{"id":325,"date":"2017-10-04T15:15:57","date_gmt":"2017-10-04T15:15:57","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/?post_type=chapter&#038;p=325"},"modified":"2018-09-28T19:42:23","modified_gmt":"2018-09-28T19:42:23","slug":"dipole-moments","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/chapter\/dipole-moments\/","title":{"raw":"Dipole Moments","rendered":"Dipole Moments"},"content":{"raw":"<div class=\"elm-header\"><\/div>\r\n<div id=\"elm-main-content\" class=\"elm-content-container\">\r\n<div id=\"skills\">\r\n<div class=\"textbox learning-objectives\">\r\n<h3>Objectives<\/h3>\r\nAfter completing this section, you should be able to\r\n<ol>\r\n \t<li>explain how dipole moments depend on both molecular shape and bond polarity.<\/li>\r\n \t<li>predict whether a molecule will possess a dipole moment, given only its molecular formula or Kekul\u00e9 structure.<\/li>\r\n \t<li>use the presence or absence of a dipole moment as an aid to deducing the structure of a given compound.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\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 term below.\r\n<ul>\r\n \t<li>dipole moment<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n<div id=\"note\">\r\n<div class=\"textbox\">\r\n<h3 class=\"boxtitle\">Study Notes<\/h3>\r\nYou must be able to combine your knowledge of molecular shapes and bond polarities to determine whether or not a given compound will have a dipole moment. Conversely, the presence or absence of a dipole moment may also give an important clue to a compound\u2019s structure. BCl<sub>3<\/sub>, for example, has no dipole moment, while NH<sub>3<\/sub> does. This suggests that in BCl<sub>3<\/sub> the chlorines around boron are in a trigonal planar arrangement, while the hydrogens around nitrogen in NH<sub>3<\/sub> would have a less symmetrical arrangement (e.g., trigonal pyramidal, T-shaped). Remember that the $\\ce{\\sf{C-H}}$ bond can usually be assumed to be nonpolar.\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"section_1\">\r\n<h3 class=\"editable\">Molecular Dipole Moments<\/h3>\r\nYou previously learned how to calculate the <strong class=\"emphasis bold\">dipole moments<\/strong> of simple diatomic molecules. In more complex molecules with polar covalent bonds, the three-dimensional geometry and the compound\u2019s symmetry determine whether there is a net dipole moment. Mathematically, dipole moments are <em class=\"emphasis\">vectors<\/em>; they possess both a <em class=\"emphasis\">magnitude<\/em> and a <em class=\"emphasis\">direction<\/em>. The dipole moment of a molecule is therefore the <em class=\"emphasis\">vector sum<\/em> of the dipole moments of the individual bonds in the molecule. If the individual bond dipole moments cancel one another, there is no net dipole moment. Such is the case for CO<sub class=\"subscript\">2<\/sub>, a linear molecule (part (a) in Figure 2.2.8). Each C\u2013O bond in CO<sub class=\"subscript\">2<\/sub> is polar, yet experiments show that the CO<sub class=\"subscript\">2<\/sub> molecule has no dipole moment. Because the two C\u2013O bond dipoles in CO<sub class=\"subscript\">2<\/sub> are equal in magnitude and oriented at 180\u00b0 to each other, they cancel. As a result, the CO<sub class=\"subscript\">2<\/sub> molecule has no <em class=\"emphasis\">net<\/em> dipole moment even though it has a substantial separation of charge. In contrast, the H<sub class=\"subscript\">2<\/sub>O molecule is not linear (part (b) in Figure 2.2.8); it is bent in three-dimensional space, so the dipole moments do not cancel each other. Thus a molecule such as H<sub class=\"subscript\">2<\/sub>O has a net dipole moment. We expect the concentration of negative charge to be on the oxygen, the more electronegative atom, and positive charge on the two hydrogens. This charge polarization allows H<sub class=\"subscript\">2<\/sub>O to hydrogen-bond to other polarized or charged species, including other water molecules.