Dimerization of Carboxylic Acids:  Reliability of Theoretical Calculations and the Effect of Solvent

1998 ◽  
Vol 102 (12) ◽  
pp. 2269-2276 ◽  
Author(s):  
Carles Colominas ◽  
Jordi Teixidó ◽  
Jose Cemelí ◽  
Francisco J. Luque ◽  
Modesto Orozco
Keyword(s):  
Carboxylic Acids ◽  
Theoretical Calculations ◽  
Effect Of Solvent

Hydration of Simple Carboxylic Acids from Infrared Spectra of HDO and Theoretical Calculations

2011 ◽  
Vol 115 (16) ◽  
pp. 4834-4842 ◽  
Author(s):  
Maciej Śmiechowski ◽  
Emilia Gojło ◽  
Janusz Stangret
Keyword(s):  
Carboxylic Acids ◽  
Infrared Spectra ◽  
Theoretical Calculations

scholarly journals Can carbonic acid protonate biological bases? Support from base protonation in methanol solvent

2019 ◽  
Vol 205 ◽  
pp. 09005
Author(s):  
Daniel Aminov ◽  
Dina Pines ◽  
M. Kiefer Philip ◽  
Snehasis Daschakraborty ◽  
T. Hynes James ◽  
...  
Keyword(s):  
Carboxylic Acid ◽  
Blood Plasma ◽  
Carboxylic Acids ◽  
Carbonic Acid ◽  
Theoretical Calculations ◽  
Decomposition Reaction ◽  
Experimental Support ◽  
Ph Indicators ◽  
Reactive Complex ◽  
Pure Methanol

In separate contributions, we have focussed on demonstrating that carbonic acid (CA) - historically considered too unstable to be a viable protonating agent - is able to protonate several types of pH indicators while behaving as a regular, moderately strong, carboxylic acid. Together with the experimental support we found for considering CA as a regular carboxylic acid are theoretical calculations demonstrating CA’s ability to protonate methylamine within 25 fs when forming with it a contact reactive complex. Here we briefly discuss a further aspect of this focus, involving the measurement of the lifetime and pKa of CA in pure methanol. The lifetime in methanol was found to be about 12-fold longer than in water, showing that the decomposition reaction of CA is solvent-dependent. The pKa change upon transferring CA from water to methanol was found to be 4.7 ± 0.1 pKa units, changing from 3.49 ± 0.03 to 8.16 ± 0.05: this change is similar to the pKa change observed for common stable carboxylic acids when these are transferred from water to methanol. These results add further support of our earlier proposal that CA can be an important protonating agent of biological bases in the blood plasma.

scholarly journals Infrared study of some 2-substituted-6-hydroxy-4-pyrimidine carboxylic acids: Correlation with MO-calculations

2000 ◽  
Vol 65 (5-6) ◽  
pp. 371-379 ◽  
Author(s):  
Ljubinka Bogunovic ◽  
Ubavka Mioc ◽  
Bratislav Jovanovic ◽  
Ivan Juranic
Keyword(s):  
Carboxylic Acids ◽  
Theoretical Calculations ◽  
Orbital Method ◽  
Mo Calculations ◽  
Hydroxy Compound ◽  
Infrared Study ◽  
Hydrogen Bond Formation ◽  
Methyl Derivatives ◽  
Dielectric Continuum ◽  
Low Solubility

The IR spectra of a series of 2-substituted-6-hydroxy-4-pyrimidine carboxylic acids (substituent = OH, SH, CH3, CH3S and NH2) were studied from the aspect of the influence of the subsitutent on the polarizability of some bonds, keto-enol tautomerism and hydrogen bond formation. The spectra were taken using solids due to the low solubility of the acids. Theoretical calculations were done using the MNDO-AM1 semiempirical molecular-orbital method. The stabilities of various tautomers were calculated simulating the dielectric continuum using the COSMO facility of the MOPAC program package. Theoretical calculations were made for all the possible tautomers of the 2-substituted-6-hydroxy-4-pyrimidine carboxylic acids. For the most stable isomers, the vibrational spectra were calculated. For the majority of the compounds the most stable isomer was identified having the structure 2-Y-6-oxo-4-carboxy-3H-pyrimidine. Besides this structure, for the 2-amino-, and 2-methyl- derivatives the zwitterionic forms have very similar stability. The 2-hydroxy compound is most stable as the 2,6-dioxo-1H, 3H isomer. The calculated vibrations for the compounds with a single stable structure correlate very well with the experimental frequencies. For the 2-methyl- and 2-amino- compounds the correlation is considerably less satisfactory. The most probable reason for this deviation is the existence of two or more tautomets in equilibrium. The correlation of the measured frequencies and the pKa values of the acids, indicate that the same tautomers exist in the solid state and in the solution.

