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CBSE Class 12-science Answered

How can aldehydes and ketones be prepared by: i) ozonolysis of alkenes ii) hydration of alkynes
Asked by padmakrith | 14 Apr, 2013, 11:44: AM
answered-by-expert Expert Answer
 i) ozonolysis of alkenes
 
  • Overall transformation :  C=C to 2 x C=O
  • Ozonolysis implies that ozone causes the alkene to break (-lysis)
  • Reagents : ozone followed by :
    • a reducing work-up, either Zn in acetic acid or dimethyl sulfide, (CH3)2S 
    • an oxidising work-up, usually H2O2 (under these conditions, carboxylic acids are obtained instead of aldehydes)
  • It is convenient to view the process as cleaving the alkene into two carbonyls
    • The substituents on the C=O depend on the substituents on the original C=C.
    • The work-up determines the oxidation state of the products
  REDUCTIVE work-up 
     OXIDATIVE work-up 
 
ii) hydration of alkynes 

Answered by | 15 Apr, 2013, 12:02: PM

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