{"id":526,"date":"2021-07-23T09:19:59","date_gmt":"2021-07-23T13:19:59","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/aperrott\/chapter\/multiple-bonds\/"},"modified":"2022-06-23T09:05:17","modified_gmt":"2022-06-23T13:05:17","slug":"multiple-bonds","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/aperrott\/chapter\/multiple-bonds\/","title":{"raw":"8.3 Multiple Bonds","rendered":"8.3 Multiple Bonds"},"content":{"raw":"<div class=\"textbox textbox--learning-objectives\">\r\n<h3><strong>Learning Objectives<\/strong><\/h3>\r\nBy the end of this section, you will be able to:\r\n<ul>\r\n \t<li>Describe multiple covalent bonding in terms of atomic orbital overlap<\/li>\r\n \t<li>Relate the concept of resonance to \u03c0-bonding and electron delocalization<\/li>\r\n<\/ul>\r\n<\/div>\r\n<p id=\"fs-idp109649680\">The hybrid orbital model appears to account well for the geometry of molecules involving single covalent bonds. Is it also capable of describing molecules containing double and triple bonds? We have already discussed that multiple bonds consist of \u03c3 and \u03c0 bonds. Next we can consider how we visualize these components and how they relate to hybrid orbitals. The Lewis structure of ethene, C<sub>2<\/sub>H<sub>4<\/sub>, shows us that each carbon atom is surrounded by one other carbon atom and two hydrogen atoms.<\/p>\r\n<span id=\"fs-idp35800208\" class=\"scaled-down\" data-type=\"media\" data-alt=\"A Lewis structure is shown in which two carbon atoms are bonded together by a double bond. Each carbon atom is bonded to two hydrogen atoms by a single bond.\"><img src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_08_03_C4H4Lewis_img-1.jpg\" alt=\"A Lewis structure is shown in which two carbon atoms are bonded together by a double bond. Each carbon atom is bonded to two hydrogen atoms by a single bond.\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n<p id=\"fs-idp40201472\">The three bonding regions form a trigonal planar electron-pair geometry. Thus we expect the \u03c3 bonds from each carbon atom are formed using a set of <em data-effect=\"italics\">sp<\/em><sup>2<\/sup> hybrid orbitals that result from hybridization of two of the 2<em data-effect=\"italics\">p<\/em> orbitals and the 2<em data-effect=\"italics\">s<\/em> orbital (<a class=\"autogenerated-content\" href=\"#CNX_Chem_08_03_sp3config\">(Figure)<\/a>). These orbitals form the C\u2013H single bonds and the \u03c3 bond in the C=C double bond (<a class=\"autogenerated-content\" href=\"#CNX_Chem_08_03_C2H4orbit\">(Figure)<\/a>)<em data-effect=\"italics\">.<\/em> The \u03c0 bond in the C=C double bond results from the overlap of the third (remaining) 2<em data-effect=\"italics\">p<\/em> orbital on each carbon atom that is not involved in hybridization. This unhybridized <em data-effect=\"italics\">p<\/em> orbital (lobes shown in red and blue in <a class=\"autogenerated-content\" href=\"#CNX_Chem_08_03_C2H4orbit\">(Figure)<\/a>) is perpendicular to the plane of the <em data-effect=\"italics\">sp<\/em><sup>2<\/sup> hybrid orbitals. Thus the unhybridized 2<em data-effect=\"italics\">p<\/em> orbitals overlap in a side-by-side fashion, above and below the internuclear axis (<a class=\"autogenerated-content\" href=\"#CNX_Chem_08_03_C2H4orbit\">(Figure)<\/a>) and form a \u03c0 bond<em data-effect=\"italics\">.<\/em><\/p>\r\n&nbsp;\r\n<div id=\"CNX_Chem_08_03_sp3config\" class=\"scaled-down\">\r\n<div class=\"bc-figcaption figcaption\">In ethene, each carbon atom is <em data-effect=\"italics\">sp<\/em><sup>2<\/sup> hybridized, and the <em data-effect=\"italics\">sp<\/em><sup>2<\/sup> orbitals and the <em data-effect=\"italics\">p<\/em> orbital are singly occupied. The hybrid orbitals overlap to form \u03c3 bonds, while the <em data-effect=\"italics\">p<\/em> orbitals on each carbon atom overlap to form a \u03c0 bond.<\/div>\r\n<span id=\"fs-idp21744512\" data-type=\"media\" data-alt=\"A diagram is shown in two parts, connected by a right facing arrow labeled, \u201cHybridization.\u201d The left diagram shows an up-facing arrow labeled, \u201cE.\u201d To the lower right of the arrow is a short, horizontal line labeled, \u201c2 s,\u201d that has two vertical half-arrows facing up and down on it. To the upper right of the arrow are a series of three short, horizontal lines labeled, \u201c2 p.\u201d Above both sets of lines is the phrase, \u201cOrbitals in an isolated C atom.\u201d Two of the lines have vertical, up-facing arrows drawn on them. The right side of the diagram shows three short, horizontal lines placed halfway up the space and each labeled, \u201cs p superscript 2.\u201d An upward-facing half arrow is drawn vertically on each line. Above these lines is one other short, horizontal line, labeled, \u201cp.