What type of isomersm exists between the following pairs of compounds ?
(i) Pentan-1-ol and 3-Methylbutan-1-ol
(ii) Ethanol and Dimethyl ether
(iii) Butan-1-ol and Butan-2-ol

Options

A. `{:("(i)","(ii)","(iii)"),("Chain isomerism","Functinal isomerism","Position isomerism"):}`
B. `{:("(i)","(ii)","(iii)"),("Function isomerism ","Chain isomerism ","isomerism Fucntional "):}`
C. `{:("(i)","(ii)","(iii)"),("Chain isomerism ","Position isomerism","Functional isomerism"):}`
D. `{:("(i)","(ii)","(iii)"),("Chain isomerism ","Position isomerism " ,"Function isomerism"):}`

Answer

To determine the type of isomerism between the given pairs of compounds, we will analyze each pair step by step.

### Step 1: Analyzing Pentan-1-ol and 3-Methylbutan-1-ol
1. **Chemical Structures**:
- Pentan-1-ol: This compound has a straight chain of 5 carbon atoms with an -OH group at the first carbon.
- 3-Methylbutan-1-ol: This compound has a branched structure with 4 carbon atoms in the main chain and a methyl group (−CH₃) on the third carbon, along with an -OH group on the first carbon.

2. **Counting Carbon Atoms**:
- Pentan-1-ol: 5 carbon atoms.
- 3-Methylbutan-1-ol: Also has 5 carbon atoms.

3. **Type of Isomerism**:
- Since both compounds have the same molecular formula (C₅H₁₂O) but differ in the arrangement of carbon atoms (one is straight-chain and the other is branched), they exhibit **chain isomerism**.

### Step 2: Analyzing Ethanol and Dimethyl Ether
1. **Chemical Structures**:
- Ethanol: CH₃CH₂OH (an alcohol).
- Dimethyl Ether: CH₃OCH₃ (an ether).

2. **Counting Atoms**:
- Both compounds have the same number of carbon (2), hydrogen (6), and oxygen (1) atoms.

3. **Type of Isomerism**:
- Since both compounds have the same molecular formula (C₂H₆O) but different functional groups (alcohol vs. ether), they exhibit **functional isomerism**.

### Step 3: Analyzing Butan-1-ol and Butan-2-ol
1. **Chemical Structures**:
- Butan-1-ol: CH₃CH₂CH₂CH₂OH (the -OH group is on the first carbon).
- Butan-2-ol: CH₃CH(OH)CH₂CH₃ (the -OH group is on the second carbon).

2. **Counting Atoms**:
- Both compounds have the same molecular formula (C₄H₁₀O).

3. **Type of Isomerism**:
- Since both compounds have the same molecular formula but differ in the position of the -OH group, they exhibit **position isomerism**.

### Summary of Isomerism Types:
- (i) Pentan-1-ol and 3-Methylbutan-1-ol: **Chain Isomerism**
- (ii) Ethanol and Dimethyl Ether: **Functional Isomerism**
- (iii) Butan-1-ol and Butan-2-ol: **Position Isomerism**