Organic Chemistry - Alkynes

Flashcards about alkynes. Topics include nomenclature, acidity, preparation, reduction, hydrohalogenation, hydration, hydroboration-oxidation, halogenation, ozonolysis, and alkylation.

Alkyne

Molecules that possess a carbon-carbon triple bond (C≡C).

Parent Chain (Alkynes)

The chain that should include the C≡C triple bond.

Alkynes Nomenclature - Location Number

Assign a locant to each substituent giving the C≡C triple bond the lowest number possible.

Terminal Alkyne

Alkynes that have a lower pKa (more acidic) than other hydrocarbons

NaNH2 (Sodium Amide)

Often used as a suitable base to deprotonate a terminal alkyne.

Geminal Dihalide

Can be used in the preparation of alkynes by elimination.

Vicinal Dihalide

Can be used in the preparation of alkynes by elimination.

Catalytic Hydrogenation

An alkyne converted to an alkane by the addition of two equivalents of H2.

Lindlar's Catalyst

A deactivated or poisoned catalyst, used to stop the reaction at the cis alkene, without further reduction.

Dissolving Metal Reduction

Reduces an alkyne to a trans alkene using sodium metal and ammonia.

Hydrohalogenation

Affords Markovnikov addition of H and X to an alkyne, same as with an alkene; excess HX affords a geminal dihalide.

Acid-Catalyzed Hydration (Alkynes)

Alkynes undergo Markovnikov hydration catalyzed with HgSO4 to compensate for the slow reaction rate from the formation of vinylic carbocation.

Keto-Enol Tautomerization

The enol tautomerizes to the ketone, with equilibrium generally favoring the ketone.

Hydroboration-Oxidation (Alkynes)

Regioselective for anti-Markovnikov addition and produces an enol that tautomerizes to the aldehyde.

Ozonolysis (Internal Alkyne)

Produces two carboxylic acids.

Ozonolysis (Terminal Alkyne)

Yields a carboxylic acid and carbon dioxide.

Alkynide Ion

Formed when terminal alkynes are completely converted with NaNH2 and are good nucleophiles undergoing SN2 reactions with alkyl halides.