1 (52)

Prévia do material em texto

44 CHAPTER 2 
 
The benzene ring on the right is “connected” to the carbonyl (C=O) groups by a series of alternating  bonds, so the 
resonance of each carbonyl group extends into the benzene ring. The carbonyl groups withdraw electron density via 
allylic carbocation resonance, making this ring electron-deficient. 
 
 
 
In summary, the benzene ring on the left is electron-rich due to resonance with the lone pairs of electrons on both 
attached oxygen atoms. The benzene ring on the left is electron-poor due to resonance with the carbonyl groups. 
 
 
 
 
2.29. 
(a) Begin by drawing all significant resonance structures. 
In this case, there are two: 
 
 
 
Both resonance structures are equally significant, so the 
resonance hybrid is the simple average of these two 
resonance structures. There are no formal charges, so 
only partial bonds need to be drawn. 
 
 
 
(b) Begin by drawing all significant resonance structures. 
In this case, there are two: 
 
 
 
Both are equally significant, so the resonance hybrid is 
the simple average of these two resonance structures. 
Both partial bonds and partial charges are required, as 
shown: 
--
Resonance hybrid 
 
(c) Begin by drawing all significant resonance structures. 
In this case, there are two: 
 
 
 
The left-hand structure is more significant because every 
atom has an octet. The resonance hybrid is a weighted 
average of these two resonance structures in which the 
oxygen atom has more of the charge than the carbon 
atom. 
 
 
(d) Begin by drawing all significant resonance structures. 
In this case, there are two: 
 
 
www.MyEbookNiche.eCrater.com