Chapter 11, Problem 11.39P

(a)

Interpretation Introduction

Interpretation:

The number of sigma and pi bonds in butadiene is to be determined.

Concept introduction:

The sigma bond is the covalent bond that is formed by the axial overlap of orbitals. The pi bond is formed by the lateral overlap of orbitals. Both types of bonds can be bonding or anti-bonding interaction. Bonding interaction takes place when there is an overlap of orbitals in the same phase and antibonding interaction occurs when the orbital overlap in opposite phase. Sigma bond is stronger than the pi bond.

All single bonds are sigma bonds. One double bond is made up of one sigma bond and one pi bond. One triple bond is made up of one sigma bond and two pi bonds.

(b)

Interpretation Introduction

Interpretation:

Whether cis-trans arrangements about the double bonds in butadiene are possible or not is to be determined.

Concept introduction:

The cis and trans forms are the types of geometrical or configurational isomers. The cis form indicates that the same functional groups are present on the same side of the carbon-carbon double bond. The trans form indicates that the same functional groups are present on the opposite side of the carbon-carbon double bond. Both isomers have the same formula but a different arrangement of functional groups around the carbon atom.