1. A Review of General Chemistry

Draw the resonance contributors of the cyclooctatrienyl dianion.

a. Which of the resonance contributors is the least stable?

Which is longer, the carbon–oxygen single bond in a carboxylic acid or the carbon–oxygen bond in an alcohol? Why?

Draw resonance contributors for the following ions:

a.

Draw the resonance contributors for the following radicals:

c.

Draw the resonance contributors for the following radicals:

d.

The given was missing some important resonance forms of the intermediates shown in brackets. Complete this mechanism by drawing all the resonance forms of these intermediates. Do your resonance forms help to explain why this reaction occurs under very mild conditions (water with a tiny trace of acid)?

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.

Which of the following has delocalized electrons?

j.

k.

l.

For each of the following compounds, draw the important resonance forms. Indicate which structures are major and minor contributors or whether they have the same energy.

(c) [H₂COCH₃]⁺

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

(c)

For each of these ions, draw the important resonance forms and predict which resonance form is likely to be the major contributor.

(a)

For each of the following compounds, draw the important resonance forms. Indicate which structures are major and minor contributors or whether they have the same energy.

(d) [H₂CNO₂]^–

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

(d)

For each of these ions, draw the important resonance forms and predict which resonance form is likely to be the major contributor.

(b)

For each of the following compounds, draw the important resonance forms. Indicate which structures are major and minor contributors or whether they have the same energy.

(e) [CH₃C(OH)₂]⁺

(f) [CH₂CHNH]^–