Orbital hybridization ethylene

Parallel p orbitals in ethylene. The pi bond in ethylene is formed by overlap of the unhybridized p orbitals on the sp2 hybrid carbon atoms. This overlap requires the two ends of the molecule to be coplanar. 

The pi molecular orbitals of ethylene. The pi bonding orbital of ethylene is formed by constructive overlap of unhybridized p orbitals on the xp"-hybrid carbon atoms. Destructive overlap of these two orbitals forms the antibonding pi orbital Combination of twop orbitals must give exaaly two molecular orbitals. 

This represents rotational stability about the ethylenic bond produced by s/ 2-orbital-hybridized carbon atoms. Since free rotation about the carbon-to-carbon axis is not possible, two stable forms of the molecule can now exist. The six components of both forms are in the same plane. The orientations of substituents X and Y relative to each other, however, 

The structure of ethylene and the orbital hybridization model for its double bond were presented m Section 2 20 and are briefly reviewed m Figure 5 1 Ethylene is planar each carbon is sp hybridized and the double bond is considered to have a a component and a TT component The ct component arises from overlap of sp hybrid orbitals along a line connecting the two carbons the tt component via a side by side overlap of two p orbitals Regions of high electron density attributed to the tt electrons appear above and below the plane of the molecule and are clearly evident m the electrostatic potential map Most of the reactions of ethylene and other alkenes involve these electrons 

The structure of ethylene and the orbital hybridization model for the double bond were presented in Section 1.17. To review. Figure 5.1 depicts the planar structure of ethylene, its bond distances, and its bond angles. Each of the carbon atoms is xp -hybridized, and the double bond possesses a o component and a tt component. The o component results when an sp orbital of one carbon, oriented so that its axis lies along the intemuclear axis, overlaps with a similarly disposed sp orbital of the other carbon. Each sp orbital contains one electron, and the resulting a bond contains two of the four electrons of the double bond. The tt bond contributes the other two electrons and is formed by a side-by-side overlap of singly occupied p orbitals of the two carbons. 

Problem 12.17 The overlap integrals for Slater sp hybrid orbitals in ethylene are  

We conclude this introduction to hydrocarbons by describing the orbital hybridization model of bonding m ethylene and acetylene parents of the alkene and alkyne families respectively 

One of the celebrated successes of orbital hybridization is the elucidation of multiple bonding, which stems from the Lewis formulation of a chemical bond as a shared electron pair. In a compound such as ethylene the saturation of the carbon valence shells can only be achieved by the sharing of two electron pairs between the two carbon atoms. 

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