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Prévia do material em texto

CHAPTER 2 41 
 
so we draw the curved arrow associated with that pattern 
(pushing over the  bond). The positive charge in the 
resulting resonance structure is next to another  bond, 
so we draw one more resonance structure, as shown here: 
 
 
 
(g) This structure exhibits a lone pair that is adjacent to 
a positive charge, so we draw one curved arrow, showing 
a lone pair becoming a  bond: 
 
 
 
(h) This compound exhibits a C=N bond (a  bond 
between two atoms of differing electronegativity), so we 
draw one curved arrow showing the  bond becoming a 
lone pair: 
 
 
(i) We begin by looking for one of the five patterns that 
employs just one curved arrow (in this case, there is 
another pattern that requires two curved arrows, but we 
will start with the pattern using just one curved arrow). 
There is a C=O bond (a  bond between two atoms of 
differing electronegativity), so we draw one curved 
arrow showing the  bond becoming a lone pair. We 
then draw the resulting resonance structure and assess 
whether it exhibits one of the five patterns. In this case, 
there is a lone pair adjacent to a positive charge, so we 
draw the curved arrow associated with that pattern 
(showing the lone pair becoming a  bond), shown here: 
 
 
 
(j) We begin by looking for one of the five patterns that 
employs just one curved arrow (in this case, there is 
another pattern that requires two curved arrows, but we 
will start with the pattern using just one curved arrow). 
There is a C=O bond (a  bond between two atoms of 
differing electronegativity), so we draw one curved 
arrow showing the  bond becoming a lone pair. We 
then draw the resulting resonance structure and assess 
whether it exhibits one of the five patterns. In this case, 
there is a lone pair adjacent to a positive charge, so we 
draw the curved arrow associated with that pattern 
(showing the lone pair becoming a  bond), shown here: 
 
 
 
 
 
2.26. 
(a) Using the skills developed in the previous SkillBuilders, we begin by drawing all significant resonance structures, 
shown below. None of the four structures have an atom with an incomplete octet, so they are all expected to be major 
contributors to the hybrid. The first resonance structure is the largest contributor because it has filled octets and the 
negative charge is on the more electronegative nitrogen atom. The other three resonance structures are approximately 
equivalent and they are less significant than the first structure because the negative charge is on the less electronegative 
carbon atom. 
 
 
 
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