Instead, alcohol oxidations are carried out in solution, using reactions in which the hydroxyl hydrogen is replaced by an atom or group that is readily eliminated together with the alpha-hydrogen. Thus, nucleophilic substitution and elimination reactions were common for alkyl halides, but rare with aryl halides. In the case where the amidine is a guanidine, then any two of the three nitrogen atoms may be in the same or different rings. For example, the Japanese patent application No.
The general base B: used in these mechanisms may be anything from water to pyridine, depending on the specific reaction.
The oxidation state of carbon increases by 2, while the chromium decreases by 3 it is reduced. An important principle of resonance is that charge separation diminishes the importance of canonical contributors to the resonance hybrid and reduces the overall stabilization. The present invention is illustrated by the following Examples. By way of example only, and without limitation, there are reported a few examples of the way of carrying out the reaction described herein. Also the hydroxides of alkali metals and of alkaline earth metals show, in the presence of iodine-based promoters, an improved activity at a temperature below the temperatures reported by the literature.
A process according to claim 1 wherein the reaction is carried out in the liquid phase in the presence of a solvent which is an alcohol. The phenol is totally converted into anisol and the selectivity relative to anisole is total. Elevated pressures can be employed if desired. The contents of the flask were refluxed for 3 hours. A second disadvantage of the sodium alkoxide catalyst is that it cannot be regenerated after the reaction has occurred.
The general base B: used in these mechanisms may be anything from water to pyridine, depending on the specific reaction. A process for the production of phenolic ethers which process comprises reacting a phenol with a compound selected from an alkyl halide, an aryl halide, a dialkyl sulphate and a diaryl sulphate in the presence as catalyst of an amidine. Since the resonance stabilization of the phenolate conjugate base is much greater than the stabilization of phenol itself, the acidity of phenol relative to cyclohexanol is increased. A process according to claim 1 wherein the amidine is a guanidine. The process of claim 1 wherein said iodide is selected from methyl iodide and potassium iodide.
The process of claim 1 wherein said base is selected from the group consisting of aliphatic and aromatic tertiary amines and hydroxides of alkali metals and alkaline earth metals.
Cyclic amidines are defined as those amidines wherein at least one of the nitrogen atoms is part of an alicyclic or heterocyclic substituted or unsubstituted hydrocarbyl ring. By the term amidine is meant a compound containing the grouping: STR1 Conveniently the free valencies on the nitrogen atom are attached to carbon atoms or hydrogen atoms and the free valency on the carbon is attached to either carbon or nitrogen atoms. Also the hydroxides of alkali metals and of alkaline earth metals show, in the presence of iodine-based promoters, an improved activity at a temperature below the temperatures reported by the literature. On completion of the reaction, the mixture is separated by rectification, upon neutralization with an inorganic acid if an alkali was the used catalyst. For the first two reactions the mechanism diagram also shows the oxidation states of carbon blue Arabic numbers and chromium Roman numbers.
A similar set of resonance structures for the phenolate anion conjugate base appears below the phenol structures. Formulas illustrating this electron delocalization will be displayed when the "Resonance Structures" button beneath the previous diagram is clicked. Examples of aryl substituents include but are not limited to phenyl, naphthyl and alkyl substituted phenyls and naphthyls. The contents of the flask were refluxed for 3 hours. For the first two reactions the mechanism diagram also shows the oxidation states of carbon blue Arabic numbers and chromium Roman numbers.
A process according to claim 1 wherein the amidine is either 1,5-diazabicyclo[4. The amidine can be supported, that is chemically and physically bonded, to an inert solid and then added to the reaction mixture. The general base B: used in these mechanisms may be anything from water to pyridine, depending on the specific reaction.
Suitable alkyl halides include C1 to C12 alkyl chlorides, bromides and iodides. An energy diagram showing the effect of resonance on cyclohexanol and phenol acidities is shown on the right. The dialkyl sulphates are preferably sulphates containing two C1 to C20 alkyl substituents, such as dimethyl or diethyl sulphate. This catalytic dehydrogenation reaction produces aldehydes as shown below and ketones, and since the carbon atom bonded to the oxygen is oxidized, such alcohol to carbonyl conversions are generally referred to as oxidation reactions. A process according to claim 15, wherein the phenol is selected from the group consisting of phenol, p-t-butylphenol, hydroquinone and thiophenol.