Ethers, alternatives

The method of hydrolysis depends on the nature of the product. It is usually sufficient to add dilute sulphuric acid to the ethereal solution and to shake thoroughly, when the magnesium enters the aqueous solution, whilst the organic compound remains in the ether. Alternatively, however, the ethereal solution may be poured on to ice and water, and then treated with dilute sulphuric acid. Should the product be affected by this acid, the hydrolysis can be carried out with an aqueous solution of ammonium chloride. In the following examples the hydrolysis is usually shown as a simple double decomposition... 

The workup is accomplished simply by dilution with water and extraction with ether. Alternately, the reaction mixture can be neutralized with acetic acid before dilution with water, etc. 

Table 5.2 A portion of Table 4-1 from the pentabromodiphenyl ether alternatives assessment as an example of the presentation of the information to inform selection of alternatives3. ... 

The toluene phase was separated and discarded. The aqueous phase, together with a precipitated water- and toluene-insoluble oil, was made alkaline and extracted repeatedly with chloroform. The chloroform solution was concentrated in vacuo. The residue was recrystallized from a mixture of acetone and ether (alternatively, from chloroform and ether), and formed needles melting at 164° to 165°C. It was identified as 3-benziloyloxy-l-azabicyclo[2.2.2]octane. 

The lanthanide chloro precursors can be prepared in high yield by trans-metalation of the dilithiated ligands with anhydrous lanthanide trichlorides followed by work-up with diethyl ether. Alternatively, the mono-DME adducts... 

Ethanol-water Minimum-boiling azeotrope Cyclohexane, benzene, heptane, hexane, toluene, gasolene, diethyl ether Alternative to extractive distillation, pressure-swing distillation... 

After the last amino acid had been incorporated, the A"-Boc protecting groups were removed before 1 g of the peptide-resin conjugate was treated with a mixture of 14 mL of HF, 1.5 mL of anisole, and 0.25 mL of methylethyl sulfide at —20 °C for 0.5 hour and at 0 °C for 0.5 hour. The HF was removed in vacuo at 0 °C, and the resulting peptide and resin mixture was washed twice with ether and twice with CHCI3 and ether alternately. The peptide was extracted five times with 2 M CH3COOH, and the extract was lyophilized. 

Unsymmetrical ketones can be obtained from symmetrical ketones by anodic oxidation of their enol ethers to the or-methoxy ketone (III) [29], reaction with R MgX, and anodic oxidation of the glycol monomethyl ether. Alternatively, the ketone may be oxidatively aminated, alkylated at C=0, and oxidized (y = OCH3 or NR2) ... 

When a polymerizable monomer is exposed to UV light in the presence of a photosensitizer, polymerization may be initiated by radicals generated by dissociation of the excited sensitizer, e.g. benzoin methyl ether. Alternatively, the excited photosensitizer may transfer its excitation energy to the monomer which, in turn, undergoes excitation and radical initiated polymerization. 

Bohnenn LJM (1979) Dimethyl ether Alternative aerosol propellant. Drug and Cosmetic Industry 125 58-74. 

In several instances, Mannich-type cyclizations can be carried out expeditiously under photochemical conditions. The photochemistry of iminium ions is dominated by pathways in which the excited state im-inium ion serves as a one-electron acceptor. The photophysical and photochemical ramifications of such single-electron transfer (SET) processes as applied to excited state iminium ions have been expertly reviewed. In short, one-electron transfer to excited state iminium ions occurs rapidly from one of several electron donors electron rich alkenes, aromatic hydrocarbons, alcohols and ethers. Alternatively, an excited state donor, usually aromatic, can transfer an electron to a ground state iminium ion to afford the same reactive intermediates. Scheme 46 adumbrates the two pathways that have found most application in intramolecular cyclizations. Simple alkenes and aromatic hydrocarbons will typically suffer addition processes (pathway A). However, alkenic and aromatic systems with allylic or benzylic groups more electrofugal than hydrogen e.g. silicon, tin) commonly undergo elimination reactions (pathway B) to generate the reactive radical pair. 

Dicarboxylic anhydrides. Duckworth prepared acid anhydrides in about 90% yield by reaction of 1 mole of trifluoroacetic anhydride with 1 mole of a dicarboxylic acid in ether. Treatment of the mono-mixed anhydride with 1 mole of pyridine then led to the anhydride and pyridinium trifluoroacetate, which was precipitated by addition of petroleum ether. Alternatively, the mixed anhydride can be cyclized by heat treatment in vacuum at about 70°. This latter method was used by Moore and Kelly to prepare the anhydride (3) of tetra-hydrofurane-cw-2,5-dicarboxylic acid (1) in >90% yield. 

Two moles (135.6 g.) of BF3 are generated as described on p. 219. It is then introduced into a dry one-liter flask containing 148 g. of diethyl ether. Alternately, the BF3 may be frozen at liquid nitrogen temperature and added as a solid. The flask is cooled in ice-salt mixture and access of atmospheric moisture is prevented by closing off theflaskwithaCaClgtube. The stream of BF3 should not be too fast because some of it will not be taken up by the ether in that case. After the end of the reaction a condenser is connected to the flask and the BF3 0(CsHb)3 distilled off at 125°C into a receiver, preferably at reduced pressure. The etherate distills readily at 38°C (6 mm.). 

First the material must be freed of any plasticizers by extraction with ether. Alternatively, dissolve the sample in tetrahydrofuran, filter off possible undissolved components, and reprecipitate it by adding methanol. After... 

Poly (S-leucinato-AT, 0) cobalt (III) -u- [3,3 -dithiobis (2,4-pentanedion-ato-0,0 )]).—Initially, 1.7460 g disulfur dichloride (12.93 mmol) in 6 mL dry dichloroethane was added dropwise to 5.0088 g Co(leu)(acac)2 (12.93 mmol) in 20 mL dimethylacetamide (DMAC) with 0.7095 g sodium carbonate (6.69 mmol) as a slurry in the dimethylacetamide solution under argon and with vigorous stirring. The mixture was stirred for 24 - 36 h and then precipitated with diethyl ether. Alternatively, the solvent was removed in vacuo at 45 C. The product was collected on a fritted funnel, washed with water, and dried in vacuo at lOO C yield, 5.5 g 95%. The polymer was fractionated (three times) by a DMAC/acetone or dimethyl sulfoxide/acetone solvent/nonsolvent precipitation to remove low molecular-weight material. 

S -Histidine dihydrochloride [1007-42-7] M 242.1, m 245°, [a]g> +47.5 (c 2, H2O). The dihydrochloride crystallises from water or aqueous EtOH and is washed with acetone, then diethyl ether. Alternatively, convert it to the histidine di-(3,4-dichlorobenzenesulfonate) salt by dissolving 3,4-dichlorobenzenesulfonic acid (1.5g/10ml) in the aqueous histidine solution with warming, and then the solution is cooled in ice. The resulting crystals (m 280° dec) can be recrystallised from 5% aqueous 3,4-dichlorobenzenesulfonic acid, then dried over... 

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