Ethers, in alcohol

The UV spectrum of 5-phenyl-3 hydroxythiophene is very similar to that of its methyl ether in alcoholic solution, indicating that it exists largely in the enol form in this solvent. The same coincidence of the wavelength maxima was also obtained for 5-phenyl-2-hydroxy-thiophene and its methyl ether. In chloroform solution, the maxima were shifted toward longer wavelengths, suggesting that the tautomeric equilibrium in this solvent is displaced more toward the keto form. ... 

The review starts with a discussion of the mechanism of keto-enol tautomerisation and with kinetic data. Included in this section are results on stereochemical aspects of enolisation (or enolate formation) and on regioselec-tivity when two enolisation sites are in competition. The next section is devoted to thermodynamic data (keto-enol equilibrium constants and acidity constants of the two tautomeric forms) which have greatly improved in quality over the last decade. The last two sections concern two processes closely related to enolisation, namely the formation of enol ethers in alcohols and that of enamines in the presence of primary and secondary amines. Indeed, over the last fifteen years, data have shown that enol-ether formation and enamine formation are two competitive and often more favourable routes for reactions which usually occur via enol or enolate. 

Since carbonyl compounds are in equilibrium with enol ethers in alcohol solution (50), a priori it can be expected that reactions which usually proceed... 

It is not surprising that cyclopropenyl ions react with a large variety of nucleophiles. The reversible equilibrium with ethers in alcohols has been discussed earlier. 

However, this unusual intermediate exists in two spin states, singlet and triplet, quite similarly to the case of carbenes (and for the same reasons, two orbitals of similar energy have only two electrons to share). In the singlet state, the CTc-x orbital remains empty so tliat this has actually tlie characteristics of a localized carbocation and reacts witli any nucleophile, and indeed in this case there is no selectivity. Typically, when generated in the singlet state the phenyl cation reacts with any nucleophile present, first of all the solvent, giving ethers in alcohols and amides in nitriles (Scheme 10). 

Monoclinic golden-yellow prisms from acetic acid, mp 256". Sublimes easily. Volatile with steam. Slightly sol io hot water, in ether, in alcohol freely sol in hot glacial acetic acid and in alkaline so Ins,... 

Some liquids are practically immiscible e.g., water and mercury), whilst others e.g., water and ethyl alcohol or acetone) mix with one another in all proportions. Many examples are known, however, in which the liquids are partially miscible with one another. If, for example, water be added to ether or if ether be added to water and the mixture shaken, solution will take place up to a certain point beyond this point further addition of water on the one hand, or of ether on the other, will result in the formation of two liquid layers, one consisting of a saturated solution of water in ether and the other a saturated solution of ether in water. Two such mutually saturated solutions in equilibrium at a particular temperature are called conjugate solutions. It must be mentioned that there is no essential theoretical difference between liquids of partial and complete miscibility for, as wdll be shown below, the one may pass into the other with change of experimental conditions, such as temperature and, less frequently, of pressure. 

Picrates of p-naphthyl alkyl ethers. Alkyl halides react with the sodium or potassium derivative of p-naphthol in alcoholic solution to yield the corresponding alkyl p-naphthyl ethers (which are usually low m.p. solids) and the latter are converted by alcoholic picric acid into the crystalline picrates ... 

Mix together 1 0 g. of pure p-naphthol and the theoretical quantity of 50 per cent, potassium hydroxide solution, add 0-5 g. of the halide, followed by sufficient rectified spirit to produce a clear solution. For alkyl chlorides, the addition of a little potassium iodide is recommended. Heat the mixture under reflux for 15 minutes, and dissolve any potassium halide by the addition of a few drops of water. The p-naphthyl ether usually crystallises out on cooling if it does not, dilute the solution with 10 per cent, sodium hydroxide solution untU precipitation occurs. Dissolve the p-naphthyl ether in the minimum volume of hot alcohol and add the calculated quantity of picric acid dissolved in hot alcohol. The picrate separates out on cooling. Recrystallise it from rectified spirit. 

