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Dual Behavior of ZSM‐5 as Brønsted Acid and Electron Acceptor in the Adsorption of N,N ′‐Diphenylhydrazine
Author(s) -
Martí Vicente,
Fornés Vicente,
García Hermenegildo,
Roth Heinz Dieter
Publication year - 2000
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/(sici)1099-0690(200002)2000:3<473::aid-ejoc473>3.0.co;2-n
Subject(s) - chemistry , brønsted–lowry acid–base theory , adsorption , zsm 5 , dual (grammatical number) , electron acceptor , acceptor , photochemistry , organic chemistry , catalysis , molecular sieve , physics , art , literature , condensed matter physics
Incorporation of N , N ′‐diphenylhydrazine into HZSM‐5 led to the formation of azobenzene and aniline (70‐80 mol‐% mass balance). The formation of azobenzene can be followed by the appearance in diffuse reflectance UV/Vis spectroscopy of a characteristic band (λ max = 420 nm). IR spectra of the extracted solids indicate that some aniline is retained in the zeolite, probably due to acid‐base interaction with active sites. The products are rationalized by two competing mechanisms: the formation of azobenzene by electron transfer to an oxidizing site, the generation of aniline by proton transfer from a Brønsted acid site. A long‐wavelength diffuse‐reflectance band (λ max = 800 nm) in the initial stages of the reaction supports the intermediacy of a radical cation. These results show that acid zeolites can exhibit a dual behavior against basic substrates with low oxidation potential, serving simultaneously as electron acceptor and Brønsted acid.