Related Experiment Video
Updated: Jul 17, 2026
09:35
Preparation of a Corannulene-functionalized Hexahelicene by Copper(I)-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units
Published on: September 18, 2016
Substitution patterns in aromatic rings by increment analysis. Model development and application to natural organic
E M Perdue1, N Hertkorn, A Kettrup
1School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia 30332, USA. mperdue@eas.gatech.edu
Analytical Chemistry
|February 1, 2007
Summary
A new model, SPARIA, predicts aromatic substitution patterns in natural organic matter using NMR data. Its inverse mode identifies possible substituent combinations from chemical shifts, aiding complex spectral analysis.
Area of Science:
- Organic Chemistry
- Spectroscopy
- Computational Chemistry
Background:
- Two-dimensional heteronuclear 1H, 13C NMR spectra of natural organic matter are complex and challenging to interpret.
- Aromatic regions in NMR spectra contain valuable information about molecular structure, but conventional analysis is difficult.
Purpose of the Study:
- To develop a computational model, Substitution Patterns In Aromatic Rings by Increment Analysis (SPARIA), for predicting and interpreting NMR spectra of natural organic matter.
- To introduce an inverse mode in SPARIA capable of determining possible aromatic substitution patterns from experimental NMR chemical shift data.
Main Methods:
- SPARIA was developed with a forward mode to predict 1H and 13C chemical shifts for various substituent combinations.
- The inverse mode of SPARIA was created to calculate all possible substituent combinations yielding chemical shifts within a specified window.
- Both modes were validated using 29 aromatic compounds and applied to natural organic matter samples.
Main Results:
- SPARIA accurately predicts chemical shifts in its forward mode, comparable to existing software.
- The inverse mode successfully identifies potential substitution patterns from given 1H and 13C chemical shifts.
- The model's performance was evaluated based on the chemical shift window size and applied to real-world natural organic matter samples.
Conclusions:
- SPARIA provides a robust tool for analyzing the complex aromatic regions of NMR spectra from natural organic matter.
- The inverse mode of SPARIA significantly enhances the interpretation of NMR data by predicting substitution patterns.
- This approach facilitates a deeper understanding of the structural characteristics of natural organic matter.
More Related Videos
Related Concept Videos
01:16Electrophilic Aromatic Substitution: Overview
In an electrophilic aromatic substitution reaction, an electrophile substitutes for a hydrogen of an aromatic compound.
01:37NMR Spectroscopy of Benzene Derivatives
Simple unsubstituted benzene has six aromatic protons, all chemically equivalent. Therefore, benzene exhibits only a singlet peak at δ 7.3 ppm in the 1H NMR spectrum. The observed shift is far downfield because the aromatic ring current strongly deshields the protons. Any substitution on the benzene ring makes the aromatic protons nonequivalent, and the protons split each other. The peak is, therefore, no longer a singlet and the splitting pattern and their associated coupling constants depend...
01:14NMR Spectroscopy of Aromatic Compounds
Aromatic compounds can be identified or analyzed using proton NMR and carbon‐13 NMR. Typically, aromatic hydrogens or hydrogens directly bonded to the aromatic rings are strongly deshielded by the aromatic ring current. Therefore, they absorb in the range of 6.5–8.0 ppm in proton NMR spectra. For instance, aromatic hydrogens directly bonded to the benzene ring absorb at 7.3 ppm. However, aromatic hydrogens of larger rings absorb farther upfield or downfield than the ideal range. Consider...
01:11Nucleophilic Aromatic Substitution: Elimination–Addition
Simple aryl halides do not react with nucleophiles. However, nucleophilic aromatic substitutions can be forced under certain conditions, such as high temperatures or strong bases. The mechanism of substitution under such conditions involves the highly unstable and reactive benzyne intermediate. Benzyne contains equivalent carbon centers at both ends of the triple bond, each of which is equally susceptible to nucleophilic attack. This 50–50 distribution of products is confirmed through isotopic...
01:14π Electron Effects on Chemical Shift: Aromatic and Antiaromatic Compounds
In aromatic compounds, such as benzene, the circulation of (4n + 2) π-electrons sets up a diamagnetic or diatropic ring current around the perimeter of the molecule. This current induces a magnetic field that opposes the external field inside the ring and reinforces it on the outside. The protons in benzene are deshielded and exhibit high chemical shifts in the range 6.5–8.5 ppm. The shielding effect at the center of the ring is evident in complex aromatic molecules, such as annulenes. In...
01:13Five-Membered Heterocyclic Aromatic Compounds: Overview
Heterocyclic aromatic compounds are cyclic compounds that are aromatic and have one or more heteroatoms—atoms other than carbon, in the ring. Depending upon the number of atoms present in the ring, they can be either five or six-membered. Examples of five-membered heterocyclic aromatic compounds include pyrrole, furan, thiophene, and imidazole. Pyrrole consists of one nitrogen atom having one lone pair of electrons. Furan and thiophene have one oxygen and one sulfur heteroatom, respectively.