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Phenylacetylene is a prototypical terminal acetylene, undergoing many reactions expected of that functional group. It undergoes semi hydrogenation over Lindlar catalyst to give styrene . In the presence of base and copper(II) salts, it undergoes oxidative coupling to give diphenylbutadiyne . [ 6 ]
Yet another method involves the coupling of iodobenzene and the copper salt of phenylacetylene in the Castro-Stephens coupling. The related Sonogashira coupling involves the coupling of iodobenzene and phenylacetylene. Diphenylacetylene is a planar molecule. The central C≡C distance is 119.8 picometers. [1]
The Hay coupling is variant of the Glaser coupling. It relies on the TMEDA complex of copper(I) chloride to activate the terminal alkyne. Oxygen (air) is used in the Hay variant to oxidize catalytic amounts of Cu(I) to Cu(II) throughout the reaction, as opposed to a stoichiometric amount of Cu(II) used in the Eglington variant. [7]
These reactions invariably involve metal-acetylide intermediates. This reaction was discovered by chemist John Ulric Nef in 1899 while experimenting with reactions of elemental sodium, phenylacetylene, and acetophenone. [3] [4] For this reason, the reaction is sometimes referred to as Nef synthesis.
Friedel–Crafts reactions have been used in the synthesis of several triarylmethane and xanthene dyes. [26] Examples are the synthesis of thymolphthalein (a pH indicator) from two equivalents of thymol and phthalic anhydride: A reaction of phthalic anhydride with resorcinol in the presence of zinc chloride gives the fluorophore fluorescein.
For example, the chloro derivative C 6 H 5 Cl is normally called chlorobenzene, although it could be called phenyl chloride. In special (and rare) cases, isolated phenyl groups are detected: the phenyl anion ( C 6 H − 5 ), the phenyl cation ( C 6 H + 5 ), and the phenyl radical ( C
An alkyne trimerisation is a [2+2+2] cycloaddition reaction in which three alkyne units (C≡C) react to form a benzene ring. The reaction requires a metal catalyst. The process is of historic interest as well as being applicable to organic synthesis. [1] Being a cycloaddition reaction, it has high atom economy.
Mild conditions allow this reaction to take place while not affecting complex or reducible groups in the reactant-acid. [3] The reaction requires the presence of a nucleophile . A metal catalyst is required. Usually Ag 2 O is chosen but other metals and even light effect the reaction. [4] Arndt-Eistert reaction with ketene intermediate.