Chapter 3

Arrange the following alcohols in order of increasing ease of dehydration \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}\) \(\begin{array}{lll}\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CH}_{2} \mathrm{OH} & \mathrm{Cl}_{3} \mathrm{CCH}_{2} \mathrm{OH} & \mathrm{F}_{3} \mathrm{CCH}_{2} \mathrm{OH}\end{array}\) (a) \(\mathrm{ii}<\mathrm{i}<\mathrm{iv}<\mathrm{iii}\) (b) \(\mathrm{iv}<\mathrm{iii}<\mathrm{ii}<\mathrm{i}\) (c) \(\mathrm{iv}<\mathrm{iii}<\mathrm{i}<\mathrm{ii}\) (d) \(\mathrm{ii}<\mathrm{i}<\mathrm{iii}<\mathrm{iv}\)

Which of the following statements are true? (i) Structural isomers are compounds with the same molecular formula, but are different in the connectivity (order of attachment) of their atoms. (ii) Stereoisomers are compounds with the same molecular formula and same order of attachment of their atoms, but are different in the orientation of their atoms or groups in space. (iii) Enantiomers are stereoisomers whose molecules are mirror images of each other. (iv) Diastereomers are stereoisomers whose molecules are not mirror images of each other. (v) A molecule with two chiral centres designated as \((\mathrm{R}, \mathrm{R})\) will have an enantiomer with two chiral centres designated as \((\mathrm{S}, \mathrm{R})\). (vi) Cis-1,2-dichlorocyclopentane and trans-1,2-dichlorocyclopentane are enantiomer to each other. (a) \(\mathrm{i}, \mathrm{ii}, \mathrm{iv}, \mathrm{vi}\) (b) \(\mathrm{i}, \mathrm{ii}, \mathrm{iii}, \mathrm{iv}\) (c) \(\mathrm{i}, \mathrm{ii}, \mathrm{iii}, \mathrm{iv}, \mathrm{vi}\) (d) \(\mathrm{ii}, \mathrm{iii}, \mathrm{iv}, \mathrm{vi}\)

Aqueous solution of which of the following compounds is electrolysed, when acetylene gas is obtained? (a) Sodium fumerate (b) Sodium maleate (c) Sodium acetate (d) Calcium carbide

Which statements are true for \(\mathrm{S}_{\mathrm{N}} 2\) reaction of alkyl halides? ii 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 bears a negative charge. vi: The greater the nucleophilicity of the nucleophile, the greater the rate of reaction. (a) \(\mathrm{i}, \mathrm{ii}, \mathrm{iv}, \mathrm{v}\) (b) \(\mathrm{i}, \mathrm{ii}, \mathrm{v}, \mathrm{vi}\) (c) \(\mathrm{i}, \mathrm{iii}, \mathrm{v}, \mathrm{vi}\) (d) \(\mathrm{i}, \mathrm{ii}, \mathrm{vi}\)

Identify major product of reaction of (E)-3-methyl-2-pentene with \(\mathrm{D}_{2} / \mathrm{Ni}\)

Test for identification of But-2-ene and benzene is (a) Tollen's Reagent test (b) \(1 \%\) Alkaline \(\mathrm{KMnO}_{4}\) (c) Iodoform test (d) \(\mathrm{Br}_{2}+\mathrm{H}_{2} \mathrm{O}\) test

The reaction of 1,3 -butadiene with HBr is shown below. At \(40^{\circ} \mathrm{C}\) the major product is the 1 . 4-addition product; however, at \(-80^{\circ} \mathrm{C}\) the major product is the 1,2 -addition product. Why are two products formed? (a) The carbocation intermediate allows delocalisation of the second double bond. (b) There are two double bonds present. (c) The fact that the carbocation is planar allows attack from both sides of the plane. (d) There are 2 moles of \(\mathrm{HBr}\).

The reaction of 1,3 -butadiene with HBr is shown below. At \(40^{\circ} \mathrm{C}\) the major product is the 1 . 4-addition product; however, at \(-80^{\circ} \mathrm{C}\) the major product is the 1,2 -addition product. Which of the two products has a lower activation energy for formation? (a) 1,4 -addition product. (b) 1,2 -addition product. (c) The products have same activation energy. (d) The relative activation energy cannot be determined.

Karl Ziegler reported that alkenes react with N-bromosuccinimide (NBS) in the presence of light to give products resulting from substitution of hydrogen by bromine at the allylic position, i.e., the position next to the double bond. Let us consider the halogenation of cyclohexene Energy level diagram for allylic, vinylic and alkylic free radicals is given . In the treatment of cyclohexene with NBS, which of the following products will be formed?

Hydroboration is a reaction in which boron hydride acts as an electrophile. \(\mathrm{R}_{2} \mathrm{BH}\) adds to a carbon-carbon double bond which acts as a nucleophile The organoborane compound then is oxidised by treatment with hydrogen peroxide in aqueous medium to form alcohol. The OH-group enters the carbon atom from the same side where the boron atom was present. Hence this reaction is highly regioselective and the boron atom attaches to that carbon atom which is less stearically hindered. \(\mathrm{R}-\mathrm{CH}=\mathrm{CH}_{2} \stackrel{\mathrm{NOC}}{\longrightarrow} \mathrm{X} ;\) Hence, \(\mathrm{X}\) is

Compound having atleast one \(\pi\) -bond gives addition reaction. Alkene behaves as a nucleophile and hence it gives an electrophilic addition reaction. Electrophilic addition reaction in most of the cases takes place by formation of carbocation as reaction intermediate. Which one of the following is NOT correct for electrophilic addition of alkenes? (a) In the first step, alkene reacts with electrophile to form a \(\pi\) -complex. (b) \(\pi\) -complex converts into carbocation and the step is a rate- determining step. (c) Product formation takes place by formation of most stable reaction intermediate. (d) Rearrange product is not formed in addition reaction with HBr.

