Arrange the given compounds is order of their basic strength
(i) Histidine, (ii) Lysine, (iii) Arginine

Options

A. `i gt ii gt iii`
B. `ii gt i gt iii`
C. `iii gt ii gt i`
D. `i gt iii gt ii`

Explanation

To arrange the compounds Histidine, Lysine, and Arginine in order of their basic strength, we will analyze the structures and the number of amino groups present in each compound. Here’s the step-by-step solution:

### Step 1: Understand the Structures of the Amino Acids
- **Histidine**: Contains an imidazole ring with a nitrogen atom, which can participate in protonation.
- **Lysine**: Contains a straight-chain structure with an amino group (NH2) at the end, making it a strong base.
- **Arginine**: Contains a guanidinium group, which has multiple nitrogen atoms that can accept protons.

### Step 2: Analyze Basic Strength
- Basic strength in amino acids is influenced by the presence of amino groups (NH2) and the ability of the molecule to stabilize the positive charge after protonation.
- **Histidine** has one amino group and a nitrogen in the ring that can affect its basicity.
- **Lysine** has two amino groups (one at the end and one in the chain), which contribute to its basicity.
- **Arginine** has three nitrogen atoms in its guanidinium group, making it the strongest base among the three.

### Step 3: Compare Basic Strength
- **Arginine** > **Lysine** > **Histidine**
- Arginine is the strongest base due to its three nitrogen atoms.
- Lysine is next with two amino groups.
- Histidine is the weakest due to the nitrogen in the ring structure, which is less available for protonation.

### Final Order of Basic Strength
The order of basic strength from highest to lowest is:
**Arginine (3) > Lysine (2) > Histidine (1)**

### Summary
The final answer is:
**3 > 2 > 1** (Arginine > Lysine > Histidine)

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