Summary of electrophilic addition reactions PDF

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Summary of electrophilic addition reactions

Type

Reagent

Product

HBr, HCl or HI

Alkyl halides with alkenes, vinyl halides with alkynes

Addition of water

H2O and H2SO4

Alcohols

Addition of halogens

Br2/organic solvent or Cl2/organic solvent

Addition of hydrogen halides

Oxymercurati on-reduction

Dibromo or dichloro alkanes with alkenes. With alkynes, the product is dibromo or dichloro alkenes. When an excess of halogen is used, the product is tetrabromo or tetrachloro alkanes Hg(O2CCH3 Alcohols with )2, H20 and alkenes, with NaBH4 alkynes the product is an enol. Enols are unstable and rearrange to either ketone or aldehyde

Markovn Syn/anti ikov’s rule Obey Both syn and anti products seen

obey

Obey

Obey

Both syn and anti products seen Only anti addition seen

Only anti addition seen

Special notes

With alkenes, the product is alkyl halide. In the case of alkynes, with one mole of HX, the product is vinyl halide(has a double bond), with two moles of HX, the product is dihalo substituted alkanes none

The reaction needs to be carried out in presence of organic solvents to get the dibromo or dichloro products. If the reaction is carried in the presence of water, the product is halohydrin as water acts as the nucleophile. When halohydrins are exposed to basic conditions, they form epoxides With alkenes, the product is alcohol, with alkynes the product is enol which rearranges to ketone or aldehyde depending on the type of alkyne

Hydroboration

BH3/H2O2 or disiamylbora ne/H2O2

Hydroxylation

KMnO4

Hydrogenatio n

H2 in presence of hydrogenatio n catalysts such as Pd, Pt, Ni, PtO2

Alcohols with alkenes. In the case of alkynes, the product is enol, which rearranges to either aldehyde or ketone Diol Alkanes with alkenes

Do not obey

Only syn addition is seen

This is the only addition reaction we have seen, where Markovnikov’s rule is not obeyed and the reaction proceeds via only syn addition

Not important NA

NA

None

Syn

When hydrogenation of alkynes is carried out in presence of H2 and regular hydrogenation catalysts, the product is alkane. This reaction does not stop at the alkene stage. However, if we wish to stop at the alkene stage, we need to use a special catalyst called Lindlar’s catalyst...