Alkynes: acidity, preparation and reactions

37 questions on Alkynes: acidity, preparation and reactions from the Hydrocarbons chapter: 8 NEET level, 16 JEE Main, 13 JEE Advanced. Each one opens with its answer and solution.

• Among the following, the hydrogen attached to carbon is most acidic in NEET level
• Which of the following gives a white precipitate with ammoniacal silver nitrate? NEET level
• But-2-yne is partially hydrogenated with H2 over Lindlar's catalyst. The product is NEET level
• Taking approximate pK_a values of propyne 25, water 15.7, ethanol 16 and ammonia 35, which base converts propyne almost completely into its anion? NEET level
• Propyne is treated with excess HBr (no peroxide). The final product is JEE Main level
• Propyne is heated with H2O in the presence of HgSO4 and dilute H2SO4. The major product is JEE Main level
• Which sequence is the best way to prepare pent-2-yne from propyne? JEE Main level
• A hydrocarbon of formula C4H6 gives a precipitate with ammoniacal silver nitrate, and on Hg(II)-catalysed hydration gives butan-2-one. The hydrocarbon is JEE Main level
• Electrolysis of a concentrated aqueous solution of potassium fumarate (potassium (E)-but-2-enedioate) gives, at the anode, besides CO2, the hydrocarbon JEE Main level
• Which of the following give a precipitate with ammoniacal silver nitrate (or ammoniacal cuprous chloride)? Select all that apply. JEE Main level
• Which of the following alkynes give exactly one ketone, and nothing else, on Hg(II)-catalysed hydration? Select all that apply. JEE Main level
• Calcium carbide containing 20 percent inert impurity by mass (10.0 g sample) reacts completely with water to form ethyne: CaC2 + 2H2O -> C2H2 + Ca(OH)2. If only... JEE Main level
• Which of the following statements about but-1-yne, HC#C-CH2CH3, are correct? Select all that apply. JEE Advanced level
• Propyne is treated successively with (i) NaNH2; (ii) CH3CH2CH2Br; (iii) H2, Lindlar's catalyst. The final product is JEE Advanced level
• A hydrocarbon X (C5H8) liberates hydrogen with sodium, gives a ketone on Hg(II)-catalysed hydration and gives 2-methylbutane on complete hydrogenation. X is JEE Advanced level
• Propyne is treated with NaNH2, then with ethanal (CH3CHO), then with aqueous acid to give P. P is hydrogenated with H2 over Lindlar's catalyst to give Q. Q is JEE Advanced level
• An alkyne A (C6H10) gives only propanoic acid on ozonolysis followed by aqueous work-up. A is reduced with Na in liquid ammonia to give B, and B is treated with... JEE Advanced level
• Which of the following statements are correct? Select all that apply. JEE Advanced level
• Propyne is hydrogenated with H2 over Lindlar's catalyst to give P. P is treated with HBr in the presence of an organic peroxide to give Q. Q reacts with sodium ... JEE Advanced level
• Which of the following gives a white precipitate with ammoniacal silver nitrate? NEET level
• Ethyne is hydrated with dilute H2SO4 and HgSO4 at 333 K. The main product is NEET level
• Which is the correct order of acidic strength of the C-H bond? NEET level
• But-2-yne is treated with H2 over Lindlar catalyst. The product is NEET level
• Pent-2-yne is reduced with sodium in liquid ammonia. The major product is JEE Main level
• Propyne is treated with NaNH2 in liquid ammonia and the product is then treated with bromoethane. The final organic product is JEE Main level
• Propyne is treated first with disiamylborane (a bulky borane) and then with H2O2 / aqueous NaOH. The main product is JEE Main level
• What is the minimum number of equivalents of NaNH2 needed in liquid ammonia to convert 1,2-dibromopropane completely into sodium propynide, CH3-C#C^-Na+? JEE Main level
• Hydration of which alkyne with dilute H2SO4 / HgSO4 gives a mixture of two isomeric ketones? JEE Main level
• Which of the following reagents react with pent-1-yne but NOT with pent-2-yne? JEE Main level
• Select the correct statement(s) about the acidity of alkynes. JEE Main level
• 80 g of commercial calcium carbide containing 20 percent (by mass) inert impurities is hydrolysed to ethyne with 85 percent yield. The ethyne is then passed thr... JEE Main level
• Ethyne is treated successively with (i) one equivalent of NaNH2, (ii) 1-bromopropane, (iii) NaNH2 (again), (iv) iodomethane, and (v) Na in liquid ammonia. The f... JEE Advanced level
• But-1-yne is converted by (i) NaNH2, (ii) bromoethane, (iii) H2 with Lindlar catalyst, (iv) Br2 in CCl4. The final product is JEE Advanced level
• Hex-3-yne is converted into hexane-3,4-diol by the sequences below. Which sequence(s) give the meso diol? JEE Advanced level
• A hydrocarbon X, C5H8, gives a white precipitate with ammoniacal AgNO3 and on catalytic hydrogenation with excess H2 gives 2-methylbutane. Hydration of X with H... JEE Advanced level
• Propyne is treated with NaNH2 in liquid ammonia, then ethanal is added, and the mixture is finally treated with aqueous acid. The product is JEE Advanced level
• Sodium ethynide, HC#C^-Na+, is treated with 2-bromo-2-methylpropane. The main outcome is JEE Advanced level