scholarly journals Structure and IR Spectra of 3(5)-Aminopyrazoles and UV-Induced Tautomerization in Argon Matrix

Molecules ◽  
2021 ◽  
Vol 26 (14) ◽  
pp. 4299
Author(s):  
Alina Secrieru ◽  
Susy Lopes ◽  
Maria L. S. Cristiano ◽  
Rui Fausto
Keyword(s):  
Ir Spectroscopy ◽  
Ir Spectra ◽  
Matrix Isolation ◽  
Energy Difference ◽  
Argon Matrix ◽  
Tautomeric Forms ◽  
Gibbs Free Energy Difference ◽  
The Matrix ◽  
Isolated Compound

The prototropic tautomerism in 3(5)-aminopyrazoles was investigated by matrix isolation infrared (IR) spectroscopy, supported by DFT(B3LYP)/6-311++G(d,p) calculations. In consonance with the experimental data, the calculations predict tautomer 3-aminopyrazole (3AP) to be more stable than the 5-aminopyrazole (5AP) tautomer (calculated energy difference: 10.7 kJ mol−1; Gibbs free energy difference: 9.8 kJ mol−1). The obtained matrix isolation IR spectra (in both argon and xenon matrices) were interpreted, and the observed bands were assigned to the tautomeric forms with help of vibrational calculations carried out at both harmonic and anharmonic levels. The matrix-isolated compound (in argon matrix) was then subjected to in situ broadband UV irradiation (λ > 235 nm), and the UV-induced transformations were followed by IR spectroscopy. Phototautomerization of the 3AP tautomer into the 5AP form was observed as the strongly prevalent reaction.

Examinations of the Matrix Isolation Fourier Transform Infrared Spectra of Organic Compounds: Part XVI

1989 ◽  
Vol 43 (6) ◽  
pp. 1008-1016 ◽  
Author(s):  
W. M. Coleman ◽  
Bert M. Gordon
Keyword(s):  
Fourier Transform ◽  
Ir Spectra ◽  
Vapor Phase ◽  
Infrared Spectra ◽  
Condensed Phase ◽  
Matrix Isolation ◽  
Absorption Bands ◽  
Argon Matrix ◽  
The Matrix ◽  
The Impact

Information concerning the matrix isolation Fourier transform infrared spectra of a series of alkanes, esters, lactones, lactams, phenols, alcohols, amides, alkenes, and ketones is presented. A comparison between the characteristics of the spectra in two matrices (argon and xenon) as well as in the absence of any matrix (bare gold disk) is drawn. The impact of these matrices on the characteristics of the IR spectra is compared with the impact observed when spectra are gathered in the vapor phase as well as the condensed phase/solid state. For the majority of compounds studied, the major absorption bands of each class of compound fall between higher values for the vapor phase and lower values for the condensed phase when either argon or xenon is used as the matrix gas. The few exceptions are discussed. The absorption bands found in the xenon matrix are usually at a lower energy than are comparable bands in the argon matrix. In most all cases, the values of absorptions for compounds on the bare disk were lower than the comparable values found in the argon matrix. These results represent the first extensive study at 10 K of the effect of different matrix gas hosts and document the proposal that preconceptions of noble gases as inert hosts for the examination of FT-IR spectra at low temperature are not valid.

In situ preparation of the nuclear matrix of Physarum polycephalum: ultrastructural and biochemical analysis of different matrix isolation procedures

1988 ◽  
Vol 90 (4) ◽  
pp. 621-628 ◽  
Author(s):  
W. Waitz ◽  
P. Loidl
Keyword(s):  
Nuclear Matrix ◽  
Physarum Polycephalum ◽  
Matrix Isolation ◽  
Protein Composition ◽  
Biochemical Properties ◽  
Agarose Beads ◽  
In Situ Preparation ◽  
The Matrix ◽  
Important Approach

A novel method for in situ preparation of nuclear matrix from whole plasmodia of Physarum polycephalum without isolation of nuclei is presented. Plasmodia are encapsulated in agarose beads and after solubilization of the cytoplasm the nuclear matrix is prepared. With this quick and easy technique nuclear matrix can be reproducibly prepared with perfect recovery. We compared the ultrastructural and biochemical properties of the matrix after three different matrix isolation procedures: preparation with high salt, ammonium sulphate and lithium diiodosalicylic acid. The results show that the ultrastructure and protein composition of the three types of matrix are very similar or even identical. We conclude that many of the conflicting results on nuclear matrix in the literature are due to perturbations of nuclear integrity during the isolation of nuclei. For this reason the new in situ method is an important approach in the standardization of nuclear matrix isolation.

