کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1406177 1501789 2012 14 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
UV-induced isomerization of β-alanine isolated in argon matrices
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی آلی
پیش نمایش صفحه اول مقاله
UV-induced isomerization of β-alanine isolated in argon matrices
چکیده انگلیسی

We have employed low-temperature matrix-isolation FTIR spectroscopy, the density functional theory and ab initio calculations at the MP2 and CCSD(T) levels of theory to determine the conformational composition of the simplest β-amino acid, β-alanine. UV irradiation and thermal annealing of the samples together with the FTIR spectra of deuterated β-alanine were used to separate bands of different conformers. A detailed study of the potential energy surface of β-alanine obtained at the MP2/aug-cc-pVDZ level of theory reveals twenty β-alanine conformers, but only five of them may exist in matrices due to their sufficiently high relative stabilities and low energy barriers separating them from each other. An analysis of the FTIR spectra allows us to confirm the presence of four β-alanine conformers in argon matrices with certainty. Two of them, conformers I and II, have an NH⋯O intramolecular H-bond, the third, conformer V, has an N⋯HO H-bond, and the fourth, conformer IV, has no intramolecular H-bonds. The relative populations of the conformers determined using the relative Gibbs free energies calculated at the CCSD(T)/CBS level of theory at 420 K are 48.1%, 23.7%, 16.8% and 3.2% for the conformers I, II, IV, and V, respectively. Some trace amount of conformer VII was also detected.


► FTIR spectra of β-alanine and β-alanine-d3 isolated in argon matrixes are obtained.
► UV irradiation is used to separate bands of β-alanine conformers.
► Populations of β-alanine conformers are determined.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Molecular Structure - Volume 1025, 10 October 2012, Pages 6–19
نویسندگان
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