UV-visible spectroscopic analysis

Attempts have been made to synthesize Ti-ZSM-48 with even higher titanium contents, but it was reported that no more than 2% titanium could be incorporated into framework positions. UV-Visible spectroscopic analysis of materials prepared with more titanium precursor indicates the presence of extra-framework Ti02, which in some cases is present also in the materials with low titanium contents. From these observations it is concluded that for Ti-ZSM-48 a limit exists in the amount of Tilv that can substitute for Silv in framework positions (Reddy, K. M. et al., 1994b). 

Table 3.12 Results Summary for UV-Visible Spectroscopic Analysis...

UV-VISIBLE SPECTROSCOPIC ANALYSIS AND ITS AMINO ACID DERIVATIVES 91... 

In contrast, Matsukawa and Hinakubo proposed Sm(II)-mediated pinacol coupling in water (Scheme 8.11).11 In all cases, the corresponding reduced product benzyl alcohols were formed in low yields. Unexpected disproportionation in water was also observed via UV-visible spectroscopic analysis. This indicated that low-valent samarium species can exist in water. Furthermore, the SmCl3-Sm and SmCl3-Mg systems were found to act as good one-electron reducing agents in water (Scheme 8.11). 

Poly(methyl methacrylate) (PMMA) nanofibers containing Ag nanoparticles were synthesized by radical-mediated dispersion polymerization. UV-visible spectroscopic analysis indicated that the Ag nanoparticles were continually released from the polymer nanofiber in aqueous solution [47]. In another study, the electrospinning conditions for PMMA were studied [48]. In this work, conductivity of the polymer solution containing Ag nanoparticles and its effect on fiber diameter were also studied. As the results showed, the maximum concentration for the electrospinning of PMMA was found to be 18 wt%, and the ratio of DMF to THF was 7 3 (v/v). The diameter of nanolibers obtained was found to be 100-400 nm when the PMMA solution contained 1,000 ppm of Ag nanoparticles [48]. 

UV-visible spectroscopic analysis of the reaction between zinc(II) and (20) shows one complex whose stoichiometry suggests a double-helical structure and one complex whose stoichiometry suggests a triple-helical structure. The complex [Zn 3(20)2] + is also observed in the analysis, and may have a structure which has a tetrahedral Zn bridging two [Zn(20)p units [26]. 

Anionic thesis of macromonomer of 1,1-diphenylethylene-type unit canying amino group has been performed in a variety of solvents. The product was characterized a combination of H NMR spectroscopic and size exclusion chromatographic analysis. Based on the UV/Visible spectroscopic analysis, the crossover reaction of /i-butyllithium (n-BuLi) with l-[4-bis(trimethylsilyl>amino]phenyl]-l-phenylethylene was found to be so slow in benzene, but it was completed in the benzene/THF mixture within 2 h. The i thesis of macromonomer of thel,l-diphenylethylene-type unit (over 95 %) canying amine-functional group (maximum 94 %) was successful on the basis of H NMR spectroscopic analysis. 

It has been well-known that 1,1-diphenylethylene is anionically non-homopolymerizable but copolymerizable with other vinyl monomers (26-28). In addition, it has been reported that the diadduct was negligibly small and monoadduct was exclusively obtained from obseivation through NMR and UV/Visible spectroscopic analysis from the reaction of poly(styiyl)lithium and l,4-bis(l-phenylethenyl)benzene DDPE) in hydrocaibon with polar additive (22). This indicates that the addition of polar additive suppresses the formation of diadduct even in benzene solution at room temperature. 

A second nucleophilic catalyst supported by PtBS is the polymer-bound di-methylaminopyridine analog that was also used in latent biphasic catalysis with the poly(JV-alkylacrylamide) support 129 [131]. This example of a nucleophilic catalyst (133) was used to catalyze formation of a t-Boc derivative of 2,6-di-methylphenol (Eq. 70). In this case, the extent of recovery of the catalyst and the yields of product were directly comparable to those seen with thermomorphic systems. The isolated yield for the first five cycles of this reaction were 34.3, 60.9,82.2,94.6, and 99%. In this case we reused catalyst 133 through 20 cycles. Yields after the first few cycles were essentially quantitative (ca. 93% average for each of 20 cycles). Separation of the polymer from the aqueous ethanol phase was quantitative as judged by either visual observation or UV-visible spectroscopic analysis. 

Quartz substrates were used for UV-visible spectroscopic analysis, as well as for gel content and weight loss measurements. Salt (NaCl) flats were used as substrates for FTIR analysis. 

The functionalities of these macromonomers could be determined by both UV-visible spectroscopic analysis ( lmax for DPE at 260 run) and by HNMR spectroscopy (vinylidene protons at 5 5.4 ppm). The functionality of the macromonomer 74 (M =3400) was estimated to be 0.6 by UV analysis and 0.83 by NMR no dimer was observed by SEC analysis [198]. The stoichiometric addition of PSLi (M =16,000) occurred quantitatively with no residual macromonomer observed by SEC [198]. 

