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Practice each question, then open the answer or worked solution.
Which of the following cannot be prepared by Sandmeyer’s reaction?
(A) Chlorobenzene
(B) Bromobenzene
(C) Iodobenzene
(D) Fluorobenzene
Ans: (C and D)
Chlorobenzene and bromobenzene are prepared by the sandmeyer’s reaction.
While fluorobenzene and iodobenzene are prepared by simple heating of diazonium salt with aqueous KI Solution.
Reduction of nitrobenzene by which of the following reagents give aniline?
(A) $\mathrm{Sn} / \mathrm{HCl}$
(B) $\mathrm{Fe} / \mathrm{HCl}$
(C) $\mathrm{H}_{2}-\mathrm{Pd}$
(D) $\mathrm{Sn} / \mathrm{NH}_{4} \mathrm{OH}$
Ans: (A, B & C)
Nitro compounds are reduced to amines by passing hydrogen gas through an acidic medium containing finely divided nickel, palladium, or platinum, as well as by reduction with metals in an acidic medium.
Which of the following species are involved in the carbylamine test?
(A) R-NC
(B) $\mathrm{CHCl}_{3}$
(C) $\mathrm{COCl}_{2}$
(D) $\mathrm{NaNO}_{2}+\mathrm{HCl}$
Ans: (A and B)
When aliphatic and aromatic primary amines are heated with chloroform and ethanolic potassium hydroxide, they form isocyanides or carbylamines, which have a foul odor. This reaction does not occur in secondary or tertiary amines.
The reagents that can be used to convert benzene diazonium chloride to benzene are
(A) $\mathrm{SnCl}_{2} / \mathrm{HCl}$
(B) $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}$
(C) $\mathrm{H}_{3} \mathrm{PO}_{2}$
(D) $\mathrm{LiAlH}_{4}$
Ans: (B and C)
Certain mild reducing agents like hypophosphorous acid (phosphinic acid) or ethanol reduce diazonium salts to arenes and themselves get oxidised to phosphorous acid and ethanol, respectively.
The Product of the following reaction is.
(A)
(B)
(C)
(D)
Ans: (A and B)
$\mathrm{NHCOCH}_{3}$ is an ortho- para directing group so ortho-para products are formed.
Arenium ion involved in the bromination of aniline is.
(A)
(B)
(C)
(D)
Ans: (A, B & C)
As the $\mathrm{NH}_{2}$ group is Ortho para directing group, so $\mathrm{Br}^{+}$attacks only at the o and p positions thus the products formed corresponds to the option A, B and C.
Which of the following amines can be prepared by Gabriel synthesis?
(A) Isobutyl amine
(B) 2-Phenylethylamine
(C) N-Methylbenzylamine
(D) Aniline
Ans: (A and B)
Gabriel synthesis is a method for producing primary amines. When phthalimide is treated with ethanolic potassium hydroxide, it forms a potassium salt of phthalimide, which when heated with an alkyl halide and then alkaline hydrolyzed yields the corresponding primary amine.
Which of the following reactions are correct?
(A)
(B)
(C)
(D)
Ans: (A and C)
(a) Primary alkyl halides react with ammonia to give primary amines. Correct reaction.
(B) Elimination process doesn’t occur with aq. KOH, hydrolysis process takes place. (B) is incorrect.
(c) Dehydrohalogenation I.e. elimination of HCl occurs which produces alkene as the product takes place with alc. KOH . (c) is correct.
(d) In this reaction, aliphatic primary amines, on treatment with nitrous acid, produce primary alcohol as a product.
Therefore (D) is incorrect.
Under which of the following reaction conditions, aniline gives p-nitro derivative as the major product?
(A) Acetyl chloride/pyridine followed by reaction with conc. $\mathrm{H}_{2} \mathrm{SO}_{4}+$ conc. $\mathrm{HNO}_{3}$
(B) Acetic anhydride/pyridine followed by conc. $\mathrm{H}_{2} \mathrm{SO}_{4}+$ conc. $\mathrm{HNO}_{3}$
(C) Dil. $\mathrm{HCl}$ followed by reaction with conc. $\mathrm{H}_{2} \mathrm{SO}_{4}+$ conc. $\mathrm{HNO}_{3}$
(D) Reaction with conc. $\mathrm{H}_{2} \mathrm{SO}_{4}+$ conc. $\mathrm{HNO}_{3}$
Ans: (A and B)
In addition to the nitro derivatives, direct nitration of aniline produces tarry oxidation products. Furthermore, aniline is protonated in the strongly acidic medium to form the anilinium ion, which is meta directing. As a result, in addition to the ortho and para derivatives, a significant amount of meta derivative is formed.
However, by protecting the $-\mathrm{NH}_{2}$ group with an acetylation reaction with acetic anhydride, the nitration reaction can be controlled and the p-nitro derivative obtained as the main product.
Which of the following reactions belong to electrophilic aromatic substitution?
(A) Bromination of acetanilide
(B) Coupling reaction of aryldiazonium salts
(C) Diazotization of aniline
(D) Acylation of aniline
Ans: (A and B)
Benzene diazonium chloride reacts with phenol to form p-hydroxy azobenzene by coupling the phenol molecule at its para position with the diazonium salt. This is referred to as a coupling reaction. This is an illustration of an electrophilic substitution reaction.
At room temperature, aniline reacts with bromine water to form a white precipitate of 2,4,6-tribromoaniline.
By acetylation with acetic anhydride to protect the $-\mathrm{NH}_{2}$ group, then carrying out the desired substitution followed by hydrolysis of the substituted amide to the substituted amine.