\r\n<div class=\"figure large medium-height editable block\">\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"609\"]<img class=\"internal\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/04151527\/946a0c562a45f719b8ad57889f03a0bf.jpg\" alt=\"\" width=\"609\" height=\"201\" \/> Figure 8 How Individual Bond Dipole Moments Are Added Together to Give an Overall Molecular Dipole Moment for Two Triatomic Molecules with Different Structures. (a) In CO2, the C\u2013O bond dipoles are equal in magnitude but oriented in opposite directions (at 180\u00b0). Their vector sum is zero, so CO2 therefore has no net dipole. (b) In H2O, the O\u2013H bond dipoles are also equal in magnitude, but they are oriented at 104.5\u00b0 to each other. Hence the vector sum is not zero, and H2O has a net dipole moment.[\/caption]\r\n\r\n<\/div>\r\nOther examples of molecules with polar bonds are shown in Figure 2.2.9. In molecular geometries that are highly symmetrical (most notably tetrahedral and square planar, trigonal bipyramidal, and octahedral), individual bond dipole moments completely cancel, and there is no net dipole moment. Although a molecule like CHCl<sub class=\"subscript\">3<\/sub> is best described as tetrahedral, the atoms bonded to carbon are not identical. Consequently, the bond dipole moments cannot cancel one another, and the molecule has a dipole moment. Due to the arrangement of the bonds in molecules that have V-shaped, trigonal pyramidal, seesaw, T-shaped, and square pyramidal geometries, the bond dipole moments cannot cancel one another. Consequently, molecules with these geometries always have a nonzero dipole moment.\r\n<div class=\"figure large editable block\">\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"750\"]<img class=\"internal\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/04151531\/152d341517999098d0a7099828edf874.jpg\" alt=\"\" width=\"750\" height=\"107\" \/> Figure 9: Molecules with Polar Bonds. Individual bond dipole moments are indicated in red. Due to their different three-dimensional structures, some molecules with polar bonds have a net dipole moment (HCl, CH2O, NH3, and CHCl3), indicated in blue, whereas others do not because the bond dipole moments cancel (BCl3, CCl4, PF5, and SF6).[\/caption]\r\n\r\n<div>\r\n<div class=\"textbox\">\r\n<p class=\"boxtitle\">Note<\/p>\r\nMolecules with asymmetrical charge distributions have a net dipole moment\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div>\r\n<div id=\"example\">\r\n<div class=\"textbox examples\">\r\n<h3>Examples<\/h3>\r\n<p class=\"boxtitle\">Example 1<\/p>\r\nWhich molecule(s) has a net dipole moment?\r\n<ol class=\"orderedlist\" start=\"1\">\r\n \t<li>H<sub class=\"subscript\">2<\/sub>S<\/li>\r\n \t<li>NHF<sub class=\"subscript\">2<\/sub><\/li>\r\n \t<li>BF<sub class=\"subscript\">3<\/sub><\/li>\r\n<\/ol>\r\n<strong class=\"emphasis bold\">Given: <\/strong>three chemical compounds\r\n\r\n<strong class=\"emphasis bold\">Asked for: <\/strong>net dipole moment\r\n\r\n<strong class=\"emphasis bold\">Strategy:<\/strong>\r\n\r\nFor each three-dimensional molecular geometry, predict whether the bond dipoles cancel. If they do not, then the molecule has a net dipole moment.\r\n\r\n[reveal-answer q=\"720157\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"720157\"]\r\n\r\n<strong class=\"emphasis bold\">Solution:<\/strong>\r\n<ol class=\"orderedlist\">\r\n \t<li>The total number of electrons around the central atom, S, is eight, which gives four electron pairs. Two of these electron pairs are bonding pairs and two are lone pairs, so the molecular geometry of H<sub class=\"subscript\">2<\/sub>S is bent (Figure 2.2.6). The bond dipoles cannot cancel one another, so the molecule has a net dipole moment.