TYPE OF CHEMICAL REACTIONS IN CARBONYL COMPOUNDS
(i) Addition across C = O bond.
(ii) Replacement of carbonyl oxygen by other groups.
(v) Reaction with alkalies
(vi) Miscellaneous reactions
It is exactly oxygen insertion between carbonyl carbon & the larger of two groups attached to it.
Illustration 1. Give a chemical test to distinguish between each of the following pair of organic compounds.
(i) propanal an propanol
(ii) propanone and propanal
Solution: (i) Propanal is an aldehyde and gives a silver mirror with Tollen’s reagent while propanol is an alcohol which do not respond silver mirror test positively.
(ii) (a) Propanone give yellow ppt. of iodoform on reaction with I2/NaOH while propanal does not react.
(b) Propanal gives silver mirror with Tollen’s reagent while propanone does not.
Illustration 2. What is Fehling’s solution?
Solution: Fehling solution is a mixture of alkaline copper sulphate (Fehling A) and sodium potassium tartrate (Fehling B).
5. Reaction with Alkalies
(A) Aldol Condensation
(B) Cannizzaro’s reaction
When the reaction is carried out in D2O instead of in H2O, it is found that there is no new C – D bond formation. This indicates that the hydrogen must come from aldehyde & not from the solvent.
Illustration 1. Identify aldehydes which can give cannizaro reaction (CR):
(a) CCl3CHO (b) (CH3)2CHCHO
(c) (CH3)3CCHCl2 (d) C6H5CHO
(C) Perkin reaction
In this reaction aromatic aldehyde is heated with an acid anhydride & its corresponding sodium salt to form condensation products which on hydrolysis
6. Miscellaneous reactions
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