Professor Vicic of Lehigh University created a database for 19F NMR ..read more

Solution NMR peak widths are mostly determined by two factors, homogeneous broadening and inhomogeneous broadening. Homogeneous broadening is governed by T2 relaxation, which is driven by the dynamics of the molecular segments. Small molecules rotate very fast in solution (>> 109 s-1), resulting in long T2 (~ seconds) and thus very sharp peaks (intrinsic peak width usually < 0.5 Hz). For polymers, there are different situations. For hydrocarbon polymers, each bond of the backbone rotates independent of the bonds that are more than 4-5 bonds away, and such rotations are almost as fast ..read more

This report includes prediction models for PS, PEO, and PMMA, as well as discussions on the models’ application and limitations, and practices for producing high-quality DOSY NMR data. Access is currently limited to the University of Massachusetts Amherst campus community only ..read more

There are many choices of line broadening functions. The most popular one is exponential line broadening, in which each time-domain data point in the FID is given an exponentially decaying weight before Fourier Transformation. The drawback of exponential line broadening is that it suppresses the beginning part of FID too quickly, which results in long tails on the feet of tall peaks on the spectrum. If you want to cut those tails and reduce peak overlap yet still suppress a lot of noise, you could try Gaussian line broadening, in which you need to define two parameters: gb and lb. gb is betwee ..read more

We often encounter decay behaviors that cannot be accurately described by a single exponential curve, e.g. in T1 relaxation curves and in diffusion NMR data. In such cases, multi-component fitting of the curves could be attempted. See the following diffusion NMR data: There is clearly a systematic deviation between the experiment data (black dots) and the single-exponential fit (red straight line). The resulting diffusion coefficient (D) has a relative error bar of ca. 5%. Upon close visual examination, we can notice that the experimental data decays faster in the beginning and decays slower ..read more

In some cases the automatic baseline correction command abs does not generate a desired baseline. This often happens when some of your peaks are broad and the correction algorithm has a hard time decide whether some data points in a certain spectral area is signal or baseline. In such cases, you can try an advanced baseline correction method: bas. Upon giving the command bas, you are offered a number of choices. I use the first and the third choices most often. Choice 1, manual baseline correction. The correction is done by manual fitting of the baseline by a fifth order polynomial: y = A + Bx ..read more

You can compare the signal integration of different data files. They will need to be acquired with the same receiver gain (rg). To ensure this, before you run your first sample, run rga, then type rg to record the receiver gain that has been determined. When you run your other samples, instead of running rga, you type rg and input the receiver gain that you wrote down for your first sample. This will ensure all the spectra that you want to compare signal areas against have been run with the same receiver gain. It is possible to use different ns for different samples, but you will need to remem ..read more

The nitrogen site of pyridine is a hydrogen bond acceptor. In the presence of a hydrogen bond donor, its 15N peak shifted upfield by more than 1 ppm. See picture below (blue: pyridine; red: pyridine + H donor). This is one way of probing the presence of hydrogen bond in solution. a ..read more

If you want to investigate the structure and behaviors of deuterium in your molecules, 2H NMR is a good method. The chemical shift of 2H is very similar to that of 1H as both nuclei experience the same electron environments. The resolution is also often as good as that for 1H. Follow these steps: Type edc. In Experiment, choose H2. Check getprosol box. Create a new file for 2H experiment. Type rsh shims.best If your sample is dissolved in a deuterated solvent, do the regular lock and shim If your sample is not in a deuterated solvent, type ii. This will stop the locking mechanism from interfe ..read more

797dd-syllabusDownload ..read more