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Conformation-Specific Pathways of B
-Alanine: A Vacuum Ultraviolet Photoionization and Theoretical Study

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We report a photoionization and dissociative photoionization study of B-alanine using IR laser desorption
combined with synchrotron vacuum ultraviolet (VUV) photoionization mass spectrometry. Fragments at m/z
=45, 44, 43, and 30 yielded from photoionization are assigned to NH3CH2CH2+, NH2CHCH3+, NH2CHCH2+,
and NH2CH2+, respectively. Some new conformation-specific dissociation channels and corresponding
dissociation energies for the observed fragments are established and determined with the help of ab initio
G3B3 calculations and measurements of photoionization efficiency (PIE) spectra. The theoretical values are
in fair agreement with the experimental results. Three low-lying conformers of the
-alanine cation, including
two gauche conformers G1+, G2+ and one anti conformer A+ are investigated by G3B3 calculations. The
conformer G1+ (intramolecular hydrogen bonding N-H· · ·OdC) is found to be another precursor in forming
the NH3CH2CH2+ ion, which is complementary to the previously reported formation pathway that only occurs
with the conformer G2+ (intramolecular hydrogen bonding O-H· · · N). Species NH2CHCH2+ may come from the contributions of G1+, G2+, and A+ via different dissociation pathways. The most abundant fragment ion, NH2CH2
+, is formed from a direct C-C bond cleavage. Intramolecular hydrogen transfer processes dominate most of the fragmentation pathways of the
B-alanine cation.

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Informasi Detail

Judul Seri

J. Phys. Chem.

No. Panggil

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Penerbit

Washington, DC : American Chemical Society., 2009

Deskripsi Fisik

J. Phys. Chem. A 2009, 113, 5838–5845

Bahasa

English

ISBN/ISSN

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Klasifikasi

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Tipe Isi

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Tipe Media

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Tipe Pembawa

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Edisi

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Subjek

KIMIA

Info Detail Spesifik

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Pernyataan Tanggungjawab

agus

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