\u201d Above both sets of lines is the phrase, \u201cOrbitals in the s p superscript 2 hybridized C atom in C subscript 2 H subscript 4.\u201d\"><img src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_08_03_sp3config-1.jpg\" alt=\"A diagram is shown in two parts, connected by a right facing arrow labeled, \u201cHybridization.\u201d The left diagram shows an up-facing arrow labeled, \u201cE.\u201d To the lower right of the arrow is a short, horizontal line labeled, \u201c2 s,\u201d that has two vertical half-arrows facing up and down on it. To the upper right of the arrow are a series of three short, horizontal lines labeled, \u201c2 p.\u201d Above both sets of lines is the phrase, \u201cOrbitals in an isolated C atom.\u201d Two of the lines have vertical, up-facing arrows drawn on them. The right side of the diagram shows three short, horizontal lines placed halfway up the space and each labeled, \u201cs p superscript 2.\u201d An upward-facing half arrow is drawn vertically on each line. Above these lines is one other short, horizontal line, labeled, \u201cp.\u201d Above both sets of lines is the phrase, \u201cOrbitals in the s p superscript 2 hybridized C atom in C subscript 2 H subscript 4.\u201d\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n\r\n&nbsp;\r\n\r\n<\/div>\r\n<div id=\"CNX_Chem_08_03_C2H4orbit\" class=\"scaled-down\">\r\n<div class=\"bc-figcaption figcaption\">In the ethene molecule, C<sub>2<\/sub>H<sub>4,<\/sub> there are (a) five \u03c3 bonds. One C\u2013C \u03c3 bond results from overlap of <em data-effect=\"italics\">sp<\/em><sup>2<\/sup> hybrid orbitals on the carbon atom with one <em data-effect=\"italics\">sp<\/em><sup>2<\/sup> hybrid orbital on the other carbon atom. Four C\u2013H bonds result from the overlap between the C atoms' <em data-effect=\"italics\">sp<\/em><sup>2<\/sup> orbitals with <em data-effect=\"italics\">s<\/em> orbitals on the hydrogen atoms. (b) The \u03c0 bond is formed by the side-by-side overlap of the two unhybridized <em data-effect=\"italics\">p<\/em> orbitals in the two carbon atoms. The two lobes of the \u03c0 bond are above and below the plane of the \u03c3 system.<\/div>\r\n<span id=\"fs-idp201403520\" data-type=\"media\" data-alt=\"Two diagrams are shown labeled, \u201ca\u201d and \u201cb.\u201d Diagram a shows two carbon atoms with three purple balloon-like orbitals arranged in a plane around them and two red balloon-like orbitals arranged vertically and perpendicularly to the plane. There is an overlap of two of the purple orbitals in between the two carbon atoms, and the other four purple orbitals that face the outside of the molecule are shown interacting with spherical blue orbitals from four hydrogen atoms. Diagram b depicts a similar image to diagram a, but the red, vertical orbitals are interacting above and below the plane of the molecule to form two areas labeled, \u201cOne pi bond.\u201d\"><img src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_08_03_C2H4orbit-1.jpg\" alt=\"Two diagrams are shown labeled, \u201ca\u201d and \u201cb.\u201d Diagram a shows two carbon atoms with three purple balloon-like orbitals arranged in a plane around them and two red balloon-like orbitals arranged vertically and perpendicularly to the plane. There is an overlap of two of the purple orbitals in between the two carbon atoms, and the other four purple orbitals that face the outside of the molecule are shown interacting with spherical blue orbitals from four hydrogen atoms. Diagram b depicts a similar image to diagram a, but the red, vertical orbitals are interacting above and below the plane of the molecule to form two areas labeled, \u201cOne pi bond.\u201d\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n\r\n<\/div>\r\n<p id=\"fs-idp52367024\">In an ethene molecule, the four hydrogen atoms and the two carbon atoms are all in the same plane. If the two planes of <em data-effect=\"italics\">sp<\/em><sup>2<\/sup> hybrid orbitals tilted relative to each other, the <em data-effect=\"italics\">p<\/em> orbitals would not be oriented to overlap efficiently to create the \u03c0 bond. The planar configuration for the ethene molecule occurs because it is the most stable bonding arrangement. This is a significant difference between \u03c3 and \u03c0 bonds; rotation around single (\u03c3) bonds occurs easily because the end-to-end orbital overlap does not depend on the relative orientation of the orbitals on each atom in the bond. In other words, rotation around the internuclear axis does not change the extent to which the \u03c3 bonding orbitals overlap because the bonding electron density is symmetric about the axis. Rotation about the internuclear axis is much more difficult for multiple bonds; however, this would drastically alter the off-axis overlap of the \u03c0 bonding orbitals, essentially breaking the \u03c0 bond.