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77-92-9 Usage

Description

Citric acid is a white, crystalline, weak organic acid present in most plants and many animals as an intermediate in cellular respiration. Citric acid contains three carboxyl groups making it a carboxylic, more specifically a tricarboxylic, acid.the name citrus originates from the Greek kedromelon meaning apple of melon for the fruit citron. Greek works mention kitron, kitrion, or kitreos for citron fruit, which is an oblong fruit several inches long from the scrublike tree Citrus medica. Lemons and limes have high citric acid content, which may account for up to 8% of the fruit's dry weight.Citric acid is a weak acid and loses hydrogen ions from its three carboxyl groups (COOH) in solution.the loss of a hydrogen ion from each group in the molecule results in the citrate ion,C3H5O(COO)33. A citric acid molecule also forms intermediate ions when one or two hydrogen atoms in the carboxyl groups ionize.the citrate ion combines with metals to form salts, the most common of which is calcium citrate. Citric acid forms esters to produce various citrates, for example trimethyl citrate and triethyl citrate.

Chemical Properties

Citric acid is a weak organic acid with the formula C6H8O7. It is a natural preservative / conservative and is also used to add an acidic, or sour, taste to foods and soft drinks. In biochemistry, the conjugate base of citric acid, citrate, is important as an intermediate in the citric acid cycle, which occurs in the metabolism of all aerobic organisms. Citric acid is a commodity chemical, and more than a million tonnes are produced every year by fermentation. It is used mainly as an acidifier, as a flavoring, and as a chelating agent.

Physical properties

CITRIC ACID, white crystalline solid, decomposes at higher temperatures, sp gr 1.542. Citric acid is soluble in H2O or alcohol and slightly soluble in ether. The compound is a tribasic acid, forming mono-, di-, and tri- series of salts and esters.It occurs in large amounts is citrus fruits, and is used widely in industry as an acidifier, as a flavoring and chelating agent. pKa values are 5.21, 4.28 and 2.92 at 25 °C (extrapolated to zero ionic strength).Citric acid is a good buffering agent for solutions between about pH 2 and pH 8. It is popular in many buffers in many techniques, electrophoresis (SSC Buffer #), to stop reactions, for biopurifications, crystallography... In biological systems around pH 7, the two species present are the citrate ion and mono-hydrogen citrate ion. the pH of a 1 mM solution of citric acid will be about 3.2.

Occurrence

Citric acid exists in greater than trace amounts in a variety of fruits and vegetables, most notably citrus fruits. Lemons and limes have particularly high concentrations of the acid; it can constitute as much as 8 % of the dry weight of these fruits (about 47 g/L in the juices ) . The concentrations of citric acid in citrus fruits range from 0.005 mol/L for oranges and grapefruits to 0.30 mol/L in lemons and limes. Within species, these values vary depending on the cultivar and the circumstances in which the fruit was grown.

History

The discovery of citric acid is credited to Jabir ibn Hayyan (Latin name Geber, 721–815). Citric acid was first isolated in 1784 by the Swedish chemist Carl Wilhelm Scheele (1742–1786), who crystallized it from lemon juice.The crystalline structure of anhydrous citric acid, obtained by cooling hot concentrated solution of the monohydrate form, was first elucidated by Yuill and Bennett in 1934 by X-ray diffraction.In 1960 Nordman and co-workers further suggested that in the anhydrous form two molecules of the acid are linked through hydrogen bonds between two –COOH groups of each monomer.

Uses

Different sources of media describe the Uses of 77-92-9 differently. You can refer to the following data:
1. citric acid has astringent and anti-oxidant properties. It can also be used as a product stabilizer, pH adjuster, and preservative with a low sensitizing potential. It is not usually irritating to normal skin, but it can cause burning and redness when applied to chapped, cracked, or otherwise inflamed skin. It is derived from citrus fruits.
2. Citric Acid is an acidulant and antioxidant produced by mold fermentation of sugar solutions and by extraction from lemon juice, lime juice, and pineapple canning residue. it is the predominant acid in oranges, lemons, and limes. it exists in anhydrous and monohydrate forms. the anhydrous form is crystallized in hot solutions and the monohydrate form is crystallized from cold (below 36.5°c) solutions. anhydrous citric acid has a solubility of 146 g and monohydrate citric acid has a solubility of 175 g/100 ml of distilled water at 20°c. a 1% solution has a ph of 2.3 at 25°c. it is a hygroscopic, strong acid of tart flavor. it is used as an acidulant in fruit drinks and carbonated beverages at 0.25-0.40%, in cheese at 3-4%, and in jellies. it is used as an antioxidant in instant potatoes, wheat chips, and potato sticks, where it prevents spoilage by trapping the metal ions. it is used in combination with antioxidants in the processing of fresh frozen fruits to prevent discoloration.

