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BACKGROUND
Principle: It is a two steps synthesis where first isonitrosoacetanilide is prepared from aniline, chloral hydrate, and hydroxylamine hydro-chloride. Finally cyclization of isonitrosoacetanilide under strong acid conditions e.g. polyphosphoric acid, yields 2,3-dioxoindoline.1
Aim: To prepare isatin from aniline and chloral hydrate
Reaction:
Use: It is an antimicrobial and used as a raw material for synthesis of various heterocyclic drug.
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REQUIREMENTS
Chemicals: Aniline
Concentrated hydrochloric acid
Chloral hydrate
Sodium sulphate decahydrate
Hydroxylamine hydrochloride
Polyphosphoric acid
Glacial acetic acid
Apparatus: Beaker
Erlenmeyer flask
Vacuum filtration apparatus
Reflux apparatus
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PROCEDURE
Aniline (2.66 g, 1.8 ml) is dissolved in concentrated hydrochloric acid (1.7 ml) and water (12 ml). A solution of chloral hydrate (3.6 g) and sodium sulphate decahydrate (52 g) in water (52 ml) is added to the first solution. Next another solution of hydroxylamine hydrochloride (4.4 g) in water (60 ml) is added and the resulting mixture is taken to reflux temperature over a period of 15 min., then heated under reflux for 5 min. The solutionis allowed to cool and the separated product is filtered. The residue is washed with cold water and dried at 100°. Isonitrosoacetanilide is obtained as buff plates, m. p. 178-179°, sufficiently pure for direct use in the next stage. Polyphosphoric acid (50 g) is added to prepared isonitrosoacetanilide, and stirred at 56° for 6 hr. The resulting mixture is poured into ice-water (250 ml), vigorously stirred, then the precipitated product is filtered off and washed with cold water. 2,3-Dioxoindoline crystallizes from glacial acetic acid (8 ml/g) as orange prisms, m.p. 197°. Yield 2 g.
Calculation
Molecular formula of aniline = C6H7N
Molecular formula of 2,3-dioxoindoline = C8H5NO2
Weight of methyl aniline = 93 g/mole
Weight of 2,3-dioxoindoline = 147 g/mole
Theoretical yield
93 g of aniline gives 147 g of 2,3-dioxoindoline
Therefore, 2.66 g of aniline would give……….. ? (X) g of 2,3-dioxoindoline
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CONCLUSION
The yield of synthesized isatin was found to be 47.6%.
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REFERENCES
1. Practical Heterocvclic Chemistry by A. O. Fitton and R. K. Smalley Published by Academic Press London and New York 1968; Page No. 11
