US EPA

1468206 

Journal Article 

Letter 

Infrared spectroscopy of gas phase benzenium ions: protonated benzene and protonated toluene, from 750 to 3400 cm-1 

Douberly, GE; Ricks, AM; Schleyer, Pv; Duncan, MA 

2008 

1 

Journal of Physical Chemistry A
ISSN: 1089-5639
EISSN: 1520-5215 

AMER CHEMICAL SOC 

WASHINGTON 

112 

22 

4869-4874 

English 

18459757 

10.1021/jp802020n 

WOS:000256270500002 

https://www.scopus.com/inward/record.uri?eid=2-s2.0-52449126423&doi=10.1021%2fjp802020n&partnerID=40&md5=83ef8c5b1ec078c1ce70295396d145ac
Exit
 

Gas phase C 6H 7 (+) and C 7H 9 (+) ions are studied with infrared photodissociation spectroscopy (IRPD) and the method of rare gas tagging. The ions are produced in a pulsed electric discharge supersonic expansion source from benzene or toluene precursors. We observe exclusively the formation of either the C 2 v benzenium ion (protonated benzene) or the para isomer of the toluenium ion (protonated toluene). The infrared spectral signatures associated with each ion are established between 750 and 3400 cm (-1). Comparing the gas phase spectrum of the benzenium ion to the spectrum obtained in a superacid matrix [ Perkampus, H. H.; Baumgarten, E. Angew. Chem. Int. Ed. 1964, 3, 776 ], we find that the C 2 v structure of the gas phase species is minimally affected by the matrix environment. An intense band near 1610 cm (-1) is observed for both ions and is indicative of the allylic pi-electron density associated with the six membered ring in these systems. This spectral signature, also observed for alkyl substituted benzenium ions and protonated naphthalene, compares favorably with the interstellar, unidentified infrared emission band near 6.2 microm (1613 cm (-1)).