Indophenol

Indophenol

Indophenol is a class of synthetic dyes that are characterized by their vibrant blue or green colors. These compounds are used in various applications, including as pH indicators, in redox reactions, and in the food industry. The most well-known indophenol is 2,6-dichloroindophenol (DCIP), which is commonly used in laboratory settings to measure vitamin C content in food and biological samples.

Chemical Structure and Properties

Indophenols are typically derived from the reaction of phenols with aromatic amines in the presence of an oxidizing agent. The general structure of indophenols includes a phenolic group linked to an amine group through a quinonoid system, which is responsible for their color.

The chemical formula for 2,6-dichloroindophenol is C₁₂H₇Cl₂NO₂, and it has a molar mass of 268.10 g/mol. It appears as a dark blue or purple crystalline powder that is soluble in water and alcohol.

Applications

As a Redox Indicator

Indophenols, particularly DCIP, are widely used as redox indicators in titrations. DCIP changes color from blue to colorless when reduced, making it useful for determining the concentration of reducing agents such as ascorbic acid (vitamin C).

In Vitamin C Analysis

The most common application of DCIP is in the determination of vitamin C content in food and biological samples. The method involves titrating a solution of the sample with a DCIP solution until a persistent color change is observed, indicating the endpoint of the reaction.

In pH Indicators

Some indophenols can also act as pH indicators due to their ability to change color with pH variations. This property is utilized in various chemical analyses and educational demonstrations.

Synthesis

The synthesis of indophenols typically involves the oxidative coupling of a phenol with an amine. For example, DCIP is synthesized by the reaction of 2,6-dichloroquinone with p-aminophenol in the presence of an oxidizing agent such as sodium hypochlorite.

Safety and Handling

Indophenols, like many synthetic dyes, should be handled with care. They can be irritants to the skin and eyes, and inhalation of dust should be avoided. Proper personal protective equipment, such as gloves and goggles, should be used when handling these compounds.

Also see

• Redox indicator
• Vitamin C
• pH indicator
• Synthetic dyes