Question

How ethyl magnesium chloride is converted into propan-1-ol?

Answer 1

Hint: Ethyl magnesium chloride is a Grignard reagent which molecular formula is \[\text{C}{{\text{H}}_{3}}\text{C}{{\text{H}}_{2}}\text{Mg}\,\text{Cl}\]
- Grignard reagents are an organo-metallic halogen compound which is represented by \[{{\text{R}}^{\text{-}}}\text{M}{{\text{g}}^{\text{2+}}}{{\text{X}}^{\text{-}}}\], where R could be an alkyl or aryl group and X represent the halogen atom.
- The alkyl group of Grignard reagents acts as a strong base and a strong nucleophile. So Grignard reagent shows either acid base reaction or nucleophilic addition reaction and reacts with only those compounds which contain acidic hydrogen or which contains carbonyl group $\text{(-C=O)}$.
- A nucleophile is a reagent that brings an electron pair. In other words, a nucleus seeking reagent is called a nucleophile.
- Propan-1-ol is an alcoholic compound in which is formed by the substitution of terminal hydrogen of propane by hydroxyl group $\text{(-OH)}$. Molecular formula of propan-1-ol is \[\text{C}{{\text{H}}_{3}}\text{-C}{{\text{H}}_{2}}\text{-C}{{\text{H}}_{2}}\text{-OH}\].


Complete Solution :
To convert ethyl magnesium chloride is converted into Propan-1-ol in the following two steps.
In the first step we will do a reaction of ethyl magnesium chloride with formaldehyde $\text{(}{{\text{H}}_{2}}\text{C=O)}$. Where the ethyl group acts as a nucleophile and performs nucleophilic addition reactions.
                             

- This is an example of nucleophilic addition reaction. In which an ethyl group of ethyl magnesium chloride acts as a nucleophile and gets attached with the carbon atom of formaldehyde by forming an intermediate transition state.
In second step hydrolysis of intermediate transition state gives \[\text{C}{{\text{H}}_{3}}\text{-C}{{\text{H}}_{2}}\text{-C}{{\text{H}}_{2}}\text{-OH}\].

Note: -Grignard reagents are highly reactive organic compounds and it can react with any source of proton to give hydrocarbons because acid base reactions are much faster than nucleophilic addition reactions. So it is therefore necessary to avoid even trace amounts of moisture from Grignard reagent.
-Rate of reaction depends on the stability of carbocation (intermediate) form in the reaction. So formaldehyde is the most reactive aldehyde toward nucleophilic addition reaction.