Preparation

By mycological fermentation using molasses and strains of Aspergillus niger; from citrus juices and pineapple wastes

Definition

ChEBI: Citric acid is a tricarboxylic acid that is propane-1,2,3-tricarboxylic acid bearing a hydroxy substituent at position 2. It is an important metabolite in the pathway of all aerobic organisms. It has a role as a food acidity regulator, a chelator, an antimicrobial agent and a fundamental metabolite. It is a conjugate acid of a citrate(1-) and a citrate anion.

Application

Citric acid is a weak organic acid that is known as a commodity chemical, as more than a million tonnes are produced every year by mycological fermentation on an industrial scale using crude sugar sol utions, such as molasses and strains of Aspergillus niger. Citric acid is widely distributed in plants and in animal tissues and fluids and exist in greater than grace amounts in variety of fruits and vegetables, most notably in citrus fruits such as lemon and limes. Citric acid is mainly used as an acidifier, flavoring agent and chelating agent. It was also used as a chemical restrainer particularly in developers for the collodion process and in silver nitrate solutions used for sensitizing salted and albumen papers.

Biotechnological Production

Fermentation is the technology of choice for citric acid synthesis. Different bacteria (e.g. Arthrobacter paraffinens and Bacillus licheniformis), filamentous fungi (e.g. Aspergilus niger and Penicillium citrinum) and yeasts (e.g. Candida tropicalis and Yarrowia lipolytica) are able to produce citric acid. Due to high productivity and easy handling, citric acid is usually produced by fermentation with A. niger. For example, a product concentration of 114 g.L-1 within 168 h has been reached by cultivation of A. niger GCMC 7 on cane molasses . On the industrial scale, submerged cultivation, surface fermentation and solid-state fermentation are used. In general, molasses, starch hydrolyzate and starch are used as substrates. However, there are various studies for alternative raw materials. Solid-state fermentation of inexpensive agricultural wastes is one possibility. For example, high yields up to 88 % have been achieved using grape pomace as substrate. Lowering the cost of product recovery is crucial. Different methods using precipitation, solvent extraction, adsorption, or in situ product recovery have been described. One interesting process could be the in situ crystallization of citric acid during fermentation to improve the economics.

Aroma threshold values

By mycological fermentation using molasses and strains of Aspergillus niger; from citrus juices and pineapple wastes

benefits

Citric acid is not a vitamin or mineral and is not required in the diet. However, citric acid, not to be confused with ascorbic acid (vitamin C), is beneficial for people with kidney stones. It inhibits stone formation and breaks up small stones that are beginning to form. Citric acid is protective; the more citric acid in your urine, the more protected you are against forming new kidney stones. Citrate, used in calcium citrate supplements and in some medications (such as potassium citrate), is closely related to citric acid and also has stone prevention benefits. These medications may be prescribed to alkalinize your urine.

General Description

Citric acid appears as colorless, odorless crystals with an acid taste. Denser than water. (USCG, 1999)

Air & Water Reactions

The pure material is moisture sensitive (undergoes slow hydrolysis) Water soluble.

Reactivity Profile

Citric acid reacts with oxidizing agents, bases, reducing agents and metal nitrates . Reactions with metal nitrates are potentially explosive. Heating to the point of decomposition causes emission of acrid smoke and fumes [Lewis].

Biochem/physiol Actions

Citric acid in dietary form can augments absorption of aluminium in antacids. It also facilitates the phytoremediation of heavy metal contaminated soil and can transform cadmium into more transportable forms.

Biotechnological Applications

Citric acid cycle Citrate, the conjugate base of citric acid is one of a series of compounds involved in the physiological oxidation of fats, proteins, and carbohydrates to carbon dioxide and water. This series of chemical reactions is central to nearly all metabolic reactions, and is the source of two-thirds of the foodderived energy in higher organisms. Hans Adolf Krebs received the 1953 Nobel Prize in Physiology or Medicine for the discovery. The series of reactions is known by various names, including the "citric acid cycle", the "Krebs cycle" or "Szent-Gy?rgyi — Krebs cycle", and the "tricarboxylic acid (TCA) cycle". Other biological roles Citrate is a critical component of bone, helping to regulate the size of calcium crystals.