Compound having atleast one \(\pi\) -bond gives addition reaction. Alkene behaves as a nucleophile and hence it gives an electrophilic addition reaction. Electrophilic addition reaction in most of the cases takes place by formation of carbocation as reaction intermediate. Consider the following statements (i) Unsymmetrical alkene gives addition product according to Markovnikov's rule. (ii) Addition reaction is a regioselective reaction. (iii) Rearranged product is formed in addition reaction. (iv) Alkene gives mixed addition product with \(\mathrm{NaCl} / \mathrm{HOH} / \mathrm{H}^{+}\). Which one is/are correct? (a) i, ii, iii and iv (b) ii, iii and iv (c) i, iii and iv (d) i, ii and iv

The structure of alkyne is linear. Terminal alkyne is acidic in character. It reacts with base to give acid-base reaction. Alkyne is nucleophile and gives electrophilic as well as nucleophilic addition reaction. Which one of the following compounds forms carbonyl production reaction with \(1 \%\) \(\mathrm{HgSO}_{4}+\operatorname{dil.} \mathrm{H}_{2} \mathrm{SO}_{4} ?\) (a) \(\mathrm{CH}_{2}=\mathrm{CH}_{2}\) (b) \(\mathrm{CH}_{3}-\mathrm{C} \equiv \mathrm{C}-\mathrm{C}_{6} \mathrm{H}_{5}\) (c) \(\mathrm{CH}_{3}-\mathrm{C} \equiv \mathrm{C}-\mathrm{CH}_{3}\) (d) Cyclohexene

The structure of alkyne is linear. Terminal alkyne is acidic in character. It reacts with base to give acid-base reaction. Alkyne is nucleophile and gives electrophilic as well as nucleophilic addition reaction. Terminal alkyne will react with which of the following? (a) Tollen's reagent (b) \(\mathrm{Sia}_{2} \mathrm{BH} / \mathrm{THE}\) (c) \(\mathrm{H}_{2} \mathrm{O} / \mathrm{HgSO}_{4} / \mathrm{H}_{2} \mathrm{SO}_{4}(\mathrm{~d})\) All of these

The structure of alkyne is linear. Terminal alkyne is acidic in character. It reacts with base to give acid-base reaction. Alkyne is nucleophile and gives electrophilic as well as nucleophilic addition reaction. Which one of the following will react with \(\mathrm{NaNH}_{2}\) ? (a) \(\mathrm{CH}_{3}-\mathrm{CH}_{3}\) (b) \(\mathrm{CH}_{2}=\mathrm{CH}_{2}\) (c) \(\mathrm{CH}_{3}-\mathrm{C} \equiv \mathrm{CH}\) (d) \(\mathrm{CH}_{3}-\mathrm{C} \equiv \mathrm{C}-\mathrm{CH}_{3}\)

An organic compound \(\mathrm{A}\left(\mathrm{C}_{5} \mathrm{H}_{11} \mathrm{Cl}\right)\) is optically active and on treatment with ethanolic KOH solution yields \(\mathrm{B}\left(\mathrm{C}_{5} \mathrm{H}_{10}\right)\) as a major product, which does not show stereoisomerism. Also A on treatment with \(\left(\mathrm{CH}_{3}\right)_{2}\) CuLi yields \(\mathrm{C}\left(\mathrm{C}_{6} \mathrm{H}_{14}\right)\), which is optically inactive. Deduce structures of \(\mathrm{A}\) to \(\mathrm{C}\). Identify structure of "A" compound

An organic compound \(\mathrm{A}\left(\mathrm{C}_{5} \mathrm{H}_{11} \mathrm{Cl}\right)\) is optically active and on treatment with ethanolic KOH solution yields \(\mathrm{B}\left(\mathrm{C}_{5} \mathrm{H}_{10}\right)\) as a major product, which does not show stereoisomerism. Also A on treatment with \(\left(\mathrm{CH}_{3}\right)_{2}\) CuLi yields \(\mathrm{C}\left(\mathrm{C}_{6} \mathrm{H}_{14}\right)\), which is optically inactive. Deduce structures of \(\mathrm{A}\) to \(\mathrm{C}\). Identify structure of "B" compound

An organic compound \(\mathrm{A}\left(\mathrm{C}_{5} \mathrm{H}_{11} \mathrm{Cl}\right)\) is optically active and on treatment with ethanolic KOH solution yields \(\mathrm{B}\left(\mathrm{C}_{5} \mathrm{H}_{10}\right)\) as a major product, which does not show stereoisomerism. Also A on treatment with \(\left(\mathrm{CH}_{3}\right)_{2}\) CuLi yields \(\mathrm{C}\left(\mathrm{C}_{6} \mathrm{H}_{14}\right)\), which is optically inactive. Deduce structures of \(\mathrm{A}\) to \(\mathrm{C}\). Identify structure of " \({ }^{\prime \prime}\) " compound

Column I (a) \(\mathrm{R}-\mathrm{CH}_{2}-\mathrm{X}\) (b) (c) \(\mathrm{CH}_{2}=\mathrm{CH}-\mathrm{X}\) (d) \(\mathrm{R}-\mathrm{COO}^{-} \mathrm{Na}^{\oplus}\) Column II (p) Corey-house reaction (q) Kolbe electrolysis (r) Wurtz reaction (s) Frankland reaction

Number of hydrocarbons formed when \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{Br}\) and \(\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{Br}\) are treated with \(\mathrm{Na}\) in the presence of dry ether is:

Number of products obtained on ozonolysis of 1,2 -dimethyl benzene is