Chapter 5

Terminal alkynes react with 9-borabicyclononane \((9-B B N)\) and then aq. alkaline hydrogen peroxide to give aldehydes because (a) Acid catalysed electrophilic addition of water follows Markovnikov's rule. (b) Acid catalysed electrophilic addition of water is anti-Markovnikov. (c) The radical addition is anti-Markovnikov. (d) Steric and electronic effects cause the boron to the terminal carbon.

In general, ketones are more reactive towards nucleophiles than esters because (a) The \(\alpha\) -protons of a ketone are more acidic than those of an ester. (b) The alkyl group in a ketone is an electron donating group due to hyperconjugation. (c) Alkoxy (RO-) groups are sterically larger than the related alkyl group. (d) Alkoxy (RO-) groups are stronger electron donating than alkyl groups via resonance.

Which of the following pairs will form the same product with phenyl hydrazine/H (a) \(\mathrm{CH}_{2} \mathrm{OH}-\mathrm{CO}-\mathrm{CH}_{3}\) and \(\mathrm{CHO}-\mathrm{CHOH}-\mathrm{CH}_{3}\) (b) Glucose and mannose (c) Glucose and fructose (d) Glucose and sucrose

The reaction of a Grignard reagent with a carboxylic acid does not give a secondary alcohol. This is because (a) Grignard reagents only react with the aldehydes, ketones, esters and epoxides. (b) The carboxylic acid is too sterically hindered to react. (c) The carboxylic acid is not electrophilic enough to react. (d) The Grignard reagent is a base, so an acid-base reaction occurs.

When 1-phenylpropyne reacts with \(\mathrm{H}_{2} \mathrm{O} / \mathrm{HgSO}_{4} / \mathrm{H}_{2} \mathrm{SO}_{4^{\prime}}\) the major product is propiophenone shown below. This is because (a) Alkyl groups are weak electron donors due to inductive effects and hyperconjugation. (b) Carbonyl groups are electron withdrawing groups due to resonance. (c) Phenyl groups can stabilise positive charge by resonance. (d) The reaction is controlled by steric factors.

When methyl benzoate is nitrated with \(\mathrm{HNO}_{3} / \mathrm{H}_{2} \mathrm{SO}_{4^{\prime}}\) the meta product is the major product. This is because (a) The \(-\mathrm{CO}_{2} \mathrm{CH}_{3}\) group is a meta director. (b) The \(-\mathrm{OCH}_{3}\) is a meta director. (c) The \(-\mathrm{NO}_{2}\) group is deactivating and a meta director. (d) Nitration usually occurs at the meta position.

\(\frac{\text { (i) } \mathrm{BH}_{3}}{\text { (ii) } \mathrm{NaOH}, \mathrm{H}_{2} \mathrm{O}_{2}}\) Identify reactant

Identify correct method of preparation of acetaldehyde from reaction of cyanide (a) \(\mathrm{Me}-\mathrm{C} \equiv \mathrm{N} \frac{\text { (i) DIBAL }}{\text { (ii) } \mathrm{H}_{3} \mathrm{O}^{+}}\) (b) \(\mathrm{Me}-\mathrm{C} \equiv \mathrm{N} \frac{\text { (i) } \mathrm{SnCl}_{2}+\mathrm{HCl}}{\text { (ii) } \mathrm{H}_{3} \mathrm{O}^{+}}\) (c) \(\mathrm{Me}-\mathrm{C} \equiv \mathrm{N} \frac{\text { (i) Conc. } \mathrm{H}_{2} \mathrm{SO}_{4}}{\text { (ii) dill. } \mathrm{NaOH}}\) (d) \(\mathrm{Me}-\mathrm{C} \equiv \mathrm{N} \frac{\text { (i) } \mathrm{Pd} / \mathrm{BaSo}_{4} / \mathrm{H}_{2}}{\text { (ii) } \mathrm{H}_{3} \mathrm{O}^{\oplus}}\)

Identify compounds that give iodoform test

Identify compounds which give PPT with Tollen’s reagent

The correct statement is (a) chloral forms stable hydrate (b) methanal is more reactive than ethanal towards nucleophilic addition (c) protonated carbonyl group is more reactive towards KCN (d) all of them

