Oxalic acid, ออกซาลิกแอซิด, กรดออกซาลิก

กรดออกซาลิก, ออกซลิกแอซิด, Oxalic acid

กรดออกซาลิก (อังกฤษ: Oxalic Acid) เป็นสารประกอบอินทรีย์ซึ่งมีสูตรโมเลกุล H2C2O4 และมีความเป็นกรดสูงกว่ากรดน้ำส้ม (อังกฤษ: Acetic Acid) 10000 เท่า เมื่ออยู่ในรูปของประจุจะเรียกว่า ออกซาเลต (oxalate) ซึ่งเป็นตัวรีดิวส์ ที่ดีเหมือนกับหมู่ลิแกนด์ (ligand) ในสารประกอบเชิงซ้อน โลหะไอออนจะไม่ละลายน้ำเมื่อรวมกับออกซาเลต เช่น แคลเซียมออกซาเลต (อังกฤษ: Calcium Oxalate) ซึ่งเป็นนิ่วที่พบในไต กรดออกซาลิกมีมวลโมเลกุล 90.03 g/mol (anhydrous) ความหนาแน่น 1.90 g/cm? (dehydrate) จุดหลอมเหลว 101-102 ?C (dehydrate) กรดออกซาลิกสามารถเตรียมได้จากการออกซิไดซ์น้ำตาลกลูโคสด้วยกรดไนตริก โดยมี vanadium pentoxide เป็นตัวเร่งปฏิกิริยา

หรือในระดับอุตสาหกรรมที่ต้องการผลิตในปริมาณที่มากจะใช้ โซเดียมไฮดรอกไซด์

ที่ร้อนดูดรับก๊าซ คาร์บอนมอนออกไซด์ ภายใต้ความดันสูงซึ่งจะได้ โซเดียมออกซาเลต

เป็นผลิตภัณฑ์ กรดออกซาลิกจะทำปฏิกิริยาให้สารประกอบ carboxylic acid อื่นๆเช่น สารประกอบ ester (dimethyloxalate), สารประกอบ acid chloride (oxalyl chloride) เป็นต้น ออกซาเลต (oxalate) ซึ่งเป็นคู่เบส (conjugate base) ของกรดออกซาลิก ยังเป็นลิแกนด์ที่ดีในการเกิดสารประกอบเชิงซ้อน โดยมีลักษณะเป็น bidentate ligand ซึ่งจะให้ 2 อิเล็กตรอนและจับกลุ่มเป็นวง 5 เหลี่ยม (MO2C2) เช่น potassium ferrioxalate, K3[Fe (C2O4) 3] หรือเป็นยา Oxaliplatin โดยมีโลหะอะตอมกลางเป็นแพลทินัม ใช้ในทางเคมีบำบัดให้กับผู้ป่วยโรคมะเร็ง

กรดออกซาลิกจะพบมากในพืช เช่น พืชตระกูล Sorrel ในกลุ่ม Oxalis หรือที่รู้จักกันคือ ส้มกบ หรือหญ้าเกล็ดหอยจีน

กรดออกซาลิก   (Oxalic acid)   มีสูตรทางเคมีคือ  C2 H2 O4  พบได้ในอาหารทั่วไป    เมื่อรับประทานอาหารที่มี  Oxalic  acid  เข้าสู่ร่างกาย  จะไปรวมกับแร่ธาตุอื่น กลายเป็นผลึกออกซาเลต   เช่น  แคลเซียมออกซาเลต  โซเดียมออกซาเลต  แมกนีเซียมออกซาเลต  และโปแตสเซียมออกซาเลต  โดยเฉพาะผลึกของแคลเซียมออกซาเลต  เกิดได้ง่ายถ้าร่างกายได้รับแคลเซียม และ Oxalic  acid  จากอาหารมากเกินไป   ปริมาณ Oxalic  acid ที่รับประทานได้แต่ละวันโดยไม่มีความเสี่ยงนั้นมีบอกไว้ว่าประมาณ  22 กรัม สำหรับคนที่มีน้ำหนักตัว 60  กิโลกรัม  หรือประมาณ 378 มิลลิกรัม/น้ำหนักตัว 1 กิโลกรัม คุณสมบัติของ Oxalic Acid คือเป็นตัวจับสนิมและไม่ทำลายโลหะ

