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NEET CHEMISTRYHydrocarbonsMedium

Question

The compound that will react most readily with gaseous bromine has the formula:

A

C3H6C_3H_6

B

C2H2C_2H_2

C

C4H10C_4H_{10}

D

C2H4C_2H_4

Step-by-Step Solution

  1. Identify the Compounds:
  • C4H10C_4H_{10}: Butane (Alkane, saturated).
  • C2H2C_2H_2: Ethyne (Alkyne, unsaturated, triple bond).
  • C2H4C_2H_4: Ethene (Alkene, unsaturated, double bond).
  • C3H6C_3H_6: Propene (Alkene, unsaturated, double bond).
  1. Reactivity Principle:
  • Alkanes react with halogens via free radical substitution, which typically requires UV light or high heat and is slower than addition reactions.
  • Unsaturated hydrocarbons (Alkenes/Alkynes) react with bromine via electrophilic addition. This reaction is generally fast and characteristic of unsaturation.
  • Alkenes vs. Alkynes: Alkenes are generally more reactive than alkynes towards electrophilic addition reactions [NCERT 11th, Ch 13, Sec 13.4.4]. This is because the π\pi-electron cloud in alkynes is more tightly held by the spsp-hybridised carbons compared to the sp2sp^2-hybridised carbons in alkenes.
  1. Compare Alkenes (Ethene vs. Propene):
  • Both Ethene (CH2=CH2CH_2=CH_2) and Propene (CH3−CH=CH2CH_3-CH=CH_2) undergo electrophilic addition.
  • Propene contains an electron-donating methyl group (−CH3-CH_3) which exerts a +I (Inductive) effect. This increases the electron density on the double bond, making it more nucleophilic and thus more reactive towards the electrophile (Br+Br^+) compared to ethene.
  • Therefore, Propene (C3H6C_3H_6) reacts most readily.

Exam Context & Concepts Covered

This question aligns with the NEET CHEMISTRY syllabus, specifically targeting concepts from Hydrocarbons. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

CHEMISTRYHydrocarbonscompoundreadilygaseousbromineformula

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