Which of the following gives positive Fehling's solution test (a) Ph-CHO (b) \(\mathrm{CH}_{3} \mathrm{CHO}\) (c) \(\mathrm{CCl}_{3} \mathrm{CHO}\) (d) All of them

The incorrect statement amongest the following is (a) The order of reduction reaction by LiAlH \(_{4}\) and that of the reduction by \(\mathrm{NaBH}_{4}\) each is two (b) Al-H bond is more ionic than B-H bond and hence LiAlH \(_{4}\) can produce larger concentration of hydride ion than that of \(\mathrm{NaBH}_{4}\) (c) LiAlH \(_{4}\) cannot reduce \(-\mathrm{NO}_{2}\) group (d) Inspite of very small rate constant of reduction of any carbonyl function other than aldehydes and ketones, the rate of reduction with LiAlH \(_{4}\) becomes appreciable due to large concentration of hydride ion

What will be the \(\mathrm{pH}\) of an acetate-acetic acid solution when the ratio of \(\left[\mathrm{CH}_{3} \mathrm{CO}_{2}\right] /$$\left[\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}\right]\) is \(10 ?\) (A table of \(\mathrm{pK}\) data is given below.) $$ \begin{array}{|lc|} \hline \text { Some useful } & \mathrm{pK}_{\mathrm{a}} \text { values } \\ \mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H} & 4.76 \\ \mathrm{H}_{3} \mathrm{PO}_{4} & 2.2 \\ \mathrm{H}_{2} \mathrm{PO}^{\rho} & 7.2 \\ \mathrm{HPO}_{4}^{2} & 12.4 \\ \hline \end{array} $$ (a) \(5.76\) (b) \(4.76\) (c) \(3.76\) (d) \(1.76\)

To convert \(\mathrm{CH}_{2}=\mathrm{CH}-\mathrm{CH}_{2} \mathrm{CHO}\) to \(\mathrm{CH}_{2}=\mathrm{CH}-\mathrm{CH}_{2} \mathrm{COOH}\), the best reagent will be (a) \(\mathrm{KMnO}_{4}\) (b) P.C.C. (c) \(\left[\mathrm{Ag}\left(\mathrm{NH}_{3}\right)_{2}\right] \mathrm{OH}\) (d) \(\mathrm{HIO}_{4}\)

\(\mathrm{CH}_{3} \mathrm{COCH}_{2} \mathrm{COOEt} \frac{\text { (i) } \mathrm{NaOEt}}{\text { (ii) } \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{Br}} \mathrm{A} \frac{\text { (i) dil. HCl }}{\text { (ii) Heat }}\) Products; Products are not in excess (a) \(\mathrm{CH}_{3} \mathrm{COCH}_{3}+\mathrm{CO}_{2}+\mathrm{EtOH}\) (b) \(2 \mathrm{~mol}\) of \(\mathrm{CH}_{3} \mathrm{COCH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3}+\mathrm{CO}_{2}\) (c) \(\mathrm{CH}_{3} \mathrm{COCH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3}+2 \mathrm{EtOH}\) (d) \(\mathrm{CH}_{3} \mathrm{COCH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3}+\mathrm{EtOH}+\mathrm{CO}_{2}\)

An organic compound \(\mathrm{A}\left(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}\right)\) neither decolourise bromine water nor changes the colour of acidic dichromate solution. A on heating with \(\mathrm{H}_{2} \mathrm{SO}_{4}\) produces an alkene which on oxidative ozonolysis gives \(\mathrm{B}\left(\mathrm{C}_{6} \mathrm{H}_{10} \mathrm{O}_{3}\right)\), which gives an yellow precipitate with \(\mathrm{NaOH} / \mathrm{I}_{2}\). The most probable structure of \(\mathrm{A}\) is

\(\mathrm{CH}_{3}-\mathrm{CH}-\mathrm{COOH}\) can be converted into \(\mathrm{CH}_{3}-\mathrm{CH}-\mathrm{CH}_{2} \mathrm{OH}\) by the use of (a) \(\mathrm{H}_{2} / \mathrm{Pd}\) (b) LiAIH \(_{4}\) (c) \(\mathrm{NaBH}_{4}\) (d) \(\mathrm{CH}_{3} \mathrm{MgBr}\)

