Chemistry XI Content
Formation of Griginard’s Reagent
| In the preparation of a griginard’s reagent great care must be taken that the reactants are absolutely dry and pure. The other experimental details are given below:|
Magnesium: magnesium ribbon is washed with ether and dried in desicater.
Ether: it is distilled over sodium metal and P2O5.
Ethyl bromide: it is purified and then distilled over P2O5.
Take dry ether in a round bottom flask and add pieces of Mg ribbon in it. Fit it with water condenser and add ethyl bromide gradually through the condenser. Heat a little so that magnesium dissolves. Cool if necessary. A clear solution of griginard’s reagent – ethyl magnesium bromide, in ether appears. This ethereal solution is used as griginard’s reagent.
C2H5–Br + Mg à C2H5–Mg–Br
| A chemical reaction in which two molecules react together in rate determining step is called bimolecular reaction. A bimolecular reaction may be SN2 or E2.|
Rate of reaction of A bimolecular reaction is expressed as:
Rate = K[R–X][Nu]
| A chemical reaction in which only one molecule takes part in rate determining step.is called an unimolecular reaction. An unimolecular reaction may be SN1 or E1.|
Rate of reaction of an unimolecular reaction is expressed as:
Rate = K[R–X]