Examinations of the Matrix Isolation Fourier Transform Infrared Spectra of Organic Compounds: Part XV

1989 ◽  
Vol 43 (6) ◽  
pp. 1004-1008 ◽  
Author(s):  
W. M. Coleman ◽  
Bert M. Gordon
Keyword(s):  
Fourier Transform ◽  
Infrared Spectra ◽  
Matrix Isolation ◽  
Fourier Transform Infrared ◽  
Argon Matrix ◽  
Fourier Transform Infrared Spectra ◽  
The Matrix ◽  
Ft Ir ◽  
Oil Components ◽  
Search Routine

Matrix isolation Fourier transform infrared spectra (MI/FT-IR) of a series of essential oil components have been described. Clear, well-defined differences were detected in the MI/FT-IR spectra of compounds having minor differences in their structure. A library search routine was found to correctly identify components of interest when visual differences were not clearly evident. The presence of discrete conformers in the argon matrix resulted in the presence of split absorptions in the carbonyl band for selected compounds.

Examinations of the Matrix Isolation Infrared Spectra of Organic Compounds: PART XIII

1989 ◽  
Vol 43 (2) ◽  
pp. 305-310 ◽  
Author(s):  
W. M. Coleman ◽  
Bert M. Gordon
Keyword(s):  
Ir Spectra ◽  
Organic Compounds ◽  
Matrix Isolation ◽  
Intramolecular Hydrogen Bonding ◽  
Double Bond Position ◽  
Absorption Bands ◽  
The Matrix ◽  
Carbon Substitution ◽  
Ft Ir ◽  
Intramolecular Hydrogen

Matrix isolation Fourier transform infrared (MI/FT-IR) spectra have been collected on a series of internal alkenes, a series of hydroxy-substituted ketones, and a series of hydroxy-substituted esters. Assignments of double bond position and geometry are possible in the alkenes, due to the resolution of absorption bands of very similar energies. The location of the absorption bands for the alkenes was found to be very similar to the values found for the vapor-phase and condensed-phase spectra. Multiple carbonyl absorptions have been found in the MI/FT-IR spectra of the hydroxy ketones and hydroxy esters. Trends in the multiplicity of the carbonyl absorption patterns for these compounds as a function of ring size and hydroxyl carbon substitution have been used to document the presence of extensive intramolecular hydrogen bonding. The argon matrix as a phase for the study of stable organic compounds has, again, with this information, been shown to be unique.

The infrared matrix isolation spectra of ND3 and NH3 in an argon matrix in the v2 bending region

1978 ◽  
Vol 31 (2) ◽  
pp. 247 ◽  
Author(s):  
JA Cugley ◽  
S Liberts ◽  
ADE Pullin
Keyword(s):  
Gas Phase ◽  
Matrix Isolation ◽  
Phase Model ◽  
Fundamental Region ◽  
Fractional Change ◽  
Argon Matrix ◽  
Rotational Constants ◽  
A Value ◽  
The Matrix

The spectra of NH3 and ND3 in an argon matrix have been obtained in the v2 (bending fundamental) region. The v2 region of ND3 has been interpreted in terms of a gas-phase model, with slightly altered rotational constants. Thus for the matrix an effective value of (B'+B') = 9.85 is required compared with 10.25 cm-1 for the gas phase. This represents a smaller fractional change than for NH3. The inversion splitting of ND3 in the argon matrix has been clearly resolved and a value of 2.0�0.1 cm-1 deduced. However, there are extra lines in the spectrum of ND3 which we cannot assign on the basis of a gas-phase model. For NH3 some vib-rotor 'lines' have been shown to be composite, in particular Q(11+) and Q(11-) are close triplets.

