1. FT-IR ANALYSIS OF PYRONE AND CHROMENE STRUCTURES IN ACTIVATED CARBON
Adrián Barroso-Bogeat, María Alexandre-Franco, Carmen Fernández-González, Vicente Gómez-Serrano
Departamento de Química Orgánica e Inorgánica, Facultad de Ciencias, Universidad de Extremadura,
Avda. de Elvas s/n, Badajoz, Spain
INTRODUCTION
OBJECTIVES
From a commercial activated carbon (AC):
To identify pyrone and chromene structures as well as their isomers by using Fourier transform infrared spectroscopy (FT-IR).
Adsorption
Catalysis
Electrochemistry
MATERIALS AND METHODS
ACTIVATED CARBON
SURFACE CHEMISTRY
Acid/base
Raw material: AC Merck®, 1.5 mm
Characterization of AC:
Incineration at 650 ºC for 12 h: ash content
Elemental analysis: C, H, N, S, and O contents
FT-IR: surface functional groups and structures
cm-1
Pellet AC/KBr with a 1:1900 ratio
Redox
Influence its
BASIC SURFACE GROUPS
properties
PYRONE STRUCTURES
CHROMENE STRUCTURES
Ash
(wt.%) C H N S O
4.72
86.50
0.51
0.26
0.64
7.37
2-pyrone
4-pyrone
2H-chromene
4H-chromene
Coumarin
Chromene-3-carboxylic acid
RESULTS AND DISCUSSION
SPECTRAL FEATURE
POSITION / cm-1
ASSIGMENT
GROUP / STRUCTURE
Shoulder
3025
ν(C-H)
Pyrone and chromene
Peaks
2972, 2883, 2823
2H-chromene, 4H-chromene
Band
1720
ν(C=O)
Pyrone, carboxylic acid
1657
4-pyrone, quinone, ketone
1636
ν(C=C)
2-pyrone, 4-pyrone,
1566
νs(C=C) skeletal
Aromatic ring
2-pyrone
ν(C=N)
Quinone monoxime
1442
ν(C=C) skeletal
δ(CH2)
Chromenes
δ(O-H)
1279
δ(O-H)-ν(C-O)
Carboxylic acid
νas(=C-O-C)
4H-chromene
Shoulders
ca. 1249
2H-chromene, 2-pyrone
1166
ν(C-C)
1114
δ(C-H)
2-pyrone phenyl ring
1024
2H-chromene, 4H-chromene, aromatic ether
ν(N-O)
Quinone oximes
901
δ(O-H)-γ(OH…O)
Carboxylic acid dimer
ν(C-O)
4-pyrone
794
Peak
740
668
γ(C-H)
Phenyl ring in 2-pyrone
625
2-pyrone ring
CONCLUSIONS
The presence of pyrone and chromene type structures in AC is proved by the appearance of their significant absorption features in the FT-IR spectrum registered for this carbon material.
FT-spectroscopy also enables to identify both couples of isomers, being 2-pyrone and 4H-chromene more amenable to identification.
Infrared analysis allows identifying other surface functional groups and structures containing not only oxygen but also nitrogen.
FT-IR spectroscopy may be regarded as a valuable tool for the analysis of surface groups in AC, even if they are very similar in composition and structure.
ACKNOWLEDGEMENTS
Adrián Barroso-Bogeat thanks Spanish Ministerio de Educación, Cultura y Deporte for the concession of a FPU grant (AP ).
Abbreviations: ν, stretching; δ, bending (in-plane); γ, bending (out-of-plane); s, symmetric;
as, asymmetric