Describe Reimer-Tiemann reaction with an example. What will be the acidity of the product as compared to the substrate?

Reimer-Tiemann reaction :- When phenol is reacted with chloroform in the presence of aqueous sodium hydroxide at 340 K followed by hydrolysis, an aldehydic group ( - CHO ) gets introduced in the ring at a position ortho to the phenolic group. Ortho hydroxy benzaldehyde or salicylaldehyde is formed as the product of the reaction. This reaction is called Reimer-Tiemann reaction. In addition to o -salicylaldehyde, small amount of p -salicylaldehyde is also formed, but the major product is ortho. The aldehyde group in salicylaldehyde is electron withdrawing group so it has higher acidity than that of phenol.

Predict the products of the following reaction. CH 3 CH 2 CH 2 - O - CH 3 + HBr →

The reaction is shown as follows : Reaction proceeded by SN 2 mechanism. So, B r - attacks the least substituted carbon of the oxonium ion and forms propanol and bromomethane.

An organic compound ‘A’ having molecular formula C 6 H 6 O gives acharacteristic colour with FeCl 3 solution. When ‘ A ’ is treated with CO 2 and NaOH at 400 K under pressure, compound ‘B’ is obtained. The compound ‘ B ’ upon acidification gives compound ‘ C ’ which reacts with acetyl chloride to form ‘ D ’ which is a popular pain killer. Deduce the structures of A, B, C and D.

1) A gives characteristics colour with FeCl 3 so A is phenol. Molecular formula of A is C 6 H 5 OH . 2) A reacts with CO 2 and NaOH , we get C 6 H 5 OH + CO 2 + NaOH → C 6 H 4 ( OH ) COONa , so molecular formula of B is C 6 H 4 ( OH ) COONa 3) B on acidification gives C : C 6 H 4 ( OH ) COONa + H + → C 6 H 4 ( OH ) COOH 4) C reacts with acetyl chloride to form D C 6 H 4 ( OH ) COOH + CH 3 COCl → C 6 H 4 ( OCOCH 3 ) COOH + HCl D is Asprin.

A solution of bromine, in methanol or ethanol cannot be used for the detection of unsaturation in organic compounds. Why?

The bromine solution is brown. In this test when bromine solution is added to the unsaturated hydrocarbon the brown colour disappears if the hydrocarbon is unsaturated. Bromine forms an additional product with unsaturated hydrocarbon. Decolourization of the orange-red colour of bromine solution indicates unsaturation. As methanol and ethanol both do not have unsaturated hydrocarbons or both are not unsaturated. The structure of methanol and ethanol is following.

How will you synthesize the isomeric ether of benzyl alcohol by Williamson synthesis?

Anisole is an isomeric ether of benzyl alcohol. It is prepared by the action of methyl bromide on sodium phenoxide by by Williamson synthesis.

Why is C 2 H 5 OH miscible with water?

C 2 H 5 OH is miscible with water because it has - OH group that allows it to form hydrogen bonds with molecules of water and both water and ethanol are polar solvents.

Salicylaldehyde is a product obtained by the action of CHCl 3 on C 6 H 5 OH in presence of aq. KOH . What is the name of the reaction?

Salicylaldehyde is a product obtained by the action of CHCl 3 on C 6 H 5 OH in presence of aq. KOH and this reaction is known as Reimer-Tiemann's reaction of phenol. In this reaction, carbene forms as an intermediate which is hydrolysed in the presence of alkali to produce salicylaldehyde.

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12th Manipur Board

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Draw the resonating structures of phenol and predict whether $OH$ group is meta directing or ortho and para directing towards electrophilic ring substitution reactions.

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