Chapter 20, Problem 20.1P

Interpretation Introduction

(a)

Interpretation: The orbitals are used to form the indicated bonds in $\text{α-}$ sinensal are to be predicted.

Concept introduction: $\text{α-}$ sinensal is a weak base and insoluble in water. It is a constituent of orange oil. The molecular formula of $\text{α-}$ sinensal is ${\text{C}}_{\text{15}}{\text{H}}_{\text{22}}\text{O}$ and its IUPAC name is $\left(\text{2E, 6E, 9E}\right)\text{-2, 6, 10-trimethyl-2, 6, 9, 11-dodecatetraenal}$.

Answer to Problem 20.1P

The orbitals are used to form bond $\left[1\right]$, bond $\left[2\right]$ and bond $\left[3\right]$ are $s{p}^2$ hybrid orbitals.

Explanation of Solution

The given structure of $\text{α-}$ sinensal is,

Figure 1

Bond $\left[1\right]$ is formed by the overlapping of $s{p}^2$ hybrid orbitals of carbonyl carbon with $s{p}^2$ hybrid orbitals of adjacent carbon. Hence, the orbitals are used to form bond $\left[1\right]$ are $s{p}^2$ hybrid orbitals.

Bond $\left[2\right]$ indicates the double bond between carbon and oxygen i.e. carbonyl bond in which one bond is pi and other one is sigma bond. The pi bond is formed by the lateral overlapping of unhybridized $\text{2p}$ orbital of carbon with $\text{2p}$ orbital of oxygen. The sigma bond is formed by head to head overlapping of $s{p}^2$ hybrid orbitals of oxygen atom and $s{p}^2$ hybrid orbitals of carbon atom. Hence, the orbitals are used to form bond $\left[2\right]$ are $s{p}^2$ hybrid orbitals.

Bond $\left[3\right]$ is formed by the overlapping of $s{p}^2$ hybrid orbitals of carbon atom with $s{p}^2$ hybrid orbitals of adjacent carbon atom. Hence, the orbitals are used to form bond $\left[3\right]$ are $s{p}^2$ hybrid orbitals.

Conclusion

The orbitals are used to form bond $\left[1\right]$, bond $\left[2\right]$ and bond $\left[3\right]$ are $s{p}^2$ hybrid orbitals.

Interpretation Introduction

(b)

Interpretation: The type of orbitals where the lone pairs on $\text{O}$ reside are to be predicted.

Concept introduction: $\text{α-}$ sinensal is a weak base and insoluble in water. It is a constituent of orange oil. The molecular formula of $\text{α-}$ sinensal is ${\text{C}}_{\text{15}}{\text{H}}_{\text{22}}\text{O}$ and its IUPAC name is $\left(\text{2E, 6E, 9E}\right)\text{-2, 6, 10-trimethyl-2, 6, 9, 11-dodecatetraenal}$.

Answer to Problem 20.1P

The type of orbitals where the lone pairs on $\text{O}$ reside are $\text{2s}$ and $\text{2p}$ orbitals.

Explanation of Solution

The oxygen atom of carbonyl carbon in $\text{α-}$ sinensal has two lone pairs. One of the lone pair of electrons is located in the $\text{2s}$ orbital and other one is located on the $\text{2p}$ orbitals of oxygen atom. Hence, the type of orbitals where the lone pairs on $\text{O}$ reside are $\text{2s}$ and $\text{2p}$ orbitals.

Conclusion

The type of orbitals where the lone pairs on $\text{O}$ reside are $\text{2s}$ and $\text{2p}$ orbitals.