Identification of carbonyl compounds by preparing their derivatives

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S.K.H. Lam Woo Memorial Secondary School

F.7 Chemistry Laboratory Report

Name: Chan Ching Wai Class: F.7H (2)

Experiment 3: Identification of carbonyl compounds by preparing their derivatives

Date of Experiment: 15-10-2010

Objective:

To identify an unknown carbonyl compound by determining the melting point of it's derivative formed from the reaction with 2,4-dinitrophenylhydrazine solution.

Introduction:

In the experiment, carbonyl compound underwent condensation reaction with 2,4-dinitrophenylhydrazine solution to form 2,4-dinitrophenylhydrazone. The solid formed was then purified by recrystallization in order to give an accurate, distinct melting point. As the 2,4-dinitrophenylhydrazone formed from different carbonyl compound would have different boiling points, by matching the measured boiling point with that stated officially, the type of carbonyl compound could be identified.

Carbonyl compound contained a C=O functional group which was polar. The electron cloud was displaced to the more electronegative oxygen atom and made the carbonyl carbon partial positive. The carbonyl carbon was hence electron deficient and susceptible to attack by electron rich nucleophile.

Carbonyl compound could undergo condensation with derivative of ammonia. In this case, carbonyl compound could serve as electrophiles and nucleophile at the same time. Water was eliminated