1. A Review of General Chemistry

Draw two important resonance structures involving the lone pair on oxygen for the molecule shown. Which carbons are most likely to act as nucleophiles?

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Draw two important resonance structures involving the C―O π bond for the molecule shown. To which carbons would you expect a nucleophile to add?

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Draw all possible resonance structures for the reactive intermediates shown.

(c) <IMAGE>

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. <IMAGE>

Draw the resonance contributors for the following radicals:

c. <IMAGE>

Draw the resonance contributors for the following radicals:

d. <IMAGE>

<IMAGE> (Solved Problem 20-1)

(a) The solution given for Solved Problem 20-1 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 at here. <IMAGE>

Redraw the hydrogen-bonded guanine-cytosine and adenine-thymine pairs shown in Figure 23-24 <IMAGE>, 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. <IMAGE>

k. <IMAGE>

l. <IMAGE>

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.

[H2COCH3]+

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

HC=O(NH2) <IMAGE>

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

a. <IMAGE>

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.

[H2CNO2]-

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

HC=O(OCH3) <IMAGE>

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

b. <IMAGE>

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

c. <IMAGE>

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.

[CH3C(OH)2]+

[CH2CHNH]-

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.

[HC=OCHC=O(H)]- <IMAGE>

[CHOCHCH]- <IMAGE>

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

g. <IMAGE>

h. <IMAGE>

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

i. <IMAGE>

j. <IMAGE>

Draw the resonance contributors of the cyclooctatrienyl dianion.

b. Which of the resonance contributors makes the smallest contribution to the hybrid

a. Draw resonance contributors for the following species, showing all the lone pairs:

3. NO2-

b. For each species, indicate the most stable resonance contributor.