A new approach to automated first‐order multiplet analysis

Abstract

The dependence of the values of NMR spin-spin coupling constants on molecular conformation can be a valuable tool in the structure determination process. The continuing increase in the resonance frequency of modern NMR spectrometers allows an increasing number of resonances to be examined using first-order multiplet analysis. While this can easily be done for the simplest patterns (doublets, triplets, quartets), more complex patterns can be extremely difficult to analyze. The task of deducing the coupling constant values from a multiplet is the reverse process of generating a conventional splitting tree from a single line (chemical shift) by sequential branching using a given set of coupling constants. We present a simple, straightforward method of deducing coupling constant values from first-order multiplets based on a general inverted splitting tree algorithm but also including a peak intensity normalization procedure that utilizes multiplet symmetry and generates a set of possible first-order intensity distribution patterns. When combined with an inverted splitting tree algorithm, it is possible to find an intensity pattern that allows the deduction of a proper set of coupling constants.

Automated structure verification based on a combination of 1D 1H NMR and 2D 1H13C HSQC spectra

“…Recently, several methods of structure verification based on the comparison of chemical shifts, integrals, and multiplicities extracted from experimental 1 H NMR spectra and predicted for proposed structures have been published. 1,2 These methods are shown to be compatible with fully automated operation, using well established procedures for extracting relevant information from the experimental 1 H NMR spectra 3,4 and enabling fully automated structure confirmation.…”

New guide for first order multiplet analysis by modified J doubling in the frequency domain

“…3,8 According to our experience, J doubling is not the exception; the minimum of integral functions that indicates the value of equal couplings becomes broader. In order to solve this problem, we proposed a new algorithm for simultaneous deconvolution of equal coupling constants.…”

“…Nevertheless, few papers have been written on pattern recognition, [1][2][3] so there is no easy way of explaining those reported methods. On the other hand, many papers have been written on how to accurately measure coupling constants [4][5][6][7][8][9][10][11] in simplex and in complex multiplets.…”

A LEAN Approach toward Automated Analysis and Data Processing of Polymers using Proton NMR Spectroscopy

“…8 This method is discussed in the next section. Once this is complete, a cycle is run, started by selecting a subregion of the spectrum, applying a baseline correction to it, aligning it with that same subregion in a reference spectrum to correct for any peak shifts, and then integrating the peak as required.…”

“…8 First, the standard deviation of the noise is determined by dividing the spectrum in a number of regions (n) and by determining the standard deviation of the signal in each of these regions. It is then assumed that there is at least one region that is free of peaks and consists of noise only.…”