound now has the <em>R<\/em> configuration).<\/div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133811\/image207.png\" alt=\"image206.png\" width=\"170\" height=\"162\" \/><\/p>\n<p>Citrate provides a more complex example. The central carbon is a prochiral center with two &#8216;arms&#8217; that are identical except that one can be designated <em>pro-R<\/em> and the other <em>pro-S<\/em>.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133812\/image209.png\" alt=\"image208.png\" width=\"169\" height=\"138\" \/><\/p>\n<p>In a reaction of the citric acid cycle (Krebs cycle), a water molecule is specifically lost on the <em>pro-R<\/em> arm (we will study this reaction in <a title=\"Organic Chemistry\/Organic Chemistry With a Biological Emphasis\/Chapter 14: Reactions with stabilized carbanion intermediates II\/Section 14.1: Michael additions, \u03b2 eliminations and reactions with electron sink cofactors\" href=\"https:\/\/chem.libretexts.org\/Textbook_Maps\/Organic_Chemistry_Textbook_Maps\/Map%3A_Organic_Chemistry_with_a_Biological_Emphasis_(Soderberg)\/14%3A_Reactions_with_stabilized_carbanion_intermediates%2C_part_II\/14.1%3A_Michael_additions%2C_%CE%B2_eliminations_and_reactions_with_electron_sink_cofactors\" rel=\"internal\">section 14.1B<\/a>).<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133815\/image211.png\" alt=\"image210.png\" width=\"582\" height=\"100\" \/><\/p>\n<p>Notice also that it is specifically the <em>pro-R<\/em> hydrogen on the <em>pro-R<\/em> arm of citrate that is lost &#8211; one more layer of stereoselectivity!<\/p>\n<div style=\"margin: auto\">\n<div class=\"textbox examples\">\n<h3>Example<\/h3>\n<div>Assign <em>pro-R <\/em>and<em>pro-S<\/em> designations to all prochiral groups in the amino acid leucine. (<em>Hint<\/em>: there are two pairs of prochiral groups!). Are these prochiral groups diastereotopic or enantiotopic?<\/div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133817\/image213.png\" alt=\"image212.png\" width=\"116\" height=\"151\" \/><\/p>\n<dl>\n<dt><strong>Answer:<\/strong><\/dt>\n<dd><a class=\"thumb\" title=\"\" href=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/107722\/5-11-2.png?revision=1\" rel=\"internal\"><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133819\/5-11-2.png\" alt=\"\" width=\"189px\" height=\"197px\" \/><\/a><\/dd>\n<\/dl>\n<\/div>\n<dl><\/dl>\n<\/div>\n<div>Although an alkene carbon bonded to two identical groups is <em>not<\/em> considered a prochiral center, these two groups <em>can<\/em> be diastereotopic. H<sub>a<\/sub> and H<sub>b<\/sub> on the alkene below, for example, are diastereotopic: if we change one, and then the other, of these hydrogens to deuterium, the resulting compounds are <em>E<\/em> and <em>Z<\/em> diastereomers.<\/div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133821\/image215.png\" alt=\"image214.png\" width=\"579\" height=\"170\" \/><\/p>\n<\/div>\n<div id=\"section_2\">\n<h3 class=\"editable\">Carbonyl and imine carbons as prochiral centers<\/h3>\n<p>Trigonal planar, sp<sup>2<\/sup>-hybridized carbons are not, as we well know, chiral centers\u2013 but they are referred to as prochiral centers if they are bonded to three different substitutuents. As you might expect, we (and the enzymes that catalyze their reactions) can distinguish between the two planar \u2018faces\u2019 of a prochiral sp<sup>2<\/sup> &#8211; hybridized group. These faces are designated by the terms <strong><em>re<\/em><\/strong> and <strong><em>si<\/em><\/strong>. To determine which is the <em>re<\/em> and which is the <em>si<\/em> face of a planar organic group, we simply use the same priority rankings that we are familiar with from the R\/S system, and trace a circle: <em>re<\/em> is clockwise and <em>si<\/em> is counterclockwise.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133824\/image217.png\" alt=\"image216.png\" width=\"413\" height=\"176\" \/><\/p>\n<p>Below, for example, we are looking down on the <em>re<\/em> face of the ketone group in pyruvate:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133827\/image219.png\" alt=\"image218.png\" width=\"358\" height=\"168\" \/><\/p>\n<p>If we flipped the molecule over, we would be looking at the <em>si<\/em> face of the ketone group. Note that the carboxylate group does not have <em>re<\/em> and <em>si<\/em> faces, because two of the three substituents on that carbon are identical (when the two resonance forms of carboxylate are taken into account).<\/p>\n<p>As we will see beginning in chapter 11, enzymes which catalyze reactions at carbonyl carbons act specifically from one side or the other.