In which reaction product formation takes place by Saytzeff rule

Options

A. `CH_3-CH_2-overset(Br)overset(|)(CH)-CH_3overset(CH_3ONa//Delta)rarr`
B. `CH_3-underset(CH_3)underset(|)overset(OH)overset(|)C-CH_3overset(conc.H_2SO_4//Delta)rarr`
C. `CH_3-underset(CH_3)underset(|)overset(Br)overset(|)C-CH_3overset(Alc.KOH//Delta)rarr`
D. `CF_3-CHCl_2overset(AlC.KOH//Delta)rarr`

Answer

To determine which reaction follows the Saytzeff rule for product formation, we need to analyze the reactions provided and apply the rule accordingly.

### Step-by-Step Solution:

1. **Understand Saytzeff's Rule**: Saytzeff's rule states that in elimination reactions, the more substituted alkene (the one with more alkyl groups attached to the double bond) is favored. This typically occurs when a halogen is eliminated from a haloalkane in the presence of a strong base.

2. **Identify the Reactions**: We need to evaluate the given reactions to see if they involve the elimination of a halogen and whether they can produce a more substituted alkene.

3. **Evaluate Each Reaction**:
- **Reaction 1**: Involves alcoholic KOH reacting with a haloalkane. Here, the halogen is eliminated, and we can form a double bond. Since there are adjacent carbons, we can apply Saytzeff's rule to favor the more substituted alkene.
- **Reaction 2**: Involves concentrated H2SO4. This reaction leads to dehydration, but since the structure is symmetric, the elimination does not favor one side over the other. Therefore, it does not follow Saytzeff's rule.
- **Reaction 3**: Similar to Reaction 2, it involves a symmetric structure with no preference for hydrogen elimination. Hence, it does not follow Saytzeff's rule.
- **Reaction 4**: Involves CF3CHCl2 reacting with alcoholic KOH. Here, there is only one adjacent carbon available for elimination, which means we cannot apply Saytzeff's rule as there is no choice for forming a more substituted alkene.

4. **Conclusion**: The only reaction that follows Saytzeff's rule is the first reaction involving alcoholic KOH.

### Final Answer:
The reaction that follows Saytzeff's rule for product formation is the first reaction involving alcoholic KOH.

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