Phenolic ethers analysis

B. Hydrogenolysis of the Phenolic Ether Biphenyl. To a solution of 10 g. (0.032 mole) of the product from Part A in 200 ml. of benzene is added 2 g. of 5% palladium-on-charcoal, and the mixture is shaken with hydrogen in a Parr apparatus at 40 p.s.i. and 35-40° for 8 hours (Note 3). The mixture is filtered, and the insoluble residue is washed with three 100-ml. portions of hot ethanol (Note 4). The filtrates are combined, and the solvent is removed by means of a rotary evaporator at 60° (12 mm.) to leave a solid residue. The product is dissolved in 100 ml. of benzene, and 100 ml. of 10% sodium hydroxide solution is added. The mixture is shaken, and the layers are separated. The aqueous layer is extracted with 100 ml. of benzene, and the original benzene layer is washed with 100 ml. of water (Note 5). The benzene solutions are combined and dried over magnesium sulfate. Removal of the benzene by distillation yields 4.0-4.7 g. (82-96%) of biphenyl as a white powder, m.p. 68-70° (Note 6). The infrared spectrum is identical with that of an authentic sample, and a purity of at least 99.5% was indicated by gas chromatography analysis. 

Phenolic Ethers. Substitution of the phenolic proton by an alkyl group results in a spectrum which closely resembles that of the neutral species of the parent phenol (4). The pesticides that fall into this group are the phenoxy compounds. Table VI shows the Amax values of some important pesticide ethers. The alkyl phenyl ethers do not exhibit a bathochromic shift with pH change into the alkaline range because there is no free phenolic proton to be lost and no charged anion is formed. This represents an important avenue in ultraviolet analysis, in which small amounts of free phenols may be determined in the presence of an excess of the corresponding phenolic ether. Figure 4 shows the spectrum of 2,4-D and its parent phenol, 2,4-dichlorophenol. In an alkaline medium. 

Repeat this analysis for the reaction of phenyl methyl ether with HI leading to phenol and methyl iodide or methanol and phenyl iodide and involving protonated phenyl methyl ether as an intermediate. (Note In this case, the appropriate empty molecular orbital is LUMO+2 the LUMO is concentrated primarily on the CO bond.) Which reaction, with ethyl propyl ether or phenyl methyl ether, appears to be more likely to give selective ether cleavage ... 

The products of the reaction are the following /-butyl-phenyl-ether (TBPE), p-/-butyl-phenol (p-TBP), o-/-butyl-phenol (o-TBP) and 2,4-di-/-butyl-phenol (2,4-DTBP). Compounds adsorbed on the external surface were recovered in methylene chloride (CH2C12) by a soxhlet treatment for 24 hours of the deactivated zeolite sample. The content of the compounds inside the zeolite (coke) was determined after dissolution, in 40 % HF at room temperature, of the catalyst recoved after 5 min, 45 min, 5h and 7.5 h extraction by CH2C12 then followed. The composition of soluble coke was investigated by analysis GC-MS. The procedure is reported in detail elsewhere [10]. 

Lee [42] determined pentachlorophenol and 19 other chlorinated phenols in sediments. Acidified sediment samples were Soxhlet extracted (acetone-hexane), back extracted into potassium bicarbonate, acetylated with acetic anhydride and re-extracted into petroleum ether for gas chromatographic analysis using an electron capture or a mass spectrometric detector. Procedures were validated with spiked sediment samples at 100,10 and lng chlorophenols per g. Recoveries of monochlorophenols and polychlorophenols (including dichlorophenols) were 65-85% and 80-95%, respectively. However, chloromethyl phenols were less than 50% recovered and results for phenol itself were very variable. The estimated lower detection limit was about 0.2ng per g. 

The TLC analysis of flavonoids was performed not only in the extract of medicinal plants and model mixtures but also in various other matrices. Thus, phenolic compounds in red wines have also been determined by TLC. Wine samples were acidified to pH 2.0 with 0.1 M HC1 and 25 ml of acidified wine was extracted with 2 X 25 ml of diethyl ether. The organic phase was evaporated to dryness and redissolved in 5.0 ml of methanol. Separation of phenolic compounds was performed on silica layers using 11 different mobile phases. In order to find the best separation system, information theory and cluster analysis was applied. The RF values determined in 11 mobile phases are compiled in Table 2.45. 

Method D The alcohol (11.5 mol) is added to TBA-Br (0.32 g, 1 mmol) in aqueous NaOH (50%, 5 ml) and the mixture is stirred for 5 min. A suspension of the halonitro-benzamide (0.1 mol) in PhMe (150 ml) is then added and the two-phase system is stirred at 40 C until the reaction is shown to be complete by TLC analysis. The mixture is cooled to room temperature and the organic phase is separated and evaporated. H20 (300 ml) is added and the ether comes out of solution. (Method D fails with phenols and with secondary and tertiary alcohols.)... 

The silyl ether (10 mmol), finely powdered NaOH (4 g, 0.1 mol) and TBA-HS04 (1.7 g, 5 mmol) in l,4-dioxane (50 ml) are stirred under argon at room temperature for ca. 2.5-3 h, until TLC analysis indicates complete cleavage of the Si-O bond. The mixture is filtered through a bed of Celite and the filtrate is evaporated to yield the phenolic product (75-99%). 

McCallum NK. 1986. Specific method for the analysis of low-molecular-weight phenols using pentafluorobenzyl ethers. Lower Hutt, New Zealand Department of Science and Industrial Research. 

However, due to the artifacts resulting from oxidation, hydrolysis of esters or ethers, or isomerization of phenolics during pretreatment of wines, as well as due to the low recovery rates of some phenolics, analysis of wine phenolics via direct injection of the filtered wine into the chromatographic column is often selected (80,82-84). For the red wine and musts (80), which were injected directly into the HPLC without sample preparation, a ternary-gradient system was often employed for phenolic compounds. Twenty-two phenolic compounds, including 10 anthocyanins, were analyzed from red wine. The separation of cinnamic acid derivatives (313 nm),... 

---