Should sodium borohydride be weighed at the beginning of lab and left on the bench until added to the reaction?

Sodium borohydride is a powerful reducing agent commonly used in organic reactions, and it is sensitive to moisture and air. It’s crucial to handle it correctly to maintain its reactivity and stability. If sodium borohydride is left on the bench exposed to air or humidity, it may begin to slowly react or degrade, leading to inconsistent results in your experiment.

Weighing the compound at the start is standard practice, but it should be added to the reaction mixture as soon as it is weighed. This minimizes its exposure to air and moisture, ensuring that it retains its full reducing power. Thus, it is essential not to let it sit on the bench for an extended period before use. This approach ensures the reliability of your results and the efficiency of the reaction being conducted.