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TYPE OF CHEMICAL REACTIONS IN CARBONYL COMPOUNDS
(i) Addition across C = O bond.
(ii) Replacement of carbonyl oxygen by other groups.
(iii) Oxidation
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(iv) Reduction
(v) Reaction with alkalies
(vi) Miscellaneous reactions
It is exactly oxygen insertion between carbonyl carbon & the larger of two groups attached to it.
Haloform Reaction
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
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(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
Solution:
(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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