NEET Chemistry: Alkynes addition and polymerization Practice Questions
9 free multiple-choice questions on Alkynes addition and polymerization (Hydrocarbons) for NEET Chemistry, each with the correct answer and a step-by-step explanation. Attempt a question, then reveal the solution to check your reasoning.
Practice thousands more NEET questions in the app →Q1. The reaction of an alkyne with bromine (Br₂) follows which fundamental reaction type?
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Correct answer: C — Electrophilic addition
The addition of Br₂ across the triple bond (C≡C) is a classic example of an electrophilic addition reaction where the π-bond acts as an electron donor to the electrophile (Br₂).
Q2. In the hydration of an alkyne, the reaction typically results in the formation of which functional group?
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Correct answer: C — Alkanol
The hydration of an alkyne (reaction with water in the presence of acid catalyst) follows Markovnikov's rule, leading to the addition of water across the triple bond to form an enol intermediate, which ultimately yields an enol and subsequent keto-enol tautomerization, resulting in an alcohol (enol form).
Q3. Which statement correctly describes the type of bond present in an alkyne?
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Correct answer: A — A carbon-carbon triple bond
An alkyne is characterized by having one triple bond (C≡C), which consists of one sigma bond and two pi bonds. This triple bond signifies the presence of three π bonds, making it more reactive than an alkene.
Q4. The reaction of an alkyne with hydrogen fluoride (HF) typically leads to the formation of which type of organic compound?
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Correct answer: B — Haloalkene
The reaction of an alkyne with HF involves the addition of H and F across the triple bond, resulting in a haloalkene (a compound containing a halogen and a double bond).
Q5. Which type of addition reaction is typically observed when a symmetrical alkyne reacts with H₂O in the presence of an acid catalyst?
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Correct answer: D — Acid-catalyzed hydration leading to ketones
Alkyne hydration under acidic conditions follows Markovnikov's rule conceptually, involving protonation followed by nucleophilic attack by water, often leading to ketone formation (or enol intermediates).
Q6. Which of the following is the primary product formed when acetylene undergoes hydrogenation (addition of H₂)?
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Correct answer: C — Ethane
Acetylene (C₂H₂) reacts with hydrogen (H₂) in an addition reaction to form the corresponding alkane, ethene (C₂H₄), which is the simplest fully saturated product.
Q7. Which reaction intermediate is crucial in the electrophilic addition reaction of HBr to an alkyne?
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Correct answer: C — Alkene intermediate
The addition of HBr to an alkyne proceeds via the formation of a vinyl cation (an alkene intermediate), which is the key intermediate in this electrophilic addition process.
Q8. In the reaction of an alkyne with an unsaturated halide, the addition mechanism generally follows which principle?
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Correct answer: A — Electrophilic addition
Alkyne reactions with unsaturated systems often proceed via electrophilic addition mechanisms, where the π-bond acts as the electron acceptor.
Q9. Alkyne compounds are generally more reactive towards electrophilic addition reactions compared to alkenes due to:
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Correct answer: D — Presence of higher electron density in the π-bond
Alkynes possess two π-bonds (or one triple bond) and higher electron density in the π-system compared to alkenes, making them more susceptible to electrophilic attack.
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