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Alkynes: Introduction

Alkynes: Applications

Among the alkynes, ethyne (acetylene) especially is used widely. Particularly, industrial ethyne chemistry in the 30s and 40s at BASF was of great economical importance. The ability of ethyne to undergo a multitude of chemical reactions with other compounds thereby providing the chemical industry with a broad range of products is crucial for its wide use.

Fig.1
Synthesis of acrylic acid from ethyne, carbon monoxide and water
Fig.2
Syntheses of acrylamides from ethyne, carbon monoxide and amines
Fig.3
Syntheses of alcohols from ethyne and formaldehyde
Fig.4
Synthesis of benzene from ethyne

Until several decades ago when it was replaced by the cheaper ethenes, ethyne was one of the most important raw materials in the chemical industry. However, ethyne continues to be of importance for many applications. Oxyhydrogen, a mixture of ethyne and pure oxygen, can generate a temperatrure of 2800 °C (3075 K ) and is being used for cutting and welding steel. Ethyne polymerizes to polyacetylene (polyethyne) in the presence of copper catalysts. When prepared by an alternative method, polyacetylene (CH)x exhibits moderate electrical conductivity. Oxidation with iodine increases the conductivity of the polymer by several powers of ten approaching the specific electrical resistance of silver. In 2000, Shirakawa, Heeger und McDiarmid received the Nobel Price for this discovery.

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