<\/p>\r\n<p id=\"fs-idp40636368\">In molecules with <em data-effect=\"italics\">sp<\/em> hybrid orbitals, two unhybridized <em data-effect=\"italics\">p<\/em> orbitals remain on the atom (<a class=\"autogenerated-content\" href=\"#CNX_Chem_08_03_spC\">(Figure)<\/a>). We find this situation in acetylene, <img class=\"alignnone wp-image-1528\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/8.3a.png\" alt=\"\" width=\"85\" height=\"15\" \/>, which is a linear molecule. The <em data-effect=\"italics\">sp<\/em> hybrid orbitals of the two carbon atoms overlap end to end to form a \u03c3 bond between the carbon atoms (<a class=\"autogenerated-content\" href=\"#CNX_Chem_08_03_C2H2\">(Figure)<\/a>). The remaining <em data-effect=\"italics\">sp<\/em> orbitals form \u03c3 bonds with hydrogen atoms. The two unhybridized <em data-effect=\"italics\">p<\/em> orbitals per carbon are positioned such that they overlap side by side and, hence, form two \u03c0 bonds. The two carbon atoms of acetylene are thus bound together by one \u03c3 bond and two \u03c0 bonds, giving a triple bond.<\/p>\r\n&nbsp;\r\n<div id=\"CNX_Chem_08_03_spC\" class=\"scaled-down\">\r\n<div class=\"bc-figcaption figcaption\">Diagram of the two linear <em data-effect=\"italics\">sp<\/em> hybrid orbitals of a carbon atom, which lie in a straight line, and the two unhybridized <em data-effect=\"italics\">p<\/em> orbitals at perpendicular angles.<\/div>\r\n<span id=\"fs-idp46978352\" data-type=\"media\" data-alt=\"A diagram of a carbon atom with two balloon-like purple orbitals labeled, \u201csp\u201d arranged in a linear fashion around it is shown. Four red balloon-like orbitals are aligned in pairs in the y and z axes around the carbon and are labeled, \u201cunhybridized p orbital,\u201d and, \u201cSecond unhybridized p orbital.\u201d\"><img src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_08_03_spC-1.jpg\" alt=\"A diagram of a carbon atom with two balloon-like purple orbitals labeled, \u201csp\u201d arranged in a linear fashion around it is shown. Four red balloon-like orbitals are aligned in pairs in the y and z axes around the carbon and are labeled, \u201cunhybridized p orbital,\u201d and, \u201cSecond unhybridized p orbital.\u201d\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n\r\n&nbsp;\r\n\r\n<\/div>\r\n<div id=\"CNX_Chem_08_03_C2H2\" class=\"scaled-down\">\r\n<div class=\"bc-figcaption figcaption\">(a) In the acetylene molecule, C<sub>2<\/sub>H<sub>2,<\/sub> there are two C\u2013H \u03c3 bonds and a <img class=\"alignnone wp-image-1495\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/7.5b.png\" alt=\"\" width=\"42\" height=\"18\" \/> triple bond involving one C\u2013C \u03c3 bond and two C\u2013C \u03c0 bonds. The dashed lines, each connecting two lobes, indicate the side-by-side overlap of the four unhybridized <em data-effect=\"italics\">p<\/em> orbitals. (b) This shows the overall outline of the bonds in C<sub>2<\/sub>H<sub>2<\/sub>. The two lobes of each of the \u03c0 bonds are positioned across from each other around the line of the C\u2013C \u03c3 bond.<\/div>\r\n<span id=\"fs-idp112665792\" data-type=\"media\" data-alt=\"Two diagrams are shown and labeled, \u201ca\u201d and \u201cb.\u201d Diagram a shows two carbon atoms with two purple balloon-like orbitals arranged in a plane around each of them, and four red balloon-like orbitals arranged along the y and z axes perpendicular to the plane of the molecule. There is an overlap of two of the purple orbitals in between the two carbon atoms. The other two purple orbitals that face the outside of the molecule are shown interacting with spherical blue orbitals from two hydrogen atoms. Diagram b depicts a similar image to diagram a, but the red, vertical orbitals are interacting above and below and to the front and back of the plane of the molecule to form two areas labeled, \u201cOne pi bond,\u201d and, \u201cSecond pi bond,\u201d each respectively.\"><img src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_08_03_C2H2-1.jpg\" alt=\"Two diagrams are shown and labeled, \u201ca\u201d and \u201cb.\u201d Diagram a shows two carbon atoms with two purple balloon-like orbitals arranged in a plane around each of them, and four red balloon-like orbitals arranged along the y and z axes perpendicular to the plane of the molecule. There is an overlap of two of the purple orbitals in between the two carbon atoms. The other two purple orbitals that face the outside of the molecule are shown interacting with spherical blue orbitals from two hydrogen atoms. Diagram b depicts a similar image to diagram a, but the red, vertical orbitals are interacting above and below and to the front and back of the plane of the molecule to form two areas labeled, \u201cOne pi bond,\u201d and, \u201cSecond pi bond,\u201d each respectively.