Water protonated

Step 2 In a solvent such as water proton transfers convert the dipolar intermediate to the carbmolamme... 

Similar conclusions were obtained from lH and 31P NMR and also from IR studies of egg phospholecithin reversed micelles in benzene by Boicelli et al. 58 61). According to the results of these experiments the water structure within the reversed phospholecithin micelles alters considerably compared with water in bulk. This becomes evident from the shortening of the relaxation time T, of the water protons split into two relaxation times T1A and T1B, indicating that there are at least two... 

The reaction is very fast in both directions, and so is always at equilibrium in water and in aqueous solutions. In every glass of water, protons from the hydrogen atoms are ceaselessly migrating between the molecules. This type of reaction, in which one molecule transfers a proton to another molecule of the same kind, is called autoprotolysis (Fig. 10.9). 

Nuclei resonating at different chemical shifts will also experience similar refocusing effects. This is illustrated by the accompanying diagram of a two-vector system (acetone and water), the nuclei of which have different chemical shifts but are refocused together by the spin-echo pulse (M, = magnetization vector of acetone methyl protons, M(v = magnetization vector of water protons). 

Water proton self-diffusion exhibits a break point and begins to increase at a = 0.85. In the case of AOT self-diffusion, a breakpoint also occurs, but AOT self-diffusion continues to slow as a decreases further. These breakpoints in both water and AOT selfdiffusion behavior at a = 0.85 coincide with the breakpoint in electrical conductivity illustrated in Fig. 1, where the onset of electrical conductivity percolation occurs. At a = 0.7 two more breakpoints in the water proton and AOT self-diffusion are seen. Water proton self-diffusion increases more markedly and AOT self-diffusion beings to increase markedly. 

A simple two-state model for the observed water proton self-diffusion may be put forward in the form... 

The order parameter values calculated from the data of Fig. 4 are illustrated in Fig. 5. The data there suggest the existence of two continuous transitions, one at a = 0.85 and another at a = 0.7. The first transition at a = 0.85, denoted by the arrow labeled a in Fig. 5, is assigned to the formation of percolating clusters and aggregates of reverse micelles. The onset of electrical percolation and the onset of water proton self-diffusion increase at this same value of a (0.85) as illustrated in Figs. 2 and 3, respectively, are qualitative markers for this transition. This order parameter allows one to quantify how much water is in these percolating clusters. As a decreases from 0.85 to 0.7, this quantity increases to about 2-3% of the water. 

X 10 cm by measuring molecularly dispersed water in toluene and by correcting for local viscosity differences between toluene and these microemulsions [36]. Values for Dfnic were taken as the observed self-diffusion coefficient for AOT. The apparent mole fraction of water in the continuous toluene pseudophases was then calculated from Eq. (1) and the observed water proton self-diffusion data of Fig. 9. These apparent mole fractions are illustrated in Fig. 10 (top) as a function of... 

We outline experimental results and provide theoretical interpretation of effect of adsorption of molecular oxygen and alkyl radicals in condensed media (water, proton-donor and aproton solvents) having different values of dielectric constant on electric conductivity of sensors. We have established that above parameter substantially affects the reversible changes of electric conductivity of a sensor in above media which are rigorously dependent on concentration of dissolved oxygen. 

In many products, the spin-relaxation properties of the components can be different due to molecular sizes, local viscosity and interaction with other molecules. Macromolecules often exhibit rapid FID decay and short T2 relaxation time due to its large molecular weight and reduced rotational dynamics [18]. Mobile water protons, on the other hand, are often found to have long relaxation times due to their small molecular weight and rapid diffusion. As a result, relaxation properties, such as T2, have been used extensively to quantify water/moisture content, fat contents, etc. [20]. For example, oil content in seeds is determined via the spin-echo technique as described according to international standards [64]. 

Fig. 2.15 Transport of protons in water. Proton tunnelling is a fast process but water molecules must first rotate to the position where the transfer is possible... 

This technique is also used as a very common diagnostic tool, since the chemical shift of water protons depends also on the mobility of the water molecules. Therefore, it is possible to discriminate between different tissues. A computer analyses the emissions from the hydrogen nuclei of water molecules... 

The longitudinal inner-sphere relaxation rate, l/Ti, of bulk water protons is given by Equation (2) 13... 

Apart from the data of thermonephelometry and HS-DSC,1H NMR studies have also revealed [27] some properties that allowed the attribution of such s-type copolymers to the protein-like ones. A marked broadening of the water proton signal was observed caused by the decreased mobility of bound water just in the vicinity of the temperature of HS-DSC peak. These data indicated the heat-induced compaction of the interior of the polymer coils, as would occur with protein-like macromolecules. Figure 5 demonstrates the experimental data, viz., the temperature dependences of signal width at half-height for the peaks of water protons recorded in D2 O-solutions of p- and s-fractions of the copolymer synthesized from the feed with an initial comonomer ratio of 85 15 (mole/mole). 

The values of A1/2 v for water protons in the D2O-solutions of the s- and p-fractions under discussion were measured over a temperature range from 20 to 55 °C [27]. The heat-induced variations of the A1/2 v parameter for these two copolymers are different (Fig. 5a and b). For instance, at temperatures from 20 to 24 °C, the line width of the water proton signal in the solution of the fraction p (Fig. 5a) broadens from 1.88 to 3.5 Hz, it narrows further... 

Fig. 5 Temperature dependences of the full width of NMR signal (A1/2 v) at half maximum measured for water protons in D2O solutions of the fractions a p and b s of poly(NVCl-co-NVIAz) synthesized at 65 °C from the feed with initial ratio of comonomers 85 15 (mole/mole) (the data from [27])...

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