Oxalic

acid is an organic compound with the formula H2C2O4. It is a colorless

crystalline solid that dissolves in water to give colorless solutions. It is

classified as a dicarboxylic acid. In terms of acid strength, it is much

stronger than acetic acid. Oxalic acid is a reducing agent and its conjugate

base, known as oxalate (C2O42?),

is a chelating agent for metal cations. Typically, oxalic acid occurs as the

dihydrate with the formula H2C2O4?2H2O. Oral consumption of oxalic acid in

excess or prolonged skin contact can be dangerous.

Biochemistry

The

conjugate base of oxalic acid (oxalate) is a competitive inhibitor of the

lactate dehydrogenase(LDH) enzyme. LDH catalyses the conversion of pyruvate to

lactic acid (End product of the Fermentation (Anaerobic) Process) oxidising the

coenzyme NADH to NAD+ and H+ concurrently. Restoring NAD+ levels are essential

to the continuation of anaerobic energy metabolism through glycolysis. As

cancer cells preferentially use anaerobic metabolism (see Warburg effect) inhibition

of LDH has been shown to inhibit tumor formation and growth, thus is an

interesting potential course of cancer treatment.

Applications

About

25% of produced oxalic acid is used as a mordant in dyeing processes. It is

used in bleaches, especially for pulpwood. It is also used in baking powder.

Cleaning

Oxalic

acid's main applications include cleaning or bleaching, especially for the

removal of rust (iron complexing agent), e.g. Bar Keepers Friend is an example

of a household cleaner containing oxalic acid. Its utility in rust removal

agents is due to its forming a stable, water soluble salt with ferric iron,

ferrioxalate ion.

Extractive metallurgy

Oxalic

acid is an important reagent in lanthanide chemistry. Hydrated lanthanide

oxalates form readily in strongly acidic solutions in a densely crystalline,

easily filtered form, largely free of contamination by nonlanthanide elements.

Thermal decomposition of these oxalate gives the oxides, which is the most

commonly marketed form of these elements.

Niche uses

Vaporized

oxalic acid, or a 3.2% solution of oxalic acid in sugar syrup, is used by some

beekeepers as a miticide against the parasitic varroa mite. Oxalic acid is

rubbed onto completed marble sculptures to seal the surface and introduce a

shine. Oxalic acid is also used to clean iron and manganese deposits from

quartz crystals.

Toxicity and safety

Oxalic

acid has toxic effects through contact and if ingested; manufacturers provide

details in Material Safety Data Sheets (MSDS). It is not identified as

mutagenic or carcinogenic; there is a possible risk of congenital malformation

in the foetus; may be harmful if inhaled, and extremely destructive to tissue

of mucous membranes and upper respiratory tract; harmful if swallowed and

causes burns; harmful, destructive of tissue and causes burns if absorbed

through skin or in contact with the eyes. Symptoms and effects include burning

sensation, cough, wheezing, laryngitis, shortness of breath, spasm,

inflammation and oedema of the larynx, inflammation and oedema of the bronchi,

pneumonitis, pulmonary oedema. In humans, ingested oxalic acid has an oral LDLo

(lowest published lethal dose) of 600 mg/kg. It has been reported that the

lethal oral dose is 15 to 30 grams. The toxicity of oxalic acid is due to kidney

failure, which arises because it causes precipitation of solid calcium

oxalate,[21] the main component of kidney stones. Oxalic acid can also cause

joint pain due to the formation of similar precipitates in the joints.

