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Low temperature matrix-isolation and solid state vibrational spectra of 5-chlor...

Author(s): Bugalho, Susana C. S. cv logo 1 ; Serra, A. C. cv logo 2 ; Lapinski, L. cv logo 3 ; Cristiano, Maria Lurdes Santos cv logo 4 ; Fausto, R. cv logo 5

Date: 2002

Persistent ID: http://hdl.handle.net/10400.1/4248

Origin: Sapientia - Universidade do Algarve


Description
The vibrational spectra of 5-chlorotetrazole (CN4HCl) isolated in an argon matrix (T ¼ 8.5 K) and in the solid state (at room temperature) were studied. The infrared spectrum of monomers of 5-chlorotetrazole isolated in an argon matrix agrees well with the spectrum predicted theoretically (DFT(B3LYP)/6-31G*) for the 2Htautomer of the compound. The bands assigned to the 1H-tautomer appear in the experimental spectrum as very low intensity features. Based on the relative intensities of the bands in the spectra of the 1H- and 2Htautomers, the relative amount of the first tautomer in this matrix can be estimated as 1%. Three matrixes were deposited with different nozzle temperatures and the enthalpy difference between the tautomers DH ¼ 8.0 kJ mol 1 was estimated using the Van’t Hoff relation. The internal energy difference between the two tautomers was predicted theoretically (DFT B3LYP/6-31G*) as 12.6 kJ mol 1. This is in reasonable agreement with experimental observations. In the crystalline phase, this compound exists in its 1H-tautomeric form. Accordingly, the IR spectrum of polycrystalline 5-chlorotetrazole is well reproduced by the spectrum predicted theoretically for the 1H- tautomer.
Document Type Article
Language English
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