Chapter 8: Reactions of Alkenes

addition

A reaction involving an increase in the number of groups attached to the alkene and a decrease in the number of elements of unsaturation.

anti addition

An addition in which two groups add to opposite faces of the double bond (as in addition of Br2)

electrophilic addition

An addition in which the electrophile (electron-pari acceptor) bonds to one of the double-bonded carbons first, followed by the nucleophile.

syn addition

An addition in which two groups add to the same face of the double bond (as in osmium tetroxide hydroxylation).

addition polymer (chain-growth polymer)

A polymer that results from rapid addition of one molecule at a time to a growing polymer chain, usually with a reactive intermediate (cation, radical, or anion) at the growing end of the chain.

alkoxy group (alkoxyl group)

(-O-R-) An alkyl group bonded through an oxygen atom, as in an ether.

alkoxymercuration

The addition of mercuric acetate to an alkene in an alcohol solution, forming an alkoxymercurial intermediate. Demercuration gives an ether.

alpha elimination (α elimination)

The elimination of two atoms or groups from the same carbon atom. These types of eliminations can be used to form carbenes.

anionic polymerization

The process of forming an addition polymer by chain-growth polymerization involving an anion at the end of the growing chain.

asymmetric induction (enantioselective synthesis)

The formation of an optically active product from an optically inactive starting material. Such a process requires the use of an optically active reagent or catalyst.

beta elimination (β elimination)

The elimination of two atoms or groups from adjacent carbon atoms. This is the most common type of elimination.

carbene, methylene

A reactive intermediate with a neutral carbon atom having only two bonds and two nonbonding electrons.

methylene, :CH2

simplest example of a carbene, state name and formula

cationic polymerization

The process of forming an addition polymer by chain-growth polymerization involving a cation at the end of the growing chain.

chain-growth polymer

another name for an addition polymer

demercuration

The removal of a mercury species from a molecule. Doing this to products of oxymercuration and alkoxymercuration is usually accomplished using sodium borohydride.

epoxide (oxirane)

A three-membered cyclic ether.

epoxidation

Forming of an epoxide, usually from an alkene.

epoxidations

A peroxyacid is generally used for alkene __________.

free-radical polymerization

The process of forming an addition polymer by chain-growth polymerization involving a free radical at the end of the growing chain.

glycol

A 1,2-diol.

halogenation

The addition of a halogen (X2) to a molecule, or the free-radical substitution of a halogen for a hydrogen.

halohydrin

A beta-haloalcohol, with a halogen and a hydroxyl group on adjacent carbon atoms.

halonium ion

A reactive, cationic intermediate with a three-membered ring containing a halogen atom; usually, a chloronium ion, a bromium ion, or an iodonium ion.

heterogenous catalysis

Use of a catalyst that is in a separate phase from the reactants. For example, a platinum hydrogenation catalyst is a solid, separate, phase from the liquid alkene.

homogeneous catalysis

Use of a catalyst that is in the same phase as the reactants. For example, the acid catalyst in a hydration is in the liquid phase with the alkene.

hydration

The addition of water to a molecule. Hydration of an alkene forms an alcohol.

alcohol

Hydration of an alkene forms a(n) _________.

hydroboration

The addition of borane (BH3) or one of its derivatives (BH3^.THF3, for example) to a molecule.

hydrogenation

The addition of hydrogen to a molecule. The most common example of this is the addition of H2 across a double bond in the presence of a catalyst (catalytic hydrogenation or catalytic reduction).

hydroxylation

The addition of two hydroxyl groups, one at each carbon of the double bond; formerly, an oxidation.

Markovnikov's rule (original statement)

When a proton acid adds to the double bond of an alkene, the proton bonds to the carbon atom that already has more hydrogen atoms.

Markovnikov's rule (extended statement)

In an electrophilic addition to an alkene, the electrophile adds in such a way as to generate the most stable intermediate.

Markovnikov orientation

An orientation of addition that obeys the original statement of Markovnikov's rule; one that gives the anti-Markovnikov product

MCPBA (meta-chloroperoxybenzoic acid)

A common reagent for epoxidizing alkenes. This reagent dissolves in common solvents such as dichloromethane. As the epoxidation takes place, the m-chlorobenzoic acid by-product precipitates out of solution.

metathesis (olefin metathesis)

Any reaction that trades and interchanges the alkyliden groups of an alkene.

monomer

One of the small molecules that bond together to form a polymer.

organic synthesis

The preparation of desired organic compounds from readily available materials.

oxidative cleavage

The cleavage of a carbon-carbon bond through oxidation. Carbon-carbon double bonds are commonly cleaved by ozonolysis/reduction or by warm, concentrated permanganate.

oxymercuration

The addition of aqueous mercuric acetate to an alkene.

ozonolysis

The use of ozone, usually followed by reduction, to cleave a double bond.

peroxide effect

The reversal of orientation of HBr addition to alkenes in the presence of peroxides. A free-radical mechanism is responsible for the peroxide effect.

peroxyacid (peracid)

A carboxylic acid with an extra oxygen atom and a peroxyl (-O-O-) linkage. The general formula is (RCO3H).

polymer

A high-molecular weight compound composed of many molecules of a smaller, simpler, compound called the monomer.

polymerization

A reaction of monomer molecules to form a polymer.

regioselective reaction

A reaction in which one direction of bond making or bond breaking occurs preferentially over all other directions.

retrosynthetic analysis

A method of working backward to solve multistep synthetic problems.

Simmons-Smith reaction

A cyclopropanation of an alkene using the carbenoid reagent generated from diiodomethane and the zinc-copper couple.

stereospecific reaction

A reaction that converts different stereoisomers of the starting material into different stereoisomers of the product.