- A product analytical study of the thermal and photolytic decomposition of some arenediazonium salts in solution
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Products of thermal and photochemical reactions of eleven arenediazonium tetrafluoroborates in various solvents have been analyzed. All compounds in most solvents undergo unimolecular heterolysis to give singlet aryl cations which are captured by solvent. This mechanism is dominant for arenediazonium ions without electron-withdrawing substituents in all solvents, and the only reaction observed in water. Additionally, appreciable yields of fluoroarenes are obtained by fluoride abstraction by the aryl cation from fluorinated solvents and from tetrafluoroborate in fluorinated solvents. Yields from photochemical processes are very similar to those from thermal reactions indicating that the main reactions proceed through common or very similar intermediates. Aryl cations formed from ion-paired diazonium ions may react with the counterion, but fragmentation of dissociated diazonium ions leads only to solvent-derived product. Some arenediazonium ions in some solvents undergo an alternative radical reaction leading principally to hydrodediazoniation. It is proposed that this reaction involves initial rate-limiting electron transfer from ethanol to the arenediazonium ion followed rapidly by homolysis of the resultant aryldiazenyl radical. Within the same solvent cage, the aryl radical then either abstracts an α-hydrogen from the ethanol radical cation generated in the first step to give the reduction product and protonated acetaldehyde, or combines with it at the oxygen to give a protonated aryl ethyl ether.
- Canning, Peter S. J.,Maskill, Howard,McCrudden, Katharine,Sexton, Brian
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p. 789 - 800
(2007/10/03)
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- Facile and efficient synthesis of fluoroalkyl aryl ethers
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A convenient and practical method for the preparation of fluoroalkyl aryl ethers via substitution of iodoalkyl fluorides is described. This method involves KF complexation of the phenol, which increases the nucleophilicity of oxygen for the formation of the ether linkage.
- Kamal, Ahmed,Pratap,Ramana, K.Venkata,Ramana,Babu, A.Hari
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p. 7353 - 7355
(2007/10/03)
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- Acid-Catalyzed Reaction of 2,2,2-Trifluorodiazoethane for Analysis of Functional Groups by 19F Nuclear Magnetic Resonance Spectrometry
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The acid-catalyzed reactions of trifluorodiazoethane with alcohols, phenols, thiols, and carboxylic acids are reported.The yield data for these trifluoroethyl derivatives suggest a simple, and in many cases, quantitative method for introduction of a fluorine tagging group.The 19F chemical shifts indicate that most functional groups (e.g., phenols, alcohols, etc.) have fairly well resolved chemical shifts regions.In addition, paramagnetic shift reagents have been utilized to selectively differentiate carboxylic acids from other active hydrogen functional groups.
- Koller, K. L.,Dorn, H. C.
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p. 529 - 533
(2007/10/02)
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