Other Protonic Solvents

Also note that the spacer concept, as verified by several laboratories (e.g.. see Perrson and Jann-asch ), has been moved forward to the immobilization of other proton solvents such as phosphonic acid, with very promising results (see Section 5). 

Effect of Water. Wood is usually treated with ammonia in the presence of some amount of water. The effect of water depends not only on the amount of water but also somewhat on the history of the wood sample and the method of treatment. Thus, when oven-dried veneer strips were treated with cold liquid ammonia-water mixtures at ambient pressure, the flexibility of the treated wood was substantially decreased when the moisture content of the ammonia was much above 10% (26). Other protonic solvents act similarly (26). In apparent contrast, the rate of sorption of ammonia from the gas phase by wood is markedly enhanced by moisture in the wood (19). Bone dry wood absorbs ammonia quite slowly at ambient temperatures but if the wood has ten to twenty percent moisture content, sorption and plasticization occur much more rapidly. Presumably the moisture opens the pore structure of the wood and also dissolves ammonia much more readily than bone-dry wood. On continued treatment, the water is presumably displaced from the wood by the ammonia... 

Other Protonic Solvents and Ion Pairs. Apart from information for the solvent liquid ammonia, little spectroscopic data are available on this topic. The reason seems to be the great complexity of spectra when solvents like methanol or ethanol are used. 

Two noteworthy chemical properties of this compound are its thermal stability and its sensitivity towards water and other protonic solvents. 

The mechanism of catalytic hydrogen wave formation in the presence of organic bases was discussed by Conway, Bockris and Lovrecek. Essentially the reaction requires the formation of an adsorbed onium compound, i.e., the addition of a proton to the heterocyclic compound which is adsorbed at the electrode surface. Electron transfer to the onium compound occurs at potentials less negative than those required to discharge HaO or other protonated solvent molecules and the product, which has characteristics of a radical, decomposes to liberate hydrogen and regenerate the heterocyclic base ... 

Other protonic solvents are nitric acid, carboxylic acids such as formic and acetic acids, as well as hydrazine, hydrogen cyanide and to a limited extent hydrogen sulphide and the other hydrogen halides ... 

The chemical shift of the hydroxyl proton signal is variable depending on solvent temperature and concentration Its precise position is not particularly significant m struc ture determination Because the signals due to hydroxyl protons are not usually split by other protons m the molecule and are often rather broad they are often fairly easy to... 

In any pure liquid, the transfer of a proton from one molecule to another (distant) molecule has been named autoprololysis. I11 any solvent this process creates a positive and a negative ion and must clearly belong to class II it will not differ from other proton transfers of class II except for the fact that the relation between Kx and K will be different. On the left-hand side of (127) and (128) there is no solute particle hence the increase in the cratic term is greater than in (119) or (121). In (128) we have Aq — +2, and... 

Water was also investigated as a proton donor for the hydrogen bond with DMSO and other Lewis bases at infinite dilution detected by means of 1H NMR54-69. A comparison of the hydrogen bonding ability of DMSO in various other aprotic solvents was presented by Delpuech70 who measured the H-NMR chemical shift of CHC13. 

Water forms hydrogen-bonded clusters with itself and with other proton donors or acceptors. Hydrogen bonds account for the surface tension, viscosity, liquid state at room temperature, and solvent power of water. 

Aprotic polar solvents such as those listed in Table 8.1 are widely used in electrochemistry. In solutions with such solvents the alkali metals are stable and will not dissolve under hydrogen evolution (by discharge of the proton donors) as they do in water or other protic solvents. These solvents hnd use in new types of electrochemical power sources (batteries), with hthium electrodes having high energy density. 

Examining Table 2, one comes to the conclusion that only Ba2+ (H20)n where n > 1 can be produced by the association reactions of M2+ with H20. For all the other ions only the monohydrate will be obtainable. For ions with high IE(M) values, even the monohydrate, M2+H20 may not be obtained because of charge transfer reactions to H20 (see equation 22). Other protic solvents will lead to charge reduction by proton transfer at different values of r. Only NH3 has been examined.71 It leads to much more facile charge reduction than H20. Many of the doubly charged ions that were observed as hydrates could not be observed as the equivalent clusters of NH3. 

This would mean that in DMSO and other aprotic solvents a proton is transferred from the amino group to the ortho-carboxylate group. 

Some ionizing solvents are of major importance in analytical chemistry whilst others are of peripheral interest. A useful subdivision is into protonic solvents such as water and the common acids, or non-protonic solvents... 

Water and other hydroxylic solvents both donate and accept protons with reasonable facility and are termed amphiprotic. 

If your compound does not happen to dissolve in CC14, you still have a shot because deuterium atoms do not give PMR signals. This is logical, since they re not protons. The problem is that deuterated solvents are expensive, so do NOT ask for, say, D20 or CDC13, the deuterated analogs of water and chloroform, unless you re absolutely sure your compound will dissolve in them. Always use the protonic solvents — H20 or CHC13 here — for the solubility test. There are other deuterated solvents, and they may or may not be available for use. Check with your instructor. 

The reactions in a non-basic aprotic solvent CH2C12 provided solely 10, the product of carbon protonation, while those carried out in an acidic protic solvent HFIP give exclusively 8K, the product of oxygen protonation. The equilibrium protonation may be favored in a protic solvent having abundant protons available. In other basic solvents, the proton donor involved in the reaction should be the conjugate acid of the solvent, and many factors may delicately control the selectivity of the reaction. 

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