Preparation of alcohols from alkenes involves the electrophilic attack on alkene carbon atom. Explain its mechanism.
The mechanism of acid catalysed addition of water (hydration) to alkenes involves the following three steps:
Step 1: Electrophilic attack by hydronium ion (H3O+) on alkene gives an intermediate, carbocation.
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.
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 why alcohols and ethers of comparable molecular mass have different boiling points.
Explain the following with an example
(i) Kolbe's reaction (ii) Reimer – Tiemann reaction –
(iii) Williamson ether synthesis (iv) Unsymmetrical ether
Phenol can be distinguished from ethanol by the reactions with ………….
(a) Br2/water (b) Na
(c) Neutral FeCl3 (d) All of these
Name the enzymes and write the reactions involved in the preparation of ethanol from sucrose by fermentation.
Assertion (A): Boiling points of alcohols and ethers are high.
Reason (R): They can form intermolecular hydrogen bonding.
Alcohols are comparatively more soluble in water than hydrocarbons of comparable molecular masses. Explain this fact.
Write the equation of the reaction of hydrogen iodide with (i)1-propoxypropane (ii)methoxybenzene, and (iii)benzyl ethyl ether
Arrange the following compounds in increasing order of acidity and give a suitable explanation:
Phenol, o-Nitrophenol, o-Cresol
Why is the C – O – H bond angle‘in alcohols slightly less than the tetrahedral angle whereas the C – O – C bond angle in ether is slightly greater?
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.
Write the equations involved in the following reactions:
(i) Reimer-Tiemann reaction
(ii) Kolbe's reaction
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
While separating a mixture of ortho and para nitrophenols by steam distillation, name the isomer which will be steam volatile. Give reason.
How is 1-propoxypropane synthesised from propan-l-ol? Write the mechanism of this reaction.
Mark the correct increasing order of reactivity of the following compounds with HBr/HCl.
Write the structures of the isomers of alcohols with molecular formula C4H10O. Which one of these isomers exhibits optical activity?
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.
Explain a process in which a biocatalyst is used in industrial preparation of a compound known to you.
(i) Draw the structures of all isomeric alcohols of molecular formula C5HI20 and give their IUPAC names.
(ii) Classify the isomers of alcohols in question (i)as primary, secondary and tertiary alcohols.
Explain how does the – OH group attached to a carbon of benzene ring activate it towards electrophilic substitution?
Name the reagents used in the following reactions:
(i)Oxidation of a primary alcohol to carboxylic acid.
(ii)Oxidation of a primary alcohol to aldehyde.
(iii)Brominationofphenolto2,4,6-tribromophenol
(iv)Benzyl alcohol to benzoic acid.
(v)Dehydration of propan-2-oI to propene.
(vi)Butan-2-one to butan-2-oL .
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.
When phenol is treated with bromine water, white precipitate is obtained. Give the structure and the name of the compound formed.
Alcohols react with active metals, e.g., Na, K, etc., to give corresponding alkoxides. Write down the decreasing order or reactivity of sodium metal towards primary, secondary and tertiary alcohols.
In Kolbe's reaction, instead of phenol, phenoxide ion is treated with carbon dioxide. Why?
