Chapter 4

Which of the following shows greater reactivity towards \(\mathrm{S}_{\mathrm{N}} 2\) reaction than \(\mathrm{CH}_{3}-\mathrm{CH}_{2} \mathrm{Br}\) with sodium methoxide? (a) \(\mathrm{CH}_{3}-\mathrm{O}-\mathrm{CH}_{2} \mathrm{Br}\) (b) \(\mathrm{CH}_{3} \mathrm{Br}\) (c) \(\mathrm{CH}_{2}=\mathrm{CH}-\mathrm{Br}\) (d) \(\mathrm{CH}_{2}=\mathrm{CH}-\mathrm{CH}_{2} \mathrm{Br}\)

Which of the following statements are correct? (a) The \(\mathrm{S}_{\mathrm{N}} 1\) reaction obeys the Ist order kinetics (b) The solvolysis of ethylbromide in ethanoic solution is first order kinetics (c) R configuration of a compound may result in \(\mathrm{R}\) and \(\mathrm{S}\) configurations in an \(\mathrm{S}_{\mathrm{N}} 2\) reaction (d) 1-Bromo-1-phenylethane shows greater reactivity towards \(\mathrm{S}_{\mathrm{N}} 1\) and \(\mathrm{S}_{\mathrm{N}} 2\) reaction compared to isopropyl bromide

Correct statements is (a) Nucleophilicity of \(\mathrm{SH}\) is greater than \(\mathrm{OH}\) in dimethyl formamide (b) Hydrazine is a better nucleophile than \(\mathrm{NH}_{3}\) (c) Phenoxide ion is more basic than acetate ion (d) \(\mathrm{CH}_{3}\) is a better nucleophile than \(\mathrm{OH}\) in a non- polar solvent

Identify the compounds that will undergo substitution reaction faster than \(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{Br}\) with \(\mathrm{OH}^{-} / \mathrm{DMSO} .\)

Which statement is / are correct in the following statements? (a) Allyl bromide gives \(S_{N} 1\) reaction but vinyl chloride does not. (b) Primary alkyl halides can give \(\mathrm{S}_{\mathrm{N}} 1\) or \(\mathrm{S}_{\mathrm{N}} 2\) reaction. This depends on the structure of the substrate and nature of solvent. (c) \(\mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}-\mathrm{CH}_{2} \mathrm{Cl}\) reacts with \(\mathrm{KCN}\) to give mixture of two isomeric products. (d) \(\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{O}-\mathrm{CH}_{2} \mathrm{Br}\) is less reactive than tert. butyl bromide for \(\mathrm{S}_{\mathrm{N}} 1\) reaction.

Which will give white ppt. with \(\mathrm{AgNO}_{3}+\mathrm{NH}_{4} \mathrm{OH}\) ?

Which of the following gives turbidity immediately with Lucas-reagent (anhy. \(\left.\mathrm{ZnCl}_{2}+\mathrm{HCI}\right) ?\)

Which of the following order is correct for dipole moment? (a) \(\mathrm{CH}_{3} \mathrm{~F}>\mathrm{CH}_{3} \mathrm{Cl}>\mathrm{CH}_{3} \mathrm{Br}>\mathrm{CH}_{3} \mathrm{I}\) (b) \(\mathrm{CH}_{3} \mathrm{Cl}>\mathrm{CH}_{3} \mathrm{Br}>\mathrm{CH}_{3} \mathrm{~F}>\mathrm{CH}_{3} \mathrm{I}\) (c) \(\mathrm{CH}_{3} \mathrm{Br}>\mathrm{CH}_{3} \mathrm{Cl}>\mathrm{CH}_{3} \mathrm{I}>\mathrm{CH}_{3} \mathrm{~F}\) (d) \(\mathrm{CH}_{3} \mathrm{Cl}>\mathrm{CH}_{3} \mathrm{~F}>\mathrm{CH}_{3} \mathrm{Br}>\mathrm{CH}_{3} \mathrm{I}\)

1-Propanol can be prepared from propene by (a) \(\mathrm{HOH} / \mathrm{H}^{\oplus}\) (b) \(\mathrm{Hg}(\mathrm{OAc})_{2} / \mathrm{H}_{2} \mathrm{O}\) and \(\mathrm{NaBH}_{4}\) (c) \(\mathrm{B}_{2} \mathrm{H}_{6}-\mathrm{THF}\) and \(\mathrm{H}_{2} \mathrm{O}_{2} / \mathrm{OH}^{-}\) (d) All of these

The decreasing order of reactivity of methyl alcohol (i), isopropyl alcohol (ii), tertiary butyl alcohol (iii) and ethyl alcohol (iv) for esterification will be (a) \(\mathrm{i}>\mathrm{ii}>\mathrm{iii}>\mathrm{iv}\) (b) \(\mathrm{iv}>\mathrm{iii}>\mathrm{ii}>\mathrm{i}\) (c) \(i>\mathrm{iv}>\mathrm{ii}>\mathrm{iii}\) (d) \(\mathrm{i}>\mathrm{iv}>\mathrm{iii}>\mathrm{ii}\)

