Question

Which of the following is used as a catalyst for preparing Grignard reagent?
A. Dry ether
B. Iodine powder
C. Activated charcoal
D. Manganese dioxide

Answer 1

Hint: A catalyst may be defined as a substance that increases the rate of the reaction but itself remains unchanged in the course of the reaction.

Complete Step by Step Solution:
A Grignard reagent may be defined as an organomagnesium compound having the general formula \[{\rm{RMgX}}\], where \[{\rm{R}}\]is an alkyl group or an aryl group and \[{\rm{X}}\]is a halogen atom.

Grignard reagents are generally prepared by reacting an alkyl halide or an aryl halide with magnesium in dry ether.
In general, the reaction may be written as shown below: where, \[{\rm{RX}}\,\]= alkyl halide or aryl halide
\[{\rm{Mg}}\]= magnesium
\[{\rm{RMgX}}\]= Grignard reagent

Ether is generally used as a solvent since it has the capacity to solvate the reagent by acting as a base for the acidic magnesium. However, for obtaining Grignard reagents from inactive halogen compounds THF (tetrahydrofuran) is used as the solvent instead of dry ether. The magnesium metal disappears and the Grignard reagents are formed with the evolution of heat. These reagents are seldom isolated in the solid state as they generally ignite spontaneously in air. Grignard reagents are usually used in the solution.
Hence, the catalyst for preparing Grignard reagent is dry ether.
Therefore, option A is correct.

Note: There are many uses for silver nitrate in our everyday life. Silver nitrate is useful in treating wounds. It is used to treat bone ulcers, burns, and acute wounds. In the laboratory, Silver nitrate is a useful reagent because of its role in the identification of halogens, such as bromine, chlorine etc.