Infrared spectroscopic confirmation of α‐lactone formation in the dissociation of a gaseous amino acid

• Published in: Journal of physical organic chemistry 2017-02, Vol.30 (2), p.n/a
• Main Authors: Wenthold, Paul G., Koirala, Damodar, Somogyi, Arpad, Poutsma, J. C.
• Format: Article
• Language: English
• Subjects: alpha‐lactone; amino acid dissociation; gas‐phase amino acid; IR multiphoton dissociation
• ISSN: 0894-3230; 1099-1395
• DOI: 10.1002/poc.3606

The product obtained upon collision‐induced dissociation of sulfonated phenylalanine in the gas phase has been investigated by using infrared multiphoton dissociation spectroscopy with a free‐electron laser. This confirms that the product formed by loss of ammonia from the amino acid is the α‐lactone, as had been deduced previously based on qualitative analysis and electronic structure calculations. Spectroscopically, the structure is confirmed by the presence of the carbonyl stretching peak at 1915 cm−1 and supported by excellent agreement between the predicted and observed S–O stretching bands. The agreement between predicted relative intensities is not as good, but can be attributed to the nonlinear process of IRMPD. Copyright © 2016 John Wiley & Sons, Ltd. In a previous study of the dissociation of sulfonated phenylalanine, the product was deduced to be an α‐lactone on the basis of indirect evidence. In this work, the IRMPD spectrum of the product is reported, which confirms the α‐lactone assignment.