Find out the total number of major products (including stereoisomers) are obtained in each of the following reactions.
(a) cis-3-heptene`+Br_(2) rarr x`
(b) trans-3-heptene `+ Br_(2) rarr y`
(c) trans-3-hexene `+ Br_(2)rarrz`
Find the value of `(x + y + z)` ?

Answer

To find the total number of major products (including stereoisomers) obtained from the given reactions, we will analyze each reaction step by step.

### Step 1: Analyze Reaction (a) - cis-3-heptene + Br₂ → x

**cis-3-heptene Structure:**
- The structure of cis-3-heptene has the two methyl groups on the same side of the double bond.

**Bromination Reaction:**
- The bromination of alkenes occurs via electrophilic addition, where Br₂ adds across the double bond.
- For cis-3-heptene, the addition of Br₂ will lead to the formation of a bromonium ion intermediate.

**Products:**
- The bromonium ion can be attacked by Br⁻ from either side, but since the starting alkene is cis, the product will be a single stereoisomer.
- The major product formed is 2,3-dibromoheptane (with both bromine atoms on adjacent carbons).

**Total Products (x):** 1 (only one stereoisomer)

### Step 2: Analyze Reaction (b) - trans-3-heptene + Br₂ → y

**trans-3-heptene Structure:**
- The structure of trans-3-heptene has the two methyl groups on opposite sides of the double bond.

**Bromination Reaction:**
- Similar to the cis-alkene, the bromination will lead to a bromonium ion intermediate.

**Products:**
- In this case, the bromonium ion can be attacked from both sides, leading to two different stereoisomers:
1. (2R,3S)-2,3-dibromoheptane
2. (2S,3R)-2,3-dibromoheptane

**Total Products (y):** 2 (two stereoisomers)

### Step 3: Analyze Reaction (c) - trans-3-hexene + Br₂ → z

**trans-3-hexene Structure:**
- The structure of trans-3-hexene is similar to trans-3-heptene but has one less carbon.

**Bromination Reaction:**
- The bromination will again lead to a bromonium ion intermediate.

**Products:**
- The attack on the bromonium ion can also yield two different stereoisomers:
1. (2R,3S)-2,3-dibromohexane
2. (2S,3R)-2,3-dibromohexane

**Total Products (z):** 2 (two stereoisomers)

### Step 4: Calculate the Total (x + y + z)

Now, we can sum the total number of major products from all three reactions:
- x = 1 (from cis-3-heptene)
- y = 2 (from trans-3-heptene)
- z = 2 (from trans-3-hexene)

**Total (x + y + z) = 1 + 2 + 2 = 5**

### Final Answer:
The value of (x + y + z) is **5**.

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