Chapter 24

In \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}\), the bond that undergoes heterolytic cleavage most readily is (a) \(\mathrm{O}-\mathrm{H}\) (b) \(\mathrm{C}-\mathrm{H}\) (c) \(\mathrm{C}-\mathrm{O}\) (d) \(\mathrm{C}-\mathrm{C}\)

The four \(C-H\) bonds of methane are broken one at a time. The cleavage of which of the following bonds has the minimum bond dissociation energy? (a) \(\mathrm{C}-\mathrm{H}\) (b) \(\mathrm{CH}-\mathrm{H}\) (c) \(\mathrm{CH}_{2}-\mathrm{H}\) (d) \(\mathrm{CH}_{3}-\mathrm{H}\)

Which one of the following behaves both as a nucleophile and as an electrophile? (a) \(\mathrm{H}_{3} \mathrm{C}-\mathrm{NH}_{2}\) (b) \(\mathrm{H}_{3} \mathrm{C}-\mathrm{OH}\) (c) \(\mathrm{H}_{3} \mathrm{C}-\mathrm{C} \equiv \mathrm{N}\) (d) \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{ONa}\)

Pick the strongest nucleophile. (a) \(\mathrm{X}\) (b) \(\stackrel{\ominus}{\mathrm{N}} \mathrm{H}_{2}\) (c) \(\mathrm{H}-\mathrm{C} \equiv \mathrm{C}\) : (d) \(\mathrm{H}\)

Which of the following has the highest nucleophi-licity? (a) \(\mathrm{F}^{-}\) (b) \(\mathrm{OH}^{-}\) (c) \(\mathrm{CH}_{3}-\) (d) \(\mathrm{NH}_{2}^{-}\)

The decreasing order of nucleophilicity of HS', \(\mathrm{RCOO}^{-}, \mathrm{RCOOH}\) and \(\mathrm{ROH}\) is (a) \(\mathrm{RCOO}^{-}>\mathrm{HS}^{-}>\mathrm{RCOOH}>\mathrm{ROH}\) (b) \(\mathrm{HS}^{-}>\mathrm{RCOO}^{-}>\mathrm{RCOOH}>\mathrm{ROH}\) (c) \(\mathrm{HS}^{-}>\mathrm{RCOO}^{-}>\mathrm{ROH}>\mathrm{RCOOH}\) (d) \(\mathrm{RCOO}^{-}>\mathrm{HS}->\mathrm{ROH}>\mathrm{RCOOH}\)

Which of the following is strongest nucleophile? (a) \(\mathrm{Br}\) (b) : OH (c) \(: \overline{\mathrm{CN}}\) (d) \(\mathrm{C}_{2} \mathrm{H}_{3} \overline{\mathrm{O}}:\)

Among the following, the strongest nucleophiles is (a) \(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{SH}\) (b) \(\mathrm{CH}_{3} \mathrm{COO}^{-}\) (c) \(\mathrm{CH}_{3}^{2} \mathrm{NH}_{2}\) (d) \(\mathrm{NCCH}_{2}\)

Free radicals are involved in mechanism of (a) Kharash effect (b) Cracking of alkanes (c) Halogenation of alkanes (d) all of these

Abnormality high heat of formation and shortening of bond length are criteria of (a) hybridisation (b) resonance (c) electron delocalisation (d) ionization

Presence of \(\mathrm{a}-\mathrm{NO}_{2}\) group around a carbonium ion (a) reduces its stability (b) increases its stability (c) Makes no change in its stability (d) none of these

The kind of delocalization involving sigma bond orbitals is called (a) inductive effect (b) hyperconjugation effect (c) electromeric effect (d) mesomeric effect

Reaction not involving a carbanion is (a) Aldol condensation (b) Claisen condensation (c) Pinacol pinacolone rearrangement (d) Michael reaction

2-methyl but-2-ene is less reactive than but-2-ene. This is due to (a) resonance (b) hyperconjugation (c) electromeric effect (d) inductive effect

A solution of \((+2)-2\)-chloro-2-phenylethane in toluene racemises slowly in the presence of small amounts of \(\mathrm{SbCl}_{5}\), due to the formation of (a) carbanion (b) carbene (c) free radical (d) carbocation

The resonance structures (a) differ only in the arrangement of electrons (b) differ in number of paired and unpaired electrons (c) differ largely in their energy content (d) do not lie in the same plane

Resonance structures of a molecule does not have (a) identical arrangement of atoms (b) nearly the same energy content (c) same number of paired electrons (d) identical bonding

