Alkenes structure and bonding

The n/b ratios are also affected by the alkene structure and are sensitive to steric hindrance. For example, dicobaltoctacarbonyl hydroformylates longer chain 1-alkenes more slowly than the shorter alkenes. Methyl substitution on the alkene chain not only slows the reaction as the methyl group is moved closer to the double bond, but the n/b ratio increases (Table 1). A quaternary carbon does not undergo CO insertion and, as a result, the aldehyde is almost never attached at a fully substituted sp1 carbon of an alkene. 

To name alkenes, we follow the basic IUPAC rules, but add the suffix -ene to indicate the main functional group is an alkene. The location of the double bond is given by a locant number, which identifies the first carbon in the double bond. The main functional group always gets the lowest number. Figure 11.9 illustrates some example alkene structures and names. 

The structures and bonding in substituted alkenes and alkynes can be described through the combined molecular orbital (MO) and VB picture presented in Section 6.5, which uses localized VB bonds to describe the molecular framework and delocalized MOs to describe the tt electrons. Let s apply this method to 2-butene (CH3CHCHCH3) and gain deeper understanding of the isomers discussed earlier. The Lewis diagram for 2-butene is... 

The structures and bonding in substituted alkenes and alkynes can be described by the combined MO-VB picture presented in Section 6.5, in which localized VB bonds describe the molecular framework and delocalized MOs describe the 77 electrons. 

New Applications of TCNE in Organometallic Chemistry, A. J. Fatiadi (1987). Selected reactions used in organometallic synthesis are reviewed. 311 references are given. Structure and bonding of metal-TCNE complexes as well as reactions of TCNE with main-group organometallics, with transition-metal complexes, with metal-coordinated alkenes and alkynes, and reactions of platinum-family complexes are discussed. 

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