Method A. Pit a 1-litre three-necked flask with a mercurj -sealed stirrer, a reflux condenser, and a dropping funnel. Place 57 g. (73-5 ml.) of dry /cr<.-butyl alcohol (1), 101 g, (106 ml.) of A.R. dimethylaniline and 100 ml. of anhydrous ether in the flask, set the stirrer in motion, and... 

The alkyl sulphides or thioethers, the sulphur analogues of the ethers, are conveniently obtained by boiling alkyl halides with anhydrous sodium sulphide in alcoholic solution, for example ... 

Beckmann rearrangement of benzophenone oxime to benz-anilide. Dissolve 2 g. of benzophenone oxime in 20 ml. of anhydrous ether in a small conical flask and add 3 g. of powdered phosphorus pentachloride (or 3 ml. of pure tbionyl chloride). Distil off the solvent and other volatile products on a water bath CAUTION ether), add 25 ml. of water, boil for several minutes and break up any lumps which may be formed. Decant the supernatant liquid, and recrystallise, in the same vessel, from boiling alcohol. The product is benzanilide, m.p. 163° confirm this by a mixed m.p. determination with an authentic specimen. 

Place 200 g. (172 -5 ml.) of redistilled furfural (1) in a 1 litre beaker, provided with a mechanical stirrer and surrounded by an ice bath. Start the stirrer and, when the temperature has fallen to 5-8°, add a solution of 50 g. of sodium hydroxide in 100 ml. of water from a separatory funnel at such a rate that the temperature of the reaction mixture does not rise above 20° (20-25 minutes) continue the stirring for a further 1 hour. Much sodium furoate separates during the reaction. Allow to cool to room temperature, and add just enough water to dissolve the precipitate (about 65 ml.). Extract the solution at least five times with 60 ml. portions of ether in order to remove the furfuryl alcohol the best results are obtained by the use of the continuous extraction apparatus (charged with 350 ml. of ether) depicted in Fig. //, 44, 2. Keep the aqueous layer. Dry the ethereal extract with a httle anhydrous... 

To a suspension of a tinc-copper couple in 150 ml of 100 ethanol, prepared from 80 g of zinc powder (see Chapter II, Exp. 18), was added at room temperature 0.10 mol of the acetylenic chloride (see Chapter VIII-2, Exp. 7). After a few minutes an exothermic reaction started and the temperature rose to 45-50°C (note 1). When this reaction had subsided, the mixture was cooled to 35-40°C and 0,40 mol of the chloride was added over a period of 15 min, while maintaining the temperature around 40°C (occasional cooling). After the addition stirring was continued for 30 min at 55°C, then the mixture was cooled to room temperature and the upper layer was decanted off. The black slurry of zinc was rinsed five times with 50-ml portions of diethyl ether. The alcoholic solution and the extracts were combined and washed three times with 100-ml portions of 2 N HCl, saturated with ammonium chloride. 

Oxidation of ethylene in alcohol with PdCl2 in the presence of a base gives an acetal and vinyl ether[106,107], The reaction of alkenes with alcohols mediated by PdCl2 affords acetals 64 as major products and vinyl ethers 65 as minor products. No deuterium incorporation was observed in the acetal formed from ethylene and MeOD, indicating that hydride shift takes place and the acetal is not formed by the addition of methanol to methyl vinyl etherjlOS], The reaction can be carried out catalytically using CuClj under oxygen[28]. 

Reduction with sodium in alcohol was unsuccessful (54). The introduction of lithium aluminium hydride has provided an elegant method for the reduction of thiazole esters to hydroxythiazoles for example, ethyl 2-methyl-4-thiazolecarboxylate (11 with lithium aluminium hydride in diethyl ether gives 2-methyl-4-(hydroxymethyl)thiazole (12) in 66 to 69% yield (Scheme 7) (53),... 

Ethers tend to dissolve in alcohols and vice versa Represent the hydrogen bonding interaction between an alcohol molecule and an ether molecule J... 

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