What does Br2 and FeBr3 do?
Mechanism: a π-bond of benzene acts as a nucleophile and “attacks” the Br2•FeBr3 complex (electrophile) leading to a resonance stabilized carbocation. Loss of a proton gives the substitution product and restores aromaticity.
What is the electrophile formed by combining Br2 and FeBr3?
The electrophile in bromination is the complex of bromine with FeBr3, formed as shown in Eq. 16.4. a resonance-stabilized carbocation intermediate. The electrophile approaches the p-electron cloud of the ring above or below the plane of the molecule.
Why is Br2 turned into a strong electrophile in the presence of FeBr3?
The bromine molecule reacts with FeBr3 by donating a pair of its electrons to the Lewis acid, which creates a more polar Br-Br bond, and thus a more reactive electrophile.
Why is FeBr3 needed in bromination?
Adding FeBr3 is just to reduce the Br−Br bond strength, speeding up the reaction (attack of the aromatic ring on the bromine is part of the rate determining step, which is slow in the bromination of benzene). It functions as a catalyst being recycled when the Br− grabs a H+ to restore aromaticity in the ring.
What is the action of Br2 on benzene?
The bromination of benzene is an example of an electrophilic aromatic substitution reaction. In this reaction, the electrophile (bromine) forms a sigma bond to the benzene ring, yielding an intermediate. Then, a proton is removed from the intermediate to form a substituted benzene ring.
What happens when bromobenzene is treated with Br2 FeBr3?
Bromobenzene reacts with bromine in the presence of febr3 to give two products called o-di-bromobenzene or p-di-bromobenzene as main products along with HBr.
Why is FeBr3 a Lewis acid?
Like most metal halides, FeBr3 is a Lewis acid, i.e. an electron pair acceptor. Lewis acids have at least one empty orbital they can use to accept an electron pair. In the case of FeBr3 the iron atom has empty 3d orbitals. Equation 5 illustrates a Lewis acid-Lewis base reaction between FeBr3 and Br2.
What happens when benzoic acid is treated with Br2 in presence of FeBr3?
Benzoic acid is then brominated, Br2, FeBr3 to give meta- bromobenzoic acid.
Why does benzene not react with Br2?
However when bromine is added to benzene, the bromine remains orange and there is no reaction. This is because: Benzene has delocalised electrons spread over 6 carbon atoms, whereas alkenes have localised electrons above and below the 2 carbon atoms in the double bond.
What happens when benzene is treated with Br2?
The reaction between benzene and bromine in the presence of either aluminum bromide or iron gives bromobenzene.
How is FeBr3 an electrophile?
FeBr3 is used as a catalyst in the bromination of benzene because of its strong Lewis acid character. Without going into detail, the bromine ( Br2 ) molecule reacts with FeBr3 and donates a pair of electrons to it. This polarizes Br2 , making it a better electrophile (more attracted to electrons).
Is Br2 a Lewis base?
Ralph Pearson classified all Lewis acids and bases as hard and soft acids and bases. Br2 and Br+ are soft Lewis acids and Br- has properties in between soft bases and hard bases. Hence Br2 is considered to be a soft Lewis acid.
What happens when benzoic acid reacts with Br2?
`o-`bromobenzoic acid`m-`bromobenzoic acid`p-`bromobenzoic acid3, 4-dibromobenzoic acid.
What products are formed when M Xylene is treated with Br2 in the presence of FeBr3?
Solution. Explanation: It is due to steric hindrance, these products will be formed, –CH3 group is o and p-directing.
Is Br activating or deactivating?
Halogens (F, Cl, Br, I) Are Deactivating Not all groups capable of pi donation are activating groups. For example, halogens (F, Cl, Br, I) tend to be deactivating.
Why Br2 is a Lewis acid?
Br2 and Br+ are soft Lewis acids and Br- has properties in between soft bases and hard bases. Hence Br2 is considered to be a soft Lewis acid. Soft acids have large acceptor atoms of low positive charge, high polarisability and low electronegativity.
Is bromine a soft base?
Sulfides are the most common soft bases in geology, although the larger halides, like bromide and iodide, are also soft. Some metals can pair with either hard or soft bases, particularly those metals from the middle of the transition metal group.
How does benzoic acid react with bromine in the presence of ferric bromide?
– In the above chemical reaction benzoic acid reacts with bromine in presence of ferric bromide reagent. – In the above chemical reaction bromine reacts with benzoic acid and forms meta bromo benzoic acid and hydrogen bromide as the products.
What happens when benzoic acid reacts with bromine water?
Hence, salicylic acid will react with bromine water, but benzoic acid won’t. Physically, bromine water is orange due to Br2, but if the bromine reacts, then the orange color will no longer be present.
What are the major products formed by treating the compound shown with Br2?
Description: Treatment of alkenes with bromine (Br2) gives vicinal dibromides (1,2-dibromides).