Safety Profile

Poison by intravenous route. Moderately toxic by subcutaneous and intraperitoneal routes. Mildly toxic byingestion. A severe eye and moderate skin irritant. An irritating organic acid, some allergenic properties. Combustible liquid. Potentially explosive reaction with metal nitrates. When heated to decomposition it emits acrid smoke and fumes.

Check Digit Verification of cas no

The CAS Registry Mumber 77-92-9 includes 5 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 2 digits, 7 and 7 respectively; the second part has 2 digits, 9 and 2 respectively.
Calculate Digit Verification of CAS Registry Number 77-92:
(4*7)+(3*7)+(2*9)+(1*2)=69
69 % 10 = 9
So 77-92-9 is a valid CAS Registry Number.
InChI:InChI=1/C6H8O7/c7-3(8)1-6(13,5(11)12)2-4(9)10/h13H,1-2H2,(H,7,8)(H,9,10)(H,11,12)/p-3

77-92-9 Well-known Company Product Price

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  • Alfa Aesar

  • (A10395)  Citric acid, 99+%   

  • 77-92-9

  • 250g

  • 165.0CNY

  • Detail
  • Alfa Aesar

  • (A10395)  Citric acid, 99+%   

  • 77-92-9

  • 1000g

  • 330.0CNY

  • Detail
  • Alfa Aesar

  • (A10395)  Citric acid, 99+%   

  • 77-92-9

  • 5000g

  • 1317.0CNY

  • Detail
  • Alfa Aesar

  • (36664)  Citric acid, anhydrous, ACS, 99.5+%   

  • 77-92-9

  • 100g

  • 210.0CNY

  • Detail
  • Alfa Aesar

  • (36664)  Citric acid, anhydrous, ACS, 99.5+%   

  • 77-92-9

  • 500g

  • 422.0CNY

  • Detail
  • Alfa Aesar

  • (36664)  Citric acid, anhydrous, ACS, 99.5+%   

  • 77-92-9

  • 2kg

  • 1226.0CNY

  • Detail
  • Sigma-Aldrich

  • (94676)  Citricacid  certified reference material, TraceCERT®

  • 77-92-9

  • 94676-100MG

  • 1,054.17CNY

  • Detail
  • Sigma-Aldrich

  • (PHR1071)  Citric acid, Anhydrous  pharmaceutical secondary standard; traceable to USP and PhEur

  • 77-92-9

  • PHR1071-1G

  • 732.19CNY

  • Detail
  • Sigma-Aldrich

  • (A1202000)  Citricacid  anhydrous, European Pharmacopoeia (EP) Reference Standard

  • 77-92-9

  • A1202000

  • 1,880.19CNY

  • Detail
  • USP

  • (1134368)  Citricacid  United States Pharmacopeia (USP) Reference Standard

  • 77-92-9

  • 1134368-200MG

  • 4,662.45CNY

  • Detail
  • Vetec

  • (V900019)  Citricacid  Vetec reagent grade, 99%

  • 77-92-9

  • V900019-500G

  • 70.20CNY

  • Detail
  • Vetec

  • (V900019)  Citricacid  Vetec reagent grade, 99%

  • 77-92-9

  • V900019-6X500G

  • 351.00CNY

  • Detail

77-92-9SDS

SAFETY DATA SHEETS

According to Globally Harmonized System of Classification and Labelling of Chemicals (GHS) - Sixth revised edition

Version: 1.0

Creation Date: Aug 12, 2017

Revision Date: Aug 12, 2017

1.Identification

1.1 GHS Product identifier

Product name citric acid

1.2 Other means of identification

Product number -
Other names 3'-hydroxybiphenyl-3-carboxylic acid

1.3 Recommended use of the chemical and restrictions on use

Identified uses For industry use only. Antimicrobial Actives;Chelating Agents;Processing Aids and Additives
Uses advised against no data available

1.4 Supplier's details

1.5 Emergency phone number

Emergency phone number -
Service hours Monday to Friday, 9am-5pm (Standard time zone: UTC/GMT +8 hours).

