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a) Aldol condensation reaction is a special reaction of aldehydes.

i) What is a Idol condensation reaction?

ii) Write the structural formula of aldol formed from ethana I.

b) Write simple chemical tests and observations used to distinguish between the following compounds:

i) Propanal and propanone

ii) Phenol and benzoic acid

c) Write the names of the reagents used to bring about the following transformations:

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a) i) Aldehydes and ketones having at least one α-hydrogen undergo a condensation reaction in the presence of dilute alkali to form β-hydroxy aldehydes (aldol) or β-hydroxy ketones (ketol) respectively. This reaction is known as Akiol condensation.

b) i) Propanal and propanone – They can be distin guished by Tollens’ Test – When propanal is warmed with freshly prepared ammonical silver nitrate solution (Tollens’ reagent), a bright silver mirror is produced due to the formation of silver metal. Here propanal is oxidised to propanoate anion while it reduces Ag+ to metallic silver. Since ketones are less reactive, propanone will not answer this test.

[Other tests: (1) Fehling’s test – Propanal gives a red precipitate on heating with Fehling’s reagent while propanone does not answer this test. (2) iodoform test – Propanone being a methyl ketone, when heated with NaOH and 12 sOlUtiOn an yellow precipitate of lodoform is formed. But propanal does not answer the jodo-form test.]

ii) Phenol and benzoic acid – When benzoic acid is treated with NaHCO3 solution there is bnsk effervescence of CO2. But phenol being less acidic than benzoic acid will not react with NaH CO3 solution.

c)

This reaction is caned Rosenmund reduction.

This reaction is called Hell-Volhard-Zelinsky (HVZ) reaction.

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