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The first part of the experiment involves the addition of water to hydrazine sulfate. H 20

is added to ionize the hydrazine sulfate and thus, the nucleophile is generated.

(Show reaction here)

Sodium acetate is also added to buffer the mixture. It is then heated for further

dissolution of the salt. After slight cooling it is filtrated using ethanol as the solvent. The filtrate

is carried for the synthesis proper.

The hydrazine solution is added with 2,4-dinitrochlorobenzene and undergoes reflux for

one hour. After reflux, the solution is filtered and washed with cold water before washing with

warm ethanol. This is for rapid recrystallization of the salts and for minimizing the trapping of

impurities. The residue is dried and weighed before characterization.

Reactions of 2,4-Dinitrophenylhydrazine to ketones and/or aldehydes to form 2,4-

Dinitrohydrazone is signaled by a yellow precipitate.

(Show reaction here)

The reaction can also be considered as an addition-elimination reaction: nucleophilic

addition of the -NH 2 group to the C=O carbonyl group, followed by the removal of a H 2O

molecule.

Specifically, when 2,4-Dinitrophenylhydrazine reacts with benzaldehyde and acetone,

the following general reactions and mechanisms are observed:

(show reaction for benzaldehyde)

(Show reaction for acetone)

Crystals of different hydrazones have characteristic melting and boiling points, allowing theidentity of a substance to be determined in a method known as derivatization (Shriner, etal.,

1998).

In this experiment, the student should be able to (1) synthesize 2,4-

Dinitrophenylhydrazine from 2,4-dinitrochlorobenzene, (2) Characterized the product through

derivatization, and (3) write all the mechanisms involved in each reactions.

http://en.wikipedia.org/wiki/Addition-elimination_reactionhttp://en.wikipedia.org/wiki/Derivatizationhttp://en.wikipedia.org/wiki/Derivatizationhttp://en.wikipedia.org/wiki/Addition-elimination_reaction

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II. List of necessary chemicals and set-ups

A. List of necessary chemicals

NAMEand

STRUCTURE

AMOUNT

(g)

Purpose in theexperiment

Physicalproperties

Hazards andprecautions/

first aid

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B. Set-Up

Figure 1.1. Reflux set-up

Figure1.2. Suction Filter set-up

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