More Details:77-92-9 SDS

77-92-9Synthetic route

3,4-dioxo-adipic acid
533-76-6

3,4-dioxo-adipic acid

citric acid
77-92-9

citric acid

Conditions
ConditionsYield
Stage #1: 3,4-dioxo-adipic acid With N-benzyl-trimethylammonium hydroxide In water at 45℃; for 6h;
Stage #2: With hydrogenchloride In water pH=2.9;
85%
4-methylene-tetrahydro-pyran
36838-71-8

4-methylene-tetrahydro-pyran

A

oxalic acid
144-62-7

oxalic acid

B

citric acid
77-92-9

citric acid

Conditions
ConditionsYield
With nitric acid; dinitrogen tetraoxideA 12%
B 70%
4-methylene-tetrahydro-pyran
36838-71-8

4-methylene-tetrahydro-pyran

citric acid
77-92-9

citric acid

Conditions
ConditionsYield
With nitric acid; dinitrogen tetraoxide 1) 0 deg C, 2 h, 2) 55 deg C, 2 h;55%
4-(Hydroxymethyl)tetrahydro-4-pyranol
87216-17-9

4-(Hydroxymethyl)tetrahydro-4-pyranol

citric acid
77-92-9

citric acid

Conditions
ConditionsYield
With nitric acid at 60℃; for 24h;50%
3-(Hydroxymethyl)-1,3,5-pentanetriol
61565-18-2

3-(Hydroxymethyl)-1,3,5-pentanetriol

citric acid
77-92-9

citric acid

Conditions
ConditionsYield
With nitric acid12%
ethanol
64-17-5

ethanol

citric acid
77-92-9

citric acid

Conditions
ConditionsYield
With citromyces
glyceric acid
473-81-4

glyceric acid

citric acid
77-92-9

citric acid

Conditions
ConditionsYield
durch Aspergillus fumaricus;
durch entarteten Aspergillus fumaricus;
mannitol
69-65-8

mannitol

A

oxalic acid
144-62-7

oxalic acid

B

citric acid
77-92-9

citric acid

Conditions
ConditionsYield
durch Einw. Aspergillus niger, bei Gegenwart von Calciumcarbonat;
durch Einw. von Aspergillus cinnamomeus in Gegenwart von Calciumcarbonat;
durch Einw. von Aspergillus fumaricus in Gegenwart von Calciumcarbonat;
mannitol
69-65-8

mannitol

citric acid
77-92-9

citric acid

Conditions
ConditionsYield
With citromyces
durch Einw.von Aspergillus niger;
durch Einw.von Aspergillus niger japonicus und Aspergillus niger cinnamomeus;
durch entarteten Aspergillus fumaricus;
durch Einw. von Aspergillus japonicus;
mannitol
69-65-8

mannitol

A

D-Fructose
57-48-7

D-Fructose

B

citric acid
77-92-9

citric acid

Conditions
ConditionsYield
beim Vergaeren durch Penicillium crustaceum und P.luteum-purpurogenum;
Conditions
ConditionsYield
durch Einw.von Aspergillus niger;
durch Einw.von Aspergillus niger japonicus und Aspergillus niger cinnamomeus;
D-Galactose
59-23-4

D-Galactose

citric acid
77-92-9

citric acid

Conditions
ConditionsYield
durch Einw.von Aspergillus niger;
durch Einw.von Aspergillus niger japonicus und Aspergillus niger cinnamomeus;
β,β'-dichloro-α-hydroxy-isobutyric acid
855634-60-5

β,β'-dichloro-α-hydroxy-isobutyric acid

potassium cyanide
151-50-8

potassium cyanide

citric acid
77-92-9

citric acid

Conditions
ConditionsYield
nachfolgende Verseifung;
3,4-dioxo-hexanedicarboxylic acid diethyl ester
3249-69-2

3,4-dioxo-hexanedicarboxylic acid diethyl ester

citric acid
77-92-9

citric acid

Conditions
ConditionsYield
With potassium hydroxide
succinic acid
5908-80-5

succinic acid

citric acid
77-92-9

citric acid

Conditions
ConditionsYield
bei der Oxydation durch Hefe;
D-gluconic acid ; calcium salt monohydrate
5743-42-0, 66905-23-5, 126259-97-0

