Chapter 14, Problem 14.60P

Interpretation Introduction

Interpretation:

Which of the two O atoms of $\text{4-pyrone}$ is more basic is to be determined.

Concept introduction:

The basicity of a molecule depends on how easily the donor atom can donate its lone pair to an electron-poor atom. The ability of an atom to donate its lone pair of electrons depends on several factors – the charge on the atom, its electronegativity, its hybridization, and the possible involvement of the lone pair in resonance. If the donor atom is relatively less electronegative, it can donate the lone pair relatively easily. A negatively charged atom can more easily donate a lone pair than a neutral atom, which in turn can more easily donate a pair than a positively charged atom. The ease of donation increases with increasing p character of the hybrid orbital containing the lone pair. If the lone pair is involved in resonance, it is delocalized and, therefore, less available for donating. Since resonance involves p orbitals that are perpendicular to the bond axis, a lone pair in an ${\text{sp}}^2$ hybrid orbital is more easily donated than one in the pure p orbital. However, if there is no resonance, a lone pair in a pure p orbital is more easily donated than one in an ${\text{sp}}^2$ hybrid orbital.