 Let's discuss another important reaction of haloalkanes that is with metals. Now haloalkanes like alkyl chloride, alkyl iodide and alkyl bromide react with metals to form an entire class of compounds called organometallic compounds. So in these compounds, carbon forms bonds with an electropositive metal like magnesium or lithium. Now among these organometallic compounds, an important class of compounds is called the Grignard reagent. In fact even the Grignard reagent was discovered as early as 1910 or 1912 by a scientist named Victor Grignard. This reagent is highly versatile and relevant even today. We use Grignard reaction extensively in synthetic chemistry to prepare new compounds or to form compounds with new cc bonds. Now to prepare a Grignard reagent, we need a starting compound which is a haloalkane. For example, let's take ethyl bromide here CH3CH2Br reacts with magnesium in the presence of dry ether to form CH3CH2MgBr. So this is our Grignard reagent. The general formula of Grignard reagent is RMGX. Now let's look at this reaction once again. In the starting compound which is our haloalkane, you can see that the CBR bond is highly polar. Bromine is highly electronegative and it draws electron density towards itself such that carbon acquires a partial positive charge and bromine here gets a partial negative charge. What about a product which is the Grignard reagent? How does the polarity change in a product? Well you can see that here carbon acquires a partial negative charge because it is more electronegative as compared to the metal magnesium. Magnesium is a highly electropositive metal right? So carbon draws electron density towards itself and gets a partial negative charge. So look at this, the polarity has reversed here. Now this is very powerful because in this case carbon acts as a nucleophile and it can attack other electrophilic species to produce new compounds or form new C-C bonds. So this polarity difference between carbon and magnesium is the reason why Grignard reagent is highly reactive. So let's look at a reaction where we can use Grignard reagent to form new C-C bonds. So let's take a simple Grignard reagent let's say methyl magnesium bromide ok CH3 MgBr and react it with an electrophilic species like ketone CH3 C double bond O CH3 as a tone the simplest ketone. So in this reaction the Grignard reagent methyl group here is nucleophilic and has a partial negative charge and here the carbon is electrophilic. It has a partial positive charge because oxygen being more electronegative draws electron density towards itself and makes the CO bond highly polar. So when these two react together the nucleophilic methyl group attacks the electrophilic carbon center and gives us this intermediate which is CH3 C CH3 O minus so oxygen N gets a counter and which is MgBr plus this methyl group of the Grignard reagent forms a new C-C bond here. So this is the new C-C bond that we talked about. Now in the next step we treat it with water and oxygen abstracts a proton from water to give us a tertiary alcohol CH3 C CH3 OH and this CH3 has come from a Grignard reagent. So this is an example of a reaction where a Grignard reagent reacts with a carbonyl compound to form alcohol. Now one of the important things we need to remember with respect to Grignard reagent is that the reactions of Grignard reagent is carried out in highly anhydrous conditions that is there should be absolutely no trace of water in the reaction mixture. But what do you think would happen to the Grignard reagent if there was water? Well we already saw how reactive Grignard reagent is right because of the polarity difference between our carbon and magnesium. So in the presence of water what happens is that, so let's take an example of a Grignard reagent let's say CH3 MgBr. This carbon being highly nucleophilic will abstract a proton from water and form a hydrocarbon and the Grignard reagent gets deactivated in the process. So this is not just true with water. Any compound that has an acidic hydrogen if it is present in the reaction mixture then our Grignard reagent is likely to get deactivated because instead of reacting with a species of interest let's say a carbonyl compound the first thing that it does is abstract this acidic hydrogen from that compound and form a hydrocarbon. So this is why it is extremely important that we carry out Grignard reaction in highly anhydrous conditions. So the most commonly used solvents in Grignard reaction are diethyl ether which is C2H5O C2H5 or even tetrahydrofuran THF. So the advantage of using these solvents is that they are polar and help stabilize the Grignard reagent but at the same time they do not have any acidic hydrogen that can deactivate the Grignard reagent. Now you see the lone pair of electrons on diethyl ether can complex with the magnesium of the Grignard reagent and help stabilize it. We will learn more about the reactions of Grignard reagents in the next chapter.