48E - Organic Chemistry (Mcmurry)

Question

Allene (see Problem 1-47) is structurally related to carbon dioxide, . Draw a picture showing the orbitals involved in the s and p bonds of  , and identify the likely hybridization of carbon.

Step-by-Step Solution

Answer

Orbitals involved is sigma bonds of carbon dioxide

Allene and carbon dioxide

Carbon dioxide is similar to allene; it has a central C atom making two double bonds. In carbon dioxide, however, the double bonds are formed with O atoms which each have two lone pairs instead of bonds to two hydrogen atoms.

Representation of orbitals

The central carbon atom is sp hybridized and has a linear geometry in carbon dioxide, while the two oxygen atoms are hybridized. In this, both oxygen atoms have trigonal planar geometry. However, their planes are rotated  about the bond axis to be perpendicular to each other. The orbitals involved in sigma bonds of carbon dioxide are represented as:

Representation of 𝛑 orbitals

In the case of pi bonds, the central carbon atom makes a pi bond to the oxygen atom on the left using the p orbitals that are oriented on the page plane. It makes a pi bond to the oxygen atom on the right using the p orbitals that are oriented perpendicular to the plane of the page. Thus, the carbon atom of carbon dioxide is sp hybridized.