The use of noble metal NPs in water purification for applications other than microbial disinfection was first reported in 2003. The chemistry reported can be summarized as reductive de-halogenation of chlorocarbons (halocarbons in general) in water solutions occurring at room temperature over silver nanoparticles wherein the C-Cl bond is cleaved with the formation of AgCl. UV-visible spectroscopic analysis of this reactivity is shown in Fig. 8A. A series of chemical events occur on the nanoparticle and amorphous carbon is observed as a product. This chemistry was soon extended to halogenated pesticides at high efficiency.A concentration of 50 ppb chlorpyrifos was reduced to less than 0.5 ppb upon passing over a... 

Satsuma, A., Shibata, J., Wada, A., Shinozaki, Y. and Hattori, T. (2003) In-situ UV-visible spectroscopic study for dynamic analysis of silver catalyst. Stud. Surf. Sci. Catal., 145, 235-238. 

The desired polyimide derivatives were prepared by condensation polymerization as shown in Scheme 1. The initial polyamic acids (PAA 1-4) could be spun onto a substrate and cured by ramping the temperature to 260 C. For those examples where X=(CF3)2C, the polyimide derivatives were soluble in organic solvents. These materials were usually spun in the preimidized form. The improved thermal stability of the arylamino substituted chromophores tethered to the polyimide backbone is obvious from the DSC analysis. The onset decomposition temperature measured by DSC of the aryl substituted polymer PI-2b is almost 40°C hi er than that of Pl-lb (Td = 376 vs 338T). Likewise, this stabilizing effect is apparent variable temperature, UV-visible spectroscopic studies of the polymer films. In this case, the absorbance at the max of the chromophore was monitored versus time at a variety of temperatures (18), While the absorbance of PI-2b (Amax 498 nm) was little changed after one hour at 275°C, that of Pl-lb (Amax 474 nm) decreased by almost 30%. In each case, the heating was conducted under an inert atmosphere. Studies such as these are the origin of the data shown in the last column of Table I. 

The analysis of purely rotational, rotational-vibrational, and electronic spectra (cf. pp. 23/30) gave rotational and vibrational constants for the electronic ground state and various excited states of PH and PD. The more accurate values were obtained, of course, by IR Fourier transform and laser spectroscopy as compared to the conventional UV-visible spectroscopic methods (conventional IR spectroscopy has never been applied to PH). 

Not mentioned in Table 2 (and often not in the original papers ) is the optical form (chirality) of the amino acids used. All the amino acids, except for glycine (R = H), contain an asymmetric carbon atom (the C atom). In the majority of cases the optical form used, whether l, d or racemic dl, makes little difference to the stability constants, but there are some notable exceptions (vide infra). Examination of the data in Table 2 reveals (i) that the order of stability constants for the divalent transition metal ions follows the Irving-Williams series (ii) that for the divalent transition metal ions, with excess amino acid present at neutral pH, the predominant spedes is the neutral chelated M(aa)2 complex (iii) that the species formed reflect the stereochemical preferences of the metal ions, e.g. for Cu 1 a 2 1 complex readily forms but not a 3 1 ligand metal complex (see Volume 5, Chapter 53). Confirmation of the species proposed from analysis of potentiometric data and information on the mode of bonding in solution has involved the use of an impressive array of spectroscopic techniques, e.g. UV/visible, IR, ESR, NMR, CD and MCD (magnetic circular dichroism). 

In a series of papers, Takekuma and co-workers374-377 have reported the synthesis of a variety of 3-guaiazulenylmethyl cations 159 [Eq. (3.44)] with full spectroscopic characterization (UV-visible, IR, multinuclear NMR) and X-ray crystal structure analysis. The corresponding 2-furyl-, 2-thienyl-, and 2-pyrrolyl-substituted... 

Compounds 1-4 were characterized by conventional spectroscopic techniques. For the stilbene compounds 1-3, the trans conformation of the double bond was confirmed by XH NMR analysis. For example, in the XH NMR spectrum of 1, the olefinic protons were detected as a doublet of doublets with resonances at 7.23 and 7.01 ppm, with a trans coupling constant of 16.3 Hz. In addition, the 13C NMR spectra of the stilbene compounds indicated the presence of a single isomer that was consistent with the desired structures. The UV/visible spectra in tetrahydrofuran solution showed a X value for 1-3 at 378 nm (e 2.6 x 10 ) and for 4 at 490 nm (e 3. ax 101 ). 

Coates, J.P., A Practical Approach to Quantitative Methods of Spectroscopic Analysis. In George, W.O. 8c Willis, H.A. (eds) Computer Methods in UV, Visible and IR Spectroscopy, Royal Society of Chemistry Cambridge, UK, 1990, pp. 95-114. 

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