How do you get an alkyl group on a benzene ring?

An alkyl group can be added to a benzene molecule by an electrophile aromatic substitution reaction called the Friedel‐Crafts alkylation reaction. One example is the addition of a methyl group to a benzene ring. The mechanism for this reaction begins with the generation of a methyl carbocation from methylbromide.

How do you make alkyl benzene?

A two-step method using Friedel–Crafts acylation to form a ketone, followed by reduction. Arenes containing at least one benzylic C–H bond are oxidized with KMnO4 to benzoic acid. Substrates with more than one alkyl group are oxidized to dicarboxylic acids. Compounds without a benzylic hydrogen are inert to oxidation.

What activates a benzene ring?

In the following diagram we see that electron donating substituents (blue dipoles) activate the benzene ring toward electrophilic attack, and electron withdrawing substituents (red dipoles) deactivate the ring (make it less reactive to electrophilic attack). The first is the inductive effect of the substituent.

Which catalyst is used during halogenation of benzene?

Benzene reacts with chlorine or bromine in an electrophilic substitution reaction, but only in the presence of a catalyst. The catalyst is either aluminum chloride (or aluminum bromide if you are reacting benzene with bromine) or iron.

How do you add an ethyl group to benzene?

To put an ethyl group on the ring (to make ethylbenzene), benzene is treated with a mixture of ethene, HCl and aluminium chloride. or better: The aluminium chloride and HCl aren’t written into these equations because they are acting as catalysts.

How do you add a halogen to a benzene ring?

The halogenation of benzene Benzene reacts with chlorine or bromine in the presence of a catalyst, replacing one of the hydrogen atoms on the ring by a chlorine or bromine atom.

How is halogenation in a benzene ring carried out write also the mechanism?

The reaction between benzene and chlorine in the presence of either aluminum chloride or iron gives chlorobenzene. As a chlorine molecule approaches the benzene ring, the delocalized electrons in the ring repel electrons in the chlorine-chlorine bond.

What is the effect of alkyl group on to benzene ring?

Alkyl substituents (e.g. -CH3, -CH2CH3) are also electron donating groups – they activate the aromatic ring by increasing the electron density on the ring through an inductive donating effect. This is the same effect that allows alkyl groups to stabilise simple carbocations.

What are ring activating groups?

Atoms or groups that make the benzene molecule more reactive by increasing the ring’s electron density are called activating groups. Activating groups serve as ortho‐para directors when they are attached to a benzene ring, meaning that they direct an incoming electrophile to the ortho or para positions.

This is known as the Clemmensen reduction and involves heating the ketone with amalgamated zinc (a mixture of zinc and mercury) and concentrated hydrochloric acid for a long time. This indirect route is the best way of getting an alkyl group attached to a benzene ring.

How do substituents on a benzene ring affect reactivity?

I. The first is the relative reactivity of the compound compared with benzene itself. Experiments have shown that substituents on a benzene ring can influence reactivity in a profound manner.

Why is ethylbenzene more reactive than benzene?

An alkyl group attached to the ring makes the ring more reactive than the original benzene. That means that something like ethylbenzene reacts faster than benzene itself. The result is that you get several ethyl groups substituted around the ring rather than just one.

How do alkyl substituents increase the nucleophilicity of aromatic rings?

Alkyl substituents such as methyl increase the nucleophilicity of aromatic rings in the same fashion as they act on double bonds. Draw the resonance structures for benzaldehyde to show the electron-withdrawing group. Draw the resonance structures for methoxybenzene to show the electron-donating group.