The reagent used for the conversion
`CH_3CH_2COOH to CH_3CH_2CH_3` , is

Options

A. `LiAlH_4`
B. Sodalime
C. Red `P` and concentrated `HI`
D. Amaigamated zinc and concentrated `HCl`

Explanation

To convert propanoic acid (CH₃CH₂COOH) to propane (CH₃CH₂CH₃), we need to identify the appropriate reagent for this transformation. The process involves reducing the carboxylic acid to an alkane. Here’s a step-by-step breakdown of the solution:

### Step 1: Identify the starting material
The starting material is propanoic acid, which has the structure CH₃CH₂COOH. It consists of three carbon atoms.

### Step 2: Determine the desired product
The desired product is propane, which has the structure CH₃CH₂CH₃. This indicates that we need to remove the carboxylic acid functional group and convert it into an alkane.

### Step 3: Consider reduction methods
The reduction of carboxylic acids can be achieved using various reagents. Common reducing agents include lithium aluminium hydride (LiAlH₄), sodium borohydride (NaBH₄), and catalytic hydrogenation (using nickel or platinum). However, these typically reduce carboxylic acids to alcohols, not alkanes.

### Step 4: Identify the correct reagent
For the conversion of a carboxylic acid directly to an alkane, decarboxylation is a suitable method. One effective reagent for this purpose is soda lime, which is a mixture of sodium hydroxide (NaOH) and calcium oxide (CaO). However, soda lime typically leads to the formation of alkanes from carboxylic acids through decarboxylation.

### Step 5: Use of red phosphorus and HI
Another method involves using red phosphorus and hydroiodic acid (HI). In this reaction, the carboxylic acid is first converted into an iodide, and then the carbonyl group is reduced, leading to the formation of propane.

### Step 6: Conclusion
The reagent used for the conversion of propanoic acid (CH₃CH₂COOH) to propane (CH₃CH₂CH₃) is red phosphorus and hydroiodic acid (HI).

### Final Answer
**Red phosphorus and hydroiodic acid (HI)** are used to convert propanoic acid to propane.

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