Question
What is organo metallic compound? Explain grignard reagent.
✓
Answer
→ 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.
→ An important class of organo-metallic compounds discovered by Victor Grignard in 1900 is alkyl magne sium halide, RMgX, referred as Grignard Reagents.
→ These reagents are obtained by the reaction of haloalkanes with magnesium metal in dry ether.
→ 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.
$\begin{array}{l}\delta-\quad \delta+\delta- \\ R - Mg X \\\end{array}$
→ 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.
RMgX + H2O → RH + Mg(OH)X
$\underset{\text{Ethyl magnesium bromide}}{CH _3 CH _2 MgBr} + H _2 O \rightarrow \underset{Ethane}{CH _3- CH _3}+ Mg ( OH ) Br$
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.
→ An important class of organo-metallic compounds discovered by Victor Grignard in 1900 is alkyl magne sium halide, RMgX, referred as Grignard Reagents.
→ These reagents are obtained by the reaction of haloalkanes with magnesium metal in dry ether.
→ 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.
$\begin{array}{l}\delta-\quad \delta+\delta- \\ R - Mg X \\\end{array}$
→ 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.
RMgX + H2O → RH + Mg(OH)X
$\underset{\text{Ethyl magnesium bromide}}{CH _3 CH _2 MgBr} + H _2 O \rightarrow \underset{Ethane}{CH _3- CH _3}+ Mg ( OH ) Br$
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.
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
- Write the structural difference between starch and cellulose.
- What type of linkage is present in Nucleic acids?
- Give one example each for fibrous protein and globular protein.
Explain the bromination of Aniline. State what is done if Mono substituted derivative of aniline is to be formed by this process.
A 5% solution (by mass) of cane sugar in water has freezing point of 271K. Calculate the freezing point of 5% glucose in water if freezing point of pure water is 273.15 K.
The molar conductivity of 0.025 mol L–1 methanoic acid is 46.1 S cm2 mol–1. Calculate its degree of dissociation and dissociation constant. Given λ0 (H+) = 349.6 S cm2 mol–1 and λ0 (HCOO–) = 54.6 S cm2 mol-1.
Match the properties given in Column I with the metals given in Column II.
| | Column I (Property) | | Column II (Metal) |
| (i) | An element which can show +8 oxidation state | (a) | Mn |
| (ii) | 3d block element that can show upto +7 oxidation state | (b) | Cr |
| (iii) | 3d block element with highest melting point | (c) | Os |
| (d) | Fe |
How many mL of 0.1 M HCl are required to react completely with 1 g mixture of Na2CO3 and NaHCO3 containing equimolar amounts of both?
If 200 mol of $H _2$ (at NTP) and 0.60 g of Cu are obtained by passing electric current in the solution of acidified water and $CuSO _4$ respectively in two electrolytic cell connected in series, then what will be the equivalent weight of Cu ?
→The $\pi$-complexes are known for transition metals only. Why?
→Give two reactions that show the acidic nature of phenol. Compare acidity of phenol with that of ethanol.
Why Haloarenes undergo electrophilic substitution reactions at o and p - position? Why it is less reactive than benzene ?