Identify correct nucleophilicity order (i) \(\mathrm{H}_{2} \mathrm{O}\) (ii) \(\mathrm{H}_{2} \mathrm{~S}\) (iii) \(\mathrm{H}_{2} \mathrm{Se}\) (a) \(\mathrm{i}>\mathrm{ii}>\mathrm{iii}\) (b) \(\mathrm{ii}>\mathrm{iii}>\mathrm{i}\) (c) \(\mathrm{i}>\mathrm{iii}>\mathrm{ii}\) (d) iii > ii \(>\) i

Identify correct nucleophilicity order (i) \(\mathrm{PH}_{3}\) (ii) \(\mathrm{NH}_{3}\) (iii) \(\mathrm{AsH}_{3}\) (a) \(\mathrm{i}>\mathrm{ii}>\mathrm{iii}\) (b) ii \(>\mathrm{iii}>\mathrm{i}\) (c) \(\mathrm{i}>\mathrm{iii}>\mathrm{ii}\) (d) \(\mathrm{iii}>\mathrm{i}>\mathrm{ii}\)

Compound [X], whose MF is \(\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{O}\) gives positive haloform test but gives no 2,4 -DNP derivative is

Williamson's synthesis is applied to prepare ether. Identify the ether from the following which cannot be prepared by it? (a) \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{C}-\mathrm{O}-\mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3}\) (b) \(\mathrm{PhOCH}_{3}\) (c) \(\mathrm{CH}_{2}=\mathrm{CH}-\mathrm{CH}_{2}-\mathrm{O}-\mathrm{CH}_{3}\) (d) \(\mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}-\mathrm{O}-\mathrm{CH}=\mathrm{CH}_{2}\)

Whatreagentcanbeused toconvert1-isopropylcyclopenteneto1-isopropyl- cyclopentanol? (a) \(\mathrm{HBr}\) (b) \(\mathrm{H}_{2} \mathrm{O}\), diluted \(\mathrm{H}_{2} \mathrm{SO}_{4}\) (c) \(\mathrm{H}_{2} / \mathrm{Pd}\) (d) \(\mathrm{H}_{2} \mathrm{O}\), neutral

\(\frac{\text { i. } \mathrm{HO}-\left(\mathrm{CH}_{2}\right)_{2}-\mathrm{OH}, \mathrm{H}^{+}}{\text {ii. Excess } \mathrm{MeMgBr}, \text { then } \mathrm{H}_{3} \mathrm{O}^{+}}\)

Which statements are true for \(\mathrm{S}_{\mathrm{N}} 2\) reaction of alkyl halides? (i) Both of the alkyl halide and nucleophile are involved in the transition state. (ii) Reaction proceeds with inversion of configuration at the substitution centre. (iii) Reaction proceeds with retention of configuration at the substitution centre. (iv) The order of reactivity is \(3^{\circ}>2^{\circ}>1^{\circ}\). (v) The nucleophile must have an unshared electron pair and bear a negative charge. (vi) The greater the nucleophilicity of the nucleophile, the greater the rate of reaction. (a) \(\mathrm{i}, \mathrm{ii}, \mathrm{v}, \mathrm{vi}\) (b) \(\mathrm{i}, \mathrm{iii}, \mathrm{v}, \mathrm{vi}\) (c) \(\mathrm{i}, \mathrm{i} \mathrm{i}, \mathrm{iv}, \mathrm{v}\) (d) \(\mathrm{i}, \mathrm{ii}, \mathrm{vi}\)

\(\frac{\mathrm{BrMg}-\left(\mathrm{CH}_{2}\right)_{4}-\mathrm{MgBr}}{\text { then } \mathrm{H}_{3} \mathrm{O}^{+}}\)

Suppose, a sample of an initially pure single enantiomer of tartaric acid \([\alpha]_{D}^{20}=+12.4^{\circ}\left(\mathrm{H}_{2} \mathrm{O}\right)\) underwent a chemical isomerization reaction which yielded 10 per cent of the other enantiomer and 20 per cent of the meso isomer, in addition to 70 per cent of the unchanged starting compound. What is the enantiomeric excess (ee.) of the major enantiomer relative to the minor enantiomer? (a) 70 per cent (b) 700 per cent (c) 75 per cent (d) \(87.5\) per cent

Suppose, a sample of an initially pure single enantiomer of tartaric acid \([\alpha]_{D}^{20}=+12.4^{\circ}\left(\mathrm{H}_{2} \mathrm{O}\right)\) underwent a chemical isomerization reaction which yielded 10 per cent of the other enantiomer and 20 per cent of the meso isomer, in addition to 70 per cent of the unchanged starting compound. If \(1.0 \mathrm{~g}\) of the total mixture (including the meso isomer) was dissolved in \(1 \mathrm{~mL}\) water and the rotation measured in a \(1 \mathrm{dm}\) cell, what value of \(\alpha_{\mathrm{D}}\) would one expect to observe? (a) \(+9.92\) (b) \(+7.44 \mathrm{C}\) (c) \(+12.4\) (d) \(+8.68\)

