During addition of bromine on ethene, the first species formed is

Options

A.
B. `C_2H_4OH^+`
C.
D. `C_2H_5^+`

Answer

To determine the first species formed during the addition of bromine to ethene, we can follow these steps:

### Step 1: Identify the Reactants
Ethene (C2H4) is the reactant in this reaction. Its structure can be represented as:
\[ \text{CH}_2 = \text{CH}_2 \]

### Step 2: Understand the Reaction Mechanism
The addition of bromine (Br2) to ethene occurs through an electrophilic addition mechanism. In this process, the double bond in ethene acts as a nucleophile and attacks a bromine molecule.

### Step 3: Formation of the Bromonium Ion
When bromine approaches the double bond, one of the bromine atoms forms a bond with one of the carbon atoms, leading to the formation of a cyclic bromonium ion. This can be represented as:
\[ \text{Br}^+ \text{CH}_2 - \text{CH}_2 \text{Br}^- \]
This intermediate is a three-membered ring structure where the bromine atom is positively charged.

### Step 4: Attack of the Nucleophile
The other bromine atom (Br-) will then attack the more substituted carbon atom of the bromonium ion, leading to the formation of the final product. However, the first species formed during the reaction is the bromonium ion.

### Conclusion
The first species formed during the addition of bromine to ethene is the bromonium ion.

### Final Answer
The first species formed is the bromonium ion (Br-CH2-CH2+).

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