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51.	Assertion : Ethers behave as bases in the presence of mineral acids. Reason : Due to the presence of lone electrons pair on the oxygen atom.A. If both assertion and reason are correct and reason is correct explanation for assertion.B. If both assertion and reason are correct but reason is not correct for assertion.C. If assertion is correct but reason is incorrect.D. If both assertion and reason are incorrect.
Answer» Correct Answer - a Reason is the corect explanation for assertion .

52.	Why are secondary and tertiary alcohols not suitable for praparing ethers by dehydration with conc. `H_(2)SO_(4)` ?
Answer» Both secondary and tertiary alcohols react wih conc. `H_(2)SO_(2)` according to `S_(N^(1))` mechanism in which carbocation intermediates are formed. These intermediates preferbly lose a `H^(+)` ion from `beta` carbon leading to alkenes as a result of elimination rather than taking part in subsitutio reactions forming ethers.

53.	Oxygen atom in ether isA. very acitveB. replaceableC. acitveD. comparatively inert.
Answer» Correct Answer - D The C-O bond has very little polarity and oxygen is comparatively inert

54.	Magnesium reacts with alkyl halide best in the solvent :A. `C_(2)H_(5)OCH_(3)`B. `C_(6)H_(5)N(CH_(3))_(2)`C. `C_(2)H_(5)OC_(2)H_(5)`D. Equally in all.
Answer» Correct Answer - C In `C_(6)H_(5)OCH_(3)` the lone pair of electron on oxygen atom is partillary delocalised by the phenyl group. Same in the case with `C_(6)H_(5)N(CH_(3))_(2).` However , it is expected to be the best solvent out of the three.

55.	Assertion (A) Bond angle is ethers is slightly less than tetrahedral angle. Reason (R) There is a repulsion between the two bulky (-R) groups.A. Assertion and reason both are correct and reason is correct explanation of assertion.B. Assertion and reasons both are wrong statements.C. Assertion is correct statement but reasons is wrong statement.D. Assertion is wrong statement but reason is correct statement
Answer» Correct Answer - B Correct assertion : Bond angle in ethers is slightly less than the tetrahedral angle.

56.	Assertion: Phenol forms `2,4,6-`tribromophenol on treatement with `Br_(2)` water at `373K`. Reason: Phenol is `o-p`-directing group.A. If both assertion and reason are correct and reason is correct explanation for assertion.B. If both assertion and reason are correct but reason is not correct for assertion.C. If assertion is correct but reason is incorrect.D. If both assertion and reason are incorrect.
Answer» Correct Answer - b Correct explanation : In aqueous solution, `Br_(2)` gets polarised `(Br^(delta+)-Br^(delta-))` and readily releases `Br^(+)` (electrophile ) for the electrophilic substitution taking place at all three available ortho and para position.

57.	Assertion (A) Like bromination of benzene, bromination of phenol is also carried out in the presence of Lewis acid. Reason (R) Lewis acid polarises the bromine molecule.A. Assertion and reason both are correct and reason is correct explanation of assertion.B. Assertion and reasons both are wrong statements.C. Assertion is correct statement but reasons is wrong statement.D. Assertion is wrong statement but reason is correct statement
Answer» Correct Answer - D Correct assertion : Unlike bromobenzene bromination of phenol is not carried in the presence of a Lewis acid.

58.	Out of o-nitrophenol and p-nitrophenol, which is more volatile ? Explain?
Answer» o-nitrophenol `(b.p=100^(@)C)` is more volatile than p-nitrophenol `(b.p.=279^(@)C)` . In o-nitrophenol, there is intramolecular hydrogen bonding while intermolecular hydrogen bonding is present in p-nitrophenol molecules. Due to the presence of greater forces of intraction, the boiling point of p-nitrophenol is more.

59.	Arrange the given compouns in decreasing order of acidity and give a suitable explanation, Phenol, o-nitrophenol, o-cresol
Answer» The increasing order of acidic strength is : o-cresol `lt` phenol `lt` p-nitrophenol.

