Alcohols ether formation

Ether alcohols Ether formation Ether hydroperoxides Etherification... 

In the lower primary alcohols, ether formation (1) takes place at lower temperatures than olefin formation (2). With secondary alcohols, the temperature difference is not appreciable and with tertiary alcohols olefin formation takes place easily on warming. 

Protection of alcohols. Ether formation from ROH and 4-XCf,H4CH2Br mediated by NaH in DMF is easily achieved. Such ethers are cleaved by Pd-catalyzed processes. 

The scope and mechanism of the reductions of esters and lactones to ethers with diborane has been reported in detail cf. ref. 279). Initial co-ordination of BH3 with the alkoxy-oxygen is considered to be the essential step in the reduction to alcohols. Ether formation seems to occur as an alternative pathway when the... 

Dehydration, Amination, and Disproportionation of Alcohols. Ether formation, dehydration and disproportionation reactions catalyzed by MTO has been carried out. Yields were found to vary dramatically depending upon the substrate. These reactions have limited synthetic value and at present offer no advantages to existing technologies in each of these areas. 

With higher alcohols, the formation of the ether becomes negligible, the reaction being limited almost entirely to reduction to the hydrocarbon. 

Trifluoromethanesulfonic acid is miscible in all proportions with water and is soluble in many polar organic solvents such as dimethylformamide, dimethyl sulfoxide, and acetonitrile. In addition, it is soluble in alcohols, ketones, ethers, and esters, but these generally are not suitably inert solvents. The acid reacts with ethyl ether to give a colorless, Hquid oxonium complex, which on further heating gives the ethyl ester and ethylene. Reaction with ethanol gives the ester, but in addition dehydration and ether formation occurs. 

Transesterification of methyl methacrylate with the appropriate alcohol is often the preferred method of preparing higher alkyl and functional methacrylates. The reaction is driven to completion by the use of excess methyl methacrylate and by removal of the methyl methacrylate—methanol a2eotrope. A variety of catalysts have been used, including acids and bases and transition-metal compounds such as dialkjitin oxides (57), titanium(IV) alkoxides (58), and zirconium acetoacetate (59). The use of the transition-metal catalysts allows reaction under nearly neutral conditions and is therefore more tolerant of sensitive functionality in the ester alcohol moiety. In addition, transition-metal catalysts often exhibit higher selectivities than acidic catalysts, particularly with respect to by-product ether formation. 

Reactions of the Side Chain. Benzyl chloride is hydrolyzed slowly by boiling water and more rapidly at elevated temperature and pressure in the presence of alkaHes (11). Reaction with aqueous sodium cyanide, preferably in the presence of a quaternary ammonium chloride, produces phenylacetonitrile [140-29-4] in high yield (12). The presence of a lower molecular-weight alcohol gives faster rates and higher yields. In the presence of suitable catalysts benzyl chloride reacts with carbon monoxide to produce phenylacetic acid [103-82-2] (13—15). With different catalyst systems in the presence of calcium hydroxide, double carbonylation to phenylpymvic acid [156-06-9] occurs (16). Benzyl esters are formed by heating benzyl chloride with the sodium salts of acids benzyl ethers by reaction with sodium alkoxides. The ease of ether formation is improved by the use of phase-transfer catalysts (17) (see Catalysis, phase-thansfer). 

Diethyl ether is the principal by-product of the reaction of ethyl alcohol with diethyl sulfate. Various methods have been proposed to diminish its formation (70—72), including separation of diethyl sulfate from the reaction product. Diethyl sulfate not only causes an increase in ether formation but is also more difficult to hydroly2e to alcohol than is ethyl hydrogen sulfate. The equiUbrium constant for the hydrolysis of ethyl hydrogen sulfate is independent of temperature, and the reaction rate is proportional to the hydrogen ion concentration (73—75). 

This ether formation arises from conversion of the phenol to a cyclohexanone, and ketal formation catalyzed by Pd-Hj and hydrogenolysis. With Ru-on-C, the alcohol is formed solely (84). 

A solution of 200 g of 1 -p-chlorophenvl-2-phenyl-4-(N-pvrrolidino)-butanol-2 in 750 ml of concentrated hydrochloric acid is refluxed for 9 hours thereby causing a dehydration of the butanol compound, and the formation of the hydrochloric acid addition salt of a 1 -p-chloro-phenyl-2-phenyl-4-(N-pyrrolidino)-butene. The hydrochloride salt formed crystallizes in the oily lower layer of the two phase reaction mixture and is removed therefrom by filtration. The filtrate is again refluxed for 9 hours, cooled to0°C,and a second crop of the hydrochloric acid addition salt of the dehydration product is obtained and filtered off. The filtrate containing residual amounts of 1 -p-chlorophenyl-2-phenyl-4-(N-pyrrolidino)-butanol-2 is again refluxed for 9 hours to yield an additional crop of the salt of the dehydration product. The several fractions of the butene compound are combined and triturated with several small portions of hot acetone and recrystallized from alcohol-ether mixture. The hydrochl or ic acid addition salt of the dehydration product, 1 -p-chlorophenyl-2-phenyl-4-(N-pyrrolidino)-butene hydrochloride, melts at about 227°C to 228°C. 

