Final answer:
BME is a reducing agent that decreases the oxidation state of other substances. It donates electrons in chemical reactions, aligning with classical definitions of reduction as the addition of hydrogen to a substance.
Step-by-step explanation:
BME, or beta-mercaptoethanol, is a reducing agent. As a reducing agent, it has the function of decreasing the oxidation state of other substances. This is answer option 2 from the provided choices. When BME acts as a reducing agent in chemical reactions, it donates electrons to other substances, thereby reducing their oxidation state. For example, reduction in classical terms was thought of as the chemical addition of hydrogen to a substance, as seen in the reaction C₂H₂ + 2H₂ → C2H6. This concept aligns with the modern understanding of reduction, whereby hydrogen (with an oxidation state of +1) is added to a compound, thus reducing the oxidation state of that compound.
Oxidation numbers help in identifying the flow of electrons in redox reactions. For instance, in the reaction 2Mg + O₂ → 2MgO, the oxidation number of magnesium increases from 0 to +2, indicating it has lost electrons and been oxidized, while oxygen's oxidation number decreases from 0 to -2, which shows it has gained electrons and been reduced. A reducing agent like BME would facilitate a similar electron transfer, leading to a decrease in the oxidation state of the substance it reduces.