The chemical shift is the resonance frequency of the nucleus relative to the standard in a magnetic field. Generally, the position and number of chemical shifts can diagnose the structure of the molecule. Chemical shifts are also used to describe signals in other forms of spectroscopy, such as optical emission spectroscopy. Some nuclei have a magnetic moment (nuclear spin), which causes different energy levels and resonance frequencies in the magnetic field. The total magnetic field experienced by the nucleus includes the local magnetic field induced by the electron flow in the molecular orbital (note that the electron itself has a magnetic moment). The electron distribution of the same type of nuclei (such as 1H, 13C, 15N) usually varies according to the local geometry (binding partner, bond length, angle between the bonds, etc.) and the local magnetic field of each nucleus. This is reflected in the spin energy level (and resonance frequency). Due to the change in electron distribution, the change in the NMR frequency of the same nucleus is called a chemical shift.
Figure 1. Chemical shift.
The assignment of NMR peaks is very important to the determination of molecular structure. It is extremely helpful to use theoretical calculation methods to predict the correct assignment of the peaks. CD ComputaBio used quantum chemistry methods to predict the chemical shifts of compounds, and compared them. The calculated and experimental values get the error range of different theoretical calculation methods. When using HF and DFT theories to calculate the chemical shift of aromatic ring carbon, the CSGT method is more accurate than the GIAO method. The improvement of calculation accuracy is not significant.
|Chemical Shift Calculation Service
|The most standard way to calculate NMR chemical shifts in quantum chemistry provided by CD ComputaBio is to first calculate the carbon and hydrogen σiso of the reference material tetramethylsilane (TMS) as the reference value, and then calculate the carbon of the material you want to study at the same level. The chemical shift is obtained by calculating the difference between the σiso of hydrogen and the reference value.
|Depends on the time you need to simulate and the time required for the system to reach equilibrium.
|Product delivery mode
|The simulation results provide you with the raw data and analysis results of molecular dynamics.
CD ComputaBio's chemical shift calculation service can reduce the cost of subsequent experiments. Chemical shift calculation service service is a personalized and customized innovative scientific research service. Before determining the corresponding analysis plan and price, each project needs to be evaluated. If you want to know more about service prices or technical details, please feel free to contact us. If you want to know more about service prices or technical details, please feel free to contact us.
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