The double bond attacks the bromine and forms a new carbon — bromine bond, while the other carbon atom becomes electron deficient. The resulting carbocation reacts with the bromine ion left from the first step to form the second carbon — bromine bond. While this mechanism is sufficient at A Level, for those looking to further study in chemistry or are interested, the more correct mechanism via a bromonium ion can be found here. Vote count: 3. No votes so far! Be the first to rate this page.
Tell us how we can improve this page in your own language if you prefer? So this bromine maybe would want to pull an electron. If this guy gets an electron, then this guy can get an electron. So you can imagine this thing as a whole really, really wants to grab an electron. It might be very good at doing it. So this is our strong electrophile. So what actually will happen in the bromination of this benzene ring-- let me draw some hydrogens here just to make things clear.
We already have hydrogens on all of these carbons. Sometimes it's important to visualize this when we're doing electrophilic aromatic substitutions.
So we already have a hydrogen on all of these molecules. So maybe this is so electrophilic it can actually break the aromatic ring, nab this electron right there. So maybe, this electron right there goes to the bromine. Maybe I should even do it this way. Just to make it clear. Kind of replaces that one. Although, obviously the electrons are a bit fungible. So maybe it goes over there.
And then when it goes to this-- let me make it clear it's going to the blue bromine. So the electron right here goes to the blue bromine. If the blue bromine gets an electron then it can let go of this blue electron.
So this blue electron can then go to this bromine right over here. And then what is our situation look like? Well if we have that, then let me draw our benzene ring first. We have our benzene ring first. So let me draw the benzene ring. This double bond, that double bond.
Let me draw all of the hydrogens. I want to do them in purple. So we have one hydrogen, two hydrogens, three hydrogens, four hydrogens, five hydrogens, and six hydrogens. This orange electron is still with this carbon right here. But that electron got nabbed by this bromine. So that electron got nabbed by this bromine right over here.
I've kind of flipped it around and now it has its other six valence electrons. One, two, three, four, five, six. The electron got taken away from this carbon. So now that carbon will have a positive charge. But we saw in the last video, it's actually resonance stabilized. That electron could jump there. That electron can jump there. So it's not as stable as a nice aromatic benzene ring like this.
But it's not a ridiculous carbocation. It's stable enough for it to exist for some small amount of time while we kind of hit our transition state. And then this molecule over here, what's it going to look like? Well this bromine had a positive charge. Now it gained an electron. Let me draw it. So you have your bromine. It gained an electron. So now it is neutral again. So let's see, it had the one, two, three, four, five, six. Now it gained this blue electron.
According to octet rule Al should have 8 electrons in outermost shell but their are only 6 electrons after bonding with Chlorine as each Cl shares one electron with Aluminium. Owing to deficiency of electrons it acts as electrophile.
Is ch3oh a nucleophile or electrophile? Weak nucleophiles are neutral and don't bear a charge. What is a Bromonium ion? A bromonium ion is formed. The bromonium ion is then attacked from the back by a bromide ion formed in a nearby reaction. In the process, the electrons in the bromine-bromine bond are repelled until they are entirely on the right-hand bromine atom, producing a bromide ion.
Is bromine a nucleophile? That is, the electrons in the diatomic bromine molecule are repelled by the alkene and are pushed back along the molecule. The positively charged bromine atom acts as an electrophile, reacting with the double carbon bond. The negatively charged bromide ion is acting as a nucleophile. Why is h2o a nucleophile? Re:Water as a nucleophile The high electronegativity of oxygen stabilizes the electrons of oxygen making it a poor nucleophile.
The hydrogen of water on the other hand, is induced electrophilic, due to the highly electronegative oxygen.
Is bromination exothermic? Preliminary step: Formation of the strongly electrophilic bromine cation. Step 1: The electrophile forms a sigma-bond to the benzene ring, generating a positively charged benzenonium intermediate. Step 2: A proton is removed from this intermediate, yielding a substituted benzene ring.
This mechanism for electrophilic aromatic substitution should be considered in context with other mechanisms involving carbocation intermediates. To summarize, when carbocation intermediates are formed one can expect them to react further by one or more of the following modes:. The cation may bond to a nucleophile to give a substitution or addition product.
The cation may transfer a proton to a base, giving a double bond product. The cation may rearrange to a more stable carbocation, and then react by mode 1 or 2.
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