Metric-Based Assessment Method for MS-T Formalism with Small Subsets of Torsional Conformers
Yicheng Chi1, Qinghui Meng1,2, Chengming He3
1Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon999077, Hong Kong.
The Journal of Physical Chemistry. A
|October 27, 2022
Summary
A new method systematically assesses multi-structural approximation with torsional anharmonicity (MS-T) variants for large molecules. It identifies key torsional conformers, explaining the accuracy of MS-T(2NN) and related methods in partition function calculations.
Area of Science:
- Computational Chemistry
- Theoretical Chemistry
- Physical Chemistry
Background:
- The multi-structural approximation with torsional anharmonicity (MS-T) method is crucial for calculating partition functions of large molecules.
- Assessing the performance of various MS-T variants is essential for accurate computational chemistry.
- Understanding torsional anharmonicity is key to molecular property predictions.
Purpose of the Study:
- To develop a systematic method for assessing and explaining the performance of MS-T variants.
- To validate the MS-T(2NN) variant for large alkanes and transition states.
- To provide a rigorous diagnostic tool for MS-T methods.
Main Methods:
- Proposed the MS-T(2NN) variant, coupling two nearest neighbor torsions.
- Developed a metric-based approach to identify dominant torsional conformers.
- Validated methods for large alkanes (n=6-10) and hydrogen abstraction transition states.
Main Results:
- MS-T(2NN) was systematically validated, showing good performance.
- The metric-based method explained MS-T(2NN)'s accuracy by focusing on dominant conformers.
- Similar observations and explanations were found for MS-2DT and MS-3DT variants.
Conclusions:
- The proposed method offers a mathematically rigorous and computationally efficient way to assess MS-T variants.
- It clarifies the role of torsional conformers in partition function calculations.
- This work provides a valuable tool for theoretical and computational chemists studying large molecules.
More Related Videos
11:04Ion Mobility-Mass Spectrometry Techniques for Determining the Structure and Mechanisms of Metal Ion Recognition and Redox Activity of Metal Binding Oligopeptides
Published on: September 7, 2019
9.3K
16:41A Protocol for Computer-Based Protein Structure and Function Prediction
Published on: November 3, 2011
68.8K
Related Concept Videos
02:11Conformations of Cyclohexane
12.8K
Cyclohexane does not exist in a planar form due to the high angle and torsional strain it would experience in the planar structure. Instead, it adopts non-planar chair and boat conformations.
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal...
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal...
12.8K
01:15¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
1.2K
The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.
1.2K
00:52¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
906
At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...
906
01:21Tandem Mass Spectrometry
1.2K
Tandem mass spectrometry is a technique that uses multiple mass analyzers in series to obtain a higher selectivity and signal-to-noise ratio for the analyte. Instruments with multiple analyzers separated by an interaction cell enable secondary fragmentation and selected study of the fragment ions.
Secondary fragmentations occur in the interaction cell and can be induced by various factors. Fragmentation induced by collision with inert gases, such as N2, Ar, He, etc., is called collision-induced...
Secondary fragmentations occur in the interaction cell and can be induced by various factors. Fragmentation induced by collision with inert gases, such as N2, Ar, He, etc., is called collision-induced...
1.2K
01:18Stress Concentrations in Circular Shafts
226
Consider the elastic torsion formula, which applies to a circular shaft with a consistent cross-section. This formula assumes that the shaft's ends are loaded with rigid plates firmly attached. However, in many cases, torques are applied to the shaft through mechanisms like flange couplings or gears, which are connected by keys inserted into keyways. This application method modifies the stress distribution near the point of torque application, causing it to deviate from the distributions...
226
01:20Bending and Torsional Moments
4.1K
Bending and torsional moments are two fundamental concepts in structural engineering. They play an important role in understanding the behavior of materials and structures under different loading conditions.
The reaction developed in a structural element when subjected to an external force causes the element to bend. When a structural element bends upwards, it creates compressive normal forces on the top and tensile normal forces on the bottom, resulting in a couple that determines the bending...
The reaction developed in a structural element when subjected to an external force causes the element to bend. When a structural element bends upwards, it creates compressive normal forces on the top and tensile normal forces on the bottom, resulting in a couple that determines the bending...
4.1K