\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n\r\n<\/div>\r\n<p id=\"fs-idp135325968\">Hybridization involves only \u03c3 bonds and lone pairs of electrons. Structures that account for these features describe the correct hybridization of the atoms. However, many structures also include resonance forms. Remember that resonance forms occur when various arrangements of \u03c0 bonds are possible. Since the arrangement of \u03c0 bonds involves only the unhybridized orbitals, resonance does not influence the assignment of hybridization.<\/p>\r\n<p id=\"fs-idp155207440\">For example, molecule benzene has two resonance forms (<a class=\"autogenerated-content\" href=\"#CNX_Chem_08_03_C6H6\">(Figure)<\/a>). We can use either of these forms to determine that each of the carbon atoms is bonded to three other atoms with no lone pairs, so the correct hybridization is <em data-effect=\"italics\">sp<\/em><sup>2<\/sup>. The electrons in the unhybridized <em data-effect=\"italics\">p<\/em> orbitals form \u03c0 bonds. Neither resonance structure completely describes the electrons in the \u03c0 bonds. They are not located in one position or the other, but in reality are delocalized throughout the ring. Valence bond theory does not easily address delocalization. Bonding in molecules with resonance forms is better described by molecular orbital theory. (See the next module.)<\/p>\r\n&nbsp;\r\n<div id=\"CNX_Chem_08_03_C6H6\" class=\"scaled-down\">\r\n<div class=\"bc-figcaption figcaption\">Each carbon atom in benzene, C<sub>6<\/sub>H<sub>6<\/sub>, is <em data-effect=\"italics\">sp<\/em><sup>2<\/sup> hybridized, independently of which resonance form is considered. The electrons in the \u03c0 bonds are not located in one set of <em data-effect=\"italics\">p<\/em> orbitals or the other, but rather delocalized throughout the molecule.<\/div>\r\n<span id=\"fs-idp4433648\" data-type=\"media\" data-alt=\"A diagram is shown that is made up of two Lewis structures connected by a double ended arrow. The left image shows six carbon atoms bonded together with alternating double and single bonds to form a six-sided ring. Each carbon is also bonded to a hydrogen atom by a single bond. The right image shows the same structure, but the double and single bonds in between the carbon atoms have changed positions.\"><img src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_08_03_C6H6-1.jpg\" alt=\"A diagram is shown that is made up of two Lewis structures connected by a double ended arrow. The left image shows six carbon atoms bonded together with alternating double and single bonds to form a six-sided ring. Each carbon is also bonded to a hydrogen atom by a single bond. The right image shows the same structure, but the double and single bonds in between the carbon atoms have changed positions.\" data-media-type=\"image\/jpeg\" \/><\/span>\r\n\r\n<\/div>\r\n<div id=\"fs-idp38327968\" class=\"summary\" data-depth=\"1\">\r\n<h3 data-type=\"title\"><strong>Key Concepts and Summary<\/strong><\/h3>\r\n<p id=\"fs-idp78398192\">Multiple bonds consist of a \u03c3 bond located along the axis between two atoms and one or two \u03c0 bonds. The \u03c3 bonds are usually formed by the overlap of hybridized atomic orbitals, while the \u03c0 bonds are formed by the side-by-side overlap of unhybridized orbitals. Resonance occurs when there are multiple unhybridized orbitals with the appropriate alignment to overlap, so the placement of \u03c0 bonds can vary.<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-idp19779216\" class=\"exercises\" data-depth=\"1\">\r\n<div id=\"fs-idp47770992\" data-type=\"exercise\">\r\n<div id=\"fs-idp197400320\" data-type=\"solution\">\r\n<p id=\"fs-idp72644016\"><\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>","rendered":"<div class=\"textbox textbox--learning-objectives\">\n<h3><strong>Learning Objectives<\/strong><\/h3>\n<p>By the end of this section, you will be able to:<\/p>\n<ul>\n<li>Describe multiple covalent bonding in terms of atomic orbital overlap<\/li>\n<li>Relate the concept of resonance to \u03c0-bonding and electron delocalization<\/li>\n<\/ul>\n<\/div>\n<p id=\"fs-idp109649680\">The hybrid orbital model appears to account well for the geometry of molecules involving single covalent bonds. Is it also capable of describing molecules containing double and triple bonds? We have already discussed that multiple bonds consist of \u03c3 and \u03c0 bonds. Next we can consider how we visualize these components and how they relate to hybrid orbitals. The Lewis structure of ethene, C<sub>2<\/sub>H<sub>4<\/sub>, shows us that each carbon atom is surrounded by one other carbon atom and two hydrogen atoms.