An electron-withdrawing group (EWG) is a substituent that pulls electron density away from an adjacent atom. It matters because, by removing electron density, it stabilises a neighbouring negative charge and can make a leaving group depart more easily. It is the opposite of an electron-donating group, which releases electron density and instead stabilises a neighbouring positive charge.

吸电子基团(EWG)是从相邻原子吸引电子云的取代基。它之所以重要,是因为它通过移除电子云稳定相邻的负电荷,并可使离去基团更容易离去。它与给电子基团相反,后者给出电子云,转而稳定相邻的正电荷。