TYPE OF CHEMICAL REACTIONS IN CARBONYL COMPOUNDS

(i)   Addition across C = O bond.

(ii)  Replacement of carbonyl oxygen by other groups.

(iii) Oxidation

(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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Class 12 Chemistry Aldehydes, Ketones and Carboxylic Acids All Topic Notes Class 12 Chemistry All Chapters Notes

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