<\/p>\n<p><span id=\"fs-idp35800208\" class=\"scaled-down\" data-type=\"media\" data-alt=\"A Lewis structure is shown in which two carbon atoms are bonded together by a double bond. Each carbon atom is bonded to two hydrogen atoms by a single bond.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_08_03_C4H4Lewis_img-1.jpg\" alt=\"A Lewis structure is shown in which two carbon atoms are bonded together by a double bond. Each carbon atom is bonded to two hydrogen atoms by a single bond.\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<p id=\"fs-idp40201472\">The three bonding regions form a trigonal planar electron-pair geometry. Thus we expect the \u03c3 bonds from each carbon atom are formed using a set of <em data-effect=\"italics\">sp<\/em><sup>2<\/sup> hybrid orbitals that result from hybridization of two of the 2<em data-effect=\"italics\">p<\/em> orbitals and the 2<em data-effect=\"italics\">s<\/em> orbital (<a class=\"autogenerated-content\" href=\"#CNX_Chem_08_03_sp3config\">(Figure)<\/a>). These orbitals form the C\u2013H single bonds and the \u03c3 bond in the C=C double bond (<a class=\"autogenerated-content\" href=\"#CNX_Chem_08_03_C2H4orbit\">(Figure)<\/a>)<em data-effect=\"italics\">.<\/em> The \u03c0 bond in the C=C double bond results from the overlap of the third (remaining) 2<em data-effect=\"italics\">p<\/em> orbital on each carbon atom that is not involved in hybridization. This unhybridized <em data-effect=\"italics\">p<\/em> orbital (lobes shown in red and blue in <a class=\"autogenerated-content\" href=\"#CNX_Chem_08_03_C2H4orbit\">(Figure)<\/a>) is perpendicular to the plane of the <em data-effect=\"italics\">sp<\/em><sup>2<\/sup> hybrid orbitals. Thus the unhybridized 2<em data-effect=\"italics\">p<\/em> orbitals overlap in a side-by-side fashion, above and below the internuclear axis (<a class=\"autogenerated-content\" href=\"#CNX_Chem_08_03_C2H4orbit\">(Figure)<\/a>) and form a \u03c0 bond<em data-effect=\"italics\">.<\/em><\/p>\n<p>&nbsp;<\/p>\n<div id=\"CNX_Chem_08_03_sp3config\" class=\"scaled-down\">\n<div class=\"bc-figcaption figcaption\">In ethene, each carbon atom is <em data-effect=\"italics\">sp<\/em><sup>2<\/sup> hybridized, and the <em data-effect=\"italics\">sp<\/em><sup>2<\/sup> orbitals and the <em data-effect=\"italics\">p<\/em> orbital are singly occupied. The hybrid orbitals overlap to form \u03c3 bonds, while the <em data-effect=\"italics\">p<\/em> orbitals on each carbon atom overlap to form a \u03c0 bond.<\/div>\n<p><span id=\"fs-idp21744512\" data-type=\"media\" data-alt=\"A diagram is shown in two parts, connected by a right facing arrow labeled, \u201cHybridization.\u201d The left diagram shows an up-facing arrow labeled, \u201cE.\u201d To the lower right of the arrow is a short, horizontal line labeled, \u201c2 s,\u201d that has two vertical half-arrows facing up and down on it. To the upper right of the arrow are a series of three short, horizontal lines labeled, \u201c2 p.\u201d Above both sets of lines is the phrase, \u201cOrbitals in an isolated C atom.\u201d Two of the lines have vertical, up-facing arrows drawn on them. The right side of the diagram shows three short, horizontal lines placed halfway up the space and each labeled, \u201cs p superscript 2.\u201d An upward-facing half arrow is drawn vertically on each line. Above these lines is one other short, horizontal line, labeled, \u201cp.\u201d Above both sets of lines is the phrase, \u201cOrbitals in the s p superscript 2 hybridized C atom in C subscript 2 H subscript 4.\u201d\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_08_03_sp3config-1.jpg\" alt=\"A diagram is shown in two parts, connected by a right facing arrow labeled, \u201cHybridization.\u201d The left diagram shows an up-facing arrow labeled, \u201cE.\u201d To the lower right of the arrow is a short, horizontal line labeled, \u201c2 s,\u201d that has two vertical half-arrows facing up and down on it. To the upper right of the arrow are a series of three short, horizontal lines labeled, \u201c2 p.\u201d Above both sets of lines is the phrase, \u201cOrbitals in an isolated C atom.\u201d Two of the lines have vertical, up-facing arrows drawn on them. The right side of the diagram shows three short, horizontal lines placed halfway up the space and each labeled, \u201cs p superscript 2.\u201d An upward-facing half arrow is drawn vertically on each line. Above these lines is one other short, horizontal line, labeled, \u201cp.