Question

Alkane is obtained from the reaction of which of the following compounds with Grignard reagent?

• A. ${\mathrm{NH}}_3$
• B. ${\mathrm{H}}_2\mathrm{O}$
• C. ${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}$
• D. All of these

Answer 1

The correct option is D

All of these

The explanation for the correct option:

• Grignard reagent: These are the organometallic compounds commonly represented by the general formula $\mathrm{R}-\mathrm{Mg}-\mathrm{X}$ in which $\mathrm{R}$ is a hydrocarbon radical $({\mathrm{CH}}_3,{\mathrm{C}}_2{\mathrm{H}}_5,{\mathrm{C}}_6{\mathrm{H}}_{5,}\mathrm{etc}.)$ and $\mathrm{X}$ is a halogen atom.
• Examples of Grignard reagents are Methylmagnesium chloride $\left({\mathrm{CH}}_3\mathrm{MgCl}\right)$, Phenylmagnesium bromide $\left({\mathrm{C}}_6{\mathrm{H}}_5\mathrm{MgBr}\right)$, etc.
• Alkanes are saturated hydrocarbons containing carbon-carbon single bonds in them.
• The reaction of the Grignard reagent with the given compounds are:

$$\begin{gathered} \left(\mathrm{a}\right){\mathrm{NH}}_3\left(\mathrm{aq}\right)+\mathrm{RMgX}\left(\mathrm{aq}\right)\stackrel{}{\to }\mathrm{RH}\left(\mathrm{aq}\right)+\mathrm{Mg}\left({\mathrm{NH}}_2\right)\mathrm{X}\left(\mathrm{aq}\right) \\ \left(\mathrm{ammonia}\right)(\mathrm{grignard}\mathrm{reagent})\left(\mathrm{alkane}\right) \\ \left(\mathrm{b}\right){\mathrm{H}}_2\mathrm{O}\left(\mathrm{aq}\right)+\mathrm{RMgX}\left(\mathrm{aq}\right)\stackrel{}{\to }\mathrm{RH}\left(\mathrm{aq}\right)+\mathrm{Mg}\left(\mathrm{OH}\right)\mathrm{X}\left(\mathrm{aq}\right) \\ \left(\mathrm{water}\right)(\mathrm{grignard}\mathrm{reagent})\left(\mathrm{alkane}\right) \\ \left(\mathrm{c}\right){\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\left(\mathrm{aq}\right)+\mathrm{RMgX}\left(\mathrm{aq}\right)\stackrel{}{\to }\mathrm{RH}\left(\mathrm{aq}\right)+\mathrm{Mg}\left({\mathrm{OC}}_2{\mathrm{H}}_5\right)\mathrm{X}\left(\mathrm{aq}\right) \\ \left(\mathrm{ethanol}\right)(\mathrm{grignard}\mathrm{reagent})\left(\mathrm{alkane}\right) \end{gathered}$$

• In all the above reactions, alkane $\left(\mathrm{RH}\right)$ is formed.

Hence, the correct option is (D).