Alkenes react via liquid bromine to provide alkyl bromides as the product. This reaction is an electrophilic addition reaction. Two bromine atoms are added to via the double bond of alkene.

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What is liquid bromine?

Liquid bromine is all set by dissolving Br2 in carbon tetrachloride (CCl4). Br2 is a non-polar molecule and also they dissettle in non-polar solvents such as carbon tetrachloride. Liquid bromine in carbon tetrachloride has red-brown colour.

Reaction of alkene and liquid bromine

If one double exists in the alkene molecule, it reacts via one molecule of Br2 and also two bromine atoms are added to the alkene to create alkyl halide compounds.

This reactivity proves, alkenes are unsaturated organic compounds.

This reaction is the reaction between alkenes and also halogens. In this tutorial, we are going to discuss about alkenes reactions through bromine liquid, and mechanisms of these reactions. We learn ethene and also bromine reaction and also propene and bromine reactivity.

Identify the reaction

When Br2(l) is mixed through alkene, ovariety / brown colour of bromine liquid is lessened.

Alkenes and bromine reactivity examples and also mechanism

Here, we are going to talk about about some reactions and also products of liquid bromine and alkenes such as ethene, propene, 2-butene and also even more. Mechanism of ethene and propene via Br2(l) are explained also.

Ethene and bromine reaction

Ethene is a symmetric alkene molecule. Ethene reacts via liquid bromine to provide 1,2-dibromoethane. Ethene and also bromine reactivity also gives a symmetrical alkyl halide compound. Two bromine atoms are attached to the two carbon atoms in the ethene molecule. This reactivity deserve to be done at room temperature or below temperatures than room temperature.


Mechanism of ethene and bromine reaction

Addition of bromine to ethene is an electrophilic enhancement reaction. Generally, bromine molecule (Br2) is not electron deficiency compound. But as a result of higher electrons thickness in the double bond of ethene, bromine molecule gets polarized. The most closed atom of bromine molecule to the double bond is positively charged (Brδ+) and other bromine atom gets negatively charged (Brδ-).

The positively charged bromine atom (electron deficiency atom) is assaulted by the double bond and make bonds through both carbon atoms of double bond. Other bromine molecule creates a bromide ion.


A cyclic brominium ion is provided as the intermediate product. Next, one carbon atom in the brominium ion is attacked by bromide ion (Br-). Then a bond in between Br- and also that carbon atom is developed and existing bromine - carbon bond in the ring is broken. A dibromide compound is created as the only product. No minor assets are provided in this reaction.

Ethene and also bromine reaction is a electrophilic addition reactivity.

Br&#delta;+ is an electrophile and it starts the reactivity. Also it adds to with the pi bond. Hence we speak to this reactivity is an electrophilic enhancement reactivity.

Propene and bromine reaction

Propene reacts with bromine and add 2 bromine atoms provide the 1,2-dibromopropane. Two bromine atoms are included to the double bond carbon. Ethene was a non polar alkene. But propene is a polar molecule. This reactivity is additionally an electrophilic enhancement reactivity.


Propene and bromine reaction mechanism

As bromine enhancement to ethene, propene and also bromine reactivity occurs in same way.

First, Br2 molecule is polarized by alkene bond. With that, electrons in the double bond assaults the positively charged Br atom and also develops a cyclic bromonium ion. Other Bromine atom is removed as a bromide ion.

As second step, produced bromide ion strikes a carbon atom which has a bond with other bromine atom. Then one of previous carbon - bromine bond is broken and a new carbon - bromine bond creates.

Alkene and bromine reactivity in the visibility of various other halide ions

In this situation, we need to go to the device of the reaction to understand also what will take place and also what are the assets can be given.

Halide ions have the right to be provided from as NaCl or NaI.

In the reactivity, Br+ is the just cation and it is linked to the two carbon atoms which had actually the double bond. So it creates cyclic brominium ion.

In following step, Br- or Cl- or I- can connect to give three different commodities if both Cl- and also I- are in the visibility via Br2.

Propene and also bromine in the existence of NaCl

Following product might be given.


According to the anion concentration, significant product is provided by higher concentrated anion.

What is the distinctions of bromine reaction with ethene and also ethyne?

Ethene aand ethyne are alkene and alkyne respectively. Alkynes likewise react with bromine liquid and also give alkyl halides as products. But difference is alkyne have the right to reacts with two bromine molecules while alkene is limited to one bromine molecule if these is only one double bond in the alkene. So 4 bromine atoms will certainly be added to the ethyne molecule when excess bromine liquid is included. Otherwise only t2 bromine atoms will br added.

What is the product of the propene and also bromine and its IUPAC name?

1,2-dibromopropane is the IUPAC name of the product which is an alkyl dihalide compound.

Importance of alkene and also bromine reaction

The product, alkyl dihalide are offered to produce alkyne. 1,2-dibromoethane is treated with alcoholic KOH to prepare ethyne.

Preparing 1,2-dibromoethane without Br2 liquid

You desire to prepare 1,2-dibromoethane from ethene. But you do not have actually liquid bromine to execute this conversion. Then, imply a technique this deserve to be done.


Ethene reacts through cold alkali KMnO4 (Baeyer"s reagent). It gives ethane-1,2-diol.

Next off ethane-1,2-diol reacts through PBr3 or HBr to produce 1,2-dibromoethane.

What is the name of the reactivity once propene reacts through bromine?

Due to addition of 2 bromine atoms via double bond, this is an addition reaction. And Brδ+ which is an electrophile starts the reaction. So this reactivity is an electrophilic addition reaction.

what form of organic reaction in between propene and also bromine water?

An electrophilic addition reactivity occurs. First, a bromine atom is included to the propene through double bond. Due to predence of water, tbelow are hydroxyl ions through bromide ion. So in the seconsd step, hydroxyl ions deserve to be included to cyclic brominium ion choose bromide ions.

Can determine benzene and alkene from this reaction

Here we are going to determine benzene and also alkene from the comparing of reaction with bromine.

Benzene and also bromine reactivity

Benzene does not react with Br22 / CCl4. Because of this brown/ orange colour is not adjusted with time.

But with alkene, oselection colour of bromine is lessened because of the reactivity.

According to the colour distinction, benzene and alkene deserve to be established.

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ethyne via bromine

As alkene, alkynes additionally react via bromine liquid. When tright here is excess bromine, four bromine atoms are added to the alkyne. So, ethyne reacts through bromine liquid to produce tetrabromoethane.

Reactions in Organic Chemistry

Propene + HBr reaction Alekene hydration - Ethene + dilute H2SO4 Alkane chlorination - Methane and Cl2 reactivity Clemmensen reduction of aldehydes and also ketones Hofmann degradation of amides Aldol condensation of aldehydes and ketones