Spectral Determinations Research Articles

VNIR-SWIR Spectroscopy, XRD and Traditional Analyses for Pedomorphogeological Assessment in a Tropical Toposequence

Tropical climate conditions favor landscape evolution and the formation of highly weathered soils under different pedogenic processes due to certain differential properties. Traditional analysis coupled with VNIR-SWIR reflectance spectroscopy and X-ray diffractometry (XRD) analyses can reveal such characteristics. Several researchers cited throughout this study already discussed the possible applications of analyses in this field. All agree that integrated knowledge (holistic) can drive the future of the soil sciences. However, few refer to the potential of soil spectroscopy in deriving pedogenetic information. Thus, this paper aimed to assess pedomorphogeological relationships in a representative toposequence of the Brazilian Midwest using traditional analyses and geotechnologies. We performed landscape observations and soil sampling in the field. The laboratory’s physical, chemical, spectral, and mineralogical determinations supported the soil classification according to the World Reference Basis (WRB/FAO) system. Based on the analysis results, we divided five profiles into two soil groups (highly and slightly weathered soils) using Pearson’s correlation and hierarchical clustering analysis (HCA). Traditional analyses determined the diagnostic attributes. Spectroscopic readings from 0.35 to 2.5 µm wavelengths and XRD supported identifying soil attributes and properties. Finally, all soil classes were correlated according to correspondent reflectance spectra and primary pedological attributes. There was a strong correlation between spectral oxide features and X-ray diffraction peaks. The HCA based on oxide content and mineral composition validated the previous soil grouping. Thus, we could assess the pedomorphogeological relationships through VNIR-SWIR spectroscopy, XRD, and traditional analyses concerning pedogenic processes through their correlation with soil properties resulting from these processes. However, periodic measurements are required, making orbital sensing a continuous data source for soil monitoring.

SPECTRAL AND CHROMATOGRAPHIC CHARACTERISATION OF THE YELLOW FOOD DYE FROM SAFFLOWER

Recently, an increasingly trend of public concern for the food safety is observed. Use of additives in food industry growing steadily. Present study deals with separation and identification of compounds from Yellow Food Dye from Safflower (YFDS). Spectral and chromatographic characteristics of YFDS were obtained and discussed. Dry powders and solutions of YFDS were examined using Thin Layer Chromatography (TLC), UV-Vis spectroscopy and reversed-phase HPLC. TLC was carried out in three systems I (HCl 0.1 M), II (aqua 50%, ethanol 45%, citric acid 5%) and III (water, butan-1-ol, acetic acid). Spectral determinations in the range of 200 to 600 nm were carried out at various pH values. HPLC method was carried out by the gradient elution technique. Chromatographic method showed that it is impossible to separate and to identify the components of the YFDS by paper chromatography. UV-Vis Spectra demonstrated that the most successful interval for the practical use of YFDS is in the pH range of pH = 4…5, since in this range the coloration activity of dyes is maximal. HPLC method demonstrated that YFDS-compounds corresponds to the composition of dry Safflower petals, which confirms its high biological activity. Powdered yellow pigment from Safflower petals is containing natural chalcones and can be successfully used in the dairy producing.

On the coefficients of skew Laplacian characteristic polynomial of digraphs

Let [Formula: see text] be a connected graph with [Formula: see text] vertices and [Formula: see text] edges. Let [Formula: see text] be the digraph obtained by orienting the edges of [Formula: see text] arbitrarily. The digraph [Formula: see text] is called an orientation of [Formula: see text] or oriented graph corresponding to [Formula: see text]. The skew Laplacian matrix of the digraph [Formula: see text] is denoted by [Formula: see text] and is defined as [Formula: see text], where [Formula: see text] is the skew matrix and [Formula: see text] is the diagonal matrix with [Formula: see text]th diagonal entry [Formula: see text]. In this paper, we obtain combinatorial representation for the first five coefficients of characteristic polynomial of skew Laplacian matrix of [Formula: see text]. We provide examples of orientations of some well-known graphs to highlight the importance of our results. We conclude the paper with some observations about the skew Laplacian spectral determinations of the directed path and directed cycle.

