Related Experiment Video
Updated: Jul 1, 2026
12:11
Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
Published on: April 8, 2020
IR low-temperature matrix and ab initio study on beta-alanine conformers.
Jan Cz Dobrowolski1, Michał H Jamróz, Robert Kołos
1National Medicines Institute, 30/34 Chełmska Street, 00-725 Warsaw, Poland. janek@il.waw.pl
Chemphyschem : a European Journal of Chemical Physics and Physical Chemistry
|September 13, 2008
Summary
This study recorded the FTIR spectra of beta-alanine in argon, revealing multiple conformers. Computational analysis confirmed at least three distinct beta-alanine structures, with potential for five more.
Area of Science:
- Spectroscopy
- Computational Chemistry
- Molecular Physics
Background:
- Beta-alanine is an important amino acid with potential for various molecular conformations.
- Understanding these conformers is crucial for interpreting its physical and chemical properties.
Purpose of the Study:
- To record and analyze the low-temperature FTIR spectra of beta-alanine in an argon matrix.
- To identify and characterize the different conformers of beta-alanine present in the matrix.
Main Methods:
- Experimental recording of Fourier-transform infrared (FTIR) spectra of beta-alanine in an argon matrix at low temperatures.
- Computational estimation of eighteen gas-phase beta-alanine conformers using B3LYP and MP2 levels with aug-cc-pVDZ basis set.
- Reoptimization of ten low-energy structures using QCISD/aug-cc-pVDZ and B3LYP/MP2 with aug-cc-pVTZ basis sets.
- Assignment of experimental spectra based on calculated anharmonic IR frequencies and conformer population estimations.
Main Results:
- The FTIR spectra exhibited a complex pattern, indicating the presence of multiple beta-alanine conformers.
- Computational analysis identified ten low-energy conformers.
- The study demonstrated the presence of at least three beta-alanine conformers in the argon matrix.
- Detailed spectral analysis suggested the potential existence of five additional conformers.
Conclusions:
- The argon-matrix FTIR spectroscopy successfully revealed the complex conformational landscape of beta-alanine.
- Computational methods were effective in assigning the experimental spectra and identifying multiple conformers.
- At least three, and potentially up to eight, beta-alanine conformers exist in the matrix, providing valuable insights into its molecular structure.
More Related Videos
Related Concept Videos
01:15¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
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.
00:52¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
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...
02:20Conformations of Butane
Unlike ethane and propane that have only two major conformations, butane has more than two conformers. The staggered form of butane in which the bulky methyl groups on the two carbons are placed on opposite sides, that is, at a dihedral angle of 180°, is the lowest energy, most stable form — called the anti conformer. This conformation is stabilized due to the absence of steric repulsion between the largely spaced out methyl groups. The other two staggered conformations are degenerate and have...
02:29Conformations of Cycloalkanes
Adolf von Baeyer attempted to explain the instabilities of small and large cycloalkane rings using the concept of angle strain — the strain caused by the deviation of bond angles from the ideal 109.5° tetrahedral value for sp3 hybridized carbons. However, while cyclopropane and cyclobutane are strained, as expected from their highly compressed bond angles, cyclopentane is more strained than predicted, and cyclohexane is virtually strain-free. Hence, Baeyer’s theory that was based on the...
02:18Conformations of Ethane and Propane
In an organic molecule, free rotation about the carbon-carbon single bond results in energetically different conformers of the molecule. Due to this rotation, called the internal rotation, ethane has two major conformations — staggered and eclipsed.
Staggered conformation is a low energy and more stable conformation with the C-H bonds on the front carbon placed at 60°dihedral angles relative to the C-H bonds on the back carbon, leading to a reduced torsional strain. In staggered ethane, the...
Staggered conformation is a low energy and more stable conformation with the C-H bonds on the front carbon placed at 60°dihedral angles relative to the C-H bonds on the back carbon, leading to a reduced torsional strain. In staggered ethane, the...