\r\n<div class=\"informalfigure large medium-height\"><img class=\"internal aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/04151533\/dea2649948182be1b7aba99f8fb07102.jpg\" alt=\"\" width=\"96\" height=\"108\" \/><\/div><\/li>\r\n \t<li>Difluoroamine has a trigonal pyramidal molecular geometry. Because there is one hydrogen and two fluorines, and because of the lone pair of electrons on nitrogen, the molecule is not symmetrical, and the bond dipoles of NHF<sub class=\"subscript\">2<\/sub> cannot cancel one another. This means that NHF<sub class=\"subscript\">2<\/sub> has a net dipole moment. We expect polarization from the two fluorine atoms, the most electronegative atoms in the periodic table, to have a greater affect on the net dipole moment than polarization from the lone pair of electrons on nitrogen.\r\n<div class=\"informalfigure large medium-height\"><img class=\"internal aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/04151534\/6bf3ad629508e59a94143abda55e502b.jpg\" alt=\"\" width=\"124\" height=\"118\" \/><\/div><\/li>\r\n \t<li>The molecular geometry of BF<sub class=\"subscript\">3<\/sub> is trigonal planar. Because all the B\u2013F bonds are equal and the molecule is highly symmetrical, the dipoles cancel one another in three-dimensional space. Thus BF<sub class=\"subscript\">3<\/sub> has a net dipole moment of zero:<\/li>\r\n<\/ol>\r\n<div class=\"informalfigure large medium-height\"><img class=\"internal aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/04151535\/fb09e5b20f1702f282205783b61340cd.jpg\" alt=\"\" width=\"119\" height=\"102\" \/><\/div>\r\n<div>\r\n\r\n[\/hidden-answer]\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div>\r\n<div id=\"exercise\">\r\n<div class=\"textbox exercises\">\r\n<h3>Exercise<\/h3>\r\n<p class=\"boxtitle\">Exercise 1<\/p>\r\nWhich molecule(s) has a net dipole moment?\r\n<ol class=\"orderedlist\">\r\n \t<li>CH<sub class=\"subscript\">3<\/sub>Cl<\/li>\r\n \t<li>SO<sub class=\"subscript\">3<\/sub><\/li>\r\n \t<li>XeO<sub class=\"subscript\">3<\/sub><\/li>\r\n<\/ol>\r\n[reveal-answer q=\"166832\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"166832\"]Answer: CH3Cl; XeO3[\/hidden-answer]\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\nIn 1923, chemists Johannes Br\u00f8nsted and Martin Lowry independently developed definitions of acids and bases based on compounds abilities to either donate or accept protons (H<sup>+<\/sup> ions). Here, acids are defined as being able to donate protons in the form of hydrogen ions; whereas bases are defined as being able to accept protons.\u00a0This took the <a title=\"Physical Chemistry\/Acids and Bases\/Acid\/Arrhenius Concept of Acids and Bases\" href=\"\/Physical_Chemistry\/Acids_and_Bases\/Acid\/Arrhenius_Concept_of_Acids_and_Bases\" rel=\"internal\">Arrhenius<\/a> definition one step further as water is no longer required to be present in the solution for acid and base reactions to occur.\r\n\r\n<\/div>\r\n<div id=\"section_2\">\r\n<div class=\"textbox exercises\">\r\n<h3>Exercises<\/h3>\r\n<div id=\"section_2\">\r\n\r\nQuestion\r\n<ol>\r\n \t<li>Determine whether each of the compounds listed below possesses a dipole moment. For the polar compounds, indicate the direction of the dipole moment.\r\n<ol>\r\n \t<li>$\\ce{\\sf{O=C=O}}$<\/li>\r\n \t<li>ICl<\/li>\r\n \t<li>SO<sub>2<\/sub><\/li>\r\n \t<li>$\\ce{\\sf{CH3-O-CH3}}$<\/li>\r\n \t<li>$\\ce{\\sf{CH3C(=O)CH3}}$<\/li>\r\n<\/ol>\r\n<\/li>\r\n<\/ol>\r\n<h3>Solution<\/h3>\r\n[reveal-answer q=\"602533\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"602533\"]\r\n<ol>\r\n \t<li><img src=\"https:\/\/chem.libretexts.org\/LibreTexts\/Athabasca_University\/Chemistry_350%3A_Organic_Chemistry_I\/Chapter_2%3A_Polar_Covalent_Bonds%3B_Acids_and_Bases\/\/LibreTexts\/Athabasca_University\/Chemistry_350:_Organic_Chemistry_I\/Chapter_2:_Polar_Covalent_Bonds;_Acids_and_Bases\/2.02_Polar_Covalent_Bonds:_Dipole_Moments##fixme\" alt=\"carbon dioxide is nonpolar\" \/><\/li>\r\n \t<li><img src=\"https:\/\/chem.libretexts.org\/LibreTexts\/Athabasca_University\/Chemistry_350%3A_Organic_Chemistry_I\/Chapter_2%3A_Polar_Covalent_Bonds%3B_Acids_and_Bases\/\/LibreTexts\/Athabasca_University\/Chemistry_350:_Organic_Chemistry_I\/Chapter_2:_Polar_Covalent_Bonds;_Acids_and_Bases\/2.02_Polar_Covalent_Bonds:_Dipole_Moments##fixme\" alt=\"net