In chemistry, the choice of a solvent is crucial.
We have many solvents and we have to be able to grade them in a lab for our reactions.
- Protic solvents
- Aprotic solvents
- Apolar solvents
- Polar solvents
1. Protic Solvents
A protic solvent is a solvent which has a hydrogen atom bound to an oxygen, nitrogen, etc.It’s a labilite H+ ables to give it to the reagents. For instance: Water, DMF, HMPT, DMSO,….
2) Aprotic solvents
Contrary to a protic solvent, an aprotic solvent hasn’t got a labile H+. For example: Chloroform, Benzene,…
An other propriety is the polarity, the solvents can be classified in two categories
3) Apolar solvents
An apolar solvent hasn’t got a dipolar moment slower than E=15 D. Like Hexane, diethyl-ether, benzene,…A non polar solvent doesn’t permit the separation of the charges and forms a pair of associated ions.
4) Polar solvents
A polar solvent has got a dipolar moment superior than 15 D. Like water (78 D) or methanol (33 D)…A polar solvent permits the separation of the charges, more the solvent is polar more it has a dissociating power, leading to the sepration of the charges.
- Note: Aprotic polar solvents are used for SN1 and protic polar solvents for SN2
When we use a chromatographic columna with silica gel to separe different products we play on the polarity of the elution solvent.