STUDIA UNIVERSITATIS BABEŞ-BOLYAI, PHYSICA, SPECIAL ISSUE, 2003
VIBRATIONAL STUDIES OF ABSORPTION CARVONE ON SOME
SURFACES
G.Damian1, V.Miclăuş2, I. Moldovan1, M.Puia1
“Babeş-Bolyai” University, Department of Physics,
Cluj-Napoca, Romania
2
“Babeş-Bolyai” University, Department of Chemistry,
Cluj-Napoca, Romania
1
ABSTRACT. FT-Raman and FT-infrared spectroscopy have been used to
investigate the sorption mechanisms of carvone (C10H14O) onto Al2O3,
and ZnO as a model for pollutant interactions with soil. The observed
frequencies of the prominent maxima in the in the Infrared and Raman
spectra of the carvone and sorbates carvone with the proposed
assignments are presented. The band shifts due to adsorption effects were
in the range of 15 cm-1 to low frequencies
INTRODUCTION
The presence of great amount of particulate matters with various
composition and structures in the Earth’s atmosphere, such as insulator oxides
(SiO2, Al2O3, ZnO, MgO, etc), involve the necessity of quantitative and qualitative
studies on the interaction between this ones and volatile organic compounds. The
chemical coupling between volatile organic compounds and particulate matter was
mentioned in as of profound importance in understanding processes of the gasaerosol chemical interactions [1, 6-7]. An understanding of the mechanisms by
which organic contaminants adsorb to mineral surfaces will be critical in predicting
their fate and transport in the environment [8]
In this paper, FT-Raman and FT-infrared spectroscopy have been used to
investigate the sorption mechanisms of carvone (C10H14O) onto Al2O3, and ZnO as
a model for pollutant interactions with soil [2-5]. Soil and clay environmental
samples are complex, heterogeneous mixtures of minerals. Therefore, model
systems such as alumina and mineral oxides are studied by vibrational
spectroscopy so that a fundamental understanding of organic interactions with
minerals can be obtained. Raman and Infrared spectroscopy are both vibrational
spectroscopic techniques which are capable of probing the organic pollutantmineral oxide interface. Even though both techniques provide vibrational
spectroscopic information, they are complementary approaches. Raman
spectroscopy of organic adsorption to mineral oxides is challenging given the
limited sensitivity of the method. Infrared spectroscopy is considered to be more
sensitive than Raman, but suffers from serious interferences due to oxide
absorption. Along with relative immunity to oxide interference, Raman is also
immune to water in the sample matrix. Since many mineral oxides are expected to
G.DAMIAN, V.MICLĂUŞ, I. MOLDOVAN, M.PUIA
have water hydrating their surfaces, they are more difficult to analyze via infrared
spectroscopy, which shows strong vibrational bands for water.
EXPERIMENTAL
The porous surfaces were dried four hours in air at 150oC before
impregnation in order to remove free water. The samples have been prepared by
stirring for two days a mixture of powder metallic oxides and liquid carvone
The FT-IR spectra of carvone, surface supports and adsorbed carvone,
were recorded in the region 4000-400 cm-1 by a Bruker EQUINOX 55
spectrometer, using an Attenuated Total Reflectance accessory with a scanning
speed of 32 cm-1 min-1 with the spectral width 2.0 cm-1. The internal reflection
element was a ZnSe ATR plate (50 x 20 x 2 mm) with an aperture angle of 45°. A
total of 128 scans were accumulated for each spectrum The FT-Raman spectra
were also recorded with the same instrument with a FRA 106 Raman module
equipped with Nd-YAG laser source operating with 200 mW in the wave number
range 3500-100 cm-1. The frequencies of all sharp bands are accurate to ±2 cm-1.
RESULTS AND DISSCUSION
Carvone (2-Methyl-5-(1-methylethenyl)-2-cyclohexene-1-one ) is a
caraway essential natural oil products (in the class of terpenes) occurring in plants
as secondary metabolites which are highly volatile and exhibit very characteristic
smells. This compound exhibits a number of
interesting biological activities, e.g., antifungal,
insecticidal and plant growth regulatory activities.
Chemical structure of the studied carvone is
presented in Figure 1. Commercial metal oxides
with the following specific surface (m2/g) were
used as surface supports: γ-Al2O3 –200, ZnO - 6.5
The recorded FT-IR and FT-Raman
Fig.1 Chemical structure of
spectra of liquid carvone and adsorbed carvove
carvone
on Al2O3 and ZnO are shown in Figures 2 and 3.
The observed frequencies of the prominent
maxima in the in the infrared and Raman spectra of the carvone and sorbates
studied carvone with the proposed assignments are summarized in Table 1.
Assignments were made on the basis of relative intensities, magnitude of
frequencies, as well as literature data of molecules of similar structure.
The band shifts due to adsorption effects were in the range of 15 cm-1 to
low frequencies. The C–H stretching vibrations (around 2800 cm-1 and 3100 cm-1 )
and the C–C deformation vibrations (1367 cm-1 ) are very similar for all aromatic
compounds. Also, the characteristic bands of the ring vibrations (1060 cm-1) were
used for identification of the sorbed products.
VIBRATIONAL STUDIES OF ABSORPTION CARVONE ON SOME SURFACES
Carvone
ZnO+Carvone
ZnO
Al2O3+Carvone
Al2O3
3500
3000
2500
2000
1500
1000
500
-1
Wavenumber (cm )
Fig.2 FT-Raman spectra of carvone, absorbed carvone on ZnO and A2O
carvone
ZnO+carvone
ZnO
Al2O3+carvone
Al2O3
3250
2750
2250
1750
1250
-1
Wavenumber (cm )
Fig.3 FT-IR spectra of carvone, absorbed carvone on ZnO and A2O3
750
G.DAMIAN, V.MICLĂUŞ, I. MOLDOVAN, M.PUIA
Table 1
Main observed bands in Raman and Infrared spectra and most probable vibrational
assignment of carvone
Observed wavenumber (cm-1)
FT-Raman
3085
2983
FT-IR
3084
2970
2924
2923
2734
2731
1673
1644
1436
1367
1061
869
706
637
568
479
1673
1644
1634
1367
1058
960
702
Assignment
C –H stretching
aromatic C H stretch
methyl C-H asym./sym. stretch
aromatic C H stretch
methyl C-H asym./sym. stretch
aromatic C H stretch
methyl C-H asym./sym. stretch
C =C stretch
C =C stretch
C –C stretching , C-H bending
C –C stretching
ring vibrations
ring breathing
C – H out-of-plane bend
C-H bend
CCC out of plane bending
CCC out of plane bending/ C = O out
of plane bending
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