\u201d Above both sets of lines is the phrase, \u201cOrbitals in the s p superscript 2 hybridized C atom in C subscript 2 H subscript 4.\u201d\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<p>&nbsp;<\/p>\n<\/div>\n<div id=\"CNX_Chem_08_03_C2H4orbit\" class=\"scaled-down\">\n<div class=\"bc-figcaption figcaption\">In the ethene molecule, C<sub>2<\/sub>H<sub>4,<\/sub> there are (a) five \u03c3 bonds. One C\u2013C \u03c3 bond results from overlap of <em data-effect=\"italics\">sp<\/em><sup>2<\/sup> hybrid orbitals on the carbon atom with one <em data-effect=\"italics\">sp<\/em><sup>2<\/sup> hybrid orbital on the other carbon atom. Four C\u2013H bonds result from the overlap between the C atoms&#8217; <em data-effect=\"italics\">sp<\/em><sup>2<\/sup> orbitals with <em data-effect=\"italics\">s<\/em> orbitals on the hydrogen atoms. (b) The \u03c0 bond is formed by the side-by-side overlap of the two unhybridized <em data-effect=\"italics\">p<\/em> orbitals in the two carbon atoms. The two lobes of the \u03c0 bond are above and below the plane of the \u03c3 system.<\/div>\n<p><span id=\"fs-idp201403520\" data-type=\"media\" data-alt=\"Two diagrams are shown labeled, \u201ca\u201d and \u201cb.\u201d Diagram a shows two carbon atoms with three purple balloon-like orbitals arranged in a plane around them and two red balloon-like orbitals arranged vertically and perpendicularly to the plane. There is an overlap of two of the purple orbitals in between the two carbon atoms, and the other four purple orbitals that face the outside of the molecule are shown interacting with spherical blue orbitals from four hydrogen atoms. Diagram b depicts a similar image to diagram a, but the red, vertical orbitals are interacting above and below the plane of the molecule to form two areas labeled, \u201cOne pi bond.\u201d\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_08_03_C2H4orbit-1.jpg\" alt=\"Two diagrams are shown labeled, \u201ca\u201d and \u201cb.\u201d Diagram a shows two carbon atoms with three purple balloon-like orbitals arranged in a plane around them and two red balloon-like orbitals arranged vertically and perpendicularly to the plane. There is an overlap of two of the purple orbitals in between the two carbon atoms, and the other four purple orbitals that face the outside of the molecule are shown interacting with spherical blue orbitals from four hydrogen atoms. Diagram b depicts a similar image to diagram a, but the red, vertical orbitals are interacting above and below the plane of the molecule to form two areas labeled, \u201cOne pi bond.\u201d\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<\/div>\n<p id=\"fs-idp52367024\">In an ethene molecule, the four hydrogen atoms and the two carbon atoms are all in the same plane. If the two planes of <em data-effect=\"italics\">sp<\/em><sup>2<\/sup> hybrid orbitals tilted relative to each other, the <em data-effect=\"italics\">p<\/em> orbitals would not be oriented to overlap efficiently to create the \u03c0 bond. The planar configuration for the ethene molecule occurs because it is the most stable bonding arrangement. This is a significant difference between \u03c3 and \u03c0 bonds; rotation around single (\u03c3) bonds occurs easily because the end-to-end orbital overlap does not depend on the relative orientation of the orbitals on each atom in the bond. In other words, rotation around the internuclear axis does not change the extent to which the \u03c3 bonding orbitals overlap because the bonding electron density is symmetric about the axis. Rotation about the internuclear axis is much more difficult for multiple bonds; however, this would drastically alter the off-axis overlap of the \u03c0 bonding orbitals, essentially breaking the \u03c0 bond.<\/p>\n<p id=\"fs-idp40636368\">In molecules with <em data-effect=\"italics\">sp<\/em> hybrid orbitals, two unhybridized <em data-effect=\"italics\">p<\/em> orbitals remain on the atom (<a class=\"autogenerated-content\" href=\"#CNX_Chem_08_03_spC\">(Figure)<\/a>). We find this situation in acetylene, <img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-1528\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/8.3a.png\" alt=\"\" width=\"85\" height=\"15\" srcset=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/8.3a.png 267w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/8.3a-65x11.png 65w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/8.3a-225x40.png 225w\" sizes=\"auto, (max-width: 85px) 100vw, 85px\" \/>, which is a linear molecule. The <em data-effect=\"italics\">sp<\/em> hybrid orbitals of the two carbon atoms overlap end to end to form a \u03c3 bond between the carbon atoms (<a class=\"autogenerated-content\" href=\"#CNX_Chem_08_03_C2H2\">(Figure)<\/a>). The remaining <em data-effect=\"italics\">sp<\/em> orbitals form \u03c3 bonds with hydrogen atoms. The two unhybridized <em data-effect=\"italics\">p<\/em> orbitals per carbon are positioned such that they overlap side by side and, hence, form two \u03c0 bonds. The two carbon atoms of acetylene are thus bound together by one \u03c3 bond and two \u03c0 bonds, giving a triple bond.