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 the benzene ring.
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 the benzene ring.
Solution and Explanation
(i)In aryl alkyl ethers, due to the +R effect of the alkoxy group, the electron density in the benzene ring increases as shown in the following resonance structure. Thus, benzene is activated towards electrophilic substitution by the alkoxy group.
(ii)It can also be observed from the resonance structures that the electron density increases more at the ortho and para positions than at the meta position. As a result, the incoming substituents are directed to the ortho and para positions in the benzene ring.
Top CBSE CLASS XII Chemistry Questions
- ${AgNO_3}$ does not decompose where :
- Azeotropic mixture of water and HCl boils at 381.5 K. By distilling the mixture it is possible to obtain
Write IUPAC names of the following compounds and classify them into primary, secondary and tertiary amines.
(i) (CH3 )2CHNH2 (ii) CH3 (CH2 )2NH2 (iii) CH3NHCH(CH3 )2
(iv) (CH3 )3CNH2 (v) C6H5NHCH3 (vi) (CH3CH2 )2NCH3 (vii) m–BrC6H4NH2
Give one chemical test to distinguish between the following pairs of compounds.
(i) Methylamine and dimethylamine
(ii) Secondary and tertiary amines
(iii) Ethylamine and aniline
(iv) Aniline and benzylamine
(v) Aniline and N-methylanilineAccount for the following:
(i) pKb of aniline is more than that of methylamine.
(ii) Ethylamine is soluble in water whereas aniline is not.
(iii) Methylamine in water reacts with ferric chloride to precipitate hydrated ferric oxide.
(iv) Although amino group is o– and p– directing in aromatic electrophilic substitution reactions, aniline on nitration gives a substantial amount of m-nitroaniline.
(v) Aniline does not undergo Friedel-Crafts reaction.
(vi) Diazonium salts of aromatic amines are more stable than those of aliphatic amines. (vii) Gabriel phthalimide synthesis is preferred for synthesising primary amines.
Top CBSE CLASS XII Alcohols, Phenols And Ethers Questions
Write the IUPAC names of the following compounds:
Write structures of the compounds whose IUPAC names are as follows:
(i)2-Methylbutan-2-ol
(ii)1-Phenylpropan-2-ol
(iii)3,5-Dimethylhexane -1,3,5-triol
(iv)2,3-Diethylphenol
(v)1- Ethoxypropane
(vi)2-Ethoxy-3-methylpentane
(vii)Cyclohexylmethanol
(viii)3-Cyclohexylpentan-3-ol
(ix)Cyclopent-3-en-1-ol
(x)3-Chloromethylpentan-1-ol.
Draw the structures of all isomeric alcohols of molecular formula C5H12O and give their IUPAC names. (ii)Classify the isomers of alcohols in question 11.3(i)as primary, secondary and tertiary alcohols.
Explain why propanol has a higher boiling point than that of the hydrocarbon, butane.
Alcohols are comparatively more soluble in water than hydrocarbons of comparable molecular masses. Explain this fact.
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Concepts Used:
Classification - Alcohols, Phenols and Ethers
Alcohols, phenols, and ethers are organic compounds that can be classified based on their molecular structure and functional groups.
Classification of Alcohols:
- Alcohols can be classified as primary, secondary, or tertiary, based on the number of alkyl groups attached to the carbon atom bearing the hydroxyl group.
- Primary alcohols have one alkyl group attached to the carbon, secondary alcohols have two, and tertiary alcohols have three.
Classification of Phenols:
- Phenols can be classified based on the number and position of the hydroxyl groups attached to the aromatic ring.
- Monohydroxy phenols have one hydroxyl group, while dihydroxy phenols have two.
- Polyhydroxy phenols have more than two hydroxyl groups.
- Resorcinol and catechol are examples of dihydroxy phenols, while tannins are examples of polyhydroxy phenols.
Classification of Ethers:
- Ethers can be classified based on the nature of the alkyl or aryl groups attached to the oxygen atom.
- Simple ethers have two alkyl or aryl groups, while mixed ethers have one alkyl and one aryl group.
- Crown ethers are cyclic ethers that contain multiple ether groups and are used as complexing agents.
In summary, alcohols, phenols, and ethers can be classified based on their molecular structure and functional groups. Understanding the classification of these compounds is important for predicting their reactivity and understanding their potential applications in various fields, including chemistry, biology, and industry.