dipole moment on iodine monochloride\" \/><\/li>\r\n \t<li><img src=\"https:\/\/chem.libretexts.org\/LibreTexts\/Athabasca_University\/Chemistry_350%3A_Organic_Chemistry_I\/Chapter_2%3A_Polar_Covalent_Bonds%3B_Acids_and_Bases\/\/LibreTexts\/Athabasca_University\/Chemistry_350:_Organic_Chemistry_I\/Chapter_2:_Polar_Covalent_Bonds;_Acids_and_Bases\/2.02_Polar_Covalent_Bonds:_Dipole_Moments##fixme\" alt=\"net dipole moment on sulfur dioxide\" \/><\/li>\r\n \t<li><img src=\"https:\/\/chem.libretexts.org\/LibreTexts\/Athabasca_University\/Chemistry_350%3A_Organic_Chemistry_I\/Chapter_2%3A_Polar_Covalent_Bonds%3B_Acids_and_Bases\/\/LibreTexts\/Athabasca_University\/Chemistry_350:_Organic_Chemistry_I\/Chapter_2:_Polar_Covalent_Bonds;_Acids_and_Bases\/2.02_Polar_Covalent_Bonds:_Dipole_Moments##fixme\" alt=\"net dipole moment on dimethyl ether\" \/><\/li>\r\n \t<li><img src=\"https:\/\/chem.libretexts.org\/LibreTexts\/Athabasca_University\/Chemistry_350%3A_Organic_Chemistry_I\/Chapter_2%3A_Polar_Covalent_Bonds%3B_Acids_and_Bases\/\/LibreTexts\/Athabasca_University\/Chemistry_350:_Organic_Chemistry_I\/Chapter_2:_Polar_Covalent_Bonds;_Acids_and_Bases\/2.02_Polar_Covalent_Bonds:_Dipole_Moments##fixme\" alt=\"net dipole moment on 2-propanone\" \/><\/li>\r\n<\/ol>\r\n[\/hidden-answer]\r\n<div id=\"s61689\">\r\n<div id=\"section_7\">\r\n<h3 id=\"Questions-61689\">Questions<\/h3>\r\n<strong>1.<\/strong>\r\n\r\nThe following molecule has no dipole moment in the molecule itself, explain.\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\/04151536\/2.2_rev.png\" alt=\"\" width=\"275\" height=\"48\" \/>\r\n\r\n<strong>2.\u00a0<\/strong>\r\n\r\nWhich of the following molecules has a net dipole?\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\/04151539\/2.22.png\" alt=\"\" width=\"373\" height=\"298\" \/>\r\n\r\n<strong>3.<\/strong>\r\n\r\nWithin reactions with carbonyls, such as a reduction reaction, the carbonyl is attacked from the carbon side and not the oxygen side. Using knowledge of electronegativity explain why this happens.\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\/04151542\/2-2-3.png\" alt=\"\" width=\"179\" height=\"149\" \/>\r\n\r\n<\/div>\r\n<div id=\"section_8\">\r\n\r\n[reveal-answer q=\"620421\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"620421\"]\r\n<h4 id=\"Solutions-61689\">Solutions<\/h4>\r\n1. The hydroxyl groups are oriented opposite of one another and therefore the dipole moments would \u201ccancel\u201d one another out. Therefore having a zero net-dipole.\r\n\r\n2. 1, 3, and 4 have a net dipoles.\r\n\r\n3. The oxygen is more electronegative than the carbon and therefore creates a dipole along the bond. This leads to having a partial positive charge on the carbon and the reduction can take place.<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/04151545\/2-2-3sol.png\" alt=\"\" width=\"111\" height=\"119\" \/>\r\n\r\n[\/hidden-answer]\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div id=\"section_3\">\r\n<h3 class=\"editable\">Contributors<\/h3>\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 \t<li>Prof. Steven Farmer (<a class=\"external\" title=\"http:\/\/www.sonoma.edu\" href=\"http:\/\/www.sonoma.edu\" target=\"_blank\" rel=\"external nofollow noopener\">Sonoma State University<\/a>)<\/li>\r\n \t<li><a title=\"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\">Organic Chemistry With a Biological Emphasis <\/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<\/div>","rendered":"<div class=\"elm-header\"><\/div>\n<div id=\"elm-main-content\" class=\"elm-content-container\">\n<div id=\"skills\">\n<div class=\"textbox learning-objectives\">\n<h3>Objectives<\/h3>\n<p>After completing this section, you should be able to<\/p>\n<ol>\n<li>explain how dipole moments depend on both molecular shape and bond polarity.<\/li>\n<li>predict whether a molecule will possess a dipole moment, given only its molecular formula or Kekul\u00e9 structure.