1 (90)

Prévia do material em texto

82 CHAPTER 3 
 
 
Alternatively, the conjugate base could be further stabilized by spreading the charge over an even larger number of 
nitrogen and oxygen atoms. For example, consider the structural changes, highlighted here: 
 
 
 
These additional structural units would enable the conjugate base to spread its negative charge over six nitrogen atoms 
and nine oxygen atoms, which should be even more stable than being spread over four nitrogen atoms and seven 
oxygen atoms. 
 
3.26. The most acidic proton belongs to the carboxylic acid group (COOH). Deprotonation of this functional group 
gives a resonance-stabilized anion in which the negative charge is spread over two oxygen atoms. 
 
 
 
 
3.27. 
(a) We compare the bases on either side of the 
equilibrium. The first (left side) has a negative charge 
on a carbon atom, while the second (right side) has a 
negative charge on a nitrogen atom, so we turn to factor 
#1 (atom). Carbon and nitrogen are in the same row of 
the periodic table, so we compare their electronegativity 
values. Nitrogen is more electronegative than carbon, so 
a negative charge will be more stable on a nitrogen atom. 
As such, the reaction favors the products. 
(b) We compare the bases on either side of the 
equilibrium. The base on the left side is a hydroxide ion, 
while the base on the right side is a resonance-stabilized 
anion, in which the negative charge is spread over one 
oxygen atom and three carbon atoms. The latter is more 
stable because of factor 2 (resonance). Therefore, the 
reaction favors the products. 
 
 
 
3.28. 
(a) First identify the acid and the base in the conversion of 2 into 3. Anion 2 has its negative charge on an oxygen 
atom, and this oxygen atom functions as a base and accepts a proton during the conversion of 2 to 3. The nearby 
hydroxyl group loses its proton during the reaction, thus it is functioning as the acid. 
To draw a mechanism, remember to use two curved arrows. The tail of the first curved arrow is placed on a lone pair 
from the base. The head of the arrow is placed on the proton of the acid. The tail of the second curved arrow is placed 
on the bond between the acidic proton and the attached oxygen atom. The head of that arrow is placed on the oxygen 
atom that receives the negative charge as a result of the process. 
 
www.MyEbookNiche.eCrater.com