Match the reactions in column I with their reagents in column II. Column I Column II (a) \(\mathrm{CH}_{3}-\mathrm{CH}_{2}=\mathrm{CH}-\mathrm{CHO} \rightarrow \mathrm{CH}_{3} \mathrm{CH}=\mathrm{CHCOOH}\) (p) LiAIH \(_{4}\) (b) \(\mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}-\mathrm{CHO} \rightarrow \mathrm{CH}_{3} \mathrm{CH}=\mathrm{CH}-\mathrm{CH}_{2} \mathrm{OH}\) (q) \(\mathrm{NaBH}_{4}\) (c) Ph-CH=CH-CHO \(\rightarrow\) Ph-CH \(_{2}-\mathrm{CH}_{2}-\mathrm{CHO}\) (r) \(\mathrm{Pd}-\mathrm{C} / \mathrm{H}_{2}\) (d) \(\mathrm{CH}_{2}=\mathrm{CH}-\mathrm{CH}_{2} \mathrm{CHO} \rightarrow \mathrm{CH}_{2}=\mathrm{CH}-\mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}\) (s) \(\mathrm{Ag}\left(\mathrm{NH}_{3}\right)_{2}^{\oplus}\)

Which of the following compound has the highest boiling point? (a) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{3}\) (b) \(\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}\) (c) \(\mathrm{CH}_{3} \mathrm{COCH}_{3}\) (d) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}\)

Match the columns. Column I (a) PCC (Pyridiniumchlorochromate) (b) NBS (N-Bromosuccinimide) (c) \(\mathrm{AlPO}_{4}\) (d) Li/Liquid \(\mathrm{NH}_{3}\) Column II (p) C1=CCc2ccccc2C1 BrC1C=CCc2ccccc21 (q) \(\mathrm{MeC} \equiv \mathrm{CMe} \longrightarrow\) (r) (s) \(\mathrm{CH}_{3} \mathrm{COOH} \longrightarrow \mathrm{CH}_{2}=\mathrm{C}=\mathrm{O}\)

What is the structure of 2,4 -hexanedione?

Match Column I with Column II. Column I (a) Aldol condensation (b) Cannizzaro reaction (c) Reformatsky reaction (d) Benzoin condensation Column II (p) Hydride ion transfer (q) Zinc enolate (r) \(\overline{\mathrm{C}} \mathrm{N}\) as catalyst (s) Enolate ion

If only one equivalent of \(\mathrm{NH}_{3}\) (one mole of \(\mathrm{NH}_{3}\) reacts with one mole of cyclohexyl chloride) was used, the reaction may not go to completion. Why? (a) \(\mathrm{NH}_{3}\) is not a strong nucleophile. Therefore, more \(\mathrm{NH}_{3}\) is needed. (b) \(\mathrm{Cl}\) is not a good leaving. Therefore, more \(\mathrm{NH}_{3}\) is needed. (c) Cyclohexyl group presents large steric hindrance. Therefore, more \(\mathrm{NH}_{3}\) is needed. (d) \(\mathrm{NH}_{3}\) will be protonated by \(\mathrm{HCl}\) as reaction proceeds. Therefore, the reaction will be incomplete.

(i) \(\mathrm{CH}_{3} \mathrm{CO}_{3} \mathrm{H}\) (ii) \(\mathrm{CH}_{3} \mathrm{MgBr}\) then \(\mathrm{H}_{3} \mathrm{O}^{+} \quad\) product is

How many products are possible when ethanal and phenyl ethanal (mixture) is treated with dil. \(\mathrm{NaOH}\) at about \(10^{\circ} \mathrm{C}\).

\(\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H} \frac{\text { (i) } \mathrm{SOCl}_{2}}{\text { (ii) 3-methylaniline }}\) (iii) LiAlH \(_{4}\), then \(\mathrm{H}_{3} \mathrm{O}^{+}\)