<\/li>\n<li>use the presence or absence of a dipole moment as an aid to deducing the structure of a given compound.<\/li>\n<\/ol>\n<\/div>\n<\/div>\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 term below.<\/p>\n<ul>\n<li>dipole moment<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<div id=\"note\">\n<div class=\"textbox\">\n<h3 class=\"boxtitle\">Study Notes<\/h3>\n<p>You must be able to combine your knowledge of molecular shapes and bond polarities to determine whether or not a given compound will have a dipole moment. Conversely, the presence or absence of a dipole moment may also give an important clue to a compound\u2019s structure. BCl<sub>3<\/sub>, for example, has no dipole moment, while NH<sub>3<\/sub> does. This suggests that in BCl<sub>3<\/sub> the chlorines around boron are in a trigonal planar arrangement, while the hydrogens around nitrogen in NH<sub>3<\/sub> would have a less symmetrical arrangement (e.g., trigonal pyramidal, T-shaped). Remember that the $\\ce{\\sf{C-H}}$ bond can usually be assumed to be nonpolar.<\/p>\n<\/div>\n<\/div>\n<div id=\"section_1\">\n<h3 class=\"editable\">Molecular Dipole Moments<\/h3>\n<p>You previously learned how to calculate the <strong class=\"emphasis bold\">dipole moments<\/strong> of simple diatomic molecules. In more complex molecules with polar covalent bonds, the three-dimensional geometry and the compound\u2019s symmetry determine whether there is a net dipole moment. Mathematically, dipole moments are <em class=\"emphasis\">vectors<\/em>; they possess both a <em class=\"emphasis\">magnitude<\/em> and a <em class=\"emphasis\">direction<\/em>. The dipole moment of a molecule is therefore the <em class=\"emphasis\">vector sum<\/em> of the dipole moments of the individual bonds in the molecule. If the individual bond dipole moments cancel one another, there is no net dipole moment. Such is the case for CO<sub class=\"subscript\">2<\/sub>, a linear molecule (part (a) in Figure 2.2.8). Each C\u2013O bond in CO<sub class=\"subscript\">2<\/sub> is polar, yet experiments show that the CO<sub class=\"subscript\">2<\/sub> molecule has no dipole moment. Because the two C\u2013O bond dipoles in CO<sub class=\"subscript\">2<\/sub> are equal in magnitude and oriented at 180\u00b0 to each other, they cancel. As a result, the CO<sub class=\"subscript\">2<\/sub> molecule has no <em class=\"emphasis\">net<\/em> dipole moment even though it has a substantial separation of charge. In contrast, the H<sub class=\"subscript\">2<\/sub>O molecule is not linear (part (b) in Figure 2.2.8); it is bent in three-dimensional space, so the dipole moments do not cancel each other. Thus a molecule such as H<sub class=\"subscript\">2<\/sub>O has a net dipole moment. We expect the concentration of negative charge to be on the oxygen, the more electronegative atom, and positive charge on the two hydrogens. This charge polarization allows H<sub class=\"subscript\">2<\/sub>O to hydrogen-bond to other polarized or charged species, including other water molecules.<\/p>\n<div class=\"figure large medium-height editable block\">\n<div style=\"width: 619px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"internal\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/04151527\/946a0c562a45f719b8ad57889f03a0bf.jpg\" alt=\"\" width=\"609\" height=\"201\" \/><\/p>\n<p class=\"wp-caption-text\">Figure 8 How Individual Bond Dipole Moments Are Added Together to Give an Overall Molecular Dipole Moment for Two Triatomic Molecules with Different Structures. (a) In CO2, the C\u2013O bond dipoles are equal in magnitude but oriented in opposite directions (at 180\u00b0). Their vector sum is zero, so CO2 therefore has no net dipole. (b) In H2O, the O\u2013H bond dipoles are also equal in magnitude, but they are oriented at 104.5\u00b0 to each other. Hence the vector sum is not zero, and H2O has a net dipole moment.