Solvents

Let's Talk Solvents

Solvents are essential in chemistry, influencing reaction outcomes by dissolving reactants and affecting their interactions. Polarity, a key property, dictates how well substances mix ("like dissolves like"). We classify solvents as polar or nonpolar, and further categorize polar solvents as protic or aprotic.

Polarity

Polar solvents possess distinct positive and negative regions, while nonpolar solvents lack this charge separation. The dielectric constant (ε) quantifies polarity, but structural features often provide clues. Water (high ε) exemplifies polarity due to O-H bonds, whereas alkanes (low ε) are nonpolar.

Polar Protic and Aprotic Solvents

Polar protic solvents (e.g., water, alcohols) contain O-H or N-H bonds, enabling hydrogen bonding. Aprotic polar solvents (e.g., DMSO, DMF, acetone, acetonitrile) lack these bonds but remain polar due to other structural features.

Solvents and Reactions

Solvent choice is critical. SN1 reactions often favor polar protic solvents, which stabilize carbocation intermediates. SN2 reactions commonly utilize polar aprotic solvents, as these do not strongly solvate the nucleophile, allowing it to attack more readily.  We will look at this in more detail next.

Solvent Chart