What is the expected product when (2-butene) reacts with bromine () in carbon tetrachloride ()?
A
(3-bromo-2-butene)
B
(2,3-dibromobutane)
C
(no reaction)
D
(4-bromo-2-butene)
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1
Identify the type of reaction: The reaction of an alkene with bromine (Br\_2) in a non-nucleophilic solvent like carbon tetrachloride (CCl\_4) is a classic example of an electrophilic addition reaction.
Understand the mechanism: Bromine adds across the double bond of the alkene via a bromonium ion intermediate, which is a three-membered ring with a positively charged bromine atom.
Determine the regiochemistry and stereochemistry: The bromonium ion is attacked by a bromide ion (Br\-) from the opposite side (anti addition), leading to a vicinal dibromide (two bromine atoms on adjacent carbons) with anti stereochemistry.
Apply this to 2-butene: The double bond between C2 and C3 will be broken, and one bromine atom will add to C2 and the other to C3, resulting in 2,3-dibromobutane.
Conclude the expected product: Since the addition is anti and across the double bond, the product is 2,3-dibromobutane, not a monobrominated alkene or no reaction.