Spectral determinations and eccentricity matrix of graphs

Let G be a connected graph on n vertices. For a vertex u∈G, the eccentricity of u is defined as ε(u)=max⁡{d(u,v)|v∈V(G)}, where d(u,v) denotes the distance between u and v. The eccentricity matrix E(G)=(ϵuv), whereϵuv:={d(u,v)if d(u,v)=min⁡{ε(u),ε(v)},0otherwise, has been firstly introduced in Chemical Graph Theory. In literature, it is also known as the DMAX-matrix. Graphs with the diameter equal to the radius are called self-centered graphs. Two non-isomorphic graphs are said to be M-cospectral with respect to a given matrix M if they have the same M-eigenvalues. In this paper, we show that, when n→∞, the fractions of non-isomorphic cospectral graphs with respect to the adjacency and the eccentricity matrix behave like those only concerning the self-centered graphs with diameter two. Secondly, we prove that a graph G has just two distinct E-eigenvalues if and only if G is an r-antipodal graph. Thirdly, we obtain many pairs of E-cospectral graphs by using strong and lexicographic products. Finally we formulate some problems waiting to be solved in order to build up a spectral theory based on the eccentricity matrix.

Investigations of the Periodic Variables in the Catalina and Linear Databases

In this study we continue spectral class determinations for large numbers of optically faint periodic variables taken from the Catalina Surveys Data Release 1 (CSDR1) and LINEAR data sets. Spectral classes and physical parameters are presented for 1184 periodic variables with periods P ≥ 10 days, taken from modern large sky area spectroscopic and photometric databases, including LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic Telescope), SDSS (Sloan Digital Sky Survey), the Hamburg Quasar Survey (HQS), the Hamburg/ESO Survey (HES), and Gaia Data Release 2 (DR2). In Gaia DR2 catalogue, luminosities are presented for 276 objects and radial velocities (RV) for 108 objects out of 1184. Spectral classes were confirmed for more than 650 objects. The majority of the variables are found to be F, G, K, M dwarfs and giants, a few dozen carbon (C) stars (N-type Asymptotic Giant Branch (AGB) stars), and a few S stars. Some periodic variables are blue objects, such as B and A stars. The periods are in the range 10 ≤ P ≤ 1504 days and Catalina magnitudes in range 11.5 ≤ V ≤ 20.0 mag. Finding new and faint evolved AGB stars in the halo of our Galaxy is the first priority. A catalogue containing multiparameter data for 1184 periodic variables from modern astronomical databases has been generated.

Experimental approach, theoretical investigation and molecular docking of 2- chloro-5-fluoro phenol antibacterial compound

The molecular structural dimerization of biologically potent 2-chloro-5-fluoro phenol (2C5FP) is optimized. A combined experimental and theoretical characteristics of vibrational spectral determinations (NMR, FT-IR and Raman) on 2-chloro-5-fluoro phenol (2C5FP) were used at DFT-B3LYP/6–31++G (d,p) level of computation. A close coherence is achieved when experimentally observed wave numbers are compared with calculated wave numbers by refinement of the scale factors. Calculated values of global chemical descriptors of the present molecule reveal significant molecular stability and chemical reactivity. Non-Linear optical (NLO) property of the present molecule is investigated by determining the second order non linear parameter of first hyperpolarizability β. Moreover, hydrogen bond and thermodynamic parameters at various temperatures are determined and discussed. Investigated compound 2C5FP possesses a better antibacterial activity against Echerichia coli, Streptococcus aureus, Pseudomonas aureus,and Staphylococcus aureus, respectively. The title molecule is subjected to molecular docking studies with two different proteins, namely Staphylococcus aureus Tyrosyl-tRNA synthetase (PDB ID: 1JIL) and human dihydroorotate dehydrogenase (hDHODH) (PDB ID: 6CJF). The results of molecular docking analysis support the antibacterial activity and demonstrate a strong interaction with the DHODH inhibitor.

Synthesis, Characterization and Biological Activity of Two New Copper (II) Complexes with N-sulfonamide Ligand

Despite the fact that a large number of chemotherapeutic anticancer agents have been discovered, cancer still remains a great cause of deaths worldwide. The purpose of our researches is to discover a new antitumor drug. In this aim, two new Cu(II) complexes, [Cu(L)2(py)2(H2O)2](C1) and [Cu(L)2(phen)](C2) with a new ligand, N-(5-trifluoromethyl-[1,3,4]-thiadiazole-2-yl)-benzensulfonamide(HL) were synthesized. The complexes were characterized by elemental analysis, spectral and magnetic determinations. The nuclease activity studies of the complexes confirm their capacity to cleavage the DNA molecule. Both complexes have in vitro antioxidant activity (DPPH, FRAP methods), in vitro (using xanthine /xanthine oxidase system) and in vivo (using S.cerevisiae)SOD mimetic activity.The results of MTT assay on two carcinoma cell lines (HeLa and WM35) indicate that both complexes have antitumor activity, but (C2) has a superior activity compared with (C1) and with Cisplatin. On normal fibroblast (HDFa), (C1) showed toxicity comparable with Cisplatin, but (C2) showed a lower one. Bacterial assays were also performed (by the disk diffusion method) and both complexes have antibacterial activity against S. aureus, E. coli, P. aeroginosa and B. cereus. All the biological studies are in concordance and show that both complexes have biologic activity but (C2)is much more active.

