Chemistry - Hydrocarbon Question with Solution | TestHub
Which of the following molecules of alkane will give only one monohalogenated product on reaction with halogen in presence of sunlight?
Options:(select one or more)
Answer:
Solution:
Question Explanation:
The question asks which alkane(s) produce only one monohalogenated product when reacted with a halogen in the presence of sunlight, meaning all hydrogen atoms in the molecule must be equivalent.
Concept: This question is based on the free radical halogenation reaction.
Solution: In free radical halogenation, substitution can occur at any hydrogen atom. If all hydrogens in an alkane are equivalent due to molecular symmetry, only one monohalogenated product is formed. Monohalogenation takes place only on saturated carbon atoms (sp³).
Option 1 (Ethane, CH₃–CH₃): All six hydrogen atoms are equivalent due to symmetry, so only one monohalogenated product is formed.
Option 2 (Propane, CH₃–CH₂–CH₃): It has two different types of hydrogens (primary and secondary), leading to more than one monohalogenated product.
Option 3 ((CH₃)₄C, neopentane): All twelve hydrogen atoms are equivalent because of its highly symmetrical structure, giving only one monohalogenated product.
Option 4: Diphenylmethane undergoes monohalogenation at the benzylic –CH₂– group due to resonance stabilization, whereas biphenyl lacks sp³ C–H bonds (all carbons are sp²), so monohalogenation does not occur.
Final Answer: Option (A), (C) & (D)