Alkene and Alkyne Reaction Summaries

Vocabulary flashcards covering the key addition, oxidation, reduction, and cleavage reactions of alkenes and alkynes, along with their associated stereochemical and regiochemical outcomes.

Markovnikov Addition

An electrophilic addition reaction where the electrophile/hydrogen attaches to the less substituted carbon and the nucleophile/halogen attaches to the more substituted carbon via a carbocation intermediate.

Keto-Enol Tautomerization

A chemical equilibrium occurring during alkyne hydration in which an enol intermediate rearranges to form a generally more stable carbonyl compound, such as a ketone or an aldehyde.

Alkyne Hydroboration

The anti-Markovnikov hydration of an alkyne producing an enol intermediate with the hydroxyl group on the least substituted carbon, which subsequently tautomerizes to yield an aldehyde.

Lindlar's Catalyst

A poisoned catalyst used in the catalytic hydrogenation of alkynes with $H_2$ that provides syn addition stereochemistry to selectively produce a cis-alkene.

Alkyne Oxidative Cleavage

The cleavage of an alkyne by an oxidizing agent such as $O_3$ or $KMnO_4$; a carbon with an alkyl substituent becomes a carboxylic acid, whereas a terminal alkyne carbon with a hydrogen substituent becomes $CO_2$.

Acetylide Anion

A strong nucleophile and strong base formed by the deprotonation of a terminal alkyne using $NaNH_2$ in liquid $NH_3$, useful in substitution reactions with alkyl halides.

Acid-Catalyzed Hydration

Addition of water across an alkene double bond catalyzed by an acid such as $H_3PO_4$, proceeding via a carbocation intermediate to yield a Markovnikov alcohol.

Oxymercuration-Demercuration

A two-step alkene hydration reaction using $1.\ Hg(OAc)_2,\, H_2O$ followed by $2.\ NaBH_4$ to produce a Markovnikov alcohol without carbocation rearrangements.

Alkene Hydroboration-Oxidation

A two-step reaction ($1.\ BH_3\text{--}THF$, $2.\ H_2O_2,\, NaOH$) that adds water across an alkene with anti-Markovnikov regiochemistry and syn stereochemistry.

Halohydrin Formation

The addition of a halogen and water ($X_2,\, H_2O$) across an alkene yielding a product with anti stereochemistry, where the hydroxyl group attaches to the more substituted carbon.

Alkene Catalytic Hydrogenation

A reduction reaction using $H_2$ in the presence of a metal catalyst ($Pd/C$ or $Pt$) that adds hydrogens across a double bond with syn stereochemistry.

Epoxidation

An oxidation reaction of an alkene using a peroxy acid such as mCPBA to form a three-membered cyclic ether (epoxide) with syn stereochemistry.

Syn Dihydroxylation

The oxidation of an alkene using $1.\ OsO_4$ followed by $2.\ NaHSO_3,\, H_2O$ to form a 1,2-diol (glycol) with syn stereochemistry.

Alkene Ozonolysis

The cleavage of an alkene double bond using ozone ($O_3$) followed by reductive workup ($Zn,\, H_3O^+$) to produce carbonyl fragments (aldehydes or ketones).

Permanganate Cleavage of Alkenes

Oxidative cleavage of an alkene using hot $KMnO_4,\, H_3O^+$; monosubstituted carbons are oxidized to carboxylic acids, disubstituted carbons form ketones, and terminal $=CH_2$ carbons are fully oxidized to $CO_2$.

Cyclopropanation (Simmons-Smith)

A reaction converting an alkene to a cyclopropane ring using a zinc-carbenoid reagent ($CH_2I_2,\, Zn(Cu)$) that proceeds with syn stereochemistry.