Protic solvent 1652563 219618525 2008-06-16T02:49:03Z Puppy8800 5404759 In [[chemistry]] a '''protic solvent''' is a [[solvent]] that has a [[hydrogen]] atom bound to an [[oxygen]] as in a [[hydroxyl]] group or a [[nitrogen]] as in an [[amine]] group. More generally, any molecular solvent which contains dissociable H<sup>+</sup>, such as [[hydrogen fluoride]], is called a '''protic solvent'''. The molecules of such solvents can donate an H<sup>+</sup> (proton). Conversely, '''aprotic solvents''' cannot donate hydrogen. Common characteristics of protic solvents: * solvents display [[hydrogen bonding]] * solvents have an [[acidic]] hydrogen (although they may be very weak acids) * solvents are able to stabilize [[ion]]s ** [[cations]] by unshared [[free electron pair]]s ** [[anions]] by hydrogen bonding Examples are [[water (molecule)|water]], [[methanol]], [[ethanol]], [[formic acid]], [[hydrogen fluoride]] and [[ammonia]]. '''Polar aprotic solvents''' are solvents that share ion dissolving power with protic solvents but lack an acidic hydrogen. These solvents generally have high [[dielectric constant]]s and high [[Chemical polarity|polarity]]. Examples are [[dimethyl sulfoxide]], [[dimethylformamide]], [[dioxane]] and [[hexamethylphosphorotriamide]]. Polar protic solvents are favorable for S<sub>N</sub>1 reactions, while polar aprotic solvents are favorable for S<sub>N</sub>2 reactions. Apart from solvent effects, polar aprotic solvents may also be essential for reactions which use strong bases, such as reactions involving [[Grignard reagent]]s or [[n-butyl lithium]]. If a protic solvent were to be used, the reagent would be consumed by a side reaction with the solvent. == References == *Loudon, G. Mark. Organic Chemistry 4th ed. New York: Oxford University Press. 2002. pg 317. [[Category:Solvents]] [[pt:Solvente prótico]] [[sv:Protiskt lösningsmedel]]