Chapter 3, Problem 46P

Interpretation Introduction

Interpretation:

The dash structural formula of DMF showing unshared electron pairs is to be drawn. The most important resonance form of DMF is to be predicted. On the basis of Lewis acid–base considerations, the greater reactivity of nucleophile in DMF is to be explained.

Concept introduction:

Electrophiles are electron-deficient species, which has positive or partially positive charge. Lewis acids are electrophiles, which accept electron pair.

Nucleophiles are electron-rich species, which has negative or partially negative charge. Lewis bases are nucleophiles, which donate electron pair.

In dash line formula, all the symbols of atoms and the bonding electron pair lines are shown.

Resonating structures are structures that have more than one equivalent Lewis structures for the same molecule or ion.

Resonance is the phenomenon of describing delocalized electrons in certain molecular ions through various forms or resonance structures and the forms contributing to the hybrid form.

The rules for drawing resonance structures are as follows:

Only nonbonding electron pairs and pi electrons can participate in conjugation in the formation of various resonating structures.

The single bonds present in the molecule do not break or form in the resonance structures.

The placement of atoms present in the molecule remains fixed.

The octet of all atoms is completely filled.

According to the convention, these structures are connected by double-headed arrows ($\stackrel{}{\leftrightarrow }$).

Movement of electrons (whether bonding or lone pair) is indicated by curved arrows.

Curved arrows are used to represent the direction of the flow of electrons in a reaction mechanism.

Curved arrows are drawn in such a way that they point from the source of an electron pair toward the atom, which receives the electron pair.

The direction of flow of electrons is always from a high electron density site to a low electron density site.

Curved arrows never represent the movement of atoms.

The movement of electrons shown by the curved arrows should not violate the octet rule for the elements, which are present in the second row of the periodic table.

The more stable structure is the structure that has more covalent bonds.

Stability of resonating structures is decreased by charge separation.

The structures that contain complete valence shells are more stable.

Reactivity of a molecule depends on the solvation of nucleophilic anions.