<\/p>\n<\/div>\n<\/div>\n<p>Other examples of molecules with polar bonds are shown in Figure 2.2.9. In molecular geometries that are highly symmetrical (most notably tetrahedral and square planar, trigonal bipyramidal, and octahedral), individual bond dipole moments completely cancel, and there is no net dipole moment. Although a molecule like CHCl<sub class=\"subscript\">3<\/sub> is best described as tetrahedral, the atoms bonded to carbon are not identical. Consequently, the bond dipole moments cannot cancel one another, and the molecule has a dipole moment. Due to the arrangement of the bonds in molecules that have V-shaped, trigonal pyramidal, seesaw, T-shaped, and square pyramidal geometries, the bond dipole moments cannot cancel one another. Consequently, molecules with these geometries always have a nonzero dipole moment.<\/p>\n<div class=\"figure large editable block\">\n<div style=\"width: 760px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"internal\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/04151531\/152d341517999098d0a7099828edf874.jpg\" alt=\"\" width=\"750\" height=\"107\" \/><\/p>\n<p class=\"wp-caption-text\">Figure 9: Molecules with Polar Bonds. Individual bond dipole moments are indicated in red. Due to their different three-dimensional structures, some molecules with polar bonds have a net dipole moment (HCl, CH2O, NH3, and CHCl3), indicated in blue, whereas others do not because the bond dipole moments cancel (BCl3, CCl4, PF5, and SF6).<\/p>\n<\/div>\n<div>\n<div class=\"textbox\">\n<p class=\"boxtitle\">Note<\/p>\n<p>Molecules with asymmetrical charge distributions have a net dipole moment<\/p>\n<\/div>\n<\/div>\n<\/div>\n<div>\n<div id=\"example\">\n<div class=\"textbox examples\">\n<h3>Examples<\/h3>\n<p class=\"boxtitle\">Example 1<\/p>\n<p>Which molecule(s) has a net dipole moment?<\/p>\n<ol class=\"orderedlist\" start=\"1\">\n<li>H<sub class=\"subscript\">2<\/sub>S<\/li>\n<li>NHF<sub class=\"subscript\">2<\/sub><\/li>\n<li>BF<sub class=\"subscript\">3<\/sub><\/li>\n<\/ol>\n<p><strong class=\"emphasis bold\">Given: <\/strong>three chemical compounds<\/p>\n<p><strong class=\"emphasis bold\">Asked for: <\/strong>net dipole moment<\/p>\n<p><strong class=\"emphasis bold\">Strategy:<\/strong><\/p>\n<p>For each three-dimensional molecular geometry, predict whether the bond dipoles cancel. If they do not, then the molecule has a net dipole moment.<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q720157\">Show Answer<\/span><\/p>\n<div id=\"q720157\" class=\"hidden-answer\" style=\"display: none\">\n<p><strong class=\"emphasis bold\">Solution:<\/strong><\/p>\n<ol class=\"orderedlist\">\n<li>The total number of electrons around the central atom, S, is eight, which gives four electron pairs. Two of these electron pairs are bonding pairs and two are lone pairs, so the molecular geometry of H<sub class=\"subscript\">2<\/sub>S is bent (Figure 2.2.6). The bond dipoles cannot cancel one another, so the molecule has a net dipole moment.\n<div class=\"informalfigure large medium-height\"><img loading=\"lazy\" decoding=\"async\" class=\"internal aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/04151533\/dea2649948182be1b7aba99f8fb07102.jpg\" alt=\"\" width=\"96\" height=\"108\" \/><\/div>\n<\/li>\n<li>Difluoroamine has a trigonal pyramidal molecular geometry. Because there is one hydrogen and two fluorines, and because of the lone pair of electrons on nitrogen, the molecule is not symmetrical, and the bond dipoles of NHF<sub class=\"subscript\">2<\/sub> cannot cancel one another. This means that NHF<sub class=\"subscript\">2<\/sub> has a net dipole moment. We expect polarization from the two fluorine atoms, the most electronegative atoms in the periodic table, to have a greater affect on the net dipole moment than polarization from the lone pair of electrons on nitrogen.