WordNet

street name for lysergic acid diethylamide (同)back breaker, battery-acid, dose, dot, Elvis, loony toons, Lucy in the sky with diamonds, pane, superman, window pane, Zen
any of various water-soluble compounds having a sour taste and capable of turning litmus red and reacting with a base to form a salt
having the characteristics of an acid; "an acid reaction"
(chemistry) a substance that initiates or accelerates a chemical reaction without itself being affected (同)accelerator
something that causes an important event to happen; "the invasion acted as a catalyst to unite the country"

PrepTutorEJDIC

酸性の / 酸味のある,すっぱい(sour) / (言葉・態度などが)厳しい,しんらつな / 酸 / すっぱいもの / 《俗》=LSD
触媒[剤]

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/05/10 16:58:24」(JST)

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In acid-catalyzed Fischer esterification, the proton binds to oxygens and functions as a Lewis acid to activate the ester carbonyl (top row) as an electrophile, and converts the hydroxyl into the good leaving group water (bottom left). Both lower the kinetic barrier and speed up the attainment of chemical equilibrium.

In acid catalysis and base catalysis a chemical reaction is catalyzed by an acid or a base. The acid is often the proton and the base is often a hydroxide ion. Typical reactions catalyzed by proton transfer are esterfications and aldol reactions. In these reactions the conjugate acid of the carbonyl group is a better electrophile than the neutral carbonyl group itself. Catalysis by either acid or base can occur in two different ways: specific catalysis and general catalysis.

Use in synthesis

Acid catalysis is mainly used for organic chemical reactions. There are many possible chemical compounds that can act as sources for the protons to be transferred in an acid catalysis system. A compound such as sulfuric acid, H₂SO₄, can be used. Usually this is done to create a more likely leaving group, such as converting an OH group to a H₂O⁺ group, which can then be eliminated as water (H₂O). Acids specifically used for acid catalysis include hydrofluoric acid (in the alkylation process), phosphoric acid, toluenesulfonic acid, polystyrene sulfonate, heteropoly acids, zeolites and graphene oxide.

With carbonyl compounds such as esters, synthesis and hydrolysis go through a tetrahedral transition state, where the central carbon has an oxygen, an alcohol group, and the original alkyl group. Strong acids protonate the carbonyl, which makes the oxygen positively charged, so that it can easily receive the double bond electrons when the alcohol attacks the carbonyl carbon. This enables ester synthesis and hydrolysis. The reaction is an equilibrium between the ester and its cleavage to carboxylic acid and alcohol. On the contrary, strong bases deprotonate the attacking alcohol or amine, which also promotes the reaction. However, bases also deprotonate the acid, which is irreversible. Therefore, in a strongly basic, aqueous environment, esters only hydrolyze.

Solid acid catalysts

In industrial scale chemistry, many processes are catalysed by "solid acids." As heterogeneous catalysts, solid acids do not dissolve in the reaction medium. Well known examples include zeolites, alumina, and various other metal oxides. Such acids are used in cracking. A particularly large scale application is alkylation, e.g. the combination of benzene and ethylene to give ethylbenzene.^[1] Many alkylamines are prepared by amination of alcohols.

Zeolite, ZSM-5 is widely used as a solid acid catalyst.

Kinetics

Specific catalysis

In specific acid catalysis taking place in solvent S, the reaction rate is proportional to the concentration of the protonated solvent molecules SH⁺.^[2] The acid catalyst itself (AH) only contributes to the rate acceleration by shifting the chemical equilibrium between solvent S and AH in favor of the SH⁺ species.

S + AH → SH⁺ + A^-

For example in an aqueous buffer solution the reaction rate for reactants R depends on the pH of the system but not on the concentrations of different acids.

This type of chemical kinetics is observed when reactant R₁ is in a fast equilibrium with its conjugate acid R₁H⁺ which proceeds to react slowly with R₂ to the reaction product; for example, in the acid catalysed aldol reaction.

General catalysis

In general acid catalysis all species capable of donating protons contribute to reaction rate acceleration.^[3] The strongest acids are most effective. Reactions in which proton transfer is rate-determining exhibit general acid catalysis, for example diazonium coupling reactions.

