“…Commercial ethyl (3), n-butyl (6), and isobutyl vinyl ethers (7) were distilled from LÍAIH4. Methyl (2) and tert-butyl vinyl ethers (5) were prepared by the alcohol exchange of 3 and 6, respectively.5 Isopropyl vinyl (4) and other alkenyl alkyl ethers (9)(10)(11)(12)(13)(14)(15) were obtained by the pyrolysis of an appropriate acetal as described previously.6 Preparations of phenyl vinyl ether (8),71,2-dimethoxyethylene (16),8 alkyl vinyl sulfides (17-20),9 and phenyl vinyl sulfide (21)10 were described before. Styrene (22) was distilled from teri-butylcatechol just before use.…”
Section: Methodsmentioning
confidence: 99%
“…Similar results were found in the hydrations of alkyl ethynyl ethers15 and sulfides16 as well as in the hydrolysis of aryl vinyl ethers and sulfides. 10 The difference in the efficiency of electronic transmission between the O and S atoms may be attributed to their lone pair electrons in 2p and 3p orbitals. Anomalies found in the hydrolysis of alkyl vinyl sulfides {p* > 0)9 were not observed here in the sulfenyl chloride addition.…”
The rates of addition of benzenesulfenyl chloride to ,/3-unsaturated ethers and sulfides have been measured in CCU at 30 °C. Reactivities of alkyl vinyl ethers and sulfides increase with the electron donating ability of alkyl group, p* being -5.4 and -1.7, respectively. /3-Alkyl and /3-methoxy substitutions enhance the reactivity of vinyl ether while -methyl substitution influences it little. Adducts are exclusively the Markownikoff type. With ethyl propenyl ethers, anti addition is slightly dominant over syn addition. It was concluded from these results that the rate-determining transition state resembles a symmetrically bridged sulfonium ion intermediate 23 and that an open carbonium ion mediates between the rate-and product-determining steps.
Comparative calculations of most stable geometries and proton affinities for a series of vinyl ethers and vinyl sulfides are made using the 4-31G and 3-21G(*) bases. While 4-31G and 3-21G(*) proton a5nities follow the same trends in the series, discrepancies arise for the molecular structures. 0x0 carbenium ions turn out to be better stabilized than their thio analogs, and interesting features in the atomic charge patterns are pointed out.
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