- 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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- Deamination Reactions, 41. Reactions of Aliphatic Diazonium Ions and Carbocations with Ethers
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Aliphatic diazonium ions and carbocations were generated by deacylation of appropriate nitrosoureas (1, 5, 9) in alcohol-ether mixtures or in 2-alkoxyethanols.Ethers were generally inferior to alcohols in capturing cationic intermediates.Formation of trialkyloxonium ions led to alkyl exchange or ring opening.The observed reactivity orders were n-butyl > isobutyl for the diazonium ions, allyl > sec-butyl > tert-butyl for the carbocations, methoxy > ethoxy and oxirane > oxetane > tetrahydrofuran for the ethers, indicating the predominance of steric effects.Neighboring group participation in 4-methoxy-1-butanediazonium ions (58) and 4,5-epoxy-1-pentanediazonium ions (74) was detectable but inefficient ( 20percent of cyclic oxonium ions).
- Kirmse, Wolfgang,Jansen, Ulrich
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p. 2607 - 2625
(2007/10/02)
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