What would be the major organic product for the reaction of but-2-yne with excess bromine?
The major organic product for the reaction of but-2-yne with excess bromine would be 2,3-dibromobutane.
The major organic product for the reaction of but-2-yne with excess bromine is 2,3-dibromobutane.
To understand why this is the major product, let's break down the reaction step-by-step:
Step 1: Addition of bromine to but-2-yne
During the reaction, the bromine molecule (Br2) adds across the triple bond of but-2-yne. Each bromine atom adds to one of the carbon atoms in the triple bond, resulting in the formation of a new carbon-bromine bond.
Step 2: Formation of 1,2-dibromo-2-butene
The initial addition of bromine produces 1,2-dibromo-2-butene as an intermediate. This intermediate is formed when one of the bromine atoms adds to the terminal carbon of the triple bond, resulting in a double bond between the two carbons.
Step 3: Rearrangement to form 2,3-dibromobutane
The 1,2-dibromo-2-butene intermediate can undergo a rearrangement called a 1,2-shift. In this rearrangement, one of the alkyl groups moves from the carbon attached to the double bond to the carbon adjacent to it, resulting in the formation of 2,3-dibromobutane.
Thus, the major product of the reaction between but-2-yne and excess bromine is 2,3-dibromobutane.
To determine the major organic product for the reaction of but-2-yne with excess bromine, we need to understand the reactivity of but-2-yne towards bromine.
But-2-yne is an alkyne, which is a highly reactive functional group known for undergoing addition reactions. In the presence of excess bromine, the bromine molecules can add to the triple bond of but-2-yne.
To visualize this reaction, let's first draw the structure of but-2-yne:
CH3 ─ C ≡ C ─ CH3
Now, we can consider the addition of bromine to but-2-yne. Each bromine molecule (Br2) adds to the triple bond, breaking the π-bond and forming a new σ-bond between carbon and bromine.
The addition can occur in two different ways, resulting in two possible products, depending on which carbon the bromine attaches to. Let's consider both possibilities:
1. Addition of bromine to the middle carbon:
CH3 ─ C ─ Br
|
CH3
2. Addition of bromine to the end carbon:
CH3
|
CH3 ─ C ─ Br
Now, let's compare the stability of these two products. The product formed by adding bromine to the middle carbon is more stable due to the presence of two alkyl groups attached to the positively charged carbon. This stabilizes the positive charge through the inductive effect, making it the major product.
Therefore, the major organic product for the reaction of but-2-yne with excess bromine is:
CH3 ─ C ─ Br
|
CH3