Alkynes Vocabulary Flashcards

A comprehensive collection of vocabulary flashcards covering the physical properties, preparation methods, addition reactions, distinguishing tests, and uses of alkynes based on the lecture notes.

Alkynes

Unsaturated hydrocarbons characterized by the presence of a carbon-carbon triple bond.

Terminal Alkynes

Alkynes in which the carbon-carbon triple bond lies at the end of the carbon chain.

Nonterminal Alkynes

Alkynes in which the carbon-carbon triple bond lies anywhere except at the terminal position (also known as internal alkynes).

Physical State Distribution of Alkynes

At room temperature, lower alkynes ($2$ to $4$ carbons) are gases, intermediate alkynes ($5$ to $8$ carbons) are liquids, and higher alkynes are solids.

Boiling Point Properties of Alkynes

Boiling points increase with increased molecular mass, decrease with chain branching, and are higher for symmetrical alkynes compared to non-symmetrical alkynes.

Dehydrohalogenation of Vicinal Dihalides

A reaction method to prepare alkynes by heating vicinal dihalides in the presence of excess $\text{KOH}$ and $\text{CH}_3\text{CH}_2\text{OH}$.

Calcium Carbide Synthesis of Ethyne

A process where $\text{CaO(s)}$ reacts with $3\text{C(s)}$ in a furnace at $3000^\text{o}\text{C}$ to form $\text{CaC}_2\text{(s)}$ and $\text{CO}$, which then reacts with cold water to generate ethyne.

Dehalogenation of Tetrahalides

A reaction that utilizes zinc ($\text{Zn}$) to remove halogens from a tetrahalide, producing an alkyne and $2\text{ZnX}_2$.

Acetylide Formation

The reaction of terminal alkynes with sodium in liquid ammonia to form acetylides, which react with alkyl halides to yield higher alkynes.

Lindlar's Catalyst

A specialized catalyst composed of palladium, $\text{CaCO}_3$, and quinoline used for the selective reduction of higher alkynes to alkenes.

Electrophilic Addition Reactions of Alkynes

Reactions made possible by loosely held $\text{π}$-electrons where alkynes react with $2$ moles of an electrophilic reagent such as halogens ($\text{H}_2$, $\text{X}_2$, $\text{HX}$).

Geminal Dihalides

Dihalide compounds formed when alkynes undergo addition with hydrogen halides in the presence of UV light following Markownikoff's rule.

Anti-Markownikoff Addition to Alkynes

An addition reaction occurring when excess $\text{HBr}$ reacts with an alkyne in the presence of an organic peroxide ($\text{ROOR}$), converting propyne into $1,1\text{-dibromopropane}$.

Hydration of Alkynes

A nucleophilic addition reaction where alkynes react with water in the presence of dilute $\text{H}_2\text{SO}_4$ and $\text{HgSO}_4$ at $60^\text{o}\text{C}$ (e.g., propyne forms propanone).

Bromine Water Test

A distinguishing reaction for alkynes where the addition of the hydrocarbon changes a red solution to colorless.

Ammoniacal Silver Nitrate Test

A chemical test that produces a white precipitate when reacted with terminal alkynes, but shows no observable change with non-terminal alkynes.

Ammoniacal Copper(I) Chloride Test

A chemical test that produces a red precipitate when reacted with terminal alkynes, but shows no observable change with non-terminal alkynes.

Alkaline KMnO4 Test

A distinguishing test for alkynes where interaction with the hydrocarbon turns a purple alkaline potassium permanganate solution colorless.

Acidified Potassium Dichromate(VI) Test

A distinguishing test for alkynes where interaction with the hydrocarbon turns an orange solution to green.

Industrial Uses of Alkynes

Practical applications of alkynes including welding, PVC manufacture, artificial fruit ripening, and pharmaceutical production.