Reduktionsmedel

Reduktionsmedel (reducing agent) is a substance that donates electrons in a redox reaction, causing another species to be reduced and the reductant to be oxidized. They are the counterpart to oxidationsmedel (oxidizing agents) and are characterized by their tendency to lose electrons. The strength of a reductant is often summarized by its standard redox potential, with more negative values indicating a greater propensity to donate electrons.

Common inorganic reductants include metal hydrides such as sodium borohydride (NaBH4) and lithium aluminium hydride (LiAlH4); hydrogen gas in the presence of a catalyst; and metals like zinc or iron in acidic media. In organic synthesis, borane reagents (for example BH3·THF), sodium borohydride, and tin(II) chloride (SnCl2) are widely used. In biology, reducing equivalents such as NADH and FADH2 transfer electrons in cellular respiration and other pathways.

Reduktionsmedel act by transferring electrons to the substrate, sometimes via proton-coupled electron transfer. Their effectiveness depends on solvent, temperature, pH, and the electronic and steric environment of the substrate. They vary in selectivity, with some reagents providing chemoselective reductions under mild conditions while others are more aggressive.

Applications span chemical synthesis, pharmaceuticals, materials science, and food chemistry, where reducing agents can act as antioxidants or as part of the synthesis or processing steps. Safety considerations include handling reactive hydrides and avoiding incompatible materials; appropriate protective equipment and ventilation are essential.