Chapter D, Problem D.11YT

Interpretation Introduction

Interpretation:

The atomic orbital overlap and MO energy diagrams for ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{Br}$ (Figs. 3-13 through 3-25 to be reviewed) are to be constructed, and these diagrams are to be used to determine its HOMO and LUMO. Whether answers agree with the ones shown in Figure D-10a is to be explained.

Concept introduction:

Molecular orbitals are constructed from the AOs of different atoms. When two atoms are brought close enough together (i.e., about a bond length apart), the AOs of one atom significantly overlap the AOs of the other atom, enabling them to undergo constructive and destructive interference, or mix, to produce new orbitals. The two $\text{C}$ atoms and the $\text{Br}$ atom are all ${\text{sp}}^{\text{3}}$ hybridized, and each $\text{H}$ atom contributes a $\text{1s}$ orbital. End-on overlap occurs in the $\text{C-H}$, $\text{C-C}$, and $\text{C-Br}$ bonding and, therefore, results in seven $\text{σ}$ bonds. When the $\text{14}$ AOs overlap, $\text{14}$ MOs are produced: seven $\text{σ}$ bonding and seven $\text{σ*}$ antibonding. This leaves three nonbonding orbitals.