Synthesis, Characterization and Biological Activity of Two New Copper (II) Complexes with N-sulfonamide Ligand

Despite the fact that a large number of chemotherapeutic anticancer agents have been discovered, cancer still remains a great cause of deaths worldwide. The purpose of our researches is to discover a new antitumor drug. In this aim, two new Cu(II) complexes, (C1) and (C2) with a new ligand, N-(5-trifluoromethyl-<1,3,4>-thiadiazole-2-yl)-benzensulfonamide(HL) were synthesized. The complexes were characterized by elemental analysis, spectral and magnetic determinations. The nuclease activity studies of the complexes confirm their capacity to cleavage the DNA molecule. Both complexes have in vitro antioxidant activity (DPPH, FRAP methods), in vitro (using xanthine /xanthine oxidase system) and in vivo (using S.cerevisiae)SOD mimetic activity.The results of MTT assay on two carcinoma cell lines (HeLa and WM35) indicate that both complexes have antitumor activity, but (C2) has a superior activity compared with (C1) and with Cisplatin. On normal fibroblast (HDFa), (C1) showed toxicity comparable with Cisplatin, but (C2) showed a lower one. Bacterial assays were also performed (by the disk diffusion method) and both complexes have antibacterial activity against S. aureus, E. coli, P. aeroginosa and B. cereus. All the biological studies are in concordance and show that both complexes have biologic activity but (C2)is much more active. Keywords: oxidative DNA cleavage, antioxidant capacity, SOD-mimetic activity, cytotoxicity, antibacterial properties

Bioactive Diketopiperazines and Nucleoside Derivatives from a Sponge-Derived Streptomyces Species.

Fractionation and purification of the ethyl acetate extract of the culture of a sponge-derived actinomycete, Streptomyces species Call-36, resulted in the isolation and identification of a new diketopiperazine, actinozine A (1), cyclo(2-OH-d-Pro-l-Leu) (2), two new nucleosides, thymidine-3-mercaptocarbamic acid (3) and thymidine-3-thioamine (4), together with cyclo(d-Pro-l-Phe) (5) and cyclo(l-Pro-l-Phe) (6). The structure assignments of the compounds were carried out by interpretation of 1D and 2D NMR data and mass spectral determinations. The absolute configurations of 1 and 2 were determined by Marfey’s method and by comparison of the experimental and TDDFT-calculated ECD spectra. Actinozine A possesses an unprecedented hydroperoxy moiety at C-2 of the proline moiety, while 3 and 4 possess unusual mercaptocarbamic acid and thiohydroxylamine functionalities at N-3 of the thymine moiety. The isolated compounds displayed variable cytotoxic and antimicrobial activities.

New Carbon Stars in the Catalina Catalog of Periodic Variables

This study is about carbon stars detected in a program of spectral type determinations for a large amount of optically faint periodic variables. These variables are taken from the Catalina Survey Data Release-1 (CSDR1) data set. As much as 967 objects were studied. Spectral classification uses the objective-prism scanned plates of the Hamburg Quasar Survey (HQS) and of the Hamburg/ESO Survey (HES). Spectra from the Sloan Digital Sky Survey (SDSS) and LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic Telescope) are also exploited. The majority of the variables in CSDR1 have not been known before. While the majority of stars are found to be F, G, K, M giants and dwarfs, a few dozens of known carbon (C-type) stars are recovered. Six are new. Some supplementary spectra obtained with the Byurakan Observatory 2.6-m telescope are shown. We study in more detail eight C-type stars. Their periods are in the range 120 – 400 days and their V-band magnitude are 14 – 16.5mag. With the assumption that they are classical asymptotic giant branch (AGB) stars and obey the Miras period-luminosity (P-L) relation, large distances (5 up to 100 kpc) are obtained. Three of them are angularly close to C stars attributed to the Sgr tidal leading arm. However, one of these seven stars, CRTS J092231.7+510740, shows significant proper-motion, as given by the recent Sloan catalog. If this motion is confirmed, e.g., by Gaia, and it is a dwarf C star, which is supported by its colors, it is at about 100 pc from the Sun. But in this case its periodic variability remains to be explained. Our work supports the view that the known sample of distant halo C stars can be increased by our method and that great care must be adopted in distance determination.

