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Scopine Isolated in the Gas Phase
Author(s) -
Écija Patricia,
VallejoLópez Montserrat,
Uriarte Iciar,
Basterretxea Francisco J.,
Lesarri Alberto,
Fernández José A.,
Cocinero Emilio J.
Publication year - 2016
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201600368
Subject(s) - chemistry , rotational spectroscopy , hyperfine structure , analytical chemistry (journal) , molecule , jet (fluid) , molecular beam , isomerization , spectroscopy , conformational isomerism , fourier transform , molecular physics , nuclear magnetic resonance , atomic physics , organic chemistry , thermodynamics , mathematical analysis , physics , mathematics , quantum mechanics , catalysis
The rotational spectrum of the tropane alkaloid scopine is detected by Fourier transform microwave spectroscopy in a pulsed supersonic jet. A nonconventional method for bringing the molecules intact into the gas phase is used in which scopine syrup is mixed with glycine powder and the solid mixture is vaporized with an ultrafast UV laser beam. Laser vaporization prevents the easy isomerization to scopoline previously observed with conventional heating methods. A single conformer is unambiguously observed in the supersonic jet and corresponds to the energetically most stable species according to quantum chemical calculations. Rotational and centrifugal distortion constants are accurately determined. The spectrum shows fine and hyperfine structure due to the hindered rotation of the methyl group and the presence of a quadrupolar nucleus ( 14 N), respectively. This additional information allows the angle of N ‐methyl inversion between the N−CH 3 bond and the bicyclic C‐N‐C plane to be determined (131.8–137.8°), as well as the internal rotation barrier of the methyl group (6.235(1) kJ mol −1 ).