(a) When 1 -chloro-2-pentene is reacted with concentrated solution of sodium ethoxide, the rate of reaction depends on the concentration of both allylhalide and ethoxide ion. The product of reaction is exclusively $$ \mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}=\mathrm{CH}-\mathrm{CH}_{2} \mathrm{OC}_{2} \mathrm{H}_{5} $$ (b) In dilute solution of sodium ethoxide, the reaction rate is dependent only on the concentration of allylhalide. (c) In the presence of traces of water, 1 -chloro-2-pentene is slowly converted to a mixture of 1 -chloro-2-pentene and 3-chloro-1-pentene In case (a) the mechanism exclusively followed by reaction is (a) \(\mathrm{S}_{\mathrm{N}} 1\) (b) \(\mathrm{S}_{\mathrm{N}} 2\) (c) \(\mathrm{E}\) (d) \(\mathrm{E}_{2}\)

Suppose, a sample of an initially pure single enantiomer of tartaric acid \([\alpha]_{D}^{20}=+12.4^{\circ}\left(\mathrm{H}_{2} \mathrm{O}\right)\) underwent a chemical isomerization reaction which yielded 10 per cent of the other enantiomer and 20 per cent of the meso isomer, in addition to 70 per cent of the unchanged starting compound. From the total mixture, chromatographic separation on silica gel (a commonly used achiral solid adsorbent) might be expected to yield one of the three components in a pure state. Which one? (a) the minor enantiomer (b) the meso isomer (c) the major enantiomer (d) the \(1: 1\) racemic form of tartaric acid

(a) When 1 -chloro-2-pentene is reacted with concentrated solution of sodium ethoxide, the rate of reaction depends on the concentration of both allylhalide and ethoxide ion. The product of reaction is exclusively $$ \mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}=\mathrm{CH}-\mathrm{CH}_{2} \mathrm{OC}_{2} \mathrm{H}_{5} $$ (b) In dilute solution of sodium ethoxide, the reaction rate is dependent only on the concentration of allylhalide. (c) In the presence of traces of water, 1 -chloro-2-pentene is slowly converted to a mixture of 1 -chloro-2-pentene and 3-chloro-1-pentene In case (a) the mechanism exclusively followed by reaction is (a) \(\mathrm{S}_{\mathrm{N}} 1\) (b) \(\mathrm{S}_{\mathrm{N}} 2\) (c) \(\mathrm{E}_{1}\) (d) \(\mathrm{E}_{2}\)

Correct statement is (a) The solvolysis of 1 -chloro-2-pentene is greater than 1 -chloropentane in water (b) The solvolysis of 1-chloro-2-pentene is lesser than 1-chloropentane in water (c) The solvolysis of 1 -chloro-2-pentene and 1-chloropentane is equal in water (d) The solvolysis of 1-chloro-2-pentene and 1-chloropentane do not take place in water

The specific rotation of \((2 \mathrm{R}, 3 \mathrm{R})-(+)-\) tartaric acid is \(+12.4^{\circ}\left(\mathrm{c}=2, \mathrm{H}_{2} \mathrm{O}\right)\). The optical rotation of a solution made up from \(10 \mathrm{~g}\) of a mixture \(\mathrm{B}\) and \(\mathrm{C}\) in \(20 \mathrm{ml}\) of water was measured in a \(10 \mathrm{~cm}\) cell. The observed rotation was \(-3.1^{\circ} .\) What is the specific rotation of the mixture? (a) \(-3.1^{\circ}\) (b) \(-6.2^{\circ}\) (c) \(-0.62^{\circ}\) (d) \(+12.4^{\circ}\)

Identify correct reactivity order for \(\mathrm{E}_{2}\) reaction with alcoholic \(\mathrm{KOH}\)

Which statements are true for \(\mathrm{S}_{\mathrm{N}} 1\) reaction of alkyl halides? (i) Both of the alkyl halide and nucleophile are involved in the transition state. (ii) Reaction proceeds with inversion of configuration at the substitution centre. (iii) Reaction proceeds via the formation of carbocation intermediate. (iv) The order of reactivity is \(3^{\circ}>2^{\circ}>1^{\circ}\). (v) The nucleophile must have an unshared electron pair and bear a negative charge. (vi) Protic solvents favour \(\mathrm{S}_{\mathrm{N}} 1\) reaction. (a) iii, iv, vi (b) ii, \(\mathrm{iv}, \underline{\mathrm{v}}\) (c) \(\mathrm{i}, \mathrm{ii}, \mathrm{vi}\) (d) \(\mathrm{i}, \mathrm{ii}, \mathrm{v}, \mathrm{vi}\)

Calculate total number of \(\alpha\) -H present in alkene formed when 2, 3-dimethyl butanol react with concentrated \(\mathrm{H}_{2} \mathrm{SO}_{4} / \Delta\)