ChemInform Abstract: NUCLEOPHILIC DISPLACEMENT WITH A SELECTIVELY SOLVATED NUCLEOPHILE: THE SYSTEM HYDRATED HYDROXIDE ION (OH-.CNTDOT.H2O) + BROMOMETHANE AT 300 K

1983 ◽  
Vol 14 (46) ◽  
Author(s):  
M. HENCHMAN ◽  
J. F. PAULSON ◽  
P. M. HIERL
Keyword(s):  
Hydroxide Ion ◽  
Nucleophilic Displacement

Reactivity of Oxy-anions [HO-, RO-, HOO- (ROO-), and O2-] as Nucleophiles and One-Electron Reducing Agents

1992 ◽  
Author(s):  
Donald T. Sawyer ◽  
R. J. P. Williams
Keyword(s):  
Solvation Energy ◽  
Oxidation Potential ◽  
Relative Reactivity ◽  
Hydroxide Ion ◽  
Nucleophilic Displacement ◽  
Amine Groups ◽  
Brønsted Base ◽  
Unifying Principles ◽  
Conjugate Base

The preceding chapter describes the primary reaction chemistry of superoxide ion (O2-. to be that of (1) a Brønsted base (proton transfer from substrate), (2) a nucleophile (via displacement or addition), (3) a one-electron reductant, and (4) a dehydrogenase of secondary-amine groups. The chemistry is characteristic of all oxy anions [HO- (RO-), HOO- (ROO-), and O2-.], but the relative reactivity for each is determined by its pKa and one-electron oxidation potential, which are strongly affected by the anionic solvation energy of the solvent matrix. The present chapter will focus on the reactivity of hydroxide ion (HO-), but the principles apply to all oxy anions and permit assessments of their relative reactivity. The reactivity of hydroxide ion (and that of other oxy anions) is interpreted in terms of two unifying principles: (1) the redox potential of the YO- / YO· (Y = H, R, HO, RO, and O) couple (in a specific reaction) is controlled by the solvation energy of the YO- anion and the bond energy of the R-OY product (RX + YO- → R-OY + X-), and (2) the nucleophilic displacement and addition reactions of YO- occur via an inner-sphere single-electron shift. The electron is the ultimate base and one-electron reductant, which, upon introduction into a solvent, is transiently solvated before it is “leveled” (reacts) to give the conjugate base (anion reductant) of the solvent.

Bifluoride Ion Mediated SuFEx Trifluoromethylation of Sulfonyl Fluorides and Iminosulfur Oxydifluorides

2018 ◽  
Author(s):  
Christopher J. Smedley ◽  
Bing Gao ◽  
Suhua Li ◽  
Qinheng Zheng ◽  
Andrew Molino ◽  
...  
Keyword(s):  
Breast Cancer Cells ◽  
Catalytic Mechanism ◽  
Bioactive Molecules ◽  
Chromatographic Purification ◽  
Rapid Exchange ◽  
Nucleophilic Displacement ◽  
Sulfur Fluoride ◽  
Reactions With Nucleophiles ◽  
New Generation ◽  
Selection Of

Sulfur-Fluoride Exchange (SuFEx) is the new generation click chemistry transformation exploiting the unique properties of S-F bonds and their ability to undergo near-perfect reactions with nucleophiles. We report here the first SuFEx based protocol for the efficient synthesis of pharmaceutically important triflones and bis(trifluoromethyl)sulfur oxyimines from the corresponding sulfonyl fluorides and iminosulfur oxydifluorides, respectively. The new protocol involves the rapid exchange of the S-F bond with trifluoromethyltrimethylsilane (TMSCF<sub>3</sub>) upon activation with potassium bifluoride in anhydrous DMSO. The reaction tolerates a wide selection of substrates and proceeds under mild conditions without need for chromatographic purification. A tentative catalytic mechanism is proposed supported by DFT calculations, involving formation of the free trifluoromethyl anion followed by nucleophilic displacement of the S-F through a five-coordinate intermediate. The preparation of a benzothiazole derived bis(trifluoromethyl)sulfur oxyimine with cytotoxic selectivity for MCF7 breast cancer cells demonstrates the utility of this methodology for the late-stage functionalization of bioactive molecules.<br>

Residual phase lignin in haft cooking related to the conditions in the cook

1997 ◽  
Vol 12 (4) ◽  
pp. 225-229
Author(s):  
Cart-in A-S. Gustavsson ◽  
Chritofer T. Lindgren ◽  
Mikael E. Lindström
Keyword(s):  
Hydrogen Sulfide ◽  
Ionic Strength ◽  
Sodium Ion ◽  
Ion Concentration ◽  
Constant Composition ◽  
Hydroxide Ion ◽  
Sulfide Ion ◽  
Residual Phase ◽  
Kraft Cooking ◽  
Very High

Abstract The amount of lignin reacting according to the slow residual phase, i.e. the residual phase lignin, is in many perspectives an interesting issue. The purpose of the present investigation was to develop a mathematical model to show how the amount of residual phase lignin in the kraft cooking of spruce chips (Picm ahies) depends on the conditions in the earlier phases of the cook. The variables studied were hydroxide ion concentration, hydrogen sulfide ion concentration and ionic strength. The liquor-to-wood ratio during pulping was very high to maintain approximately constant chemical concentrations throughout each experiment (so called "constant composition" cooks). An increase in hydroxide ion concentration andtor hydrogen sulfide ion concentration leads to a decrease in the amount of residual phase lignin, while an increase in ionic strength, i.e. sodium ion concentration, leads to an increase. A signiticant result is that the hydrogen sulfide ion concentration has a pronounced influence on the amount of residual phase lignin during a cook at a low hydroxide ion concentration. The amount of residual phase lignin expressed as % lignin on wood, L,, can be described by the following equation developed for "constant composition" cooks (when cooking with a constant sodium ion concentration of 2 mol/L): LT=0,55-0.32*[HO-](-1,3)*ln[HS-] This equation is valid for a concentration of HO- in the range from 0.17 to 1.4, and a hydrogen sulfide ion concentration from 0.07 to 0.6 mol/L.

Sign in / Sign up

Export Citation Format

Share Document