Nitration is an example of aromatic electrophilic substitution and its rate depends upon the group already present in the benzene ring. Out of benzene and phenol, which one is more easily nitrated and why?
Phenol is more easily nitrated than benzene because the —OH group in phenol increases the electron density at o- and p-positions in benzene ring by +R effect. Nitration which is an electrophilic substitution reaction takes place more readily where the electron density is more.
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.
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.
Assertion (A): Ethanol is a weaker acid than phenol.
Reason (R): Sodium ethoxide may be prepared by the reaction of ethanol with aqueous NaOH.
Explain the following with an example
(i) Kolbe's reaction (ii) Reimer – Tiemann reaction –
(iii) Williamson ether synthesis (iv) Unsymmetrical ether
How is 1-propoxypropane synthesised from propan-l-ol? Write the mechanism of this reaction.
Explain why alcohols and ethers of comparable molecular mass have different boiling points.
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.
Name the enzymes and write the reactions involved in the preparation of ethanol from sucrose by fermentation.
Assertion (A): Bond angle in ethers is slightly less than the tetrahedral angle. Reason (R): There is a repulsion between the two bulky (-R) groups.
Predict the major product of acid catalysed dehydration of
(i) 1-nicthylcyclohcxanoland
(ii) butan-1-ol
Write structures of the compounds whose IUPAC names are as follows:
(i)2-Methylbutan-2-ol
(ii)l-Phcnylpropan-2-ol
(iii)3,5-DimethyIhexane-l,3,5-triol
(iv)2,3-Dicthylphenol
(v)1-Ethoxypropane
(vi)2-Ethoxy-3-methylpentane
(vii) Cyclohexylmethanol
(viii) 3-Cyclohexylpcntan-3-ol
(ix)Cyclopcnt-3-en-l-ol
(x)4-ChIoro-3-ethylbutan-l-ol
Preparation of ethers by acid dehydration of secondary or tertiary alcohols is not a suitable method.Give reason.
Write the structures of the isomers of alcohols with molecular formula C4H10O. Which one of these isomers exhibits optical activity?
Preparation of alcohols from alkenes involves the electrophilic attack on alkene carbon atom. Explain its mechanism.
Assertion (A): IUPAC name of the compound
Reason (R): In IUPAC nomenclature, ether is regarded as hydrocarbon derivative in which a hydrogen atom is replaced by -OR or -OAr group [where R = alkyl group and Ar = aryl group]
Assertion (A): Boiling points of alcohols and ethers are high.
Reason (R): They can form intermolecular hydrogen bonding.
Which of the following is an appropriate set of reactants for the preparation of l-methoxy-4- nitrobenzene and why?
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
Phenol can be distinguished from ethanol by the reactions with ………….
(a) Br2/water (b) Na
(c) Neutral FeCl3 (d) All of these
Explain why is OH group in phenols more strongly held as compared to OH group in alcohols.
Why is the reactivity of all three classes of alcohols with cone. HCl and ZnCl2 (Lucas reagent) different?
In Kolbe's reaction, instead of phenol, phenoxide ion is treated with carbon dioxide. Why?
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.
Assertion (A): p-Nitrophcnol is more acidic than phenol.
Reason (R): Nitro group helps in the stabilization of the phenoxide ion by dispersal of negative charge due to resonance.
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 reactions of Williamson synthesis of 2-ethoxy-3-methylpentane starting from ethanol and 3-methylpentan-2-ol.
Alcohols are comparatively more soluble in water than hydrocarbons of comparable molecular masses. Explain this fact.