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"CNX_Chem_08_03_spC\" class=\"scaled-down\">\n<div class=\"bc-figcaption figcaption\">Diagram of the two linear <em data-effect=\"italics\">sp<\/em> hybrid orbitals of a carbon atom, which lie in a straight line, and the two unhybridized <em data-effect=\"italics\">p<\/em> orbitals at perpendicular angles.<\/div>\n<p><span id=\"fs-idp46978352\" data-type=\"media\" data-alt=\"A diagram of a carbon atom with two balloon-like purple orbitals labeled, \u201csp\u201d arranged in a linear fashion around it is shown. Four red balloon-like orbitals are aligned in pairs in the y and z axes around the carbon and are labeled, \u201cunhybridized p orbital,\u201d and, \u201cSecond unhybridized p orbital.\u201d\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_08_03_spC-1.jpg\" alt=\"A diagram of a carbon atom with two balloon-like purple orbitals labeled, \u201csp\u201d arranged in a linear fashion around it is shown. Four red balloon-like orbitals are aligned in pairs in the y and z axes around the carbon and are labeled, \u201cunhybridized p orbital,\u201d and, \u201cSecond unhybridized p orbital.\u201d\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<p>&nbsp;<\/p>\n<\/div>\n<div id=\"CNX_Chem_08_03_C2H2\" class=\"scaled-down\">\n<div class=\"bc-figcaption figcaption\">(a) In the acetylene molecule, C<sub>2<\/sub>H<sub>2,<\/sub> there are two C\u2013H \u03c3 bonds and a <img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-1495\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/7.5b.png\" alt=\"\" width=\"42\" height=\"18\" srcset=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/7.5b.png 102w, https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/7.5b-65x27.png 65w\" sizes=\"auto, (max-width: 42px) 100vw, 42px\" \/> triple bond involving one C\u2013C \u03c3 bond and two C\u2013C \u03c0 bonds. The dashed lines, each connecting two lobes, indicate the side-by-side overlap of the four unhybridized <em data-effect=\"italics\">p<\/em> orbitals. (b) This shows the overall outline of the bonds in C<sub>2<\/sub>H<sub>2<\/sub>. The two lobes of each of the \u03c0 bonds are positioned across from each other around the line of the C\u2013C \u03c3 bond.<\/div>\n<p><span id=\"fs-idp112665792\" data-type=\"media\" data-alt=\"Two diagrams are shown and labeled, \u201ca\u201d and \u201cb.\u201d Diagram a shows two carbon atoms with two purple balloon-like orbitals arranged in a plane around each of them, and four red balloon-like orbitals arranged along the y and z axes perpendicular to the plane of the molecule. There is an overlap of two of the purple orbitals in between the two carbon atoms. The other two purple orbitals that face the outside of the molecule are shown interacting with spherical blue orbitals from two hydrogen atoms. Diagram b depicts a similar image to diagram a, but the red, vertical orbitals are interacting above and below and to the front and back of the plane of the molecule to form two areas labeled, \u201cOne pi bond,\u201d and, \u201cSecond pi bond,\u201d each respectively.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_08_03_C2H2-1.jpg\" alt=\"Two diagrams are shown and labeled, \u201ca\u201d and \u201cb.\u201d Diagram a shows two carbon atoms with two purple balloon-like orbitals arranged in a plane around each of them, and four red balloon-like orbitals arranged along the y and z axes perpendicular to the plane of the molecule. There is an overlap of two of the purple orbitals in between the two carbon atoms. The other two purple orbitals that face the outside of the molecule are shown interacting with spherical blue orbitals from two hydrogen atoms. Diagram b depicts a similar image to diagram a, but the red, vertical orbitals are interacting above and below and to the front and back of the plane of the molecule to form two areas labeled, \u201cOne pi bond,\u201d and, \u201cSecond pi bond,\u201d each respectively.\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<\/div>\n<p id=\"fs-idp135325968\">Hybridization involves only \u03c3 bonds and lone pairs of electrons. Structures that account for these features describe the correct hybridization of the atoms. However, many structures also include resonance forms. Remember that resonance forms occur when various arrangements of \u03c0 bonds are possible. Since the arrangement of \u03c0 bonds involves only the unhybridized orbitals, resonance does not influence the assignment of hybridization.