Indium-Mediated Addition of 4-Bromocrotonic Acid to Aldehydes and Ketones—A Simple, High Yielding Route to α-Allyl-β-Hydroxy Carboxylic Acids

2004 ◽  
Vol 57 (2) ◽  
pp. 135 ◽  
Author(s):  
Michael C. Bowyer ◽  
Charles M. Gordon ◽  
Sarah K. Leitch ◽  
Adam McCluskey ◽  
Craig Ritchie
Keyword(s):  
Ionic Liquid ◽  
Carboxylic Acids ◽  
Simple Procedure ◽  
Effect Of Solvent ◽  
Reaction Proceeds ◽  
Aldehydes And Ketones ◽  
Hydroxy Carboxylic Acids ◽  
Ethanol Ethanol

We report a simple procedure for the indium-mediated addition of 4-bromocrotonic acid to a variety of aldehydes and ketones. In all instances the reaction proceeds exclusively with α-addition and typically in moderate to good yields (42–100%). The effect of solvent is minimal allowing a wide choice of conditions (methanol, ethanol, ethanol/water, water, tetrahydrofuran, and the ionic liquid [bmIm][BF4]).

Acidity in water (pKa values) of carboxylic acids derived from simple heterocycles (azoles and azines)

1990 ◽  
Vol 55 (1) ◽  
pp. 72-79 ◽  
Author(s):  
Carlos Cativiela ◽  
Jean-Louis Dejardin ◽  
José Elguero ◽  
José I. Garcia ◽  
Emmanuel Gonzalez ◽  
...  
Keyword(s):  
Carboxylic Acids ◽  
Theoretical Calculations ◽  
Additive Models ◽  
Carboxylic Group ◽  
Pka Values

The pKa of eighteen heterocyclic carboxylic acids derived from thiophene, furan, pyrrole, benzothiophene, benzofuran, indole, pyridine and quinoline have been determined by spectrophotometry and potentiometry. The values thus obtained are discussed using additive models of the Free-Wilson type. Some theoretical calculations within the AM1 approximation have been carried out in order to understand why annelation effects are dependent on the position, α or β, of the carboxylic group. In the case of pyridine and quinoline carboxylic acids, the problem of tautomerism between neutral and zwitterionic forms has been considered.

Carboxylic acids as anchoring components on aluminum oxide for the alignment relay technique of single-walled carbon nanotubes

2021 ◽  
Vol 45 (12) ◽  
pp. 5340-5349
Author(s):  
Monika R. Snowdon ◽  
Shirley Wang ◽  
Nour Mashmoushi ◽  
Scott W. Hopkins ◽  
Derek J. Schipper
Keyword(s):  
Carbon Nanotubes ◽  
Carboxylic Acid ◽  
Aluminum Oxide ◽  
Carboxylic Acids ◽  
Theoretical Calculations ◽  
Single Walled Carbon Nanotubes ◽  
Single Walled Carbon ◽  
Walled Carbon Nanotubes

We illustrate using a carboxylic acid anchoring component in the Alignment Relay Technique on silica and alumina surfaces. We present theoretical calculations on the interactions between the iptycenes' various pockets and the carbon nanotubes.

scholarly journals NMR investigation and theoretical calculations of the effect of solvent on the conformational analysis of 4',7-di-hydroxy-8-prenylflavan

Química Nova ◽  
2004 ◽  
Vol 27 (3) ◽  
pp. 371-377 ◽  
Author(s):  
Antônio Flávio de Carvalho Alcântara ◽  
Ana Frazão Teixeira ◽  
Izelene Felício da Silva ◽  
Wagner Batista de Almeida ◽  
Dorila Piló-Veloso
Keyword(s):  
Conformational Analysis ◽  
Theoretical Calculations ◽  
Effect Of Solvent

XUV Absorption Spectra of Carbon Ions

1988 ◽  
Vol 102 ◽  
pp. 71-73
Author(s):  
E. Jannitti ◽  
P. Nicolosi ◽  
G. Tondello
Keyword(s):  
Absorption Spectra ◽  
Cross Section ◽  
Theoretical Calculations ◽  
Photoionization Cross Section ◽  
Carbon Ions

AbstractThe photoabsorption spectra of the carbon ions have been obtained by using two laser-produced plasmas. The photoionization cross-section of the CV has been absolutely measured and the value at threshold, σ=(4.7±0.5) × 10−19cm2, as well as its behaviour at higher energies agrees quite well with the theoretical calculations.

Relative Intensities in ED Patterns From Thin Gold Films

1972 ◽  
Vol 30 ◽  
pp. 636-637
Author(s):  
R. H. Morriss ◽  
J. D. C. Peng ◽  
C. D. Melvin
Keyword(s):  
Theoretical Calculations ◽  
Diffraction Theory ◽  
Gold Films ◽  
Reasonable Accuracy ◽  
Experimental Conditions ◽  
Crystal Perfection ◽  
Heavy Atoms ◽  
Fine Focus ◽  
Convergent Beam ◽  
Beam Diffraction

Although dynamical diffraction theory was modified for electrons by Bethe in 1928, relatively few calculations have been carried out because of computational difficulties. Even fewer attempts have been made to correlate experimental data with theoretical calculations. The experimental conditions are indeed stringent - not only is a knowledge of crystal perfection, morphology, and orientation necessary, but other factors such as specimen contamination are important and must be carefully controlled. The experimental method of fine-focus convergent-beam electron diffraction has been successfully applied by Goodman and Lehmpfuhl to single crystals of MgO containing light atoms and more recently by Lynch to single crystalline (111) gold films which contain heavy atoms. In both experiments intensity distributions were calculated using the multislice method of n-beam diffraction theory. In order to obtain reasonable accuracy Lynch found it necessary to include 139 beams in the calculations for gold with all but 43 corresponding to beams out of the [111] zone.

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