Nonprotonic

Nonprotonic refers to chemical species or reactions that do not involve the transfer or presence of protons (hydrogen ions, H+). This is in contrast to protic substances or reactions, which are characterized by proton activity. Protic solvents, for example, are capable of donating a proton and typically contain hydrogen atoms bonded to highly electronegative atoms like oxygen or nitrogen. Nonprotonic solvents, conversely, lack this ability to donate protons and are often polar aprotic solvents, such as dimethyl sulfoxide (DMSO) or acetonitrile, which can solvate cations well but do not readily solvate anions through hydrogen bonding.

In the context of acid-base chemistry, nonprotonic acids are substances that can accept a pair of electrons to form a coordinate covalent bond, often referred to as Lewis acids, as opposed to Brønsted-Lowry acids which donate protons. Similarly, nonprotonic bases are electron-pair donors, known as Lewis bases. Reactions that occur in nonprotonic media may exhibit different kinetics and mechanisms compared to those in protic solvents due to the absence of proton solvation and hydrogen bonding effects. The term "nonprotonic" emphasizes the lack of proton involvement in a particular chemical context.