Used primarily as an alkylating agent in organic synthesis, especially in ethylation reactions. It is effective in transferring ethyl groups to nucleophilic substrates such as amines, thiols, and enolates. Commonly employed in pharmaceutical manufacturing, biological research (as a mutagen), and research laboratories for modifying molecular structures. Due to its reactivity, potential toxicity, and mutagenic properties, it requires careful handling and is typically used under controlled conditions.