Chapter 13

Draw the stereochemical structures of the products in the following reactions: [1994-4 Marks] \(\mathrm{R}-\mathrm{C} \equiv \mathrm{C}-\mathrm{R} \frac{\mathrm{H}_{2}}{\text { Lindlar catalyst }}\)

How would you distinguish between 2 -butyne and 1-butyne.

Which of the following compounds will exhibit geometrical isomerism ? [2000S] (a) 1-Phenyl-2-butene (b) 3-Phenyl-1-butene (c) 2-Phenyl-1-butene (d) 1,1-Diphenyl-1-propene

A certain hydrocarbon \(A\) was found to contain \(85.7\) percent carbon and \(14.3\) per cent hydrogen. This compound consumes 1 molar equivalent of hydrogen to give a saturated hydrocarbon \(B .1 .00 \mathrm{~g}\) of hydrocarbon \(A\) just decolourized \(38.05 \mathrm{~g}\) of a 5 per cent solution (by weight) of \(\mathrm{Br}_{2}\) in \(\mathrm{CCl}_{4}\). Compound \(A\), on oxidation with concentrated \(\mathrm{KMnO}_{4}\), gave compound \(C\) (molecular formula \(\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{O}\) ) and acetic acid. Compound \(C\) could easily be prepared by the action of acidic aqueous mercuric sulphate on 2 - butyne. Determine the molecular formula of \(A\) and deduce the structure of \(A, B\) and \(C\).

anti-Markovnikoff addition of HBr is not observed in : [1985-1 Mark] (a) propene (b) 1-butene (c) but-2-ene (d) pent-2-ene

Baeyer's reagent is : (a) alkaline permanganate solution (b) acidified permanganate solution (c) neutral permanganate solution (d) aqueous bromine solution

Which of the following compounds will exhibit cis-trans (geometrical) isomerism? [1983] (a) 2-butene (b) 2 -butyne (c) 2-butanol (d) butanal

Write the structural formula of the major product in each of the following cases: (i) the compound obtained by the hydration of ethyne is treated with dilute alkali

Which of the following decolourises alkaline \(\mathrm{KMnO}_{4}\) solution (a) \(\mathrm{C}_{3} \mathrm{H}_{8}\) (b) \(\mathrm{C}_{2} \mathrm{H}_{4}\) (c) \(\mathrm{CH}_{4}\) (d) \(\mathrm{CCl}_{4}\)

1 , 3-Butadiene with bromine in molar ratio of \(1: 1\) generates predominantly ...............

Which one of the following has the smallest heat of hydrogenation per mole? [1993 - 1 Mark] (a) 1-butene (b) trans-2-butene (c) cis -2-butene (d) 1,3 -butadiene

Assertion : Addition of \(\mathrm{Br}_{2}\) to 1 -butene gives two optical isomers. Reason : The product contains one asymmetric carbon.

An alkene (A) \(\mathrm{C}_{16} \mathrm{H}_{16}\) on ozonolysis gives only one product (B) \(\mathrm{C}_{8} \mathrm{H}_{8} \mathrm{O}\). Compund (B) on reaction with \(\mathrm{NaOH} / \mathrm{I}_{2}\) yields sodium benzoate. Compound (B) reacts with \(\mathrm{KOH} / \mathrm{NH}_{2} \mathrm{NH}_{2}\) yielding a hydrocarbon (C) \(\mathrm{C}_{8} \mathrm{H}_{10}\). Write the structures of compounds (B) and (C). Based on this information, two isomeric structures can be proposed for alkene (A). Write their structures and identify the isomer which on catalytic hydrogenation \(\left(\mathrm{H}_{2} / \mathrm{Pd}-\mathrm{C}\right)\) gives a racemic mixture.

Complete the following reactions with appropriate structures of products/reagents. \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CH}=\mathrm{CH}_{2} \stackrel{\mathrm{Br}_{2}}{\longrightarrow}[\mathrm{A}]\) $$ \frac{\text { (i) } \mathrm{NaNH}_{2}(3.0 \text { equiv.) }}{\text { (ii) } \mathrm{CH}_{3} \mathrm{I}}[\mathrm{B}] $$

The hydrocarbon \(A\), adds one mole of hydrogen in the presence of a platinum catalyst to form \(n\)-hexane. When \(A\) is oxidized vigorously with \(\mathrm{KMnO}_{4}\), a single carboxylic acid, containing three carbon atoms, is isolated. Give the structure of \(A\) and explain.

Give the structures of the major organic products from3-ethyl-2pentene under each of the following reaction conditions. [1996 - 3 Marks] (a) HBr in the presence of peroxide (b) \(\mathrm{Br}_{2} / \mathrm{H}_{2} \mathrm{O}\) (c) \(\mathrm{Hg}(\mathrm{OAc})_{2} / \mathrm{H}_{2} \mathrm{O} ; \mathrm{NaBH}_{4}\)

An organic compound \(\mathbf{E}\left(\mathrm{C}_{5} \mathrm{H}_{8}\right)\) on hydrogenation gives compound \(\mathbf{F}\left(\mathrm{C}_{5} \mathrm{H}_{12}\right)\). Compound \(\mathbf{E}\) on ozonolysis gives formaldehyde and 2 ketopropanal. Deduce the structure of compound \(\mathbf{E}\).

1,4 -Pentadiene reacts with excess of \(\mathrm{HCl}\) in the presence of benzoyl peroxide to give compound \(X\) which upon reaction with excess of \(\mathrm{Mg}\) in dry ether forms \(Y\). Compound \(Y\) on treatment with ethyl acetate followed by dilute acid yields \(Z\). Identify the structures of compounds \(X, Y\) and \(Z\)

When gas \(A\) is passed through dry \(\mathrm{KOH}\) at low temperature, a deep red coloured compound \(B\) and a gas \(C\) are obtained. The gas \(A\), on reaction with but-2-ene, followed by treatment with \(\mathrm{Zn} / \mathrm{H}_{2} \mathrm{O}\) yields acetaldehyde. Identify A. B and C. [1994 - 3 Marksl

Identify, \(\mathbf{D}\left(\mathrm{C}_{6} \mathrm{H}_{12}\right)\), an optically active hydrocarbon which on catalytic hydrogenation gives an optically inactive compound, \(\mathrm{C}_{6} \mathrm{H}_{14}\)

Identify, \(\mathbf{B}\left(\mathrm{C}_{4} \mathrm{H}_{8}\right)\) which adds on HBr in the presence and in the absence of peroxide to give the same product, \(\mathrm{C}_{4} \mathrm{H}_{9} \mathrm{Br}\).

Give reasons for the following : (i) Propene reacts with HBr to give isopropyl bromide but does not give \(n\) propyl bromide. [1983-1 Mark] (ii) The central carbon-carbon bond in 1,3 - butadiene is shorter than that in \(n\)-butane.