Question

You are attempting the reduction of quinone with sodium borohydride. After adding the 0.05 g of NaBH4 you note that the solution remains yellow. Following the procedure, you continue to add increments of 0.05 g NaBH4. You note that the yellow color remains even after the addition of 0.10 g of extra NaBH4. Several students around you are experiencing a similar problem. Propose a cause for this and suggest a solution.

Answer 1

When benzoquinone reacts with sodium borohydride, which is yellow in color, white and colorless hydroquinone is formed.

Step-by-step explanation:

The reaction described below should occur. However, even as we add more sodium borohydride, the color stays yellow. This implies that the solution must contain unreacted benzoquinone. Furthermore, NaBH4 is a kind of hydride (H-), and the reaction starts with the addition of hydride.

The acid oxygen is protonated once more to produce a neutral primary alcohol. As sodium borohydride is a reducing agent, adding more will not cause the benzoquinone to react with it, increasing the amount of NaBH4 will not affect the color of the benzoquinone.

Often, benzoquinone is very vulnerable to solid minerals, acids, and alkalis, causing it to condense and decompose.