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133829\/image221.png\" alt=\"image220.png\" width=\"626\" height=\"163\" \/><\/p>\n<p>Notice that the &#8216;hydrogenation&#8217; reaction above is specific not only in terms of which face of the carbonyl group is affected, but also in terms of which of the two diastereotopic hydrogens on NADH is transferred (we will study this type of reaction in more detail in <a title=\"Organic Chemistry\/Organic Chemistry With a Biological Emphasis\/Chapter 16: Oxidation and reduction reactions\/Section 16.4: Hydrogenation\/\/dehydrogenation reactions of carbonyls, imines, and alcohols\" href=\"https:\/\/chem.libretexts.org\/Textbook_Maps\/Organic_Chemistry_Textbook_Maps\/Map%3A_Organic_Chemistry_with_a_Biological_Emphasis_(Soderberg)\/16%3A_Oxidation_and_reduction_reactions\/16.04%3A_Hydrogenation%2F%2F%2F%2Fdehydrogenation_reactions_of_carbonyls%2C_imines%2C_and_alcohols\" rel=\"internal\">section 16.4<\/a>).<\/p>\n<div>\n<div class=\"textbox examples\">\n<h3>Example<\/h3>\n<div id=\"section_2\">\n<div>\n<div>\n<div>\n<p>For each of the carbonyl groups in uracil, state whether we are looking at the <em>re<\/em> or the <em>si<\/em> face in the structural drawing below.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133831\/image223.png\" alt=\"image222.png\" width=\"72\" height=\"135\" \/><\/p>\n<div><\/div>\n<div>\n<dl>\n<dt><strong class=\"emphasis bold\">Answer:<\/strong><\/dt>\n<dd><a class=\"thumb\" title=\"\" href=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/107723\/5-11-3.png?revision=1\" rel=\"internal\"><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133833\/5-11-3.png\" alt=\"\" width=\"350px\" height=\"256px\" \/><\/a><\/dd>\n<\/dl>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"textbox exercises\">\n<h3>Exercises<\/h3>\n<div id=\"section_3\">\n<div id=\"s61692\">\n<p><strong>1.<\/strong><\/p>\n<p>State which of the following hydrogen atoms are<em> pro-R<\/em> or <em>pro-S<\/em>.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133835\/5.11.png\" alt=\"\" width=\"593\" height=\"150\" \/><\/p>\n<p><strong>2.<\/strong><\/p>\n<p>Identify which side is Re or Si<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05133837\/5.112.png\" alt=\"\" width=\"448\" height=\"194\" \/><\/p>\n<\/div>\n<div>\n<dl>\n<dt><strong class=\"emphasis bold\">Answer:<\/strong><\/dt>\n<dd>\n<div>\n<p><strong>1.<\/strong><\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q497360\">Show Answer<\/span><\/p>\n<div id=\"q497360\" class=\"hidden-answer\" style=\"display: none\">Left compound: Ha = pro-S and Hb = pro-R Right compound: Ha = pro-R\u00a0 and Hb = pro-S<\/div>\n<\/div>\n<p><strong>2.<\/strong><\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q586755\">Show Answer<\/span><\/p>\n<div id=\"q586755\" class=\"hidden-answer\" style=\"display: none\">A \u2013 Re; B \u2013 Si; C \u2013 Si; D \u2013 Re<\/div>\n<\/div>\n<\/div>\n<\/dd>\n<\/dl>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"section_3\">\n<div>\n<div>\n<h3 class=\"editable\">Contributors<\/h3>\n<ul>\n<li><a title=\"http:\/\/chemwiki.ucdavis.edu\/Organic_Chemistry\/Organic_Chemistry_With_a_Biological_Emphasis\" href=\"https:\/\/chem.libretexts.org\/Textbook_Maps\/Organic_Chemistry_Textbook_Maps\/Map%3A_Organic_Chemistry_with_a_Biological_Emphasis_(Soderberg)\" rel=\"internal\"><strong>Organic Chemistry With a Biological Emphasis <\/strong><\/a>by\u00a0<a class=\"external\" title=\"http:\/\/facultypages.morris.umn.edu\/~soderbt\/\" href=\"http:\/\/facultypages.morris.umn.edu\/%7Esoderbt\/\" target=\"_blank\" rel=\"external nofollow noopener\">Tim Soderberg<\/a>\u00a0(University of Minnesota, Morris)<\/li>\n<\/ul>\n<\/div>\n<ul>\n<li><a class=\"external\" title=\"http:\/\/science.athabascau.ca\/staff-pages\/dietmark\" href=\"http:\/\/science.athabascau.ca\/staff-pages\/dietmark\" target=\"_blank\" rel=\"external nofollow noopener\">Dr. Dietmar Kennepohl<\/a> FCIC (Professor of Chemistry, <a class=\"external\" title=\"http:\/\/www.athabascau.ca\/\" href=\"http:\/\/www.athabascau.ca\/\" target=\"_blank\" rel=\"external nofollow noopener\">Athabasca University<\/a>)<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<\/div>\n","protected":false},"author":44985,"menu_order":11,"template":"","meta":{"_candela_citation":"[]","CANDELA_OUTCOMES_GUID":"","pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-898","chapter","type-chapter","status-publish","hentry"],"part":22,"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/pressbooks\/v2\/chapters\/898","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/wp\/v2\/users\/44985"}],"version-history":[{"count":7,"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/pressbooks\/v2\/chapters\/898\/revisions"}],"predecessor-version":[{"id":2271,"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/pressbooks\/v2\/chapters\/898\/revisions\/2271"}],"part":[{"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/pressbooks\/v2\/parts\/22"}],"metadata":[{"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/pressbooks\/v2\/chapters\/898\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/wp\/v2\/media?parent=898"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/pressbooks\/v2\/chapter-type?post=898"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/wp\/v2\/contributor?post=898"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/wp\/v2\/license?post=898"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}