Notes Unsaturated Hydrocarbons

Notes Unsaturated Hydrocarbons - Notes Unsaturated...

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Notes Unsaturated Hydrocarbons: Alkenes, Alkynes and Aromatics Saturated and Unsaturated Hydrocarbons: You may have read the above title and asked yourself, “unsaturated hydrocarbon, well what is a saturated hydrocarbon?” Saturated refers to the number of atoms a the carbons are bonded to. If an organic compound is composed only of single bonds it is saturated. Meaning there is no where for another atom to bond to the carbons; this type of hydrocarbon is referred to as an alkane. An unsaturated hydrocarbon will have double or triple bonds, these types of hydrocarbons are referred to as alkenes, for double bonds, or alkynes, for triple bonds. This means you could bond more atoms to these carbons, if the double or triple bonds were broken. If you have a 2-carbon compound the most hydrogen atoms this compound could hold would be 6. If there is a double bond the compound will have 4 hydrogens and if there is a triple bond, the compound will have 2 hydrogen atoms. See the below chemical and structural formulas. alkane alkene alkyne ethane ethene ethyne C 2 H 6 C 2 H 4 C 2 H 2 C C H H H H H H C C H H H H C C H H C-C Bond length 154pm C-C Bond length 134pm C-C Bond length 120pm carbons have bonds to 4 different atoms carbons have bonds to 3 different atoms carbons have bonds to 2 different atoms geometric shape around carbons tetrahedral geometric shape around carbons trigonal planar geometric shape around carbons linear Carbon Hybridization sp 3 Carbon Hybridization sp 2 Carbon Hybridization sp suffix -ane suffix -ene suffix -yne
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Why the different shapes around the carbon atoms? Hybridization. Linus Pauling won a Noble prize for the development of a theory to describe why carbon atoms were able to form 4 bonds. Depending upon the number and types of bonds will dictate the hybridization of a carbon atom. A carbon atom with four single bonds is designated as sp 3 , with two single bonds and one double bond sp 2 and with one single and one triple or with two double bonds is designated as sp . When carbon atoms are bonded using all single bonds, sp 3 , a molecular shape is formed. In this instance the carbon atom forms bonds with 4 different objects, resulting in a tetrahedral shape, the blue sections of the below picture. This shape is formed by the repulsion of the electrons which surround all atoms. So, if four objects are connected to a central object the farthest these objects can be from each other forms a tetrahedral shape. The angle between these bonds is 109.5 ° . This shape is the result of the addition of one s orbital and three p orbitals, hence the name sp 3 . When carbon atoms are bonded using one double bond and two single bonds, sp 2 , a molecular shape is formed. In this instance the carbon atom forms bonds with 3 objects, resulting in a triangular shape (the blue sections of the below picture). This shape is formed by the repulsion of the electrons which surround all atoms. So, if three objects are connected to a central object the farthest these objects can be from each other forms a triangular shape. The angles
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This note was uploaded on 04/19/2010 for the course CHEMSITRY CH 106 taught by Professor Kovacich during the Spring '10 term at Portland CC.

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Notes Unsaturated Hydrocarbons - Notes Unsaturated...

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