Decomposition reactions ethers

We have studied the thermal decomposition of diaryl ether in detail, since the cleavage of ether linkage must be one of the most responsible reactions for coal liquefaction among the various types of decomposition reaction and we found that the C-0 bond of polynucleus aromatic ethers is cleaved considerably at coal liquefaction temperature. 

The thermal decomposition of />-nitrotriphenylmethyl hydroperoxide in benzene gives -nitrophenol 32%, phenol 9%, >-nitro-triphenylcarbinol 23%, -nitrobenzophenone 14%, and no benzo-phenone the decomposition in ether plus sulfuric acid gives -nitro-benzophenone 94% and phenol 81%.817 The latter reaction is very probably ... 

Klein and Virk (22) have pointed out that a key concerted decomposition reaction may involve adjacent (ortho) hydroxyl and ether structures on an aromatic ring, for example,... 

Experimental. Butenylmagnesium chloride was prepared from crotyl chloride and magnesium chips in ether. Decomposition reactions of butenylmagnesium chloride were carried out at room temperature using H20 and D20. Butenes were condensed at — 20 °C. and analyzed on a FB-4 Shandon ionization chromatograph. 

Dibutyl ether is the only solvent suitable for this reaction. Dibutyl ether has relatively low volatility and complexes with trimethylaluminum without solvent decomposition. Dibutyl ether complexes with BBr, sulTiciently strongly to slow the rate of reaction ofBBrj with AIMe, to a safe rate. Boron tribromide reacts explosively with trimethylaluminum in diethyl ether or anisole solutions because of the weak complexation between these solvents and BBr,. Tetra-hydrofuran and p-dioxane undergo decom X)sition reactions with trimethylaluminum, and thus are unsuitable as solvents in this synthesis. 

When ethers are heated with concentrated strong acid halides they undergo decomposition reactions. Alcohols and alkyl halides are the products. 

Analysis of reaction rate constants in model systems shows that at room temperature, the main reaction leading to regeneration of nitroxyl radicals is their interaction with peroxide radicals, (Reaction 11) and at elevated temperatures (more than 80°) the main reaction is that of hydroxylamine ether decomposition (Reaction 15) (53). 

If ether was substituted for alcohol the same equilibrium mixtures were obtained at all temperatures up to 450° C., which have been mentioned above, provided, of course, that other conditions are identical. This appears to substantiate Ipatiew s opinion that a condition of equilibrium is maintained in the system. Above 450° C. ether decomposes energetically to give ethylene, this latter reaction being in all probability non-reversible. The statement is made, however, that the addition of water vapor to ether seems to hinder decomposition of the ether since no ethylene is formed under these conditions even at temperatures well above 450° C. it is interesting to note that at higher temperatures diolefins were detected among the products of the decomposition of ether. (Heated in the presence of an iron catalyst at 570° C. under pressure, ether decomposed to give acetaldehyde as the main product of the reaction. 

Ethers are generally spoken of as inert compounds. What is really meant is that they do not react with metals, alkalies, and most acids at ordinary temperatures with appreciable velocity. As pointed out, the properties of the olefinated hydrogen afford an explanation. The same holds true for tertiary amines. It has already been pointed out that a difference is shown in the stability, or better, the reactions of the olefinated hydrogen depending upon the other substances present. Thus, in the presence of chlorides, such as zinc chloride, etc., ethyl iodide reacts less rapidly than the chloride. The same relative order was observed with ammonium chloride, bromide, iodide, and hydroxide. The decomposition of ethers by heating with hydrogen iodide, a method used for the determination of the amount of ether groups present in compounds, may be explained on the same basis. They are simple displacement reactions. The existence of the intermediate addition compounds (oxonium salts) has been proven ... 

Olefins can be prepared by the dehydrogenation of paraffins, dehydration of alcohols, or decomposition of ethers and halides, if vapours of these substrates are passed over metals or metal oxides at elevated temperatures (300-600°C). Dehydration reactions have been most widely studied and by careful selection of the catalyst and the reaction conditions the direction and stereochemistry of elimination can be controlled. However, dehydration often has to compete with dehydrogenation, and isomerisation of olefinic products by the acidic sites on the catalyst can reduce the synthetic utility of these reactions. Most frequently alumina has been used as the catalyst and the advantages and complexities of the method are amply illustrated by the dehydration of alcohols. Surface-catalysed eliminations have been the subject of several reviews "". ... 

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