Hydrocarbons

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• Predict the correct intermediate and product in the following reaction :H_3C-C CH [HgSO_4]H_2O,\ H_2SO_4 intermediate (A) → product (B) Answer: 3. A : H₃C-C(OH)=CH₂ B : H₃C-C(=O)-CH₃ Key idea: hydration of an alkyne (Kucherov reaction) first gives an enol, which tautomerises... Alkynes: acidic character and addition reactions 1 answer
• Which one is the correct order of acidity ? Answer: 1. CHequiv CH > CH₃-Cequiv CH > CH₂=CH₂ > CH₃-CH₃ Key idea: acidity of a C-H bond increases with the s-character of carbon. Ethyne (... Alkynes: acidic character and addition reactions 1 answer
• With respect to the conformers of ethane, which of the following statements is true ? Answer: 3. Both bond angles and bond length remains same Key idea: conformers differ only by rotation about the C-C single bond. Staggered a... Alkanes: conformations, halogenation mechanism 1 answer
• The compound that will react most readily with gaseous bromine has the formula Answer: 4. C₃H₆ Key idea: gaseous Br₂ adds readily across a C=C bond; a more electron-rich alkene reacts faster. C₃H₆ (propene) beats C₂H₄ b... Alkenes: geometrical isomerism, electrophilic addition, Markovnikov and peroxide effect 1 answer
• Which of the following can be used as the halide component for Friedel-Crafts reaction? Answer: 3. Isopropyl chloride Key idea: Friedel-Crafts alkylation needs an alkyl halide that can give a carbocation. Aryl halides (bromobenz... Electrophilic substitution: halogenation, nitration, Friedel-Crafts 1 answer
• In the given reaction [benzene + cyclohexene, HF, 0 C -> P] the product P is Answer: 2. [structure shown in figure] Key idea: HF protonates the alkene to give a carbocation, which alkylates benzene (Friedel-Crafts alk... Electrophilic substitution: halogenation, nitration, Friedel-Crafts 1 answer
• The correct statement regarding the comparison of staggered and eclipsed conformations of ethane, is : Answer: 4. The staggered conformation of ethane is more stable than eclipsed conformation, because staggered conformation has no torsional s... Alkanes: conformations, halogenation mechanism 1 answer
• Consider the nitration of benzene using mixed conc. H_2SO_4 and HNO_3. If a large amount of KHSO_4 is added to the mixture, the rate of nitration will be : Answer: 2. slower Key idea: nitration needs the nitronium ion, formed by HNO₃+2H₂SO₄⇌ NO₂^++H₃O^++2HSO₄^- KHSO₄ adds a large amount of HSO₄^... Electrophilic substitution: halogenation, nitration, Friedel-Crafts 1 answer
• In the reaction H-C CH [(2)\ CH_3CH_2Br](1)\ NaNH_2/liq.NH_3 X [(2)\ CH_3CH_2Br](1)\ NaNH_2/liq.NH_3 Y, X and Y are : Answer: 1. X = 1-Butyne ; Y = 3-Hexyne Key idea: the terminal alkyne H is acidic, so NaNH₂ removes it and the acetylide ion attacks the alky... Alkynes: acidic character and addition reactions 1 answer