D-gluconic acid ; calcium salt monohydrate

A

oxalic acid
144-62-7

oxalic acid

B

citric acid
77-92-9

citric acid

Conditions
ConditionsYield
bei der Einw.einer Aspergillus niger-Varietaet;
Oxalacetic acid
328-42-7

Oxalacetic acid

citric acid
77-92-9

citric acid

Conditions
ConditionsYield
With sodium carbonate und folgende Oxydation mit H2O2;
ethyl bromoacetate
105-36-2

ethyl bromoacetate

oxalic acid diethyl ester
95-92-1

oxalic acid diethyl ester

citric acid
77-92-9

citric acid

Conditions
ConditionsYield
With magnesium; benzene der Triaethylester entsteht;
With diethyl ether; magnesium der Triaethylester entsteht;
ethyl bromoacetate
105-36-2

ethyl bromoacetate

diethyl oxaloacetate
108-56-5

diethyl oxaloacetate

citric acid
77-92-9

citric acid

Conditions
ConditionsYield
With zinc der Triaethylester entsteht;
(2E)-but-2-enedioic acid
110-17-8

(2E)-but-2-enedioic acid

A

oxalic acid
144-62-7

oxalic acid

B

citric acid
77-92-9

citric acid

Conditions
ConditionsYield
bei der Einw. von Aspergillus niger;
(2E)-but-2-enedioic acid
110-17-8

(2E)-but-2-enedioic acid

citric acid
77-92-9

citric acid

Conditions
ConditionsYield
bei der Einw. von Hirnbrei;
glycerol
56-81-5

glycerol

A

oxalic acid
144-62-7

oxalic acid

B

citric acid
77-92-9

citric acid

Conditions
ConditionsYield
Vergaerung durch Aspergillus japonicus und Aspergillus cinnamomeus;
Vergaerung durch Aspergillus fumaricus;
Vergaerung durch Aspergillus niger;
glycerol
56-81-5

glycerol

citric acid
77-92-9

citric acid

Conditions
ConditionsYield
durch Citromycesarten;
beim Abbau durch Citromyces glaber;
With citromyces
hydrogen cyanide
74-90-8

hydrogen cyanide

diethyl 1,3-acetonedicarboxylate
105-50-0

diethyl 1,3-acetonedicarboxylate

citric acid
77-92-9

citric acid

Conditions
ConditionsYield
Verseifen des entstandenen Produktes erst mit konz. Salzsaeurre, dann mit Natronlauge;
potassium cyanide
151-50-8

potassium cyanide

diethyl 1,3-acetonedicarboxylate
105-50-0

diethyl 1,3-acetonedicarboxylate

citric acid
77-92-9

citric acid

Conditions
ConditionsYield
With diethyl ether ueber mehrere Stufen;
Oxalacetic acid
328-42-7

Oxalacetic acid

3-Hydroxybutyric acid
300-85-6, 625-71-8

3-Hydroxybutyric acid

citric acid
77-92-9

citric acid

Conditions
ConditionsYield
durch Nierencyclophorase unter aeroben Bedingungen;
3-Hydroxybutyric acid
300-85-6, 625-71-8

3-Hydroxybutyric acid

citric acid
77-92-9

citric acid

Conditions
ConditionsYield
Einw. von Rinderhirnbrei unter aeroben Bedingungen;
citric acid
77-92-9

citric acid

benzyl alcohol
100-51-6

benzyl alcohol

tribenzyl citrate
631-25-4

tribenzyl citrate

Conditions
ConditionsYield
toluene-4-sulfonic acid In toluene for 18h; Heating / reflux;100%
With hydrogenchloride In xylene for 12h; Esterification; Heating;95%
at 160 - 165℃;
With hydrogenchloride; xylene
(+)-trans-2-(2-chlorophenyl)-8-(2-hydroxymethyl-1-methyl-pyrrolidin-3-yl)-5,7-dimethoxy-chromen-4-one

(+)-trans-2-(2-chlorophenyl)-8-(2-hydroxymethyl-1-methyl-pyrrolidin-3-yl)-5,7-dimethoxy-chromen-4-one

citric acid
77-92-9

citric acid

(+)-trans-2-(2-chlorophenyl)-8-(2-hydroxymethyl-1-methyl-pyrrolidin-3-yl)-5,7-dimethoxy-chromen-4-one citrate