The alkyl chain distribution of the base alcohol in alcohol sulfates is easily determined by gas chromatography. However, alcohol sulfates and alcohol ether sulfates are not volatile and require a previous hydrolysis to yield the free alcohol. The extracted free alcohol can be injected directly [306] or converted to its trimethylsilyl derivative before injection [307]. Alternatively, the alcohol sulfate can be decomposed by hydroiodic acid to yield the alkyl iodides of the starting alcohols [308]. A preferred method forms the alkyl iodides after hydrolysis of the alcohol sulfate which are analyzed after further extraction of the free alcohol, thus avoiding the formation of hydrogen sulfide. This latter method is commonly used to determine the alkyl chain distribution of alcohol ether sulfates. 

Loss of catalytic activity resulting from internal displacements is not usually a serious problem below temperatures of about 100 C. However, highly active R-groups, such as benzyl, methyl and allyl, undergo internal displacement more readily, particularly in the presence of strong nucleopfiles. For instance, the presence phenolates and thiolates may lead to the formation of benzyl alcohol, ethers, or sulphides from benzyl-substituted quaternary ammonium salts. 

Ether formation from alcohol and alkanoyl chloride Wacker-Chemie Bachhuber (1993)... 

Such esterifications and acetal formations are achieved through enzyme catalyses. However, such reactions are relatively rare in aqueous conditions chemically. This is because the reversed reactions, hydrolysis, are much more favorable entropically. Kobayashi and co-workers found that the same surfactant (DBSA) that can catalyze the ether formation in water (5.2 above) can also catalyze the esterification and acetal formations reactions in water.52 Thus, various alkanecarboxylic acids can be converted to the esters with alcohols under the DBSA-catalyzed conditions in water (Eq. 5.6). Carboxylic acid with a longer alkyl chain afforded the corresponding ester better than one with a shorter chain at equilibrium. Selective esterification between two carboxylic acids with different alkyl chain lengths is therefore possible. 

Interestingly, the less strained 1-methylcyclooctene afforded neither ether formation, isomerization, nor reduction. Further studies have shown that water<82) and carboxylic acids<81> undergo additions analogous to alcohols ... 

In solvents that have donor properties, solubility leads to complex formation to give species such as S A1C13 (where S is a solvent molecule). Beryllium chloride is soluble in solvents such as alcohols, ether, and pyridine, but slightly soluble in benzene. 

Difficulties that arise using simple primary alcohols (ketal and enol-ether formation) may be avoided by using phenol or f-butyl alcohol.360... 

The second route for ether formation is initiated by protonation of the carbene followed by capture of the cation with alcohol (8). Finally a concerted insertion into the oxygen-hydrogen bond of the alcohol (8) has been considered, but there is no experimental support for this path. The... 

The rate constants kTS and kST define an equilibrium constant (ATeq) connecting the singlet and triplet carbenes. An estimate of Ktq, and hence AGSX, for BA can be obtained from the experiments described above. The time resolved spectroscopic measurements indicate that BA reacts with isopropyl alcohol with a rate constant some five times slower than the diffusion limit (Table 7). This, in conjunction with the picosecond timescale measurements, gives a value for ksr. The absence of ether formation from the sensitized irradiation, when combined with the measured rate constant for reaction of 3BA with isopropyl alcohol, gives an upper limit for k-. These values give Keq and thus AGST 2 5.2 kcal mol-1 (Table 8). 

Ions of the later transition metals such as Pt+ may not form [MO]+ ions with water and alcohols as shown in Table I for the reaction of Pt+ with methanol, where the formation of Pt+-CO or Pt+-H2 ions are preferred (102). As previously mentioned, Cr+ and Mn+ appear to be much less reactive than any of the other transition metals. The Cr+ ion was reported to be unreactive to primary alcohols but initiated dehydration of branched-chain alcohols it was also described as being unreactive toward propanal and acetone (9). The Mn+ ion has received scant attention due to its reduced activity. The reactions of Fe+, Co+, and Ni+ with alcohols, ethers, aldehydes, and ketones have been extensively covered (9). These ions are more reactive than Cr+ and Mn+ and generally react with alcohols causing dehydration. 

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