Protons magnetically coupled

The distances between the peaks of multiplets can provide additional structural information. These distances are all about 7 Hz in the methyl isopropyl ketone spectrum (Figures 13-26 and 13-27). These splittings are equal because any two magnetically coupled protons must have equal effects on each other. The distance between adjacent peaks of the Hc multiplet (split by Hb) must equal the distance between the peaks of the Hb doublet (split by Hc). 

Each proton a is magnetically coupled to one b proton, splitting the absorption into a doublet. Similarly, each proton b is magnetically coupled to one proton a, splitting the H absorption into a doublet. The coupling constant is 8 Hz, suggesting that the magnetically coupled protons and H are ortho to each other. 

The pulse sequence used in homonuclear 2D y-resolved spectroscopy is shown in Fig. 5.18. Let us consider a proton, A, coupled to another proton, X. The 90° pulse bends the magnetization of proton A to the y -axis. During the first half of the evolution period, the two vectors (faster... 

We have seen that copper(II) is a slowly relaxing metal ion. Magnetic coupling of copper to a fast relaxing metal ion increases the electron relaxation rate of copper, as clearly shown by the NMRD profiles of tetragonal copper(II) complexes reacting with ferricyanide (105) (Fig. 38). The electron relaxation time, estimated from the relaxation rate of the water protons coordinated to the copper ion, is 3 x 10 ° s, a factor of 10 shorter than in the absence of ferricyanide. 

As illustrated in Fig. 3, the proton relaxation in super-paramagnetic colloids occurs because of the fluctuations of the dipolar magnetic coupling between the nanocrystal magnetization and the proton spin. The relaxation rate increases with the fluctuation correlation time and with the magnitude of this fluctuation. Different processes cause the fluctuation of the magnetic interaction. 

A clear demonstration of the effects of the magnetic coupling are shown in Fig. 16 where the liquid proton signal intensity is plotted as a function of the frequency offset of a preparation pulse (84,87). The essence of the... 

The importance of the magnetic coupling is easily seen in Fig. 17 which shows two water proton MRD profiles for serum albumin solutions at the same composition (89). The approximately Lorentzian dispersion is obtained for the solution, and reports the effective rotational correlation time for the protein. The magnetic coupling between the protein and the water protons carries the information on the slow reorientation of the protein to the water spins by chemical exchange of the water molecules and protons between the protein and the bulk solution. When the protein is cross-linked with itself at the same total concentration of protein, the rotational motion of the protein... 

The enzyme requires two copper ions per subunit for full expression of activity (18), but, unlike tyrosinase and hemocyanin, there is an absence of magnetic coupling between the two Cu(II) sites and both appear to be separate, isolated mononuclear copper sites (17). The process of dioxygen binding and activation appears to involve interaction of the doxygen molecule with only one copper ion, and it is also found that a proton is requir for the hydroxylation of substrate (19). 

Rule 5 When a group of magnetically equivalent protons interacts with more than one group of protons, its resonance will take the form of a multiplet of multiplets. For example, the resonanee due to the A protons in a system A M X will have the multiplicity of (p+l)(w+l). The multiplet patterns are ehained e.g. a proton coupled to 2 different protons will be split to a doublet by eoupling to the first proton then each of the component of the doublet will be split further by coupling to the second proton resulting in a symmetrical multiplet with 4 lines (a doublet of doublets). 

The giso values obtained for the two signals are those expected for five-coordinated oxochromate(V) complexes. At pH 2-6, the XH hyperfine splitting of the signal at giSO i arises from the coupling of two magnetically equivalent protons and may... 

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