But-`2`-ene reacts with `H_(2)` in the presence of Lindlar's catalyst. The predominant product of reaction is

Options

A. butane
B. buta-`1,3`-diene
C. cis-but-`2`-ene
D. trans-but-`2`-ene

Explanation

To determine the predominant product of the reaction of But-2-ene with hydrogen (H₂) in the presence of Lindlar's catalyst, follow these steps:

### Step 1: Understand the Reactants
But-2-ene is an alkene with the formula C₄H₈. It has a double bond between the second and third carbon atoms. The structure can be represented as:

```
H H
\ /
C=C
/ \
H CH₃
```

### Step 2: Identify the Catalyst
Lindlar's catalyst is a poisoned palladium catalyst that facilitates the partial hydrogenation of alkynes to cis-alkenes. In this case, we are dealing with an alkene (But-2-ene), but the principle remains the same: it promotes syn addition of hydrogen across the double bond.

### Step 3: Reaction Mechanism
When But-2-ene reacts with H₂ in the presence of Lindlar's catalyst, the double bond will undergo hydrogenation. The addition of hydrogen occurs in a syn fashion, meaning both hydrogen atoms will add to the same side of the double bond.

### Step 4: Determine the Product
The syn addition of hydrogen to But-2-ene results in the formation of a saturated alkane. Since the addition is syn, the product will have both methyl groups (CH₃) on the same side, leading to the formation of cis-Butane.

### Step 5: Naming the Product
The product formed is cis-Butane. The longest carbon chain consists of four carbon atoms, and since the two methyl groups are on the same side, it is classified as cis.

### Final Answer
The predominant product of the reaction of But-2-ene with H₂ in the presence of Lindlar's catalyst is **cis-Butane**.

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