Which of the following statements is not correct (a) cyclopentadiene has an acidic hydrogen (b) squaric acid is highly acidic (c) aniline is more basic than ammonia (d) aniline is less basic than ammonia

The electromeric effect involves (a) a slight displacement of \(\sigma-\) electrons (b) a slight displacement of \(\pi\)-electrons (c) the complete transfer of \(\sigma\)-electrons (d) the complete transfer of \(\pi\)-electrons

Chlorine gas is exposed to ultraviolet light in a closed container. The reactive species expected to be formed are (a) \(\mathrm{Cl}\). (b) \(\mathrm{Cl}^{+}\) (c) \(\mathrm{Cl}^{-}\) (d) \(\mathrm{Cl}\)

Which of the following species on photolysis does give a carbene? (a) (b) \(\mathrm{CH}_{2}=\mathrm{C}=\mathrm{O}\) (c) \(\mathrm{CCl}_{4}\) (d) \(\mathrm{CHCl}_{3}\)

When a dextro rotatory alkyl halide is subjected to \(\mathrm{SN}^{1}\) reaction, the product obtained is (a) dextro rotatory (b) leavo rotatory (c) a racemic mixture (d) meso.

The reaction \(\mathrm{CH}_{3} \mathrm{Br}+\mathrm{OH} \longrightarrow \mathrm{CH}_{3} \mathrm{OH}+\) \(\mathrm{Br}\) - follows (a) SN \(^{1}\) mechanism (b) \(\mathrm{SN}^{2}\) mechanism (c) either of the above two (d) none of these

The compound that will react most readily with \(\mathrm{NaOH}\) to form methanol is (a) \(\left(\mathrm{CH}_{3}\right)_{4} \mathrm{~N}^{+} \mathrm{I}^{-}\) (b) \(\mathrm{CH}_{3} \mathrm{OCH}_{3}\) (c) \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~S}^{+} \mathrm{I}^{-}\) (d) \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{CCl}\)

In the presence of peroxide, hydrogen chloride and hydrogen iodide do not undergo anti-Markownikoff's addition to alkenes because (a) both are highly ionic (b) one is oxidizing and the other is reducing (c) one of the steps is endothermic in both the cases (d) all the steps are exothermic in both the cases

Which of the following is not polar? (a) tert-Butyl free radical (b) tert-Butyl carbocation (c) tert-Butyl carbanion (d) allyl cabanion

Resonance energy per benzene ring is maximum for (a) naphthalene (b) anthracene (c) benzene (d) phenanthrene

In buta- 1,3 -diene, the \(\mathrm{C}_{2}-\mathrm{C}_{3}\) bond length is (a) \(1.20 \AA\) (b) \(1.35 \AA\) (c) \(1.54 \AA\) (d) \(1.46 \AA\)

The most stable carbonium ion is (a) \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CH}^{+}\) (b) \(\mathrm{CH}_{3} \mathrm{CH}_{2}^{+}\) (c) \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{C}-\mathrm{CH}_{2}^{+}\) (d) \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{C}^{+}\)

Which of the following compounds possesses the \(\mathrm{C}-\mathrm{H}\) bond with the lowest bond dissociation energy? (a) n-pentane (b) toluene (c) benzene (d) 2,2 -dimethylpropane

Which of the following intermediate has the complete octet around the carbon atom? (a) free radical (b) carbene (c) carbanion (d) carbonium ion

Amongst the following, the compound that can most readily get sulphonated is (a) benzene (b) toluene (c) nitrobenzene (d) chlorobenzene

The major product obtained on treatment of \(\mathrm{CH}_{3}\) \(\mathrm{CH}_{2} \mathrm{CH}(\mathrm{F}) \mathrm{CH}_{3}\) with \(\mathrm{CH}_{3} \mathrm{O} / \mathrm{CH}_{3} \mathrm{OH}\) is (a) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}\left(\mathrm{OCH}_{3}\right) \mathrm{CH}_{3}\) (b) \(\mathrm{CH}_{3} \mathrm{CH}=\mathrm{CHCH}_{3}\) (c) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}=\mathrm{CH}_{2}\) (d) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OCH}_{3}\)

Pyridine is less basic than triethylamine because (a) pyridine has aromatic character (b) nitrogen in pyridine is sp \(^{2}\) hybridised (c) pyridine is a cyclic system (d) in pyridine, lone pair of nitrogen is delocalised.