\n<div class=\"informalfigure large medium-height\"><img loading=\"lazy\" decoding=\"async\" class=\"internal aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/04151534\/6bf3ad629508e59a94143abda55e502b.jpg\" alt=\"\" width=\"124\" height=\"118\" \/><\/div>\n<\/li>\n<li>The molecular geometry of BF<sub class=\"subscript\">3<\/sub> is trigonal planar. Because all the B\u2013F bonds are equal and the molecule is highly symmetrical, the dipoles cancel one another in three-dimensional space. Thus BF<sub class=\"subscript\">3<\/sub> has a net dipole moment of zero:<\/li>\n<\/ol>\n<div class=\"informalfigure large medium-height\"><img loading=\"lazy\" decoding=\"async\" class=\"internal aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/04151535\/fb09e5b20f1702f282205783b61340cd.jpg\" alt=\"\" width=\"119\" height=\"102\" \/><\/div>\n<div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div>\n<div id=\"exercise\">\n<div class=\"textbox exercises\">\n<h3>Exercise<\/h3>\n<p class=\"boxtitle\">Exercise 1<\/p>\n<p>Which molecule(s) has a net dipole moment?<\/p>\n<ol class=\"orderedlist\">\n<li>CH<sub class=\"subscript\">3<\/sub>Cl<\/li>\n<li>SO<sub class=\"subscript\">3<\/sub><\/li>\n<li>XeO<sub class=\"subscript\">3<\/sub><\/li>\n<\/ol>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q166832\">Show Answer<\/span><\/p>\n<div id=\"q166832\" class=\"hidden-answer\" style=\"display: none\">Answer: CH3Cl; XeO3<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<p>In 1923, chemists Johannes Br\u00f8nsted and Martin Lowry independently developed definitions of acids and bases based on compounds abilities to either donate or accept protons (H<sup>+<\/sup> ions). Here, acids are defined as being able to donate protons in the form of hydrogen ions; whereas bases are defined as being able to accept protons.\u00a0This took the <a title=\"Physical Chemistry\/Acids and Bases\/Acid\/Arrhenius Concept of Acids and Bases\" href=\"\/Physical_Chemistry\/Acids_and_Bases\/Acid\/Arrhenius_Concept_of_Acids_and_Bases\" rel=\"internal\">Arrhenius<\/a> definition one step further as water is no longer required to be present in the solution for acid and base reactions to occur.<\/p>\n<\/div>\n<div id=\"section_2\">\n<div class=\"textbox exercises\">\n<h3>Exercises<\/h3>\n<div id=\"section_2\">\n<p>Question<\/p>\n<ol>\n<li>Determine whether each of the compounds listed below possesses a dipole moment. For the polar compounds, indicate the direction of the dipole moment.\n<ol>\n<li>$\\ce{\\sf{O=C=O}}$<\/li>\n<li>ICl<\/li>\n<li>SO<sub>2<\/sub><\/li>\n<li>$\\ce{\\sf{CH3-O-CH3}}$<\/li>\n<li>$\\ce{\\sf{CH3C(=O)CH3}}$<\/li>\n<\/ol>\n<\/li>\n<\/ol>\n<h3>Solution<\/h3>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q602533\">Show Answer<\/span><\/p>\n<div id=\"q602533\" class=\"hidden-answer\" style=\"display: none\">\n<ol>\n<li><img decoding=\"async\" src=\"https:\/\/chem.libretexts.org\/LibreTexts\/Athabasca_University\/Chemistry_350%3A_Organic_Chemistry_I\/Chapter_2%3A_Polar_Covalent_Bonds%3B_Acids_and_Bases\/\/LibreTexts\/Athabasca_University\/Chemistry_350:_Organic_Chemistry_I\/Chapter_2:_Polar_Covalent_Bonds;_Acids_and_Bases\/2.02_Polar_Covalent_Bonds:_Dipole_Moments##fixme\" alt=\"carbon dioxide is nonpolar\" \/><\/li>\n<li><img decoding=\"async\" src=\"https:\/\/chem.libretexts.org\/LibreTexts\/Athabasca_University\/Chemistry_350%3A_Organic_Chemistry_I\/Chapter_2%3A_Polar_Covalent_Bonds%3B_Acids_and_Bases\/\/LibreTexts\/Athabasca_University\/Chemistry_350:_Organic_Chemistry_I\/Chapter_2:_Polar_Covalent_Bonds;_Acids_and_Bases\/2.02_Polar_Covalent_Bonds:_Dipole_Moments##fixme\" alt=\"net dipole moment on iodine monochloride\" \/><\/li>\n<li><img decoding=\"async\" src=\"https:\/\/chem.libretexts.org\/LibreTexts\/Athabasca_University\/Chemistry_350%3A_Organic_Chemistry_I\/Chapter_2%3A_Polar_Covalent_Bonds%3B_Acids_and_Bases\/\/LibreTexts\/Athabasca_University\/Chemistry_350:_Organic_Chemistry_I\/Chapter_2:_Polar_Covalent_Bonds;_Acids_and_Bases\/2.02_Polar_Covalent_Bonds:_Dipole_Moments##fixme\" alt=\"net dipole moment on sulfur dioxide\" \/><\/li>\n<li><img decoding=\"async\" src=\"https:\/\/chem.libretexts.org\/LibreTexts\/Athabasca_University\/Chemistry_350%3A_Organic_Chemistry_I\/Chapter_2%3A_Polar_Covalent_Bonds%3B_Acids_and_Bases\/\/LibreTexts\/Athabasca_University\/Chemistry_350:_Organic_Chemistry_I\/Chapter_2:_Polar_Covalent_Bonds;_Acids_and_Bases\/2.02_Polar_Covalent_Bonds:_Dipole_Moments##fixme\" alt=\"net