Solvents (protic, aprotic, polar, apolar)

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.

  1. Protic solvents
  2. Aprotic solvents
  3. Apolar solvents
  4. 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.

 

 

 

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