The most reactive alkene HBr among the following is

Options

A. `(CH_(3))_(2)C=C(CH_(3))_(2)`
B. `CH_(2)=CH_(2)`
C. `(CH_(3))_(2)=CH_(2)`
D. `CH_(3)CH=CHCH_(3)`

Explanation

To determine the most reactive alkene among the given options, we will analyze the substitution of each alkene. The reactivity of alkenes is generally influenced by the degree of substitution; more substituted alkenes tend to be more reactive. Here’s a step-by-step solution:

### Step 1: Understand Alkene Substitution
Alkenes can be classified based on the number of alkyl groups attached to the carbon atoms involved in the double bond. The more alkyl groups (or substituents) attached, the more stable and reactive the alkene is.

### Step 2: Identify Alpha Hydrogens
Alpha hydrogens are the hydrogens attached to the carbon atoms that are adjacent to the carbon atoms of the double bond. To find the most reactive alkene, we need to count the alpha hydrogens for each option.

### Step 3: Analyze Each Option
Let's denote the options as A, B, C, and D. We will draw the structures of each alkene and count the alpha hydrogens.

#### Option A:
- Structure: C=C with two methyl groups on each carbon.
- Alpha Hydrogens: Each carbon has 3 alpha hydrogens (from the two methyl groups), totaling 6 alpha hydrogens.

#### Option B:
- Structure: C=C with no substituents.
- Alpha Hydrogens: There are no alpha hydrogens because there are no carbons adjacent to the double bond.

#### Option C:
- Structure: C=C with one methyl group on one carbon and two on the other.
- Alpha Hydrogens: The first carbon has 3 alpha hydrogens, and the second carbon has 3 alpha hydrogens, totaling 6 alpha hydrogens.

#### Option D:
- Structure: C=C with two methyl groups on one carbon and one on the other.
- Alpha Hydrogens: The first carbon has 3 alpha hydrogens, and the second carbon has 3 alpha hydrogens, totaling 6 alpha hydrogens.

### Step 4: Compare the Alpha Hydrogen Counts
- Option A: 6 alpha hydrogens
- Option B: 0 alpha hydrogens
- Option C: 6 alpha hydrogens
- Option D: 6 alpha hydrogens

### Step 5: Determine the Most Reactive Alkene
From the analysis, we see that Option A has the highest degree of substitution (most substituted alkene), making it the most reactive alkene among the options provided.

### Conclusion
The most reactive alkene among the given options is **Option A**.

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