<\/p>\n<p id=\"fs-idp155207440\">For example, molecule benzene has two resonance forms (<a class=\"autogenerated-content\" href=\"#CNX_Chem_08_03_C6H6\">(Figure)<\/a>). We can use either of these forms to determine that each of the carbon atoms is bonded to three other atoms with no lone pairs, so the correct hybridization is <em data-effect=\"italics\">sp<\/em><sup>2<\/sup>. The electrons in the unhybridized <em data-effect=\"italics\">p<\/em> orbitals form \u03c0 bonds. Neither resonance structure completely describes the electrons in the \u03c0 bonds. They are not located in one position or the other, but in reality are delocalized throughout the ring. Valence bond theory does not easily address delocalization. Bonding in molecules with resonance forms is better described by molecular orbital theory. (See the next module.)<\/p>\n<p>&nbsp;<\/p>\n<div id=\"CNX_Chem_08_03_C6H6\" class=\"scaled-down\">\n<div class=\"bc-figcaption figcaption\">Each carbon atom in benzene, C<sub>6<\/sub>H<sub>6<\/sub>, is <em data-effect=\"italics\">sp<\/em><sup>2<\/sup> hybridized, independently of which resonance form is considered. The electrons in the \u03c0 bonds are not located in one set of <em data-effect=\"italics\">p<\/em> orbitals or the other, but rather delocalized throughout the molecule.<\/div>\n<p><span id=\"fs-idp4433648\" data-type=\"media\" data-alt=\"A diagram is shown that is made up of two Lewis structures connected by a double ended arrow. The left image shows six carbon atoms bonded together with alternating double and single bonds to form a six-sided ring. Each carbon is also bonded to a hydrogen atom by a single bond. The right image shows the same structure, but the double and single bonds in between the carbon atoms have changed positions.\"><img decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-content\/uploads\/sites\/1463\/2021\/07\/CNX_Chem_08_03_C6H6-1.jpg\" alt=\"A diagram is shown that is made up of two Lewis structures connected by a double ended arrow. The left image shows six carbon atoms bonded together with alternating double and single bonds to form a six-sided ring. Each carbon is also bonded to a hydrogen atom by a single bond. The right image shows the same structure, but the double and single bonds in between the carbon atoms have changed positions.\" data-media-type=\"image\/jpeg\" \/><\/span><\/p>\n<\/div>\n<div id=\"fs-idp38327968\" class=\"summary\" data-depth=\"1\">\n<h3 data-type=\"title\"><strong>Key Concepts and Summary<\/strong><\/h3>\n<p id=\"fs-idp78398192\">Multiple bonds consist of a \u03c3 bond located along the axis between two atoms and one or two \u03c0 bonds. The \u03c3 bonds are usually formed by the overlap of hybridized atomic orbitals, while the \u03c0 bonds are formed by the side-by-side overlap of unhybridized orbitals. Resonance occurs when there are multiple unhybridized orbitals with the appropriate alignment to overlap, so the placement of \u03c0 bonds can vary.<\/p>\n<\/div>\n<div id=\"fs-idp19779216\" class=\"exercises\" data-depth=\"1\">\n<div id=\"fs-idp47770992\" data-type=\"exercise\">\n<div id=\"fs-idp197400320\" data-type=\"solution\">\n<p id=\"fs-idp72644016\">\n<\/div>\n<\/div>\n<\/div>\n","protected":false},"author":1392,"menu_order":4,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[48],"contributor":[],"license":[],"class_list":["post-526","chapter","type-chapter","status-publish","hentry","chapter-type-numberless"],"part":468,"_links":{"self":[{"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/pressbooks\/v2\/chapters\/526","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/wp\/v2\/users\/1392"}],"version-history":[{"count":4,"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/pressbooks\/v2\/chapters\/526\/revisions"}],"predecessor-version":[{"id":2139,"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/pressbooks\/v2\/chapters\/526\/revisions\/2139"}],"part":[{"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/pressbooks\/v2\/parts\/468"}],"metadata":[{"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/pressbooks\/v2\/chapters\/526\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/wp\/v2\/media?parent=526"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/pressbooks\/v2\/chapter-type?post=526"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/wp\/v2\/contributor?post=526"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/aperrott\/wp-json\/wp\/v2\/license?post=526"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}