When keeping the pH at a constant level but changing the buffer concentration a change in rate signals a general acid catalysis. A constant rate is evidence for a specific acid catalyst.

References

^ Michael Röper, Eugen Gehrer, Thomas Narbeshuber, Wolfgang Siegel "Acylation and Alkylation" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2000. doi:10.1002/14356007.a01_185
^ "IUPAC Compendium of Chemical Terminology, 2nd Edition (1997)". www.iupac.org. Retrieved 2009-11-22.
^ "IUPAC Compendium of Chemical Terminology, 2nd Edition (1997)". www.iupac.org. Retrieved 2009-11-22.

UpToDate Contents

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English Journal

ZnCl2-mediated practical protocol for the synthesis of Amadori ketoses.

Harohally NV1, Srinivas SM2, Umesh S2.Author information 1Food Safety and Analytical Quality Control Laboratory, CSIR-CFTRI, KRS Road, Mysore 570020, Karnataka, India. Electronic address: nani.shankar@gmail.com.2Food Safety and Analytical Quality Control Laboratory, CSIR-CFTRI, KRS Road, Mysore 570020, Karnataka, India.AbstractAn efficient and practical protocol for the synthesis of Amadori ketoses N-(1-deoxy-d-fructose-1-yl) amino acid (amino acid=l-valine (1), l-leucine (2), l-isoleucine (3), l-tryptophan (4), l-phenylalanine (5), l-arginine (6) has been accomplished by employing ZnCl2 as a catalyst. The developed method circumvents protection and deprotection steps as well as tedious ion-exchange and column chromatographic techniques. The accomplished Amadori ketoses showed moderate to weak angiotensin I converting enzyme (ACE) inhibitory activity.
Food chemistry.Food Chem.2014 Sep 1;158:340-4. doi: 10.1016/j.foodchem.2014.02.094. Epub 2014 Mar 5.
An efficient and practical protocol for the synthesis of Amadori ketoses N-(1-deoxy-d-fructose-1-yl) amino acid (amino acid=l-valine (1), l-leucine (2), l-isoleucine (3), l-tryptophan (4), l-phenylalanine (5), l-arginine (6) has been accomplished by employing ZnCl2 as a catalyst. The developed metho
PMID 24731352

Improved interfacial oxygen reduction by ethylenediamine tetraacetic acid in the cathode of microbial fuel cell.

Gong XB1, You SJ2, Wang XH1, Zhang JN1, Gan Y3, Cui CW1, Ren NQ4.Author information 1State Key Laboratory of Urban Water Resource and Environment (SKLUWRE), Harbin Institute of Technology (HIT), Harbin 150090, PR China.2State Key Laboratory of Urban Water Resource and Environment (SKLUWRE), Harbin Institute of Technology (HIT), Harbin 150090, PR China. Electronic address: sjyou@hit.edu.cn.3Department of Catalysis Science and Engineering, School of Chemical Engineering and Technology, Harbin Institute of Technology (HIT), Harbin 150001, PR China.4State Key Laboratory of Urban Water Resource and Environment (SKLUWRE), Harbin Institute of Technology (HIT), Harbin 150090, PR China. Electronic address: rnq@hit.edu.cn.AbstractIn this study, ethylenediamine tetraacetic acid (EDTA) was investigated as a new kind of non-polymeric catalyst binder to improve interfacial oxygen reduction reaction (ORR) for the cathode of microbial fuel cell (MFC). The electrochemical analysis and MFC tests show negative correlation between ORR activity and molar concentration of EDTA applied during electrode preparation. In particular, the 0.02mol/L-EDTA yields higher ORR activity than other binder materials like Nafion, water, 0.1mol/L-EDTA and 0.2mol/L-EDTA, as indicated by the strongest response of ORR current and the smallest charge-transfer resistance. Accordingly, the MFC with cathode of 0.02mol/L-EDTA produced a maximum power density of 722mW/m(2), accounting for a value approximately 42% higher than that of commercial Nafion binder (5wt%, 507mW/m(2)). The improved ORR activity should be attributed to the enhanced proton transfer from phosphate ions to EDTA-involved three-phase boundary as a result of dipole ion bonds on nitrogen atoms having unshared pair of electrons in EDTA molecule.
Biosensors & bioelectronics.Biosens Bioelectron.2014 Aug 15;58:272-5. doi: 10.1016/j.bios.2014.02.073. Epub 2014 Mar 6.
In this study, ethylenediamine tetraacetic acid (EDTA) was investigated as a new kind of non-polymeric catalyst binder to improve interfacial oxygen reduction reaction (ORR) for the cathode of microbial fuel cell (MFC). The electrochemical analysis and MFC tests show negative correlation between ORR
PMID 24657648

