Deuterium isotope effects and the bunnett w factor in elimination reactions of 4-alkoxyimino-5,6-dihydro-6-alkoxyaminopyrimidin-2(1H-)one in strong acid media

Abstract

Für die Eliminierung von Hydroxylamin (IIIa) aus dem Iminopyrimidinon (Ia)erreichen die Geschwindigkeitskonstanten in Mineralsäuren, TFA oder CF3 SO3H bei einer Acidität von ‐O.8 ein Maximum.

β-Ureido acids and dihydrouracils. Part 15. Effect of allylic strain on ring opening of 1,6-disubstituted dihydrouracils

“…6 times in the pair (3) and (5) and ca. 4 times in the phenyl derivatives (6) and (7) which is in rough accord with the lowest estimate of kl in (S), and the observed value of kl for (7).…”

“…These limiting values of the individual constants for (5) correspond to a situation where the overall 125-fold decrease in rate compared with that of ( 3) is brought about by a factor of 25 in the ring-opening step, k3/k-l, and only of 5 in the addition step k,. rate of the phenyl derivatives (6) and (7), which correlates with the smaller tendency of (7) to adopt an axial conformation. As can be seen from Table 2 the contribution of the individual rate constants is similar to (S), the major effect being due to the ring-opening step.…”

“…The nitrogen-substi tuted derivatives (9) and (10) are, however, 0.5 pK units weaker acids, demonstrating the direct field effect of an axial carboxylate group. Sterically the carboxy-group is similar to phenyl but has a smaller conformational energy in cyclohe~anes.~~ The rate decrease brought about by an N-methyl group in (9) compared with (8) in klk3/kbl is greater than that observed with the phenyl derivatives (6) and (7) which is due to a larger drop in kl. Since the combined steric and polar effect of an axial carboxylate group most probably strongly reduces k , this could be attributed to a greater decrease in the population of the equatorial conformation.…”

Coordinated trifluoromethanesulfonate and fluorosulfate

“…83 Oxidative addition of halogen or interhalogen to I-(0S02F) produces IX2(S03F) and I2X(S03F), which are apparently ionic solids, forming solvated IX2+ and I2X+ solvated cations in FS03H. 97 The I(0S02F)2+ cation can be generated by reaction of I(0S02F)3 via (12) performed in S206F2 solvent for several days at room temperature.64 A reaction of BrS03F in excess Sn(0-S02F)4 yields eventually the Br(III) analogue,64 where oxidation of Br(I) by S206F2 must be involved. Reactions involving peroxydisulfuryl difluoride most likely involve the FS020radical,98 which can act as an effi-cient oxidant.…”

Influence of Proton Activity in H2/H2 Cells: Implications for Fuel-Cell Operation with Low Relative Humidities

“…43,44 We applied the proton activities of H 2 SO 4 and TFMSA reported by Nordstrom and Atkins. 45,46 To cover the Nafion® proton activity range of 68 to 390, H 2 SO 4 and TFMSA of up to 7 and 5 mol dm −3 were selected, which afforded the proton activities of 300 and 250, respectively. However, due to the dissolution of platinum and the foaming of the aqueous solution, the TFMSA concentration was limited to a maximum of 1.5 mol dm −3 .…”