(+)-trans-2-(2-chlorophenyl)-8-(2-hydroxymethyl-1-methyl-pyrrolidin-3-yl)-5,7-dimethoxy-chromen-4-one citrate

Conditions
ConditionsYield
In methanol100%
In methanol100%
Dutogliptin
852329-66-9

Dutogliptin

citric acid
77-92-9

citric acid

(2R)-1-{7-[(9R)-pyrrolidin-9-ylamino]-acetyl}-pyrrolidine-2-boronic acid citrate

(2R)-1-{7-[(9R)-pyrrolidin-9-ylamino]-acetyl}-pyrrolidine-2-boronic acid citrate

Conditions
ConditionsYield
In isopropyl alcohol at 30℃; for 0.5h;100%
1-(4-dimethylamino-4-phenyl-cyclohexyl)-3-propyl-thiourea

1-(4-dimethylamino-4-phenyl-cyclohexyl)-3-propyl-thiourea

citric acid
77-92-9

citric acid

1-(4-dimethylamino-4-phenyl-cyclohexyl)-3-propyl-thiourea citrate

1-(4-dimethylamino-4-phenyl-cyclohexyl)-3-propyl-thiourea citrate

Conditions
ConditionsYield
In ethanol at 5℃; for 4h;100%
1-(4-dimethylamino-4-phenyl-cyclohexyl)-3-[2-(1H-indol-3-yl)-1-methyl-ethyl]-thiourea

1-(4-dimethylamino-4-phenyl-cyclohexyl)-3-[2-(1H-indol-3-yl)-1-methyl-ethyl]-thiourea

citric acid
77-92-9

citric acid

1-(4-dimethylamino-4-phenyl-cyclohexyl)-3-[2-(1H-indol-3-yl)-1-methyl-ethyl]-thiourea citrate

1-(4-dimethylamino-4-phenyl-cyclohexyl)-3-[2-(1H-indol-3-yl)-1-methyl-ethyl]-thiourea citrate

Conditions
ConditionsYield
In ethanol at 5℃; for 4h;100%
1-[2-(4-dimethylamino-4-phenyl-cyclohexyl)-ethyl]-3-[2-(1H-indol-3-yl)-ethyl]-thiourea

1-[2-(4-dimethylamino-4-phenyl-cyclohexyl)-ethyl]-3-[2-(1H-indol-3-yl)-ethyl]-thiourea

citric acid
77-92-9

citric acid

1-[2-(4-dimethylamino-4-phenyl-cyclohexyl)-ethyl]-3-[2-(1H-indol-3-yl)-ethyl]-thiourea cytrate

1-[2-(4-dimethylamino-4-phenyl-cyclohexyl)-ethyl]-3-[2-(1H-indol-3-yl)-ethyl]-thiourea cytrate

Conditions
ConditionsYield
In ethanol at 5℃; for 4h;100%

77-92-9Relevant articles and documents

-

Warneford,Hardy

, (1926)

-

Discovery and Biosynthesis of Bolagladins: Unusual Lipodepsipeptides from Burkholderia gladioli Clinical Isolates**

Challis, Gregory L.,Dashti, Yousef,Jian, Xinyun,Mahenthiralingam, Eshwar,Mullins, Alex J.,Nakou, Ioanna T.,Webster, Gordon

, (2020)

Two Burkholderia gladioli strains isolated from the lungs of cystic fibrosis patients were found to produce unusual lipodepsipeptides containing a unique citrate-derived fatty acid and a rare dehydro-β-alanine residue. The gene cluster responsible for the

SYNTHESIS OF 4-(HYDROXYMETHYL)TETRAHYDRO-4-PYRANOL - A NEW INTERMEDIATE FOR THE PREPARATION OF SYNTHETIC CITRIC ACID

Gevorkyan, A. A.,Kazaryan, P. I.,Sargysyan, M. S.,Petrosyan, K. A.,Mkrtumyan, S. A.

, p. 712 - 713 (1983)

The hydroxylation of 4-methylenetetrahydropyran with hydrogen peroxide in the presence of various acidic catalysts was investigated.The oxidation of 4-(hydroxymethyl)tetrahydro-4-pyranol with concentrated nitric acid leads to citric acid in 50percent yield.

Absolute stereochemical course of the 3-carboxymuconate cycloisomerases from Pseudomonas putida and Acinetobacter colcoaceticus: Analysis and implications

Chari,Whitman,Kozarich,et al.