Eco-friendly synthesis of silver and gold nanoparticles with enhanced bactericidal activity and study of silver catalyzed reduction of 4-nitrophenol.

Naraginti S1, Sivakumar A2.Author information 1Chemistry Division, School of Advanced Sciences, VIT University, Vellore 632 014, India.2Chemistry Division, School of Advanced Sciences, VIT University, Vellore 632 014, India. Electronic address: svkmr7627@gmail.com.AbstractThe present study reports a simple and robust method for synthesis of silver and gold nanoparticles using Coleus forskohlii root extract as reducing and stabilizing agent. Stable silver nanoparticles (AgNPs) and gold nanopoarticles (AuNPs) were formed on treatment of an aqueous silver nitrate (AgNO3) and chloroauric acid (HAuCl4) solutions with the root extract. The nanoparticles obtained were characterized by UV-Visible spectroscopy, Transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR). UV-Vis and TEM analysis indicate that with higher quantities of root extract, the interaction is enhanced leading to size reduction of spherical metal nanoparticles. XRD confirms face-centered cubic phase and the diffraction peaks can be attributed to (111), (200), (222) and (311) planes for these nanoparticles. These synthesized Ag and Au nanoparticles were found to exhibit excellent bactericidal activity against clinically isolated selected pathogens such as Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus). The synthesized AgNPs were also found to function as an efficient green catalyst in the reduction of anthropogenic pollutant 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by sodium borohydride, which was apparent from the periodical color change from bright yellow to colorless, after the addition of AgNPs.
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy.Spectrochim Acta A Mol Biomol Spectrosc.2014 Jul 15;128:357-62. doi: 10.1016/j.saa.2014.02.083. Epub 2014 Mar 12.
The present study reports a simple and robust method for synthesis of silver and gold nanoparticles using Coleus forskohlii root extract as reducing and stabilizing agent. Stable silver nanoparticles (AgNPs) and gold nanopoarticles (AuNPs) were formed on treatment of an aqueous silver nitrate (AgNO3
PMID 24681320

Japanese Journal

流動接触分解触媒の酸性質が重質重油分解へ与える影響

平松義文,會田洋兵,梅木孝
Journal of the Japan Petroleum Institute 55(5), 319-325, 2012-09
NAID 40019420819

Induced-fit motion of a lid loop involved in catalysis in alginate lyase A1-III.

Mikami Bunzo,Ban Mizuho,Suzuki Sachiko,Yoon Hye-Jin,Miyake Osamu,Yamasaki Masayuki,Ogura Kohei,Maruyama Yukie,Hashimoto Wataru,Murata Kousaku
Acta crystallographica. Section D, Biological crystallography 68(Part 9), 1207-1216, 2012-09
… The structures of two mutants (H192A and Y246F) of a mannuronate-specific alginate lyase, A1-III, from Sphingomonas species A1 complexed with a tetrasaccharide substrate [4-deoxy-L-erythro-hex-4-ene-pyranosyluronate-(mannuronate)(2)-mannuronic acid] were determined by X-ray crystallography at around 2.2 Å … The final models of the complex forms, which comprised two monomers (of 353 amino-acid residues each), 268-287 water molecules and two tetrasaccharide substrates, had R factors of around 0.17. …
NAID 120004920434