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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"
acceleration of a chemical reaction induced the presence of material that is chemically unchanged at the end of the reaction; "of the top 50 commodity chemicals, 30 are created directly by catalysis and another 6 are made from raw materials that are catalytically produced" (同)contact action

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
(化学反応の)触媒現象,触媒作用

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/07/14 11:41:37」(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 the proton donor and the base is the proton acceptor. 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

Nature of the acid

Classical Bronsted acids

Acid catalysis is mainly used for organic chemical reactions. Many acids can function as sources for the protons. Acid used for acid catalysis include hydrofluoric acid (in the alkylation process), phosphoric acid, toluenesulfonic acid, polystyrene sulfonate, heteropoly acids, zeolites.

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 these oxides, which function as Lewis acids: silico-aluminates (zeolites, alumina, silico-alumino-phosphate), sulfated zirconia, and many transition metal oxides ( titania, zirconia, niobia, and more). Such acids are used in cracking. Many solid Bronsted acids are also employed industrially, including sulfonated polystyrene, solid phosphoric acid, niobic acid, and heteropolyoxometallates^[1]

A particularly large scale application is alkylation, e.g., the combination of benzene and ethylene to give ethylbenzene. Another major application is the rearrangement of cyclohexanone oxime to caprolactam.^[2] Many alkylamines are prepared by amination of alcohols, catalyzed by solid acids.

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

Enzymatic catalysis

Many enzymes operate by acid-catalysis.

Applications

In one role, acids enhance the ability of leaving groups. For example, hydroxyl (OH^-) is a poor leaving group, but water is a good one. Thus acids are used to convert alcohols into other classes of compounds, such as thiols and amines.

For the hydrolysis of esters, strong acids protonate the carbonyl oxygen, making the carbonyl carbon more electrophilic and susceptible to hydration. In this way, acids enable the hydrolysis of esters. Similarly they also catalyze the transesterification, where instead of water as the nucleophile, alcohol attacks the carbocation.

Mechanism

The kinds of acid catalysis are recognized, specific acid catalysis and general acid catalysis.^[3]

Specific catalysis

In specific acid catalysis, protonated solvent is the catalyst. The reaction rate is proportional to the concentration of the protonated solvent molecules SH⁺.^[4] 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. This kind of catalysis is common for strong acids in polar solvents, such as water.

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.^[5] The strongest acids are most effective. Reactions in which proton transfer is rate-determining exhibit general acid catalysis, for example diazonium coupling reactions.

{\text{rate}}=-{\frac {{\text{d}}[{\ce {R1}}]}{{\text{d}}t}}=k_{1}{\ce {[SH+][R1][R2]}}+k_{2}{\ce {[AH1][R1][R2]}}+k_{3}{\ce {[AH2][R1][R2]}}+...

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. When reactions are conducted in nonpolar media, this kind of catalysis is important because the acid is often not ionized.

References

^ Busca, Guido "Acid Catalysts in Industrial Hydrocarbon Chemistry" Chemical Reviews 2007, volume 107, 5366-5410. doi:10.1021/cr068042e
^ 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
^ Lowry, T. H.; Richardson, K. S., "Mechanism and Theory in Organic Chemistry," Harper and Row: 1981. ISBN 0-06-044083-X
^ "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

Ultrasonics promoted synthesis of thiazolidinones from 2-aminopyridine and 2-picolilamine.

Gouvêa DP, Bareño VD, Bosenbecker J, Drawanz BB, Neuenfeldt PD, Siqueira GM, Cunico W.SourceNúcleo de Química Aplicada, Universidade Federal de Pelotas - UFPel, Campus Universitário, s/n°, 96010-900 Pelotas, RS, Brazil.
Ultrasonics sonochemistry.Ultrason Sonochem.2012 Nov;19(6):1127-31. Epub 2012 Mar 21.
The efficient multicomponent synthesis of thiazolidinones from the reaction of arenealdehydes, mercaptoacetic acid and 2-picolilamine or 2-aminopyridine under ultrasound irradiation are reported. The reaction with 2-aminopyridine needs a Lewis acid catalysis to afford the corresponding 2-aryl-3-(pyr
PMID 22483740

Synthesis and thermal characterization of xylan-graft-polyacrylonitrile.

Unlü CH, Oztekin NS, Atıcı OG.SourceIstanbul Technical University, Faculty of Science and Letters, Department of Chemistry, Maslak TR34469, Istanbul, Turkey.
Carbohydrate polymers.Carbohydr Polym.2012 Oct 1;90(2):1120-6. Epub 2012 Jun 25.
In this study emulsion polymerization of acrylonitrile using xylan from agricultural waste material (corn cob) and cerium ammonium nitrate was investigated in terms of catalyst acid. Stock ceric solutions were prepared using either nitric or perchloric acid as catalyst. Optimum conditions were deter
PMID 22840048

Japanese Journal

Retro-aldol-type fragmentation of reducing sugars preferentially occurring in polyether at high temperature: Role of the ether oxygen as a base catalyst

Matsuoka Seiji,Kawamoto Haruo,Saka Shiro
Journal of Analytical and Applied Pyrolysis 93, 24-32, 2012-01
… Such inter- and intramolecular H-bonding (H-donation) may also be involved in the thermal decomposition of the melt sugar as an activation (acid catalysis) mechanism. …
NAID 120003726128

Overexpression of synthesized cephalosporin C acylase containing mutations in the substrate transport tunnel(ENZYMOLOGY, PROTEIN ENGINEERING, AND ENZYME TECHNOLOGY)

Wang Ying,Yu Huimin,Song Wensi,An Ming,Zhang Jing,Luo Hui,Shen Zhongyao
Journal of bioscience and bioengineering 113(1), 36-41, 2012-01
… Cephalosporin C (CPC) acylase converts CPC into 7-aminocephalosporanic acid (7-ACA) by single-step enzymatic catalysis. … Site-directed mutagenesis of the residues around the active center showed that not only the residues that were adjacent to the CPC D-α-aminoadipyl moiety, but also the residues that were in the substrate transport tunnel (Leu666, Ala675, Leu677), played crucial roles in catalysis as the ones locating in active center. …
NAID 110008897350