Glycol cleavage: HlO4, Pb(OAc)4 | Chemistry Optional Notes for UPSC PDF Download

 Page 1


 
              
  
? Glycol cleavage is a specific type of organic chemistry oxidation.  
? The carbon –carbon bond in a vicinal diol (glycol) is cleaved and replaced with two carbon –oxygen double bonds. 
Depending on the substitution pattern in the diol, either ketones or aldehydes may be formed. 
? Glycol cleavage is an important reaction in the laboratory because it is useful for determining the structures of 
sugars. After cleavage takes place the ketone and aldehyde fragments can be inspected and the location of the 
former hydroxyl groups ascertained. 
 
 
 
 
 
 
 
 
Periodic acid (HIO
4
) and lead tetraacetate [Pb(OAc)
4
]. 
 
? Glycol cleavage by periodic acid is called Malaprade periodic acid oxidation. 
 
 
 
 
 
 
 
 
 
Page 2


 
              
  
? Glycol cleavage is a specific type of organic chemistry oxidation.  
? The carbon –carbon bond in a vicinal diol (glycol) is cleaved and replaced with two carbon –oxygen double bonds. 
Depending on the substitution pattern in the diol, either ketones or aldehydes may be formed. 
? Glycol cleavage is an important reaction in the laboratory because it is useful for determining the structures of 
sugars. After cleavage takes place the ketone and aldehyde fragments can be inspected and the location of the 
former hydroxyl groups ascertained. 
 
 
 
 
 
 
 
 
Periodic acid (HIO
4
) and lead tetraacetate [Pb(OAc)
4
]. 
 
? Glycol cleavage by periodic acid is called Malaprade periodic acid oxidation. 
 
 
 
 
 
 
 
 
 
 
              
  
 
? A GEMINAL DIOL (or GEM-DIOL) is any organic compound having two hydroxyl functional groups (-OH) 
bound to the same carbon atom. The two hydroxyls in a geminal diol are easily converted to a carbonyl or keto 
group C=O by loss of one water molecule, thus turning the diol into a ketone. Conversely, ketones tend to 
combine with water to form the corresponding geminal diols. The equilibrium in water solution may be shifted 
towards either compound; for example, the equilibrium constant for the conversion of acetone (H
3
C)
2
C=O to 
propane-2,2-diol (H
3
C)
2
C(OH)
2
 
 
 
 
 
? VICINAL (from Latin vicinus = neighbor) when any two functional groups bonded to two adjacent carbon atoms. 
For example the molecule 2,3-dibromobutane carries two vicinal bromine atoms. 
 
 
 
 
? PERIODIC ACID is the highest oxoacid of iodine, in which the iodine exists in oxidation state VII. Like all 
periodates it can exist in 2 forms: ORTHOPERIODIC ACID, with the chemical formula H
5
IO
6
 and 
METAPERIODIC ACID, which has the formula HIO
4
. 
Iodine oxidation 
state 
-1 +1 +3 +5 +7 
Name Hydrogen iodide Hypoiodous acid Iodous acid Iodic acid Periodic acid 
Formula HI HIO HIO
2
 HIO
3
 HIO
4
 or H
5
IO
6
 
  
 
Iodous acid 
 
Iodic acid 
 
Hypoiodous acid 
 
Orthoperiodic acid 
 
Metaperiodic acid