Textbook Question
Predict the products of reaction of pent-1-yne with the following reagents.
d. H2, Pd/BaSO4, quinoline
e. 1 equivalent of Br2
f. 2 equivalents of Br2
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10. Addition Reactions
Alkyne Halogenation
Multiple Choice
Predict the major, organic product of the following reaction.
A
B
C
D
Verified step by step guidance1
Identify the starting material as a cyclopropyl alkyne, which is a compound containing a triple bond between two carbon atoms, each of which is also part of a cyclopropane ring.
Recognize that the reagent is Br2 (bromine) in one equivalent, which suggests a halogenation reaction. In the presence of an alkyne, one equivalent of Br2 will add across the triple bond to form a dibromoalkene.
Understand that the addition of Br2 to an alkyne typically proceeds via an anti-addition mechanism, leading to the formation of a trans-dibromoalkene.
Consider the stereochemistry of the product. Since the reaction involves anti-addition, the two bromine atoms will add to opposite sides of the former triple bond, resulting in a trans configuration.
Draw the major organic product, ensuring that the two bromine atoms are added to the carbons that were originally part of the triple bond, and that they are on opposite sides, reflecting the anti-addition mechanism.
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