Organic Reactions
| Description: GATE (Chemistry) | |
| Number of Questions: 15 | |
| Created by: Amish Majumdar | |
| Tags: GATE Addition Reactions Identification of Functional Groups by Chemical Tests |
Assertion: When acetylene reacts with methylmagnesium bromide, hydrogen is evolved. Reason: Grignard reagent is an organometallic compound of Mg+2.
Which of the following statements is/are false? A. Dehydration of 1-methylcyclohexanol with H2SO4 gives methylenecyclohexane. B. Lewisite is obtained by addition of AlCl3 to ethyne. C. Lindlar’s catalyst is palladium supported over calcium carbonate partially poisoned by addition of lead acetate.
Which of the following statements is/are true? A. Benzene reacts with isobutyl chloride in presence of anhydrous AlCl3 to give isobutylbenzene. B. Reduction of 2-butyne with NaNH2 in liquid NH3 gives cis-2-butene. C. Baeyer’s reagent can be used to distinguish cyclopropane from propene.
Assertion: Benzene reacts with Cl2 in presence of light to form BHC. Reason: BHC is also called gammexane or 666.
Assertion: Lewisite is less poisonous than mustard gas. Reason: Lewisite is obtained by the action of aluminium trichloride with acetylene in presence of anhydrous AsCl3.
Assertion: Benzene does not decolourise Br2 water. Reason: Benzene is stabilized by resonance due to delocalization of π-electrons.
Assertion: In Kolbe’s electrolytic method, if there are n-carbon atoms in the parent acid, the alkane produced will have (n-1) carbon atoms. Reason: Ethylene and acetylene cannot be prepared by this method.
Assertion: Treatment of 1, 3-dibromopropane with zinc produces cyclopropane. Reason: The reaction of alkyl halides with zinc dust is called frankland reaction.
Assertion: Propene is more reactive than ethene towards electrophilic addition reactions. Reason: Hyperconjugation effect of the CH3 group increases the electron density in the double bond.
Assertion: During cracking of alkanes, C-C rather than C-H bonds break. Reason: The bond dissociation energy of C-C bond is lower than that of C-H bond.
Assertion: Addition of HBr to HC ≡ C − CH2 − CH = CH2 gives HC ≡ C − CH2 − CHBr − CH3 and not H2C = CBr − CH2 − CHBr − CH3. Reason: A triple bond is less reactive than a double bond.
Assertion: Activation fuels contain a high percentage of highly branched chain alkanes. Reason: The octane number of branched chain alkanes is lower than that of straight chain alkanes.
Assertion: 1-Chlorobutane on heating with alcoholic KOH undergoes dehydrohalogenation to yield 1-butene as the major product. Reason: The reaction does not occur through carbocation intermediate but instead occurs by a concerted mechanism.
Assertion: 1-Butenol on dehydration with conc. H2SO4 mainly produces 1-butene. Reason: The initially formed primary carbocation rearranges to more stable secondary carbocation before losing a proton to form 2-butene as the major product.
Assertion: The octane number of branched chain hydrocarbon is higher than that of unbranched chain hydrocarbons. Reason: The branched chain hydrocarbons are more volatile than unbranched chain hydrocarbons.