Hydrolysis of ethers

The hydrolysis of diethyl ether to ethanol can be effected by using inorganic oxides such as alumina as catalysts. Methyl t-butyl ether can be hydrolyzed to obtain t-butyl alcohol in the presence of strongly acidic cation-exchange resins at 340 - 400 K.  

Similarly, glycol mono-/-alkyl ether can be hydrolyzed to obtain tertiary alcohols with strongly acidic cation-exchange resins. For example, ethyleneglycol mono- -butyl ether gives -butyl alcohol at 350 — 400 K. 

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Proposed mechanism of the hydrolysis of ether bond in aromatic-based PEMs. (From lojoiu, C. et al. 2005. Fuel Cells 5 344-354.)... 

Figure 4-38. The proton acting as a Lewis acid in the hydrolysis of ethers.

Decomposition of diazonium salts obtained from 2-aminothiazoIe (4) (29. 34. 35) could be an interesting reaction to introduce 0 in A-4-thiazoline-2-one. Acidic hydrolysis of ethers (36. 37). oxidative hydrolysis... 

Benzaldehydes (lg, 2g, 3g) are liberated in the same way but originate in part from other sources (cf. Fig. 6.1.2). The presence of benzoic acids (lh, 2h, 3h) and ferulic acid (1 j) can be explained by hydrolysis of ether or ester linkages. p-Flydroxybenzoic and p-coumaric acids (3h and 3j, respectively) are attached to certain types of lignins by ester linkages and their occurrence in the acidolysis mixtures is, in these cases, at least primarily due to the hydrolysis of these linkages. 

Zeolites have also been successfully applied in the reverse reaction, i.e. the hydrolysis of ethers to alcohols. A relevant example is the splitting of bis(3-hydroxypropyl)ether. This compound is a by-product in 1,3-propanediol synthesis, which can be performed by hydration of acrolein and reduction of 3-hydroxypropanal (23). In the hydrolysis of bis(3-hydroxypropyl)ether, a 20 weight % aqueous solution of the ether is passed over a ZSM-5 catalyst at 240°C ... 

Both ethers and thioethers are hydrolyzed via acid-catalysis to the alcohol or thiol, but are reasonably stable at neutral and basic conditions. Hydrolysis of ethers and thioethers is usually only observed if attached to an aryl group or other cationic stabilizing groups (e.g., API cefamandole nafate thiother hydrolysis [16]). 

Similar to the hydrolysis of esters, the hydrolysis of ethers occurs at high pressures without the addition of acid catalysts. As for other hydrolysis reactions, high density and the addition of NaCl improves the reaction rate and selectivity of hydrolysis relative to other degradation reactions. Under optimal conditions, the reaction leads only to the respective alcohols. Examples of ethers investigated are methoxynaphthalenes [21], dibenzylether [7, 22], anisols [23], and from cellulose to glucose, fructose and oligomers [24]. 

This set of equations has no analytical solution, but can be solved with the help of numeric calculations. Also, these equations can be solved if to enter various assumptions and suppositions simplifying the reaction schema. From end site 3 of kinetic curves on a Figure 7 are possible to calculate an effective rate constant of hydrolysis of ether links k p supposing, that on this site the filament was completely saturated with alkali and the reaction happens in kinetic area. The change of value k as a function of temperature and concentrations of alkah is featured by the equation ... 

Having substituted values of a number of parameters [5, 29] in the equation (10), we shall receive dependence of an effective constant of speed of hydrolysis of ether links on temperature and thermodynamic parameters of the media ... 

Hydrolytic reactions, which are best documented, include saponification of esters, hydrolysis of amides, and hydrolysis of ethers (glycosides). Except for ester saponification, all the other reactions proceed at a measurable rate only by enzymic catalysis. Hydrolytic enzymes are regular constituents of the digestive tract and lysosomes. They are responsible for the biodegradation of polyesters, polyamides (including polypeptides), polysaccharides and, probably, polyurethanes. 

Table 12.2 gives the properties of sub- and supercritical water. Subcritical water is the water that is in a state under a pressurized condition at temperatures above its boiling point under ambient pressure and below the critical point Tc = 374°C Pc = 22.1 MPa, pc = 320 kg/cm ). The dielectric constant of liquid water decreases with increasing temperature (Nanda et al., 2014b). At temperatures from 277 to 377°C, the dielectric constant becomes as low as those of polar organic solvents. The ionic product of water is maximized at temperatures between 227 and 372°C depending upon the pressure (Kruse and Dinjus, 2007). Thus, subcritical water acts as acid and/or base catalysts for reactions, such as hydrolysis of ether/ester bonds, and also as a solvent for the extraction of low molecular mass products (Brunner, 2009). 

The hydrolysis of ethers has been revisited. In aqueous acid, ethers react via a car-benium ion intermediate when a stable carbenium ion can form but the ionization is concerted with proton transfer from an complex to the ether oxygen occur-... 

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