Question

The alkene 3-methyl-1-butene is reacted with br2 in aqueous solution.

Answer 1

When 3-methyl-1-butene reacts with Br2 in aqueous solution, a halogenation reaction occurs, resulting in a dibrominated alkane. Bromine atoms are added to the alkene, breaking the double bond and forming an alkane with the same carbon skeleton.

Step-by-step explanation:

The product formed when 3-methyl-1-butene reacts with Br2 in aqueous solution is a dibrominated alkane. This reaction is a type of halogenation, in which a halogen molecule, in this case bromine, is added to an alkene, causing the double bond to break and forming two new single bonds. Each carbon atom that was part of the double bond will attach to one bromine atom, resulting in the formation of an alkane with the same carbon skeleton as the original alkene but with bromine atoms added.

The general mechanism for the addition of bromine to an alkene goes as follows:

• The alkene's double bond acts as a nucleophile, attacking the bromine molecule and forming a bromonium ion intermediate.
• Water or a nucleophile present in the aqueous solution opens the bromonium ion, leading to the formation of a vicinal dibromide, where 'vicinal' indicates that the bromine atoms are attached to adjacent carbon atoms.

The reaction of alkenes with bromine is sometimes used as a test for unsaturation, as the typically brownish-red color of the bromine solution disappears when the reaction occurs. In educational settings, this reaction demonstrates the chemical behavior of alkenes and principles like nucleophilic attack and the stability of carbocations.

Answer 2

When 3-methyl-1-butene reacts with Br2 in aqueous solution, the major product formed is 2,3-dibromobutane.

Step-by-step explanation:

The reaction between 3-methyl-1-butene and Br2 in aqueous solution follows an electrophilic addition mechanism. In the presence of water, bromine (Br2) undergoes a reaction called bromination with the alkene. The double bond of the alkene acts as the nucleophile, attacking the electrophilic bromine. The result is the addition of a bromine atom to each carbon of the double bond, forming a vicinal dibromide. In this specific case, 2,3-dibromobutane is the major product.

In the reaction, the bromine atoms add to the carbon atoms at positions 2 and 3 of the butene, leading to the formation of the product. The reaction mechanism involves the generation of a bromonium ion intermediate, which is then attacked by water molecules, resulting in the final product. The preference for the addition of bromine at positions 2 and 3 is influenced by factors such as steric hindrance and the stability of the intermediate formed during the reaction.

In summary, the reaction of 3-methyl-1-butene with Br2 in aqueous solution leads to the formation of 2,3-dibromobutane as the major product due to the electrophilic addition of bromine to the double bond, and the specific regioselectivity is determined by the reaction conditions and the stability of reaction intermediates.