NEETChemistryHydrocarbons
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): 1-Chloro-1-phenylbutane undergoes dehydrohalogenation with alcoholic KOH at a faster rate than 3-chloro-1-phenylbutane. Reason (R): 3-Chloro-1-phenylbutane contains more number of -hydrogen atoms than 1-chloro-1-phenylbutane. In the light of the above statements, choose the most appropriate answer
Options
- ABoth Assertion (A) and Reason (R) are correct and Reason (R) is the correct explanation of Assertion (A)
- BBoth Assertion (A) and Reason (R) are correct but Reason (R) is not the correct explanation of Assertion (A)
- CAssertion (A) is correct but Reason (R) is incorrect
- DAssertion (A) is incorrect but Reason (R) is correct
Correct answer
B. Both Assertion (A) and Reason (R) are correct but Reason (R) is not the correct explanation of Assertion (A)
Step-by-step solution
Assertion (A) is correct: The rate of dehydrohalogenation (E2 reaction) depends on the thermodynamic stability of the product alkene. 1-Chloro-1-phenylbutane yields 1-phenylbut-1-ene, where the newly formed double bond is in conjugation with the benzene ring, providing high stability. 3-Chloro-1-phenylbutane yields 1-phenylbut-2-ene, where the double bond is isolated from the benzene ring. Thus, 1-chloro-1-phenylbutane reacts at a faster rate. Reason (R) is correct: 3-Chloro-1-phenylbutane ( C₆H₅-CH₂-CH₂-CH(Cl)-CH₃