NMR spectroscopy titrations

As unambiguously evidenced by NMR spectroscopy, titration of 9Zn in CDCI3 solution with one equivalent of a linear ditopic N-ligand leads rapidly to the quantitative assembling of sandwich-like 2 2 supramolecular adducts of formula [(9Zn)2(Ar-L)2j (L = 4,4 -bipy, 13 L = 4 -fransDPyP, 14 L = 4 -tra sDPyP-npm, 15), formed by two parallel metallacycles connected by two bridging ligands which are axially bound to the zinc-porphyrins (Scheme 3) [68,72,73]. 

Various standard experimental techniques employed in physical chemistry, such as NMR spectroscopy, titration, fluorescence spectroscopy, etc., are used routinely to determine the partition coefficients in solubilization studies, and a large number of publications tabulate the experimental results obtained in terms of equilibrium constants (14, 16). 

In addition to modem spectroscopic methods ( H nmr spectroscopy, ftir spectroscopy) and chromatographic methods (gc, hplc), HBr titration (29) is suitable for the quantitative analysis of ethyleneimine samples which contain relatively large amounts of ethyleneimine. In this titration, the ethyleneimine ring is opened with excess HBr in glacial acetic acid, and unconsumed HBr is back-titrated against silver nitrate. 

Modem analytical techniques have been developed for complete characteri2ation and evaluation of a wide variety of sulfonic acids and sulfonates. The analytical methods for free sulfonic acids and sulfonate salts have been compiled (28). Titration is the most straightforward method of evaluating sulfonic acids produced on either a laboratory or an iadustrial scale (29,30). Spectroscopic methods for sulfonic acid analysis iaclude ultraviolet spectroscopy, iafrared spectroscopy, and and nmr spectroscopy (31). Chromatographic separation techniques, such as gc and gc/ms, are not used for free... 

The trimetaUic uranyl cluster (U02)3(C03) 3 has been the subject of a good deal of study, including nmr spectroscopy (179—182) solution x-ray diffraction (182), potentiometric titration (177,183,184), single crystal x-ray diffraction (180), and exafs spectroscopy in both the soHd and solution states (180). The data in this area have consistendy led to the proposal and verification of a trimeric (U02)3(C03) 3 cluster (181,182,185). 

The complexation of 6, ciprofloxacin, and lomefloxacin with metals ions were studied in aqueous solution (pD 2.5 37 °C) by and NMR spectroscopy (99MI18). Titration experiments have revealed that the binding ability of 6 towards Al " " ion is much stronger than that of ciprofloxacin and lomefloxacin. Other metal ions (Ca " " and Mg " ") formed much weaker complexes. 

Earlier studies using thermal denaturation analysis and spectrophotomet-ric titration with TxA T and CxC-C" containing DNA triplexes showed that coralyne binds strongly to these triplexes by intercalation and does not exhibit a significant sequence-selectivity [222]. In a later study by Morau Allen et al. [217], employing DNase footprinting, thermal denaturation analysis, UV-visible spectrophotometric titrations, circular dichroism and NMR spectroscopy, showed that coralyne is fully intercalated into TxA T triplex DNA whereas in C GxC triplex, it is partially intercalated due to electrostatic repulsion between the cationic alkaloid and the protonated cytosine [217]. Kepler et al. [223] demonstrated that coralyne intercalated to parallel triplex DNA but did not intercalate to antiparallel triplex DNA. Recently Hud and coworkers [219,224] demonstrated that duplex poly(dA) poly(dT) is trans-... 

Several modem analytical instruments are powerful tools for the characterisation of end groups. Molecular spectroscopic techniques are commonly employed for this purpose. Nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy and mass spectrometry (MS), often in combination, can be used to elucidate the end group structures for many polymer systems more traditional chemical methods, such as titration, are still in wide use, but employed more for specific applications, for example, determining acid end group levels. Nowadays, NMR spectroscopy is usually the first technique employed, providing the polymer system is soluble in organic solvents, as quantification of the levels of... 

Quenching polystyryllithium and polybutadienyllithiums with A-benzylidenemethyl-amine (PhCH=NMe) in benzene solution leads to amine-functionalized polymers (equation 103), that can be characterized by SEC, TLC, acid-base titration and H and C NMR spectroscopies. The end groups are monomeric. Gradual addition of Et20 reduces the yields. This is attributed to increased reactivity of the alkyllithium residues in the polymer, bringing about a concurrent metallation reaction of the imine reagent (e.g. equation 101) . 

Dialkyl peroxides (continued) colorimetry, 707-8 flame ionization detection, 708 NMR spectroscopy, 708 titration methods, 707 UV-visible spectrophotometry, 707-8 enthalpies of reactions, 153-4 graft polymerization initiation, 706 hydroperoxide determination, 685 peroxide transfer synthesis, 824-5 stmctural characterization, 708-16 electrochemical analysis, 715-16 electron diffraction, 713 mass spectrometry, 714 NMR spectroscopy, 709-11 thermal analysis, 714-15 vibrational spectra, 713-14 X-ray crystallography, 711-13 synthesis... 

Functionality Measurement of Phenolated Lignin. It is important to have knowledge of the functionality of the phenolated lignin from the point of view of further chemical modification. The amount of bound phenol in the phenolysis reaction has been measured by titrating the phenol extracted from the reaction mixture (15). This indirect method measures the unreacted phenol and determines bound phenol as the difference between the initial charge and the titrated phenol. This is sometimes misleading. 1H NMR spectroscopy is another candidate for the determination of the amount of bound phenol. However, this calculation is difficult since the number of protons before and after the phenolysis reaction is unknown. 

The assembly formation of heterobidentate ligated complexes was studied in detail using bidentate ligand 13"b as a typical example (Figure 8.8). UV/Vis titrations and NMR spectroscopy experiments showed that the pyridyl moiety of b selectively coordinates to thezinc(ii)porphyrinl3withabindingconstantofK(ib) = 3.8x lO m. An increase in the Kfor 13 b to 64.5 X lO was observed in the presence of metal... 

The identification of the ancient oil sample was confirmed by other analytical techniques, including infrared spectroscopy, titration, and gas chromatography. A full account will be published elsewhere our purpose here is to show how much useful information could be gained from NMR spectrometry alone. 

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