Electrophilic addition

In organic chemistry, an electrophilic addition reaction is an addition reaction where in chemical compound a pi bond is removed by the creation of two new covalent bonds. In electrophilic additions common substrates have a carbon-carbon double bond or triple bond.

Related Topics:
Organic chemistry - Addition reaction - Chemical compound - Pi bond - Covalent bond - Double bond - Triple bond

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Y-Z + C=C → Y-C-C-Z

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The driving force for this reaction is the formation of an electrophile Y+ that forms a covalent bond with a electron-rich unsaturated system (-C=C-) (step 1). The positive charge on Y is transferred to the carbon - carbon bond.

Related Topics:
Electrophile - Covalent bond - Unsaturated

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step (1) Y+ + -C=C- → Y-C-C+-

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In step 2 of an electrophilic addition the positively charged intermediate combines with (Z) that is electron-rich to form the second covalent bond.

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step (2) Y-C-C+- + Z → Y-C-C-Z

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Step 2 is also found in a SN1 reaction. The exact nature of the electrophile and the nature of the positively charged intermediate is not always clear and depends on reactants and reaction conditions.

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In all asymmetric addition reactions to carbon regioselectivity is important and often determined by Markovnikov's rule. Organoborane compounds give anti-Markovnikov additions. Electrophilic attack to an aromatic system results in electrophilic aromatic substitution rather than an addition reaction.

Related Topics:
Regioselectivity - Markovnikov's rule - Organoborane - Aromatic - Electrophilic aromatic substitution

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