dipole moment on dimethyl ether\" \/><\/li>\n<li><img decoding=\"async\" src=\"https:\/\/chem.libretexts.org\/LibreTexts\/Athabasca_University\/Chemistry_350%3A_Organic_Chemistry_I\/Chapter_2%3A_Polar_Covalent_Bonds%3B_Acids_and_Bases\/\/LibreTexts\/Athabasca_University\/Chemistry_350:_Organic_Chemistry_I\/Chapter_2:_Polar_Covalent_Bonds;_Acids_and_Bases\/2.02_Polar_Covalent_Bonds:_Dipole_Moments##fixme\" alt=\"net dipole moment on 2-propanone\" \/><\/li>\n<\/ol>\n<\/div>\n<\/div>\n<div id=\"s61689\">\n<div id=\"section_7\">\n<h3 id=\"Questions-61689\">Questions<\/h3>\n<p><strong>1.<\/strong><\/p>\n<p>The following molecule has no dipole moment in the molecule itself, explain.<\/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\/04151536\/2.2_rev.png\" alt=\"\" width=\"275\" height=\"48\" \/><\/p>\n<p><strong>2.\u00a0<\/strong><\/p>\n<p>Which of the following molecules has a net dipole?<\/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\/04151539\/2.22.png\" alt=\"\" width=\"373\" height=\"298\" \/><\/p>\n<p><strong>3.<\/strong><\/p>\n<p>Within reactions with carbonyls, such as a reduction reaction, the carbonyl is attacked from the carbon side and not the oxygen side. Using knowledge of electronegativity explain why this happens.<\/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\/04151542\/2-2-3.png\" alt=\"\" width=\"179\" height=\"149\" \/><\/p>\n<\/div>\n<div id=\"section_8\">\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q620421\">Show Answer<\/span><\/p>\n<div id=\"q620421\" class=\"hidden-answer\" style=\"display: none\">\n<h4 id=\"Solutions-61689\">Solutions<\/h4>\n<p>1. The hydroxyl groups are oriented opposite of one another and therefore the dipole moments would \u201ccancel\u201d one another out. Therefore having a zero net-dipole.<\/p>\n<p>2. 1, 3, and 4 have a net dipoles.<\/p>\n<p>3. The oxygen is more electronegative than the carbon and therefore creates a dipole along the bond. This leads to having a partial positive charge on the carbon and the reduction can take place.<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\/04151545\/2-2-3sol.png\" alt=\"\" width=\"111\" height=\"119\" \/><\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"section_3\">\n<h3 class=\"editable\">Contributors<\/h3>\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<li>Prof. Steven Farmer (<a class=\"external\" title=\"http:\/\/www.sonoma.edu\" href=\"http:\/\/www.sonoma.edu\" target=\"_blank\" rel=\"external nofollow noopener\">Sonoma State University<\/a>)<\/li>\n<li><a title=\"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\">Organic Chemistry With a Biological Emphasis <\/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<\/div>\n","protected":false},"author":311,"menu_order":15,"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-325","chapter","type-chapter","status-publish","hentry"],"part":76,"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/pressbooks\/v2\/chapters\/325","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\/311"}],"version-history":[{"count":9,"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/pressbooks\/v2\/chapters\/325\/revisions"}],"predecessor-version":[{"id":2126,"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/pressbooks\/v2\/chapters\/325\/revisions\/2126"}],"part":[{"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/pressbooks\/v2\/parts\/76"}],"metadata":[{"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/pressbooks\/v2\/chapters\/325\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/wp\/v2\/media?parent=325"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/pressbooks\/v2\/chapter-type?post=325"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/wp\/v2\/contributor?post=325"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/wp\/v2\/license?post=325"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}