Question
What is organo metallic compound? Explain grignard reagent.
✓
Answer
$\rightarrow$ Most organic chlorides, bromides and iodides react with certain metals to give compounds containing canr bon-metal bonds. Such compounds are known as organo-metallic compounds.
$\rightarrow$ An important class of organo $-$ metallic compounds discovered by Victor Grignard in $1900$ is alkyl magne sium halide $,\ce{RMgX},$ referred as Grignard Reagents.
$\rightarrow$ These reagents are obtained by the reaction of haloalkanes with magnesium metal in dry ether.
$\rightarrow$ In the grignard reagent, the carbon $-$ magnesium bond is covalent but highly polar, with carbon pulling electrons from electropositive magnesium; the magnesium halogen bond is essentially ionic.
$\delta- \delta+\delta-$
$\ce{R - Mg X}$
$\rightarrow$ Grignard reagents are highly reactive and react with any source of proton to give hydrocarbons. Even water, alcohols, amines are sufficiently acidic to convert them to corresponding hydrocarbons.
$\ce{RMgX + H_2O \rightarrow RH + Mg(OH)X}$
$\underset{\text{Ethyl magnesium bromide}}{\ce{CH _3 CH _2 MgBr + H _2 O}} \rightarrow \underset{\text{Ethane}}{\ce{CH _3- CH _3}} + \ce{Mg ( OH ) Br}$
It is therefore necessary to avoid even traces of moisture from a Grignard reagent.
That is why reaction is carried out in dry ether. On the other hand, this could be considered as one of the methods of converting halides to hydrocarbons.
$\rightarrow$ An important class of organo $-$ metallic compounds discovered by Victor Grignard in $1900$ is alkyl magne sium halide $,\ce{RMgX},$ referred as Grignard Reagents.
$\rightarrow$ These reagents are obtained by the reaction of haloalkanes with magnesium metal in dry ether.
$\rightarrow$ In the grignard reagent, the carbon $-$ magnesium bond is covalent but highly polar, with carbon pulling electrons from electropositive magnesium; the magnesium halogen bond is essentially ionic.
$\delta- \delta+\delta-$
$\ce{R - Mg X}$
$\rightarrow$ Grignard reagents are highly reactive and react with any source of proton to give hydrocarbons. Even water, alcohols, amines are sufficiently acidic to convert them to corresponding hydrocarbons.
$\ce{RMgX + H_2O \rightarrow RH + Mg(OH)X}$
$\underset{\text{Ethyl magnesium bromide}}{\ce{CH _3 CH _2 MgBr + H _2 O}} \rightarrow \underset{\text{Ethane}}{\ce{CH _3- CH _3}} + \ce{Mg ( OH ) Br}$
It is therefore necessary to avoid even traces of moisture from a Grignard reagent.
That is why reaction is carried out in dry ether. On the other hand, this could be considered as one of the methods of converting halides to hydrocarbons.
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