1057_RG_4_08

1057_RG_4_08 - Chem 1057 J Walcott LEARNING STRATEGIES C EN...

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Chem 1057 J. Walcott LEARNING STRATEGIES CENTER Fall 2008 Review Guide #4 Lectures: 9/15/08 – 9/19/08 and Chapters 3 and 5 I. Alkenes Any molecule with a carbon - carbon double bond is an alkene. The carbons are sp 2 hybridized with bond angles of 120 ° . Six atoms are in a plane with the π electrons above and below the plane. Because of the location of the π electrons, alkenes can form new bonds in addition reactions. The shape of an alkene and bond polarity, which determine the dipole moment of the molecule, are important and relate to its reactivity. Alkene Nomenclature and Stereoisomers A. You should understand the nomenclature rules discussed in Chem 3570 on 9/15. B. Stereoisomers are compounds that have the same bonding connectivity, but differ in the arrangement of groups in 3 dimensional space. 1. Alkenes can have stereoisomers since internal rotation about a C=C double bond is restricted. In order to have a stereoisomer, both double bond C atoms must be bonded to 2 different groups. 2. If both double bond C atoms are bonded to one H atom and one substituent, the alkene can be designated as cis or trans . = same side of double bond; = opposite sides of double bond. 3. More generally, an alkene can be designated as (E) or (Z). (E) = high priority groups on opposite sides of double bond; (Z) = high priority groups on same side of double bond. You should understand the Cahn-Ingold-Prelog system for assigning priorities ie. the relative priorities depend on the atomic numbers of the atoms bonded to the sp 2 carbon.
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This note was uploaded on 12/17/2008 for the course CHEM 3570 taught by Professor Ganem, b during the Fall '06 term at Cornell.

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1057_RG_4_08 - Chem 1057 J Walcott LEARNING STRATEGIES C EN...

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