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Nomenclature of Alkynes

Nomenclature of Alkynes

Alkynes are unsaturated hydrocarbons characterized by the presence of carbon-carbon triple bonds and have a general formula CnH2n-2. The nomenclature of alkynes follows a set of rules similar to alkanes and alkenes; however, alkynes bear the suffix "-yne" instead of "-ane" or "-ene." There are two approaches to naming alkynes:

Preparation of Alkynes: Alkylation Reaction

Preparation of Alkynes: Alkylation Reaction

Introduction
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.

Electrophilic Addition to Alkynes: Halogenation

Electrophilic Addition to Alkynes: Halogenation

Introduction
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.

Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation

Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation

Introduction
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.

Free-Radical Chain Reaction and Polymerization of Alkenes

Free-Radical Chain Reaction and Polymerization of Alkenes

The conversion of alkenes to macromolecules called polymers is a reaction of high commercial importance. The structure of the polymer is defined by a repeating unit, while the terminal groups are considered insignificant. The average degree of polymerization represents the number of repeating units in the polymer molecule and is denoted by the subscript n.

Structure and Physical Properties of Alkynes

Structure and Physical Properties of Alkynes

Introduction:
In nature, compounds containing both carbon and hydrogen are known as "hydrocarbons". Aliphatic hydrocarbons are compounds whose molecules contain saturated single bonds (i.e., alkanes) or unsaturated double or triple bonds. Alkenes contain carbon–carbon double bonds and have a structural formula CnH2n. Unsaturated hydrocarbons containing carbon–carbon triple bonds are called "alkynes" and are structurally represented by the formula CnH2n-2.
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Updated: Mar 17, 2026

Constructing Cyclic Peptides Using an On-Tether Sulfonium Center

Constructing Cyclic Peptides Using an On-Tether Sulfonium Center

Published on: September 28, 2022

Cyclic polymers from alkynes.

Christopher D Roland¹, Hong Li¹, Khalil A Abboud¹

¹Department of Chemistry, University of Florida, Center for Catalysis, PO Box 117200, Gainesville, Florida 32611, USA.

Nature Chemistry

|July 22, 2016

Summary

This summary is machine-generated.

Researchers developed a new tungsten catalyst to synthesize cyclic conjugated polymers, overcoming challenges in creating these unique macrocyclic materials for advanced applications.

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Area of Science:

Polymer Chemistry
Materials Science
Catalysis

Background:

Cyclic polymers exhibit distinct physical properties compared to linear polymers.
Synthesis of cyclic polymers, especially conjugated polyacetylenes, is challenging.
Cyclic conjugated polyacetylenes are largely unexplored, limiting property investigation.

Purpose of the Study:

To develop a method for synthesizing cyclic conjugated polyacetylenes.
To investigate the influence of cyclic topology on polymer properties.
To enable access to a diverse range of cyclic conjugated polymers.

Main Methods:

Development of a novel tungsten catalyst supported by a tetraanionic pincer ligand.
Catalytic polymerization of alkynes to form conjugated macrocycles.
Characterization using gel-permeation chromatography, light scattering, viscometry, and chemical tests.

Main Results:

The catalyst enables rapid formation of conjugated macrocycles in high yield.
The catalytic mechanism involves tethering polymer ends to the metal center, overcoming cyclization penalties.
Experimental data unambiguously confirmed the cyclic topology of the synthesized polymers.

Conclusions:

A new catalytic system provides efficient access to cyclic conjugated polyacetylenes.
This breakthrough allows for the study of structure-property relationships in cyclic conjugated polymers.
The methodology is versatile, enabling the synthesis of various cyclic polymers by monomer selection.