Aprotisk

Aprotisk is the Swedish term for aprotic, used in chemistry to describe solvents or reagents that do not contain acidic hydrogen atoms and cannot donate protons in chemical reactions. The corresponding English term is aprotic. In discussions of solvents, aprotiska lösningar are contrasted with protiska lösningar, which contain O–H or N–H bonds and can donate protons.

Etymology and usage: The word aprotisk is formed from a- meaning without and prot- from protos (first) with a common adjectival suffix. It is used to classify solvents and reagents by their ability to donate hydrogen and participate in hydrogen bonding. The term emphasizes absence of exchangeable protons rather than overall acidity.

Definition and properties: An aprotic solvent lacks O–H and N–H bonds and therefore cannot act as a Brønsted acid in proton transfer processes. Such solvents are typically polar but do not donate hydrogen bonds. They often accept protons or stabilize cations through dipole interactions, which affects reaction mechanisms, particularly nucleophilic substitution and organometallic processes. Aprotic solvents often enable higher reactivity of anions in SN2 reactions because the anions are less solvated by hydrogen bonding.

Common examples and applications: Widely used aprotic solvents include acetonitrile, dimethyl sulfoxide (DMSO), and dimethylformamide (DMF). Acetone and nitromethane are also considered polar aprotic. These solvents are preferred in many organic syntheses and catalytic reactions where strong nucleophiles are required, and in procedures where hydrogen bonding would otherwise dampen reactivity.

See also: Protic solvent, SN2 reactions, polar aprotic solvent concept.