CHM 221- Electrophiles and Nucleophiles

Reaction Intermediates

“steps” of reaction, react as soon as they form

Free Radical

carbon with 3 bonds, one unpaired electron

Carbocation

Carbon with 3 bonds, positive formal charge

Carbanion

Carbon with three bonds and a lone pair, negative formal charge

Carbenes

Carbon with two bonds and a lone pair

similar in energy and size

Bonds are strongest when made by overlapping orbitals that are

Homolytic Breaking

Breaking of bond results in one electron each for each product

Nonpolar solvents

What type of solvents are used for homolytic breaking?

Polar solvents

What type of solvents are used for heterolytic breaking?

bonds broken - bonds formed

Bond dissociation energy equation

endothermic

If delta H > 0

Nucleophile

Electron rich center, donates electrons

Electrophile

Electron deficient center, accepts electrons

Acid Base Reactions

These reactions will happen first if possible

OH-, SH-, H3CO-, H3CS-, ROH, RSH, RNH2, pi electrons of alkene

Common Nucleophiles

Carbocations, Carbonyls, Alkyl Halides

Common Electrophiles

Tertiary

Most stable carbocation

methyl, primary

These two types of carbocations willl not form and are too unstable

Hyperconjugation

Name for formation of double bond between carbocation and beta carbon

Proton Transfer Reactions, Nucleophilic attacks, Leaving Groups

Reversible Reactions

Carbocation Rearrangements, Nucleophilic Attacks

Irreversible Reactions

Nucleophilic attack, proton transfer, leaving group, Carbocation Rearrangements

The four types of reactions

rate = k[A]

First order equation

rate = k[A][B]

Second order equation

Transition States

Not even an intermediate, just a midpoint

Hammond Postulate

Chemical species similar in energy are similar in structure

Products

In endothermic reactions, is the transition state closer to reactants or products?

Concerted

One step reaction