Which of the following groups would you introduce into a dye to make it water soluble

Options

A. `-NO_2`
B. `-Cl`
C. `-SO_3H`
D. `-OH`

Answer

To determine which group to introduce into a dye to make it water-soluble, we need to consider the properties of the functional groups and their ability to form hydrogen bonds with water. Here’s a step-by-step solution:

### Step 1: Understand Water Solubility
Water solubility is largely influenced by the ability of a substance to form hydrogen bonds with water molecules. Functional groups that can participate in hydrogen bonding will enhance the solubility of a compound in water.

**Hint:** Look for functional groups that can form hydrogen bonds with water.

### Step 2: Analyze the Given Groups
We need to evaluate the functional groups provided in the options. The focus should be on groups that can either donate or accept hydrogen bonds.

**Hint:** Identify the functional groups that can either donate a hydrogen atom (like -OH) or have electronegative atoms that can accept hydrogen bonds (like -O or -N).

### Step 3: Identify the SO3H Group
The SO3H group (sulfonic acid) is known for its strong polar nature and ability to form hydrogen bonds. When this group is introduced into a dye, it can interact with water molecules effectively, making the dye more soluble.

**Hint:** Consider how the SO3H group interacts with water molecules.

### Step 4: Confirm the Presence of Hydrogen Bonding
The presence of the -OH group in the SO3H structure allows it to form hydrogen bonds with water. This is crucial for increasing the solubility of the dye in water.

**Hint:** Remember that hydrogen bonding is key to solubility in water.

### Step 5: Conclusion
Based on the analysis, the introduction of the SO3H group into a dye will enhance its water solubility due to the ability to form hydrogen bonds with water molecules.

**Final Answer:** The correct group to introduce into a dye to make it water-soluble is the SO3H group (option C).

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