Chapter 8 Notecards

the installation of hydroxyl groups on adjacent carbons, such as by the reaction of OsO4 or KMnO4 with an alkene.

a reaction that results in an increase in the number of groups attached to a pair of atoms joined by a double or triple bond. An addition reaction is the opposite of an elimination reaction.

An addition that places the parts of the adding reagent on opposite faces of the reactant.

An addition reaction where the hydrogen atom of a reagent becomes bonded to an alkene or alkyne at the carbon having the fewer hydrogen atoms initially. This orientation is the opposite of that predicted by Markovnikov’s rule.

A compound bearing a bromine atom and a hydroxyl group on adjacent (vicinal) carbons.

An ion containing a positive bromine atom bonded to two carbon atoms.

An uncharged species in which a carbon atom is divalent. The species :CH2, called methylene, is a carbene.

A carbene-like species. A species such as the reagent formed when diiodomethane reacts with a zinc–copper couple. This reagent, called the Simmons–Smith reagent, reacts with alkenes to add methylene to the double bond in a stereospecific way.

A compound bearing a chlorine atom and a hydroxyl group on adjacent (vicinal) carbons.

A process by which a starting material is converted into a product containing adjacent alcohol functionalities (called a “1,2-diol” or “glycol”).

A Lewis acid, an electronpair acceptor, an electron-seeking reagent.

A diol.

A compound bearing a halogen atom and a hydroxyl group on adjacent (vicinal) carbons.

An ion containing a positive halogen atom bonded to two carbon atoms.

The addition of water to a molecule, such as the addition of water to an alkene to form an alcohol.

The addition of a boron hydride (either BH3 or an alkylborane) to a multiple bond.

A rule for predicting the regiochemistry of electrophilic additions to alkenes and alkynes that can be stated in various ways. As originally stated (in 1870) by Vladimir Markovnikov, the rule provides that “if an unsymmetrical alkene combines with a hydrogen halide, the halide ion adds to the carbon with the fewer hydrogen atoms.” More commonly the rule has been stated in reverse: that in the addition of HX to an alkene or alkyne the hydrogen atom adds to the carbon atom that already has the greater number of hydrogen atoms. A modern expression of Markovnikov’s rule is: In the ionic addition of an unsymmetrical reagent to a multiple bond, the positive portion of the reagent (the electrophile) attaches itself to a carbon atom of the reagent in the way that leads to the formation of the more stable intermediate carbocation.

The carbene with the formula :CH2.

A reaction in which the carbon-carbon double bond of an alkene or alkyne is both cleaved and oxidized, yielding compounds with carbon-oxygen double bonds.

The addition of iOH and iHgO2CR to a multiple bond.

A twostep process for adding the elements of water (H and OH) to a double bond in a Markovnikov orientation without rearrangements. An alkene reacts with mercuric acetate (or trifluoroacetate), forming a bridged mercurinium ion. Water preferentially attacks the more substituted side of the bridged ion, breaking the bridge and resulting, after loss of a proton, in an alcohol. Reduction with NaBH4 replaces the mercury group with a hydrogen atom, yielding the final product.

The oxidative cleavage of a multiple bond using O3 (ozone). The reaction leads to the formation of a cyclic compound called an ozonide, which is then reduced to carbonyl compounds by treatment with dimethyl sulfide (Me2S) or zinc and acetic acid.

A reaction that yields only one (or a predominance of one) constitutional isomer as the product when two or more constitutional isomers are possible products.

In reactions where chirality centers are altered or created, a stereoselective reaction produces a preponderance of one stereoisomer. Furthermore, a stereoselective reaction can be either enantioselective, in which case the reaction produces a preponderance of one enantiomer, or diastereoselective, in which case the reaction produces a preponderance of one diastereomer.

A reaction in which a particular stereoisomeric form of the reactant reacts in such a way that it leads to a specific stereoisomeric form of the product.

An addition that places both parts of the adding reagent on the same face of the reactant.

An oxidation reaction in which an alkene reacts to become a 1,2-diol (also called a glycol) with the newly bonded hydroxyl groups added to the same face of the alkene.

A compound that functions as the equivalent of a molecular fragment needed in a synthesis.

The fragments that result (on paper) from the disconnection of a bond. The actual reagent that will, in a synthetic step, provide the synthon is called the synthetic equivalent.