Important Alcohol Formulas for JEE and NEET

 Page 2


  
           
          
        
       
 
    
        
       
    
  
        
           
     
  
   
      
       
      
      
  
             
          
           
  
e.g.
alcohol Isopropyl
OH
|
CHCH CH
3 3
    
bromide Isopropyl
Br
|
CHCH CH
3 3
S
N
2 reaction :
ROH + PCl
5
?? ?
 RCl + POCl
3
ROH + PCl
3
?? ?
 RCl + H
3
PO
3
ROH + SOCl
2
Pyridine
???? ? RCl + SO
2 
+ HCl
Williamson?s synthesis :
It is the reaction in which sodium or potassium alkoxide is heated with an
alkyl halide (S
N
2).
R O + R?X
1
? 2
) g ( X OR R X ....... R ........ O R
? 2 1
?
2
?
1
? ?? ?
?
?
This method is particularly useful for preparing mixed ethers.
Nucleophilic Aromatic Substitution of aryl halides(S
N
2Ar):
? An electron withdrawing group at ortho or para positions with respect to a
good leaving groups are necessary conditions for S
N
2 Ar.
 + Nu
?
 
RDS
I Step
? ? ? ? ?
?
  
II Step
) fast ( X
?
?
? ? ? ? ? ?
?
 
Intermediate ion is stabilized by resonance. and are stable salts called
Meisenheimer salts.
? A group that withdraws electrons tends to neutralize the negative charge
of the ring and this dispersal of the charge stabilizes the carbanion.
  G withdraws electrons : stabilizes carbanion, activates the
        Ar-S
N
2 reaction.
(? (CH
3
)
3
, ?NO
2
, ?CN, ?SO
3
H, ?COOH, ?CHO, ?COR, ?X)
Page 3


  
           
          
        
       
 
    
        
       
    
  
        
           
     
  
   
      
       
      
      
  
             
          
           
  
e.g.
alcohol Isopropyl
OH
|
CHCH CH
3 3
    
bromide Isopropyl
Br
|
CHCH CH
3 3
S
N
2 reaction :
ROH + PCl
5
?? ?
 RCl + POCl
3
ROH + PCl
3
?? ?
 RCl + H
3
PO
3
ROH + SOCl
2
Pyridine
???? ? RCl + SO
2 
+ HCl
Williamson?s synthesis :
It is the reaction in which sodium or potassium alkoxide is heated with an
alkyl halide (S
N
2).
R O + R?X
1
? 2
) g ( X OR R X ....... R ........ O R
? 2 1
?
2
?
1
? ?? ?
?
?
This method is particularly useful for preparing mixed ethers.
Nucleophilic Aromatic Substitution of aryl halides(S
N
2Ar):
? An electron withdrawing group at ortho or para positions with respect to a
good leaving groups are necessary conditions for S
N
2 Ar.
 + Nu
?
 
RDS
I Step
? ? ? ? ?
?
  
II Step
) fast ( X
?
?
? ? ? ? ? ?
?
 
Intermediate ion is stabilized by resonance. and are stable salts called
Meisenheimer salts.
? A group that withdraws electrons tends to neutralize the negative charge
of the ring and this dispersal of the charge stabilizes the carbanion.
  G withdraws electrons : stabilizes carbanion, activates the
        Ar-S
N
2 reaction.
(? (CH
3
)
3
, ?NO
2
, ?CN, ?SO
3
H, ?COOH, ?CHO, ?COR, ?X)
  
 ? A group that releases electrons tends to intensify the negative charge,
destabilizes the carbanion, and thus slows down reaction.
G (?NH
2
, ?OH, ?OR, ?R)releases electrons : destabilizes carbanion,
deactivates  the Ar-S
N
2 reaction.
Element effect :
Reactivity order towards S
N
2Ar with different halogens
Ar-F > Ar-Cl > Ar-Br > Ar-I