Ingestion of ethylene glycol results in oxalic acid as a metabolite which can

also cause acute kidney failure. Oxalic acid is a chemical compound that has

the simplest structure of all dicarboxylic acids. The salt of this ubiquitous

acid is called oxalate (ethanedioate).

History

of oxalic acid: Oxalic acid was first discovered in 1769 by the German

pharmacist Johann Christian Wiegleb in the plant Oxalis (Oxalis acetosella,

from which the name "oxalic acid" is derived). It was synthesized

from inorganic compounds by the chemist Friedrich W?hler in 1924.

DICARBOXYLIC  ACIDS

Although

the dicarboxylic acids do not occur in appreciable amounts as components of

animal or vegetal lipids, they are in general important metabolic products of

fatty acids since they originate from them by oxidation. Dicarboxylic acids are

suitable substrates for preparation of organic acids for the pharmaceutical and

food industries. Furthermore, they are useful materials for the preparation of

fragrances, polyamides, adhesives, lubricants, and polyesters. They have the

general type formula HOOC-(CH2)n-COOH

In

vegetal, a great variety of molecular forms of dicarboxylic acids are found :

simple forms with a straight carbon chain or a branched chain complex forms

with a dicarboxylic acid and an alkyl side chain : alkylitaconates 1 - Simple

forms of dicarboxylic acids Short-chain dicarboxylic acids are of great

importance in the general metabolism and up to n=3 they cannot be considered as

lipids since their water solubility is important. The simplest of these

intermediates is oxalic acid (n=0), the others are malonic (n=1), succinic

(n=2) and glutaric (n=3) acids. Local: 

Oxalic Acid (also called Ethanedioic Acid) is a colourless, crystalline,

toxic organic compound belonging to the family of dicarboxylic acids; melting

at 187 C; soluble in water, alcohol, and ether. It occurs in the form of its

metal salts (usually calcium or potassium) in many plants. It is commercially

manufactured by heating sodium formate in the presence of an alkali catalyst to

form sodium oxalate, which should be converted to free oxalic acid when treated

with sulfuric acid. It is also prepared by oxidizing carbohydrates with nitric

acid, by heating saw dust with caustic alkalies or by fermentation of sugar

solutions in the presence of certain molds. Oxalic acid is the only possible

compound in which two carboxyl groups are joined directly; for this reason

oxalic acid is one of the strongest acids in organic compounds. Unlike other

carboxylic acids, oxalic acid (and formic acid) is readily oxidized and combine

with calcium, iron, sodium, magnesium, or potassium to form less soluble salts

called oxalates. Oxalic acid and oxalates are useful as reducing agents for

photography, bleaching, and rust removal. They are widely used as an purifying

agent in pharmaceutical industry, precipitating agent in rare-earth metal

processing, bleaching agent in textile and wood industry, rust-remover for

metal treatment, grinding agent, waste water treatment. acid rinse in laundries

and removing scale from automobile radiators. Applications: Purifying agent,

Precipitating agent, Bleaching agent, Metal treatment, Grinding agent, Waste

water treatment, Reducing agent

Dicarboxylic

acid is a compound containing two carboxylic acid, -COOH, groups. Straight

chain examples are shown in table. The general formula is HOOC(CH2)nCOOH, where

oxalic acid's n is 0, n=1 for malonic acid, n=2 for succinic acid, n=3 for

glutaric acid, and etc. In substitutive nomenclature, their names are formed by

adding -dioic' as a suffix to the name of the parent compound. They can yield

two kinds of salts, as they contain two carboxyl groups in its molecules. The

range of carbon chain lengths is from 2, but the longer than C 24 is very rare.