Spectroscopy of Dwarf Stars Around the North Celestial Pole**Based on observations collected with the 1.65 m telescope and VUES spectrograph at the Molėtai Astronomical Observatory of Institute of Theoretical Physics and Astronomy, Vilnius University, for the SPFOT survey.

New space missions (e.g., NASA-TESS and ESA-PLATO) will perform an in-depth analysis of bright stars in large fields of the celestial sphere searching for extraterrestrial planets and investigating their host-stars. Asteroseismic observations will search for exoplanet-hosting stars with solar-like oscillations. In order to achieve all the goals, a full characterization of the stellar objects is important. However, accurate atmospheric parameters are available for less than 30% of bright dwarf stars of the solar neighborhood. In this study we observed high-resolution (R = 60,000) spectra for all bright (V < 8 mag) and cooler than F5 spectral class dwarf stars in the northern-most field of the celestial sphere with radius of 20° from the α(2000) = 161.°03 and δ(2000) = 86.°60 that is a center of one of the preliminary ESO-PLATO fields. Spectroscopic atmospheric parameters were determined for 140 slowly rotating stars, for 73% of them for the first time. The majority (83%) of the investigated stars are in the TESS object lists and all of them are in the preliminary PLATO field. Our results have no systematic differences when compared with other recent studies. We have 119 stars in common with the Geneva–Copenhagen Survey, where stellar parameters were determined photometrically, and find a 14 ± 125 K difference in effective temperatures, 0.01 ± 0.16 in log g, and −0.02 ± 0.09 dex in metallicities. Comparing our results for 39 stars with previous high-resolution spectral determinations, we find only a 7 ± 73 K difference in effective temperatures, 0.02 ± 0.09 in log g, and −0.02 ± 0.09 dex in metallicities. We also determined basic kinematic and orbital parameters for this sample of stars. From the kinematical point of view, almost all our stars belong to the thin disk substructure of the Milky Way. The derived galactocentric metallicity gradient is −0.066 ± 0.024 dex kpc−1 (2.5σ significance) and the vertical metallicity gradient is −0.102 ± 0.099 dex kpc−1 (1σ significance) that comply with the latest inside-out thin disk formation models, including those with stellar migration taken into account.

The spectral determinations of some classes of multicone graphs

The main goal of the work is to characterize new families of multicone graphs which are determined by their spectra. A multicone graph is obtained from the join of a clique and a regular graph. Let n be a natural number, the friendship graph consists of n edge-disjoint triangles that all of them have only one in common vertex. In this paper, we present new classes of multicone graphs that friendship graphs are special classes of them and we show these graphs and their complements are determined by their adjacency spectra as well as their Laplacian spectra. It is proved that complement of special families of these graphs, are determined by their adjacency spectra. Additionally, we prove that graphs cospectral with these graphs are perfect.

Preparation of Single Substituted Phenyl Porphyrins Form &amp;lt;i&amp;gt;Meso&amp;lt;/i&amp;gt;-Tetraphenyl Porphyrin-Synthetic Example from Symmetric Porphyrin into Asymmetric Porphyrins

Two asymmetric porphyrins, 5-(4-chloromethylphenyl)-10, 15, 20-triphenyl porphyrin and 5-(4-formylphenyl)-10, 15, 20-triphenyl porphyrin, were successfully prepared by the symmetric meso-tetraphenyl porphyrin and relative molecular configurations and properties were characterized by spectral determinations. This work presented an example for synthesis of asymmetric porphyrin derivatives from the symmetric porphyrin. Both asymmetric porphyrins are reactive in molecular assembly, the concerned reactions including alkylation with Grignard reagents, etherification with alcohols, aldol condensation and Mannich reaction for modification and enhancing their functionality. In this work, the reaction conditions were improved, synthetic strategy and route were confirmed.

Bioactive 2(1H)-Pyrazinones and Diketopiperazine Alkaloids from a Tunicate-Derived Actinomycete Streptomyces sp.