60.	Assertion (A) p-nitrophenol is more acidic than phenol. Reason (R) Nitro group helps in the stabilisation of the phenoxide ion by dispersal of negative charge due to resonance.A. Assertion and reason both are correct and reason is correct explanation of assertion.B. Assertion and reasons both are wrong statements.C. Assertion is correct statement but reasons is wrong statement.D. Assertion is wrong statement but reason is correct statement
Answer» Correct Answer - A Reason is the correct explanation of assertion

61.	The carbon-oxygen bond in phenol is slightly stronger than that in methanol. Why ?
Answer» In phenol, oxygen atom is linked to `sp^(2)` hybridised carbon wyhile it is linked ot `sp^(3)` hyridised carbon atom in methanol. This implies that C-O bond in phenol has partial double bond character on account of resonance and has greater bond dissociation energy. it is therfore. stonger.

62.	Explain why alcohols and ethers of comparable molecular mass have different boiling points?
Answer» Ethers have less boiling points than th isomeric alcohols. For example, n-butyl alcohol `(C_(4)H_(9)OH)` boils at 390 K while dethyl ether `(C_(2)H_(5)-O-C_(2)H_(5))` has boiling point of 308 K . In alcohols, the molecules are linked by intermolecular hydrogen bonding which is absent in isomeric ethers.Consequently , alcohols boil at higher temerature.

63.	Why are boiling points of ethrs lower than those of alcohols of comparable molecular masses ?
Answer» The boiling points of ehters are lower than those of alcohols of compareble of comparable molecular masses. For example, the boiling points of isomeric n-bytyl alcohol `(C_(4)H_(9)OH)` and diethyl ether `(C_(2)H_(5)-O-C_(2)H_(5))` are 390 K and 308 K respectively. The large difference in the boiling may be attributed to the following reasons : (i) O-H bond in alcohol is more polar C-O bond in ether. (ii) Intermolecular hydrogen bonding is present in the molecules of alcohol while it is almost absent in the ether molecules.

64.	Assertion: Alcohols have higher boiling points than ethers of comparable molecular masses. Reason: Alcohols and ethers are isomerism in nature.A. If both assertion and reason are correct and reason is correct explanation for assertion.B. If both assertion and reason are correct but reason is not correct for assertion.C. If assertion is correct but reason is incorrect.D. If both assertion and reason are incorrect.
Answer» Correct Answer - b Correct explanation : Intermolecular H-bonding is present in alcohols and not it ethers.

65.	Phenol is more reactive than benzene towards electrophilic substitution reaction. In case of Phenol, the intermediate carbocation is more resonance stabilised.A. If both assertion and reason are correct and reason is correct explanation for assertion.B. If both assertion and reason are correct but reason is not correct for assertion.C. If assertion is correct but reason is incorrect.D. If both assertion and reason are incorrect.
Answer» Correct Answer - b Correct explanation : In phenol , the -OH group is an activating group and actives the benzene ring towards electrophilic subsitution reactions.

66.	IUPAC name of the compound `CH_(3)-underset(CH_(3))underset(\|)(CH)-OCH_(3)` is............ .A. 1-Methoxy-1-methylethaneB. 2-Methoxy-2-methylethaneC. 2-MethoxypropaneD. Isopropylmethyl ether.
Answer» Correct Answer - C it is the correct answer.

67.	Write the strucrtures of the products. `(CH_(3))_(2)CH-OCH_(3)underset("heat")overset("HI(excess)")rarr`
Answer» In this case, the ethereal oxygen will b initially protonated by the `H^(+)`. This is followed by the attack of `I^(-)` on the protonated ether and this prefers ot combine with `CH_(3)` group rather than isopropyl group. The reaction proceeds as follows : `underset("Methyl isopropyl ether")((CH_(3))_(2)CH-OCH_(3))overset(H^(+))rarr(CH_(3))_(2)CH-underset("Protonated ether")underset(H)underset(\|)overset(o+)O-CH_(3)overset(I^(-))rarr(CH_(3))_(2)underset("alcohol")underset("Isopropyl")(CHOH)+underset("iodide")underset("Methyl")(CH_(3)I)overset(HI)rarrunderset("Isopropyl iodide")((CH_(3))_(2)CHI)+H_(2)O` Thus, `CH_(3)I and (CH_(3))_(2)CHI` are formed as the products.