Benzyl alcohol concentration

The pyridine-catalysed lead tetraacetate oxidation of benzyl alcohols shows a first-order dependence in Pb(OAc)4, pyridine and benzyl alcohol concentration. An even larger primary hydrogen kinetic isotope effect of 5.26 and a Hammett p value of —1.7 led Baneijee and Shanker187 to propose that benzaldehyde is formed by the two concurrent pathways shown in Schemes 40 and 41. Scheme 40 describes the hydride transfer mechanism consistent with the negative p value. In the slow step of the reaction, labilization of the Pb—O bond resulting from the coordination of pyridine occurs as the Ca—H bond is broken. The loss of Pb(OAc)2 completes the reaction with transfer of +OAc to an anion. 

Figures 3 and 4 report the photoreactivity results obtained from representative runs carried out at different initial benzyl alcohol concentrations and two lamp powers for all of these runs, the same amount of cafalysf was used.

In Figures 3-5, the concentration values reported for fhe zero time correspond to those of the starting solution, that is, without catalyst and irradiation. It must be reported that at the end of dark period (lasting 30 min) the benzyl alcohol concentration in the suspension is a little lesser than that of fhe starfing solufion. The calculations of photoad-sorbed amounf, however, have been performed by hypothesizing that all the molecules present on the catalyst surface participate in the... 

Figure 3 Experimental values of benzyl alcohol concentration vs. irradiation time. Home-prepared catalyst amount 0.4 g L lamp power, 125 W. The empty symbols indicate the concentration of starting solution. The solid lines represent the Langmuir photoadsorption model [Equation (19)] (Yurdakal et at, 2008b).

Figure 5 Experimental values of benzyl alcohol concentration vs. irradiation time.

Figure 5 reports the results obtained from runs carried out with different amounts of catalyst for all these runs the same initial benzyl alcohol concentration and lamp power were used. 

The effect of catalyst amount on photoadsorption capacity is shown in Figure 9. This figure reports the benzyl alcohol moles photoadsorbed per unit mass of catalyst vs. the catalyst amount the reported data refer to runs carried out at equal initial benzyl alcohol concentration and lamp power. From the observation of data of Figure 9, a decrease of specific photoadsorption capacity by increasing the catalyst amount, differently from that expected on thermodynamic basis for which an increase of catalyst amount determines a corresponding increase of adsorbed substrate, may be noted. 

Figure 9 Photoadsorbed amount of benzyl alcohol per unit mass of catalyst, ns/W, vs. the mass of catalyst. Initial benzyl alcohol concentration, 1 mM, lamp power, 125 W (Yurdakal et al., 2008b).

FIG. 1 Effect of benzyl alcohol concentration on the viscosity of the 0.01 mol L CTAB/KBr micellar system. 

B. Effect of Benzyl Alcohol Concentration on Rg, R, and Mw of Mixed Alcohol and CTAB Micelles in the Presence of KBr Salt... 

In the 0.01 mol L CTAB/0.1 mol L KBr micellar system, the micelles are rodlike [18]. The effect of benzyl alcohol concentration on the radius of gyration R, the hydrodynamic radius and the weight-averaged molar mass of the micelles in this system is given in Table 1. In order to compare the LLS data with viscosity data, the latter are also listed in Table 1. It is seen that the Rg, Rt, and M of micelles go through marked maxima upon addition of benzyl alcohol in the CTAB/KBr system and the largest size of the micelles appears at the highest viscosity. 

C. Variation in the Solubilization Location of Benzyl Alcohol with Benzyl Alcohol Concentration in CTAB/KBr Micellar System... 

In the 0.01 mol L CTAB/0.1 mol L KBr system, the dependence of the chemical shifts and the shape of the signals of —CH3, —(CH2>i3—and N—(CH3)3 groups of the CTAB molecule on benzyl alcohol concentration is shown in Fig. 2. In the H NMR spectra, the resonance signals 1, 2, and 3 represent —CH3, —(CH2)i3—, and N—(CH3)3 groups, respectively, of the CTAB molecule. It can be seen from Fig. 2 that the peak due to the long-chain methylenes of the CTAB molecule shows marked line broadening when the benzyl alcohol concentration is more than 0.6%, at which the... 

FIG. 2 Effect of benzyl alcohol concentration on H NMR spectra of CTAB in 0.01... 

The variations in the H chemical shift (AS = So S, where So is the H chemical shift of CTAB molecules in 0.01 mol L CTAB/0.1 mol L KBr without benzyl alcohol and S is the H chemical shift of the same system with benzyl alcohol) directly indicate the effect of benzyl alcohol concentration on that of CTAB molecules. In the presence of 0.1 mol L KBr salt, the variations in H chemical shifts of the resolved signals of the CTAB molecule with benzyl alcohol concentration are shown in Fig. 3. A value AS > 0 means an upheld shift of the H chemical shift for the CTAB molecule. 

FIG. 3 Variations of chemical shifts of protons of CTAB in micelles with benzyl alcohol concentration in 0.01 mol L CTAB/0.1 mol KBr solution. 

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