As a part of our ongoing effort to allocate marine microbial bioactive leads, a tunicate-derived actinomycete, Streptomyces sp. Did-27, was investigated. Three new 2(1H)-pyrazinones derivatives, (S)-6-(sec-butyl)-3-isopropylpyrazin-2(1H)-one (1), (S)-3-(sec-butyl)-6-isopropylpyrazin-2(1H)-one (2) and (S)-6-(sec-butyl)-3-isobutylpyrazin-2(1H)-one (3), together with the known (1H)-pyrazinones analogues deoxymutaaspergillic acid (4), 3,6-diisobutyl-2(1H)-pyrazinone (5) and 3,6-di-sec-butyl-2(1H)-pyrazinone (6), and the diketopiperazine alkaloids cyclo(6-OH-d-Pro-l-Phe) (7), bacillusamide B (8), cyclo(l-Pro-l-Leu) and cyclo(l-Pro-l-Ile) (10) were isolated from this strain. The structures of the compounds were determined by study of their one- and two-dimensional NMR spectra as well as high-resolution mass spectral determinations. Compound 4 was reported previously as a synthetic product, while compound 6 was reported as 2-hydroxy-3,6-di-sec-butylpyrazine. Herein, we report the complete NMR data for compounds 4 and 6. The compounds were evaluated for their cytotoxic activities against three cell lines. Compound 5 showed potent and selective activity against HCT-116 cell line with IC50 of 1.5 μg/mL, while 1–10 showed variable cytotoxic activities against these cancer cell lines. These results provide further understanding about the chemistry and bioactivities of the alkylated 2(1H)-pyrazinone derivatives.

Bioactive Hydantoin Alkaloids from the Red Sea Marine Sponge Hemimycale arabica.

In the course of our continuing efforts to identify bioactive secondary metabolites from Red Sea marine invertebrates, we have investigated the sponge Hemimycale arabica. The antimicrobial fraction of an organic extract of the sponge afforded two new hydantoin alkaloids, hemimycalins A and B (2 and 3), together with the previously reported compound (Z)-5-(4-hydroxybenzylidene)imidazolidine-2,4-dione (1). The structures of the compounds were determined by extensive 1D and 2D NMR (COSY, HSQC and HMBC) studies and high-resolution mass spectral determinations. Hemimycalins A (2) and B (3) represent the first examples of the natural N-alkylated hydantoins from the sponge Hemimycale arabica. Compounds 1–3 displayed variable antimicrobial activities against E. coli, S. aureus, and C. albicans. In addition, compound 1 displayed moderate antiproliferative activity against the human cervical carcinoma (HeLa) cell line. These findings provide further insight into the chemical diversity as well as the biological activity of this class of compounds.

Theonellamide G, a Potent Antifungal and Cytotoxic Bicyclic Glycopeptide from the Red Sea Marine Sponge Theonella swinhoei

In our search for bioactive metabolites from marine organisms, we have investigated the polar fraction of the organic extract of the Red Sea sponge Theonella swinhoei. Successive chromatographic separations and final HPLC purification of the potent antifungal fraction afforded a new bicyclic glycopeptide, theonellamide G (1). The structure of the peptide was determined using extensive 1D and 2D NMR and high-resolution mass spectral determinations. The absolute configuration of theonellamide G was determined by chemical degradation and 2D NMR spectroscopy. Theonellamide G showed potent antifungal activity towards wild and amphotericin B-resistant strains of Candida albicans with IC50 of 4.49 and 2.0 μM, respectively. Additionally, it displayed cytotoxic activity against the human colon adenocarcinoma cell line (HCT-16) with IC50 of 6.0 μM. These findings provide further insight into the chemical diversity and biological activities of this class of compounds.

Schiff base bridged biporphyrin: Synthesis, characterization and spectral properties

Chromophoric molecules with mono-aminophenyl, 5-aminophenyl-10, 15, 20-triphenyl porphyrin, were chemically reduced from the precursors of 5-nitrophenyl-10, 15, 20-triphenyl porphyrin. The titled Schiff base bridged biporphyrins were furthermore prepared by condensation of 5-aminophenyl-10, 15, 20-triphenyl porphyrin with terephthalaldehyde. This novel conjugated Schiff base biporphyrin was well characterized by spectral determinations. Experimental results indicated that the titled compound possessed fluorescence enhancement in near infrared region. Compared with tetraphenyl porphyrin, both ultraviolet–visible absorption and fluorescence spectra of the titled compound appeared with slightly red shift. Photo experiments revealed that, after violet irradiation, the color of a chloroform solution with the titled compound changed sharply from pale green to dark green along with sensitively spectral variation during ultraviolet–visible absorption and electron paramagnetic resonance determinations. This sensitively photochromic mechanism was well explained by molecular recognition of the titled compound towards hydrogen chloride from the decomposition of the chloroform solvent. The titled compound was sensitive in recognizing towards hydrogen chloride.