Examinations of the Matrix Isolation Fourier Transform Infrared Spectra of Organic Compounds: Part VIII

1988 ◽  
Vol 42 (2) ◽  
pp. 304-309 ◽  
Author(s):  
W. M. Coleman ◽  
Bert M. Gordon
Keyword(s):  
Fourier Transform ◽  
Organic Compounds ◽  
Vapor Phase ◽  
Infrared Spectra ◽  
Matrix Isolation ◽  
Fourier Transform Infrared ◽  
Argon Matrix ◽  
Fourier Transform Infrared Spectra ◽  
The Matrix ◽  
Ft Ir

Matrix isolation Fourier transform infrared (MI/FT-IR) data has been presented that documents the presence of discrete conformers in an argon matrix for a series of ketones. The distribution of conformers in the matrix was related to the structure of the molecule, in that rigid structures (i.e., small rings, bicyclic systems, and unsaturated systems) displayed simple carbonyl absorption patterns relative to those of their less rigid counterparts. Also, conformer isolation was seen for halosubstituted ketones. These results are in agreement with previous findings concerning the vapor-phase (VP) spectra of these molecules.

Examinations of the Matrix Isolation Fourier Transform Infrared Spectra of Organic Compounds: Part XII

1989 ◽  
Vol 43 (2) ◽  
pp. 298-304 ◽  
Author(s):  
W. M. Coleman ◽  
Bert M. Gordon ◽  
Brian M. Lawrence
Keyword(s):  
Fourier Transform ◽  
Ir Spectra ◽  
Infrared Spectra ◽  
Matrix Isolation ◽  
Fourier Transform Infrared ◽  
Fourier Transform Infrared Spectra ◽  
The Matrix ◽  
Ft Ir ◽  
Nanogram Level ◽  
C Nmr

Matrix isolation Fourier transform infrared spectra (MI/FT-IR), mass spectra (MS), carbon-13 Nuclear Magnetic Resonance (13C-NMR) spectra, condensed-phase infrared spectra, and vapor-phase infrared (IR) spectra are presented for a series of terpene compounds. Subtle differences in positional and configurational isomers commonly found with terpenes could be easily detected by the MI/FT-IR spectra. The results are comparable in some aspects to those obtainable from 13C-NMR and thin-film IR; however, most importantly, they are acquired at the low nanogram level for MI/FT-IR, as compared to the milligram level for the other techniques. These results represent an advance in the technology available for the analysis of complex mixtures such as essential oils containing terpene-like molecules.

In situ FT-IR spectroscopy investigations of dimethyl carbonate synthesis: on the contribution of gas-phase species

RSC Advances ◽  
2016 ◽  
Vol 6 (21) ◽  
pp. 17288-17289 ◽  
Author(s):  
F. C. Meunier
Keyword(s):  
Ir Spectroscopy ◽  
Ir Spectra ◽  
Gas Phase ◽  
Dimethyl Carbonate ◽  
Ft Ir ◽  
Ft Ir Spectroscopy

Gas-phase contributions need to be subtracted from in situ IR spectra collected over solids to reveal the spectrum of adsorbates.

The Nature of Chemisorbed CO2 in Zeolite A

2019 ◽  
Author(s):  
Przemyslaw Rzepka ◽  
Zoltán Bacsik ◽  
Andrew J. Pell ◽  
Niklas Hedin ◽  
Aleksander Jaworski
Keyword(s):  
Solid State ◽  
Ir Spectroscopy ◽  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
Surface Coverage ◽  
Gas Mixtures ◽  
Mas Nmr ◽  
Significant Fraction ◽  
Zeolite A

Formation of CO<sub>3</sub><sup>2-</sup> and HCO<sub>3</sub><sup>-</sup> species without participation of the framework oxygen atoms upon chemisorption of CO<sub>2</sub> in zeolite |Na<sub>12</sub>|-A is revealed. The transfer of O and H atoms is very likely to have proceeded via the involvement of residual H<sub>2</sub>O or acid groups. A combined study by solid-state <sup>13</sup>C MAS NMR, quantum chemical calculations, and <i>in situ</i> IR spectroscopy showed that the chemisorption mainly occurred by the formation of HCO<sub>3</sub><sup>-</sup>. However, at a low surface coverage of physisorbed and acidic CO<sub>2</sub>, a significant fraction of the HCO<sub>3</sub><sup>-</sup> was deprotonated and transformed into CO<sub>3</sub><sup>2-</sup>. We expect that similar chemisorption of CO<sub>2</sub> would occur for low-silica zeolites and other basic silicates of interest for the capture of CO<sub>2</sub> from gas mixtures.

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