Which of the following undergoes nucleophillic substitution exclusively by \(\mathrm{SN}^{1}\) mechanism? (a) ethyl chloride (b) isopropyl chloride (c) chlorobenzene (d) benzyl chloride

In the presence of peroxide, hydrogen chloride and hydrogen iodide do not undergo antiMarkownikoff's addition to alkenes because (a) both are highly ionic (b) one is oxidizing and the other is reducing (c) one of the steps is endothermic in both the cases (d) all the steps are exothermic in both the cases

The reaction intermediate in \(\mathrm{E}_{1 \mathrm{Cb}}\) is (a) Carbonium ion (b) carbon free radical (c) Carbanion (d) Carbene

Which one of the following pairs is correctly matched? (a) Saytzeff rule, least substituted alkene (b) Hoffmann rule, most substituted alkene (c) \(\mathrm{E}_{1}\) cb reaction, Hoffmann elimination (d) \(\mathrm{E}_{1}\) reaction, Hoffmann elimination

Anti-Markownikoff addition of HBr is not observed in (a) Propene (b) Butene 1 (c) Pent-2-ene (d) But-2-ene

Which among the given acids has lowest pKa value? (a) Chloroacetic acid (b) Bromoacetic acid (c) Nitroacetic acid (d) Cyanoacetic acid

Which one of the following is least acidic? (a) Phenol (b) 0 -fluorophenol (c) m-fluorophenol (d) p-fluorophenol

Out of these acids, the strongest acid is (a) o-nitrobenzoic acid (b) \(\mathrm{p}-\) nitrobenzoic acid (c) \(\mathrm{m}-\) nitrobenzoic acid (d) benzoic acid

Which one of the following is a sec-allylic carbocation? (a) \(\mathrm{CH}_{2}-\mathrm{CH}=\mathrm{CH}_{2}\) (b) \(\mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}-\mathrm{CH}_{2}\) (c) \(\mathrm{C}_{6} \mathrm{H}_{3}-\mathrm{CH}=\mathrm{CH}\) (d) \(\mathrm{CH}_{3}-\mathrm{CH}-\mathrm{CH}=\mathrm{CH}_{2}\)

When pent-2-ene is treated with HI in presence of a peroxy acids the major product obtained is (a) 2-Iodo-pentane (b) 3-Iodo-pentane (c) both of these (d) none of these

Which is correct about \(\mathrm{SN}^{1}\) reaction? (a) Here reaction intermediate is carbocation (b) It is favoured by polar solvents (c) It is favoured by stability of carbocation (d) all of these

Among the given compounds, the most susceptible to nucleophilic attack at the carbonyl group is (a) \(\mathrm{MeCOCl}\) (b) \(\mathrm{MeCHO}\) (c) \(\mathrm{MeCOOMe}\) (d) \(\mathrm{Me} \mathrm{CO}-\mathrm{O}-\mathrm{CO} \mathrm{Me}\)

The most stable free radical among the following is (1) \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CH}_{2}\) (2) \(\mathrm{CH}_{3}-\dot{\mathrm{C}} \mathrm{H}-\mathrm{CH}_{3}\) (3) \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CHCH}_{3}\) (4) \(\mathrm{CH}_{3} \mathrm{CH}_{2}\) (a) \(3>1>4>2\) (b) \(1>3>2>4\) (c) \(3>1>2>4\) (d) \(3>2>1>4\)

In which case, the intermediate involved is incorrect? (a) Pinacol - pinacolone rearrangement - carbocation (b) Hofmann's bromamide reaction \(-\) Nitrene (c) Aldol condensation - carbocation (d) Anti Markonikoff's addition of HBr to propene Free radical.

Arrange the following free radicals in order of stability: (1) Benzyl (2) Allyl (3) Methyl (4) Vinyl (a) \(4>3>2>1\) (b) \(1>2>3>4\) (c) \(1>3>4>2\) (d) \(4>3>1>2\)

The order of effectiveness of \(o-\) and \(p\) - directing groups is (a) \(\mathrm{OH}>\mathrm{NR}_{2}>\mathrm{NH} \cdot \mathrm{COCH}_{3}>\mathrm{Cl}>\mathrm{CH}_{3}\) (b) \(\mathrm{OH}>\mathrm{Cl}>\mathrm{CH}_{3}>\mathrm{NR}_{2}>\mathrm{NH} . \mathrm{COCH}_{3}\) (c) \(\mathrm{OH}>\mathrm{NH} \cdot \mathrm{COCH}_{3}>\mathrm{Cl}>\mathrm{NR}_{2}>\mathrm{CH}_{3}\) (d) \(\mathrm{OH}>\mathrm{CH}_{3}>\mathrm{NH} . \mathrm{COCH}_{3}>\mathrm{Cl}>\mathrm{NR}_{2}\)