Influence of the solvent in the formation of different 1D and 2D coordination polymers from the reaction of copper(II) phthalate with pyrazole

From the reaction of Cu(Pht)(H2O) (Pht=o-benzene dicarboxylate) with pyrazole (Hpz), four different 1D or 2D Coordination Polymers (CPs), [Cu(Pht)(Hpz)2]·CH2Cl2, 1, [{Cu(Pht)(Hpz)4}3]·3.5Hpz·H2O, 2, [{Cu(Pht)(Hpz)2}2·0.5H2O], 3, and [Cu(Pht)(Hpz)2], 4, where Pht dianions bridge two or three mononuclear Cu(Hpz)x moieties (x=2, 4), as well as the compound [Cu(Pht)(Hpz)4]·MeOH, 5, have been obtained, depending on the solvent employed. All compounds are air stable and have been characterized through elemental analyses and spectral determinations (IR, ESI-MS, magnetic susceptibility) and 1–4 also by single crystal X-ray diffraction studies. The self-assemblies of compounds 1–4 in different solvents generate different 1D and 2D CPs as a consequence of the presence of different crystallization solvent molecules in the supramolecular cavities.

Spidast: a new modular software to process spectrointerferometric measurements★

Extracting stellar fundamental parameters from Spectrointerferometric (SPI) data requires reliable estimates of observables and with robust uncertainties (visibility, triple product, phase closure). A number of fine calibration procedures are necessary throughout the reduction process. Testing departures from centrosymmetry of brightness distributions is a useful complement. Developing a set of automatic routines called spidast (made available to the community) to reduce, calibrate and interpret raw data sets of instantaneous spectrointerferograms at the spectral channel level, we complement (and in some respects improve) the ones contained in the amdlib Data Reduction Software. Our new software spidast is designed to work in an automatic mode, free from subjective choices, while being versatile enough to suit various processing strategies. spidast performs the following automated operations: weighting of non-aberrant SPI data (visibility, triple product), fine spectral calibration (subpixel level), accurate and robust determinations of stellar diameters for calibrator sources (and their uncertainties as well), correction for the degradations of the interferometer response in visibility and triple product, calculation of the centrosymmetry parameter from the calibrated triple product, fit of parametric chromatic models on SPI observables, to extract model parameters. spidast is currently applied to the scientific study of 18 cool giant and supergiant stars, observed with the VLTI/AMBER facility at medium resolution in the K band. Because part of their calibrators have no diameter in the current catalogues, spidast provides new determinations of the angular diameters of all calibrators. Comparison of spidast final calibrated observables with amdlib determinations shows good agreement, under good and poor seeing conditions.

Spectroscopic and Thermodynamic Evidence of Dimer and Trimer Hydrogen Bonded Complex Formation between Chloroform and 2-Butanone. Excess Molar Enthalpy for the Chloroform + 2-Butanone Binary System at 303 K

FT-Raman and FT-infrared spectra of pure chloroform (A) and 2-butanone (B), as well as of the binary system chloroform + 2-butanone, were recorded to investigate the type and nature of the intermolecular complexes formed when both chemicals are mixed. The optimized structures and vibrational frequencies for 2-butanone, chloroform, and their 1:1 and 1:2 complexes were calculated by means of density functional theory (DFT) techniques using the B3LYP functional combined with the 6-31G(d,p) and 6-311++G(d,p) basis set. The recorded FTIR and Raman spectra confirm the existence of these types of hydrogen-bonded complexes, making it possible, furthermore, to calculate the heteroassociation constants. Heat of mixing at 303 K over the whole mole fraction range at atmospheric pressure was also measured. The excess molar enthalpy was fitted to a Redlich-Kister-type equation, using least-squares to obtain its dependence on concentration. The ideal associated solution model was also used to calculate these equilibrium constants among the chemical species in solution, which compare well with that calculated with the spectral determinations and the enthalpy of hydrogen bond formation. Furthermore, the McGlashan-Rastogi linearization test was also used to provide thermodynamic evidence about the stoichiometry of the formed complexes.