Give two reactions that show the acidic nature of phenol. Compare its acidity with that of ethanol.
The reactions showing acidic nature of phenol are:
(a) Reaction with sodium: Phenol reacts with active metals like sodium to liberate H, gas.
(b) Reaction with NaOH: Phenol dissolves in NaOH to form sodium phenoxide and water.
Phenol is more acidic than ethanol. This is due to the reason that phenoxide ion left after the loss of a proton from phenol is stabilized by resonance, while ethoxide ion left after less of a proton from ethanol, is not.
Assertion (A): Phenol forms 2,4, 6-tribromophenol on treatment with Br2 in carbon disulphide at 273 K.
Reason (R): Bromine polarizes in carbon disulphide.
Assertion (A): Phenols give o-nitrophenol and p-nitrophenol on nitration with cone. HNO3 and H2SO4 mixture.
Reason (R): -OH group in phenol is o-,p-directing.
Write the names of reagents and equations for the preparation of the following ethers by Williamson's synthesis:
(i)1-Propoxypropane
(ii)Ethoxybenzene
(iii)2-Methoxy-2-methylpropane
(iv)1-Methoxyethane
Ethers can be prepared by Williamson's synthesis in which an alkyl halide is reacted with sodium alkoxide. Di-tert-butyl ether cannot be prepared by this method. Explain.
While separating a mixture of ortho and para nitrophenols by steam distillation, name the isomer which will be steam volatile. Give reason.
Explain how does the – OH group attached to a carbon of benzene ring activate it towards electrophilic substitution?
Explain the fact that in aryl alkyl ethers (i) the alkoxy group activates the benzene ring towards electrophilic substitution and (ii) it directs the incoming substituents to ortho and para positions in benzene ring.
Arrange the following compounds in increasing order of acidity and give a suitable explanation:
Phenol, o-Nitrophenol, o-Cresol
Give structures of the products you would expect when each of the following alcohol reacts with (a)HCl-ZnCl2 (b)HBrand (c) SOCl2
(i)Butan-1-ol
(ii)2-Methylbutan-2-ol
Write the equation of the reaction of hydrogen iodide with (i)1-propoxypropane (ii)methoxybenzene, and (iii)benzyl ethyl ether
When phenol is treated with bromine water, white precipitate is obtained. Give the structure and the name of the compound formed.
Write the structures of the isomers of alcohols with molecular formula C4H10O. Which one of these isomers exhibits optical activity?
Match the starting materials given in Column I with the products formed by these (Column II) in the reaction with HI.
Assertion (A): o-Nitrophenol is less soluble in water than the m- and p-isomers.
Reason (R): m-Nitrophenol and p-Nitrophenol exists as associated molecules.
Predict the major product of acid catalysed dehydration of
(i) 1-nicthylcyclohcxanoland
(ii) butan-1-ol
Which of the following is an appropriate set of reactants for the preparation of l-methoxy-4- nitrobenzene and why?
Alcohols are comparatively more soluble in water than hydrocarbons of comparable molecular masses. Explain this fact.
You are given benzene, cone. H2S04and NaOH. Write the equations for the preparation of phenol using these reagents.
Illustrate with examples the limitations of Willamson synthesis for the preparation of certain types of ethers.
Which of the following are used to convert RCHO into RCH2OH?
(a) H2/Pd
(b) LiAlH4
(c) NaBH4
(d) Reaction with RMgX followed by hydrolysis
Phenol can be distinguished from ethanol by the reactions with ………….
(a) Br2/water (b) Na
(c) Neutral FeCl3 (d) All of these
Why is the reactivity of all three classes of alcohols with cone. HCl and ZnCl2 (Lucas reagent) different?
Explain why alcohols and ethers of comparable molecular mass have different boiling points.
Assertion (A): Like bromination of benzene, bromination of phenol is also carried out in the presence of Lewis acid.
Reason (R): Lewis acid polarizes the bromine molecule.
Show how will you synthesise
(i)1 -phenylethanol from a suitable alkene.
(ii)cyclohexylmethanol using an alkyl halide by an SN2 reaction.
(iii) Pentan-l-ol using a suitable alkyl halide?
Give equations of the following reactions:
(i)Oxidation of propan-l-ol with alkaline KMnO4 solution.
(ii)Bromine in CS2 with phenol.
(iii)Dilute HNO3 acid with phehoL
(iv)Treating phenol with chloroform in presence of aqueous NaOH.
Explain the following with an example
(i) Kolbe's reaction (ii) Reimer – Tiemann reaction –
(iii) Williamson ether synthesis (iv) Unsymmetrical ether
