Anion, free

Phase transfer catalysis succeeds for two reasons First it provides a mechanism for introducing an anion into the medium that contains the reactive substrate More important the anion is introduced m a weakly solvated highly reactive state You ve already seen phase transfer catalysis m another form m Section 16 4 where the metal complexmg properties of crown ethers were described Crown ethers permit metal salts to dissolve m nonpolar solvents by surrounding the cation with a lipophilic cloak leav mg the anion free to react without the encumbrance of strong solvation forces... 

Transfer of a single electron to O2 generates the potentially damaging superoxide anion free radical (02 ), the destructive effects of which are amphfied by its giv-... 

Molina, L.M. and Hammer, B. (2005) Oxygen adsorption at anionic free and supported Au clusters. Joumal of Chemical Physics, 123, 161104-1-161104-5. 

This paper discusses the use of specific ion electrodes for determining the anion-free water. This method is simpler and more accurate at low electrolyte concentration than ordinary chemical methods. It is potentially useful for oilfield application and laboratory automation. The mobility of this water is also examined under forced conditions with pressure gradients. It is expected that by using the methods developed in this paper, one may obtain a better understanding of the clay properties. 

The amount of anion-free water was calculated by a material balance of chloride and water in the system. The calculation can be simplified by using volume concentrations. Details of the calculation are illustrated in Appendix I. 

Figure 1. Anion-free Water As A Function of NaCl Concentration.

Mobility of The Anion-Free Water. It is well known that water in the electrical double layer is under a field strength of 10 -10 V/cm and that the water has low dielectric constants (36). Since anion-free water is thought to be the water in the electrical double layer between the clay and the bulk solution, at high electrolyte concentrations, the double layer is compressed therefore, the water inside is likely quite immobile. At low electrolyte concentrations, the electrical double layer is more diffuse, the anion-free water is expected to be less immobile. Since the evaluation of the shaly formation properties requires the knowledge of the immobile water, experiments were conducted to find out the conditions for the anion-free water to become mobile. 

By definition, the anion-free water is free of salt. When pressure is applied to a clay-brine slurry to force out water (as that described in the experimental section), the solution that flows out of the cell should maintain the same chloride concentration as the brine s if the anion-free water is immobile. Otherwise, the concentration of the chloride decreases. Pressure forces water to flow through the pores with a certain velocity meanwhile, the pore size... 

Table II shows the result of compaction experiments with Glen Rose Shale. Column 2 gives the equilibrium NaCl concentration of the solution before the compaction experiment. Column 3 gives the anion-free water calculated as shown in Appendix I. Column 4 gives the amount of the bulk solution which has the NaCl concentration given in Column 2. Column 5 gives the total amount of fluid flowing out of...

Experiments No. 1,2 and 3 were performed at gas pressure beginning at 15 psi and stepping up to 77 psi. The total fluid collected was less than the bulk solution in the system. The concentration of chloride in the fluid collected in these three runs was about the same as the values given in Column 2. It was concluded that under these conditions, the anion-free water was immobile. It was observed that under the same applied pressure, the higher the NaCl concentration, the faster the flow rate — consistent with observations reported by Engelhardt and Gaida (38). 

In order to increase the flow rate without too much pressure, Experiment 4 was performed with a Fann filter press which has a wider cross sectional area. A constant air pressure of 100 psi was applied, the flow rate was 26 times that of Experiment 1 while the NaCl concentration was only slightly higher than that of Experiment 1. Although the flow rate was much increased in Experiment 4, the result was similar to Experiment 1. The water retained in the clay (Column 8) determined by drying was found to be close to the amount of anion-free water. The porosity of the sediment was 0.4 and the average pore diameter was 4466 X. It was concluded from this experiment, that the anion-free water was immobile even at 100 psi and 7.4 ft/day. The pore size distributionQof the sample showed 90% of the pores to have a diameter above 350 A and less than 3% of the pores to have a diameter below 100 X (Figure 4). 

