Ether Acids

Ether acids are usually used to flotate fluorite, barite and dolomite. Meanwhile, they also perform a certain coUecling capability in the flotation of malachite, ilmenite, pyrite, and towanite. Compared with general carboxylic acids, the application characteristics of ether acids can be given by the following  

Based on the difference in collecting performances of ether acids toward several minerals, flotation separation of fluorite and calcite can be obtained with the help of depressant (such as dextrine and water glass). 

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Unlike ECF, direct fluorination does not alter the carbon backbone preparation of isomerically pure acids is possible (18). Both direct fluorination and ECF permit a great variety of stmctures to be made, but each method is better at certain types of stmctures than the other. Ether acids are produced in good yields, by direct fluorination (17), while ECF of ether-containing acids is fair to poor depending on the substrate. Despite much industrial interest, the costs and hazards of handling fluorine gas have prevented commercial application of this process. 

Deep fluorinalion of alkanes, ethers, acid fmlides, esters, alkyl chlorides, most ketones, ketals, orthoesters, and combinations of these functional groups produces principally the perfluonnated analogues (Table 2) Chlorine substituents (or chloro groups) usually survive fluorination... 

Ather-prober, m. ether tester, -saure, /. ether acid (compound which is both an ether and an acid) lampic acid (06s.i. -schicht,/. ether layer, -schwefelsaure, /. alkylsulfuric acid, specif, ethylsulfuric acid, -schwingtmg, /. vibration of the ether, ethereal vibration. 

Acid catalyzed intramolecular Diels-Alder reactions in lithium perchlorate-diethyl ether acid promoted migration of terminal dienes prior to [4 + 2] cycioaddition in conformationally restricted substrates [101]... 

Methyl vinyl ether See Methyl vinyl ether Acids... 

Arylalkanoic acid esters, 72 166 Arylaldehydes, microwave-accelerated transformation to nitriles, 76 580-581 Aryl alkyl ethers, acid cleavage of, 70 569 Arylalkylsulfones, 9 273 Arylamine dye intermediates, 9 272t... 

Refluxing in acid protonates the end ether to give a nice stable carbocation. Loss of CO2 from this carbocation gives a new dienol ether. Acidic hydrolysis of this dienol ether gives the product enone in the usual fashion. 

Chemical instability of medicinal agents may take many forms, because the drugs in use today are of such diverse chemical constitution. Chemically, drug substances are alcohols, phenols, aldehydes, ketones, esters, ethers, acids, salts, alkaloids, glycosides, and others, each with reactive chemical groups having different stability characteristics. Chemically, the most frequently encountered destructive processes involve hydrolysis and oxidation. 

Classical organic chemistry provides a wide variety of potential analytes for electron ionization, the only limitation being that the analyte should be accessible to evaporation or sublimation without significant thermal decomposition. These requirements are usually met by saturated and unsaturated aliphatic and aromatic hydrocarbons and their derivatives such as halides, ethers, acids, esters, amines, amides etc. Heterocycles generally yield useful El spectra, and flavones, steroids, terpenes and comparable compounds can successfully be analyzed by El, too. Therefore, El represents the standard method for such kind of samples. 

Methyl-1 -phenylethyl)-4-(2-propynyloxy)benzene, 3760 I Methyl vinyl ether, Acids, 1221 Nitrilotris(oxiranemethane), 3181... 

Addition of water (36) or alcohols (37—39) direcdy to butadiene at 40—100°C produces the corresponding unsaturated alcohols or ethers. Acidic ion exchangers have been used to catalyze these reactions. The yields for these latter reactions are generally very low because of unfavorable thermodynamics. At 50°C addition of acetic acid to butadiene produces the expected butenyl acetate with 60—100% selectivity at butadiene conversions of 50%. The catalysts are ion-exchange resins modified with quaternary ammonium, quaternary phosphonium, and ammonium substituted ferrocenyl ions (40). Addition of amines yields unsaturated alkyl amines. The reaction can be catalyzed by homogeneous catalysts such as Rh[P(C(5H5)3]3Q (41) or heterogeneous catalysts such as MgO and other solid bases (42). 

Figure 5. C-A and - A Curves for Alcohols-Ethers, Glycols-Ethers, Water-Ethers, Acids-Ethers, Alcohols-Ketones, Glycol-Ketones, Alcohols-Phenols, and Phenols-Ketones...

Hydroxy-trart.v-cinnamic acid, 3130 /V-Hydroxymethyl acrylamide, 1566 Methacrylic acid, 1525 f Methyl acrylate, 1526 f Methyl methacrylate Propionaldehyde, 1909 f Methyl vinyl ether Acids, 1217... 

The oldest investigation was conducted by Warnell [54] in 1967 who telomerised HFPO or tetrafluoroethylene epoxide by ring opening with two co-iodofluoro-carbon ether acid fluorides producing the corresponding adducts, as follows ... 

Several strong protonic acids are commercially available. Trifluoro-methanesulfonic (triflic) acid, fluorosulfonic acid, and perchloric acid may be obtained and stored in a pure state. The first two can be conveniently purified by distillation (b.p. 162° C and 165° C, respectively) [12], perchloric acid is less frequently used due to its oxidative properties and difficulties in handling (explosive). Complex acids HPF6 (HF + PF5) and HSbF6 (HF + SbF5) are available as complexes with ethers. Acids of H + BF30H- type are often the real initiators of polymerization initiated with Lewis acids (e.g., BF3) if water is not rigorously excluded from the system. 

In a short known reaction sequence, enal 250 was obtained from commercially available material 184). With methylamine and magnesium sulfate imine 251 was formed and combined with acyl chloride 252 185) (>4 steps). The use of low temperatures for this acylation led exclusively to the less substituted dienamide 253. The desired basic skeleton of dendrobine 254 was obtained by cyclizing 253 at 180°C in an acceptable 50% yield, Adduct 254 was accompanied by small amounts of the exo-adduct. Epoxidation led exclusively to exo-epoxide 255, which by means of trimethylsilyltriflate was converted into the allylic silyl ether. Acid treatment liberated the hydroxy group and subsequent oxidation of alcohol 256 led to enone 163, an intermediate of Inubushi s dendrobine synthesis and thus concluded this formal synthesis. The intermediate 163 was obtained from commercially not available materials in seven steps in 22.5% overall yield. To reach ( )-dendrobine according to Inubushi et al. would afford six additional steps, reducing the overall yield to 0.4% without including the preparation of the starting materials from commercially available compounds. 

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