, p. 5514 - 5519 (1987)

The absolute stereochemical course of the 3-carboxymuconate cycloisomerases [EC 5.5.1.2; 2-carboxy-5-oxo-2,5-dihydrofuran-2-acetate lyase (decyclizing)] from Pseudomonas putida and Acinetobacter calcoaceticus has been determined by chemical and 1H NMR methods. The product of the enzyme-catalyzed reaction in 2H2O was detected by NMR and trapped by catalytic hydrogenation to afford 5-[2H]homocitrate lactone. Subsequent chemical degradation of the monodeuteriated homocitrate lactone gave (2r,3S)-2-[2H]citrate as determined by 1H NMR analysis. The product of the cycloisomerase reaction was established as (4R,5R)-5-[2H]-4-carboxymuconate, indicating that the lactonization proceeded by an anti addition - the mechanistic and stereochemical antipode of the previously studied muconate cycloisomerase from P. putida and 3-carboxymuconate cycloisomerase from Neurospora crassa. The anti addition probably represents the lower energy pathway for the reaction and suggests that the evolutionary relationship between the two classes of cycloisomerases is more remote than previously believed.

Kusnetzow

, p. 341 (1925)

Stern et al.

, (1956)

Cyanide as a primordial reductant enables a protometabolic reductive glyoxylate pathway

Krishnamurthy, Ramanarayanan,Pulletikurti, Sunil,Yadav, Mahipal,Yerabolu, Jayasudhan R.

, p. 170 - 178 (2022/02/11)

Investigation of prebiotic metabolic pathways is predominantly based on abiotically replicating the reductive citric acid cycle. While attractive from a parsimony point of view, attempts using metal/mineral-mediated reductions have produced complex mixtures with inefficient and uncontrolled reactions. Here we show that cyanide acts as a mild and efficient reducing agent mediating abiotic transformations of tricarboxylic acid intermediates and derivatives. The hydrolysis of the cyanide adducts followed by their decarboxylation enables the reduction of oxaloacetate to malate and of fumarate to succinate, whereas pyruvate and α-ketoglutarate themselves are not reduced. In the presence of glyoxylate, malonate and malononitrile, alternative pathways emerge that bypass the challenging reductive carboxylation steps to produce metabolic intermediates and compounds found in meteorites. These results suggest a simpler prebiotic forerunner of today’s metabolism, involving a reductive glyoxylate pathway without oxaloacetate and α-ketoglutarate—implying that the extant metabolic reductive carboxylation chemistries are an evolutionary invention mediated by complex metalloproteins. [Figure not available: see fulltext.].

Catalytic Oxidation of VOCs over SmMnO3 Perovskites: Catalyst Synthesis, Change Mechanism of Active Species, and Degradation Path of Toluene

Liu, Lizhong,Sun, Jiangtian,Ding, Jiandong,Zhang, Yan,Jia, Jinping,Sun, Tonghua

, p. 14275 - 14283 (2019/10/17)

Highly active samarium manganese perovskite oxides were successfully prepared by employing self-molten-polymerization, coprecipitation, sol-gel, and impregnation methods. The physicochemical properties of perovskite oxides were investigated by XRD, N2 adsorption-desorption, XPS, and H2-TPR. Their catalytic performances were compared via the catalytic oxidation of toluene. The perovskite prepared by self-molten-polymerization possessed the highest catalytic capacity, which can be ascribed to its higher oxygen adspecies concentration (Olatt/Oads = 0.53), higher surface Mn4+/Mn3+ ratio (Mn4+/Mn3+ = 0.95), and best low-temperature reducibility (H2 consumption = 0.27; below 350 °C). The most active catalyst also exhibited good cycling and long-term stability for toluene oxidation. After a multistep cycle reaction and a long-term reaction of 42 h, the toluene conversion maintained above 99.9% at 270 °C. Mechanistic study hinted that lattice oxygen was involved in toluene oxidation. The oxidation reaction was dependent on the synergism of lattice oxygen, adsorbed oxygen, and oxygen vacancies. The degradation pathway of toluene, researched by diffuse reflectance infrared Fourier transform spectroscopy and online mass spectrometry technologies, demonstrated that a series of organic byproducts existed at a relatively low temperature. This work provides an efficient and practical method for selecting highly active catalysts and for exploring the catalytic mechanism for the removal of atmospheric environmental pollution.

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