Why do alkenes undergo electrophilic addition reaction?
Alkenes undergo electrophilic addition reactions. bond electrons forming a bond with an electrophile. For unsymmetrical alkenes, the electrophile adds to the sp2 carbon that is bonded to the most hydrogens.
Addition reactions are limited to chemical compounds that have multiple bonds, such as molecules with carbon–carbon double bonds (alkenes), or with triple bonds (alkynes). Addition reactions are also encountered in polymerizations and called addition polymerization.
- The actual reaction is known as homolytic fission and produces alkenes, which are the basis for the economically important production of polymers. Thermal cracking is currently used to "upgrade" very heavy fractions or to produce light fractions or distillates, burner fuel and/or petroleum coke.
- In using arrow pushing, "curved arrows" or "curly arrows" are superimposed over the structural formulae of reactants in a chemical equation to show the reaction mechanism. The arrows illustrate the movement of electrons as bonds between atoms are broken and formed.
- Markovnikov's rule (Markovnikov addition): In an addition reaction of a protic acid HX (hydrogen chloride, hydrogen bromide, or hydrogen iodide) to an alkene or alkyne, the hydrogen atom of HX becomes bonded to the carbon atom that had the greatest number of hydrogen atoms in the starting alkene or alkyne.
Alkenes and alkynes are unsaturated - they have π -bonds, so don't have the full number of hydrogen that they could have. The alkenes and alkynes want to form more σ -bonds and have a structure more like an alkane, so they undergo addition reactions.
- Alkenes do not generally undergo substitution reactions because every unsaturated compound aims to get saturated and hence undergo addition . With the exception of benzene. Benzene and most aromatic compounds like furan, pyrrole have resonance which gives them extraordinary stability.
- Arenes contain double bonds just like alkenes but they do not undergo electrophilic addition because these would result to their loss of ring aromaticity. The order of substitution on aromatic compounds is governed by the nature of substituents present in the aromatic ring.
- Hydrocarbons. Most of the compounds in crude oil are hydrocarbons. This means that they only contain hydrogen and carbon atoms, joined together by chemical bonds. There are different types of hydrocarbon, but most of the ones in crude oil are alkanes.
All of the products are now saturated, as they contain only single carbon-to-carbon bonds. The addition of hydrogen, reaction (2), is also known as hydrogenation. The addition of water, reaction (4), is a very important reaction to remember, because it produces alcohols. Addition of water is also known as hydration.
- All of the products are now saturated, as they contain only single carbon-to-carbon bonds. The addition of hydrogen, reaction (2), is also known as hydrogenation. The addition of water, reaction (4), is a very important reaction to remember, because it produces alcohols. Addition of water is also known as hydration.
- The formation of poly(ethene) from ethene is an example of addition polymerisation.In addition polymerisation small unsaturated monomers (monomerswith carbon to carbon double bonds) join up by the opening of the doublebond allowing them to join up to form a long carbon chain.
- 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. A pair of electrons from the carbon double bond move onto the positive bromine atom.
Updated: 17th September 2018