Adição de Haletos e Carbocátions

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CHAPTER 8 241 
 
 
8.5. 
(a) In this case, Markovnikov addition of HBr involves 
the formation of a new chiral center. As such, we expect 
both possible stereochemical outcomes. That is, we 
expect a pair of enantiomers, as shown: 
 
 
 
(b) In this case, Markovnikov addition of HCl does not 
involve the formation of a new chiral center (the  
carbon of the resulting alkyl halide bears two propyl 
groups): 
 
HCl
Cl
 
 
(c) In this case, Markovnikov addition of HBr involves 
the formation of a new chiral center. As such, we expect 
both possible stereochemical outcomes. That is, we 
expect a pair of enantiomers, as shown: 
 
 
(d) In this case, Markovnikov addition of HI involves the 
formation of a new chiral center. As such, we expect 
both possible stereochemical outcomes. That is, we 
expect a pair of enantiomers, as shown: 
 
 
(e) In this case, Markovnikov addition of HCl does not 
involve the formation of a new chiral center (the  
carbon of the resulting alkyl halide bears two methyl 
groups): 
 
 
 
(f) In this case, addition of HCl involves the formation 
of a new chiral center. As such, we expect both possible 
stereochemical outcomes. That is, we expect a pair of 
enantiomers, as shown: 
 
 
 
8.6. 
(a) Protonation of the alkene requires two curved 
arrows, as shown, and leads to the more stable, 
secondary carbocation (rather than a primary 
carbocation). This secondary carbocation then 
undergoes a hydride shift, shown with one curved arrow, 
generating a more stable, tertiary carbocation. In the 
final step (nucleophilic attack), the carbocation is 
captured by a bromide ion. This step requires one 
curved arrow, going from the nucleophile (bromide) to 
the electrophile (the carbocation), as shown: 
 
 
 
(b) Protonation of the alkene requires two curved arrows, 
as shown, and leads to the more stable, secondary 
carbocation (rather than a primary carbocation). This 
secondary carbocation then undergoes a hydride shift, 
shown with one curved arrow, generating a more stable, 
tertiary carbocation. In the final step (nucleophilic 
attack), the carbocation is captured by a bromide ion. 
This step requires one curved arrow, going from the 
nucleophile (bromide) to the electrophile (the 
carbocation), as shown: 
 
 
 
(c) Protonation of the alkene requires two curved 
arrows, generating a secondary carbocation. This 
secondary carbocation then undergoes a methyl shift, 
shown with one curved arrow, generating a more stable, 
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