The term long chain refers to C 12 up to C 24 commonly. Carboxylic acids have

industrial application directly or indirectly through acid halides, esters,

salts, and anhydride forms, polymerization, and etc. Dicarboxylic acids can

yield two kinds of salts or esters, as they contain two carboxyl groups in one

molecule. It is useful in a variety of industrial applications include;

Plasticizer for polymers

Biodegradable solvents and lubricants

Engineering plastics

Epoxy curing agent

Adhesive and powder coating

Corrosion inhibitor

Perfumery and pharmaceutical

Electrolyte

There

are almost infinite esters obtained from carboxylic acids. Esters are formed by

removal of water from an acid and an alcohol. Carboxylic acid esters are used

as in a variety of direct and indirect applications. Lower chain esters are used

as flavouring base materials, plasticizers, solvent carriers and coupling

agents. Higher chain compounds are used as components in metalworking fluids,

surfactants, lubricants, detergents, oiling agents, emulsifiers, wetting agents

textile treatments and emollients, They are also used as intermediates for the

manufacture of a variety of target compounds. The almost infinite esters

provide a wide range of viscosity, specific gravity, vapor pressure, boiling

point, and other physical and chemical properties for the proper application

selections.

Specifications

colorless

transparent crystal, melting point:101degree.Easily soluble in ethanol, soluble

in water, slightly soluble in aether

uses:

Metallurgy industry :As precipitating and resolving agent for rare earth metal, etc.

Organic Synthesis:For 2133 rein,ures form aldehyde powder etc.

Light

industry:Polishing of DA LI stone, removing rust bleaching products of leather,

wood and aluminium etc.

Printing Industry: Dyeing agent

Medicine Industry: For making tetracydine ,HCl etc.

Others:

As laboratory agent, solvents activato and basic materials for chemical

industry.

Usage

2 : Pharmaceutical industry,precipitating agent of rare earth

elements,bleaching,metal and marble polish,cleanser removing stains,tanning industry,printing

and dyeing catalytic agent,anti-shrinkage finishing of paper,manufacturing

oxalates.

What Oxalic Acid Is

Oxalic

acid is, of course, a chemical substance. At high concentrations, it is a

dangerous poison, but such immediately toxic levels are not found in foodstuffs

but rather in manufactures, such as some bleaches, some anti-rust products, and

some metal cleaners (among other things). It is also a naturally occurring

component of plants, and is found in relatively high levels in dark-green leafy

foods (relatively high, though, is just that).

The

chemical formula for oxalic acid is C2O2(OH)2. An acid (from the Latin acidus,

meaning "sour") is typically a corrosive substance with a sharp, sour

taste (but tasting an acid can be extremely dangerous, depending on its

strength). Acids can range from very mild to very strong, and a given type of

acid can be made weaker by diluting it (with, for example, water). Oxalic acid

is inherently a strong acid: it is about 3,000 times stronger than acetic acid,

which is the chemical name for the acid in ordinary vinegar (usually sold as

around a 5% solution of acetic acid). Oxalic acid is so strong that it is

widely used industrially for bleaching and heavy-duty cleaning, notably for

rust removal. If oxalic acid is not heavily diluted--as it is in plants--it is

quite dangerous to humans, being both toxic and corrosive.

The

effects of oxalic acid in the human body, when ingested in foods, flow from its

ability to combine chemically with certain metals commonly found in--and

important to--the human body, such as magnesium and calcium. When oxalic acid

combines with such metals, the result is, in chemical terms, a "salt"

(table salt is just one specimen of the general class of salts); those

oxalic-acid+metal salts are called oxalates. Since oxalic acid is not (so far

as is known today) a useful nutrient, it is--like all such unneeded components

of diet--processed by the body to a convenient form, those oxalates, and that

byproduct is then eventually excreted--in this case, in the urine.

Oxalic Acid

C2H2O4,2H2O Mol. Wt. 126.07

Ethanedioic acid  6153-56-6

Content Oxalic Acid contains 99.5 101.0% of oxalic acid (C2H2O4.2H2O).

Description Oxalic Acid occurs as colorless crystals. It is odorless.

Usage 2 :

Descaling,

bleaching, printing and dyeing, clean buildings, cleaning,metal and marble,

etc. Also used as antioxidant in food manufacturing.

 

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