It was decided to increase the pressure in subsequent experiments to push the anion-free water out. Experiments 5 and 6 were performed at 400 psi at a NaCl concentration around 0.01 M. Experiments 5-10 were performed in the compaction cell as described in the experimental section. This apparatus was rated for 10,000 psi. The pressure regulation at 400 psi region was about 100 psi. Some evaporation occurred that made the total fluid collection less than expected from total material balance. NaCl concentration of the collected fluid could not be measured accurately. However, the amount of fluid collected and the amount of water retained in the sediments in Experiments 5 and 6 clearly indicated some anion-free water was mobilized. 

Run NaCl Anion-free Bulk Fluid Pressure Initial Flow Rate Residual H2O Porosity Av. Pore... 

Anion-free water determined by using a chloride ion electrode agrees well with data given in the literature. (2) A new equation has been proposed for the bound water calculation. (3) The mobility of the anion-free water was found to be affected by pressure, porosity and electrolyte concentration. (4) Compaction experiments indicated that the anion-free water will not move until all the bulk water has been removed. (5) It is possible to increase the ratio of bound water to bulk water in a sample through compaction experiment. 

Theoretical calculahons suggested that the normal binding is thermodynamically favored when the anion-free complexes are considered, but ion-pairing has... 

They could also be 111 layers of (anion-free) Th, cf. next section... 

CARBOCATIONS, C ARB ANIONS, FREE RADICALS, CARBENES, AND NITRENES... 

Polymerization of isobutylene, in contrast, is the most characteristic example of all acid-catalyzed hydrocarbon polymerizations. Despite its hindered double bond, isobutylene is extremely reactive under any acidic conditions, which makes it an ideal monomer for cationic polymerization. While other alkenes usually can polymerize by several different propagation mechanisms (cationic, anionic, free radical, coordination), polyisobutylene can be prepared only via cationic polymerization. Acid-catalyzed polymerization of isobutylene is, therefore, the most thoroughly studied case. Other suitable monomers undergoing cationic polymerization are substituted styrene derivatives and conjugated dienes. Superacid-catalyzed alkane selfcondensation (see Section 5.1.2) and polymerization of strained cycloalkanes are also possible.118... 

The next two chapters demonstrate the power of anionic, free-radical and electron-transfer processes in the systematic construction of highly functionalized five- and six-membered carbocycles. 

Anion Free Ion (mmol/Iiter) Complex with Cation (mmol/liter) ... 

Many reactions occur in which one organic compound is convened into another. The molecular details of the intemiediate steps by which compounds are converted into new products are called reaction mechanisms. The four broad classes of reaction mechanisms are cationic, anionic, free radical, and multicenter processes in which neither charged species nor odd electron species is involved. Examples of each type will be given, but many variations can exist within each type. Also, varying degrees of sophistication exist in our knowledge of the exact reaction pathways that organic compounds follow. The examples discussed show only the major steps involved. 

H. Ohshima, Y. Yoshie, S. Auriol and I. Gilibert, Antioxidant and pro-oxidant actions of flavonoids effects on DNA damage induced by nitric oxide, per-oxynitrite and nitroxyl anion, Free Radic. Biol. Med., 25 (1998) 1057-1065. M.K. Johnson and G. Loo, Effects of egpigallocatechin gallate and quercetin on oxidative damage to cellular DNA, Mutat. Res., 459 (2000) 211-218. 

A macromonomer is a macromolecule with a reactive end group that can be homopolymerized or copolymerized with a small monomer by cationic, anionic, free-radical, or coordination polymerization (macromonomers for step-growth polymerization will not be considered here). The resulting species may be a star-like polymer (homopolymerization of the macromonomer), a comblike polymer (copolymerization with the same monomer), or a graft polymer (copolymerization with a different monomer) in which the branches are the macromonomer chains. 

---