- Influence of Boiling on the Radiolysis of Diglyme
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The radiolysis of diethylene glycol dimethyl ether (diglyme) in a boiling state has been studied for the first time. Boiling facilitates the cleavage of internal C–O bonds, weakens the cage effect and diglyme regeneration processes, and facilitates the exchange and dimerization reactions of radicals. As compared with radiolysis at room temperature, the amount of unsaturated products of diglyme fragmentation formed during irradiation in the boiling state is smaller by a factor of 4, and the disproportionation products of heavy radicals are found in negligible amounts, if any. The yield of radiolytic decomposition of diglyme under boiling conditions is ～15 molecule/100 eV, which is higher than that at room temperature by a factor of almost 1.5.
- Vlasov,Kholodkova,Ponomarev
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p. 312 - 318
(2018/08/01)
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- A Simple, effective boron-halide ethoxylation catalyst
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Boron esters B(OR)3, readily derived from boric acid and alcohols, combine with iodide or bromide to catalyze the ethoxylation of alcohols and phenols, giving good rates and narrow product distributions. The combined action of a weak electrophile [B(OR)3] and a weak nucleophile (halide) allows for the ethoxylation of base-sensitive alcohols. Experiment suggests a new mechanism for this commercially important reaction proceeding through key β-haloalkoxy intermediates.
- Moloy, Kenneth G.
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body text
p. 821 - 826
(2010/07/05)
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- Direct methylation of primary and secondary alcohols by trimethyl phosphate to prepare pure alkyl methyl ethers
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Primary and secondary alcohols and diols react autocatalytically with trimelhyl phosphate plus small amounts of polyphosphoric acid at 185°C to give the corresponding methyl ethers. High purity and good yields are achieved when the ether is distilled from the reaction mixture as it is formed. By controlled addition even low-boiling alcohols can be methylated successfully. The reaction mechanism is undetermined. Peroxide formation in ethers is inhibited by storage over 10 molal KOH. Pure isotropic optical crystals are used for refractometer calibration. Improved physical property and NMR data (1H and 13C) are reported for thirteen methyl ethers. Simple two-point linear extrapolation of NMR shifts (especially 13C) to infinite dilution produces highly reproducible δ°-values (to 0.01 ppm or better) which uniquely characterize a molecule even when unidentified and/or not isolated from a mixture. This capability appears not to have been recognized in the literature. Acta Chemica Scandinavica 1998.
- Van Dyke Tiers, George
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p. 1223 - 1233
(2007/10/03)
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- Process for the production of methyl-blocked ethoxylates
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A process for preparing a methyl-blocked ethoxylate comprises heating at 180°-320° C., in the presence of a catalytically effective amount of a noble metal catalyst, an unsubstituted ethoxylate of 3 or more ethoxy units, or a monoalkyl-, monoaryl-, mono- or di-alkylamino- or mono- or di-arylamino ethoxylate of 2 or more ethoxy units, or a monoalkyl- or monoaryl-N,N-bis(ethoxylate) of 2 or more ethoxy units, all of which are derived from vicinal glycols, whereby there is prepared a corresponding methyl-blocked ethoxylate product which, for an unsubstituted ethoxylate starting material is a dimethylethoxylate having two fewer ethoxy units than the starting ethoxylate, and for the other ethoxylate starting materials, is a methylethoxylate having one less ethoxy unit in each ethoxylate group of the starting material.
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