Cleavage of Ether Linkage

0-dealkylation also represents an ether cleavage reaction in which only an alkyl group is removed as opposed to larger molecular groups. 

Pesticides, such as benzoic acid herbicides, organophosphates, carbamates, methoxy-i -triazines, phenylureas, and phenoxyalkanoates, have an ether linkage or an alkoxy group. 

---

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. 

Figure 3.12 Cleavage of ether linkages during sulfite pulping.

The problem with solvents is that in most cases they decompose under the reaction conditions used in the reductive carbonylation reaction. Solvent decomposition can occur in a variety of ways including (i) acid cleavage of ether linkages by HI and HCo(CO), (ii) well known hydrolysis and halogenation reactions. 

Pyrolysis in the presence of tetramethylammonium hydroxide (TMAH) at a lower temperature of 300° C was studied for both PES and PSF [11]. In this study, the main component for the thermally assisted hydrolysis and methylation of PES was dimethyl derivative of bis(4-hydroxyphenyl)sulfone. This compound was formed through selective cleavages of ether linkages maintaining intact the sulfone structures. For PSF thermally assisted hydrolysis and methylation at 300° C, the main constituents were dimethyl derivative of bis(4-hydroxyphenyl)isopropylidene (bisphenol A) and also dimethyl derivative of bis(4-hydroxyphenyl)sulfone. A partial decomposition of the sulfone groups in PSF during the THM reaction also was noted. The findings also were confirmed by matrix assisted laser desorption mass spectrometric measurements. 

Thus the 1 1 stoichiometric balance between the bisphenate and the activated halide is disturbed which will result in the preparation of only low molecular weight oligomers. The second problem associated with the use of excess base is the possible cleavage of ether linkages at high temperatures (Equation 3) ... 

Acidolysis was introduced in lignin chemistry as a procedure for the isolation of lignin, mainly from woody materials [64], This method is one of the most widely used methods to isolate lignin easily from wood, since the method consists of the acid treatment of lignin in a water-dioxane solution. This method is also used for the cleavage of ether linkage. Some examples of representative chemical structures obtained by acidolysis are shown in Scheme 2 [65-68]. 

---