1. A Review of General Chemistry

Draw the important resonance forms of the following free radicals.

b.

Allylic halides have the structure

b. Draw the resonance structures of the allylic cations formed by ionization of the following halides.

(i)

(ii)

A carboxylic acid has two oxygen atoms, each with two nonbonding pairs of electrons.

(a) Draw the resonance forms of a carboxylic acid that is protonated on the hydroxy oxygen atom.

(b) Compare the resonance forms with those given previously for an acid protonated on the carbonyl oxygen atom.

(c) Explain why the carbonyl oxygen atom of a carboxylic acid is more basic than the hydroxy oxygen.

b. Draw the resonance forms for ozone (bonded O–O–O)

c. Sulfur dioxide has one more resonance form than ozone. Explain why this structure is not possible for ozone.

Two resonance structures are shown for each molecule. Use the arrow-pushing formalism to represent the electron flow from the structure on the left to the one on the right.

(f)

All of the rings of the four heterocyclic bases are aromatic. This is more apparent when the polar resonance forms of the amide groups are drawn, as is done for thymine here. Redraw the hydrogen-bonded guanine-cytosine and adenine-thymine pairs shown in Figure 23-24, using the polar resonance forms of the amides. Show how these forms help to explain why the hydrogen bonds involved in these pairings are particularly strong. Remember that a hydrogen bond arises between an electron-deficient hydrogen atom and an electron-rich pair of nonbonding electrons.

Use resonance structures to identify the areas of high and low electron density in the following compounds:

i.

j.

Use resonance structures to identify the areas of high and low electron density in the following compounds:

(c)

Which is a correct statement?

A. The delocalization energy of an ester is about 18 kcal/mol, and the delocalization energy of an amide is about 10 kcal/mol.

B. The delocalization energy of an ester is about 10 kcal/mol, and the delocalization energy of an amide is about 18 kcal/mol.

3-Bromocyclohexene is a secondary halide. It undergoes S_N1 substitution about as fast as most tertiary halides. Use resonance structures to explain this enhanced reactivity.

The following compound can become protonated on any of the three nitrogen atoms. One of these nitrogens is much more basic than the others, however.

a. Draw the important resonance forms of the products of protonation on each of the three nitrogen atoms.

Draw the resonance contributors for the following radicals:

a.

For each of the molecules shown, do the following:

(i) Identify all pushable pairs.

(ii) Identify all places where electrons can be pushed.

(iii) Draw one valid resonance structure.

(a)

Draw the resonance contributors of the peptide bond in the less stable configuration.

Which of the following has delocalized electrons?

a.

b.

c.