Organic Chemistry: Alkenes, Alkynes, and Reaction Mechanisms

Vocabulary practice flashcards covering organic chemistry reactions of alkenes and alkynes, reaction stereochemistry and regiochemistry, mechanisms (carbocation rearrangement, halohydrin formation, radical bromination), and multi-step synthesis.

Electronegativity Chart

A periodic table reference displaying the relative tendency of elements to attract bonding electrons, ranging up to a maximum value of $4.0$ for Fluorine ($F$).

Adamantane

A rigid, cage-like polycyclic alkane that is a low-cost byproduct of oil refinement, serving as the starting material for synthesizing antiviral pharmaceuticals such as rimantadine.

Rimantadine

An adamantyl-derived amine pharmaceutical approved as an antiviral medication for the treatment and prevention of influenza (flu) infections.

1-Methylcyclohexene

A cyclic alkene with an endocyclic double bond substituted by a methyl group, often evaluated in addition reactions to illustrate Markovnikov regioselectivity and syn/anti stereoselectivity.

3,3-Dimethyl-1-butene

A terminal alkene possessing a quaternary carbon adjacent to the double bond, which undergoes a 1,2-methyl shift during electrophilic additions to form a more stable tertiary carbocation.

Halohydrin

A compound containing a halogen atom and a hydroxyl group located on adjacent carbon atoms (such as 1-bromo-2-butanol), formed by the anti-addition of halogen and water across an alkene.

Lindlar's Catalyst ($H_2$, Lindlar)

A deactivated, poisoned palladium catalyst that selectively hydrogenates alkynes via syn-addition to produce cis-alkenes ((Z)-alkenes) without over-reducing to alkanes.

Dissolving Metal Reduction ($Na$, $NH_3$)

A chemical transformation using alkali metal in liquid ammonia that stereoselectively reduces internal alkynes via anti-addition into trans-alkenes ((E)-alkenes) through radical anion intermediates.

Hydroboration-Oxidation of Alkynes ($(sia)_2BH$, then $H_2O_2$, $NaOH$)

An anti-Markovnikov hydration pathway utilizing bulky disiamylborane followed by basic oxidation to convert terminal alkynes into enols that tautomerize to aldehydes.

Oxymercuration-Hydration of Alkynes ($HgSO_4$, $H_2SO_4$, $H_2O$)

A mercuric-ion catalyzed electrophilic addition of water across an alkyne with Markovnikov regioselectivity, forming an enol intermediate that rapidly tautomerizes into a methyl ketone.

Syn-Dihydroxylation ($OsO_4$, $NaHSO_3$)

An oxidation reaction that installs two hydroxyl groups onto the identical face of an alkene via a cyclic osmate ester intermediate, yielding a syn-1,2-diol (glycol).

Ozonolysis ($O_3$, then $Me_2S$)

An oxidative cleavage process that completely cleaves carbon-carbon double bonds using ozone followed by a reductive dimethyl sulfide workup to yield ketones and aldehydes.

Allylic Bromination ($NBS$, light)

A selective radical substitution reaction using N-bromosuccinimide under photochemical conditions to install a bromine atom at the allylic position of an alkene without competing addition across the double bond.

Alkyne Alkylation

A synthetic strategy where a terminal alkyne is deprotonated by a strong base such as sodium amide ($NaNH_2$) to form a nucleophilic acetylide anion, followed by an $S_N2$ substitution with an unhindered alkyl halide.

1,2-Methyl Shift

An intramolecular carbocation rearrangement wherein a methyl group migrates with its bonding pair of electrons to an adjacent electron-deficient carbocation to form a more stable tertiary carbocation.

Bromonium Ion Intermediate

A cyclic, three-membered, positively charged intermediate formed during the electrophilic addition of bromine to an alkene, which blocks one face and dictates stereospecific anti-addition.

Radical Bromination Mechanism

A three-stage free-radical chain mechanism consisting of photochemical homolytic initiation, regioselective hydrogen abstraction and halogen transfer propagation steps, and radical recombination termination steps.

Reductive Amination ($NH_3$, $NaBH_4$)

A synthetic transformation where a carbonyl group (such as a ketone) condenses with ammonia to form an imine, which is subsequently reduced in situ by sodium borohydride to yield an amine.

Markovnikov's Rule

A mechanistic principle predicting that during electrophilic addition to an unsymmetrical alkene, the proton adds to the less substituted carbon atom to generate the more stable, more highly substituted carbocation intermediate.

Anti-Addition

A stereochemical mode of addition where two incoming substituents add to opposite faces of a pi system, generating products with trans or anti-coplanar configurations.