Glyoxylic acid
Encyclopedia
Glyoxylic acid or oxoacetic acid is an organic compound
. Together with acetic acid, glycolic acid
, and oxalic acid, glyoxylic acid is one of the C2 carboxylic acid
s. It is a colourless solid that occurs naturally and is useful industrially.
OCHCO2H, i.e. containing an aldehyde
functional group
(see image in upper right). In fact the aldehyde is not observed in solution or as a solid. In general aldehydes with electron-withdrawing substituents often exist mainly as their hydrate. Thus, the formula for glyoxylic acid is really (HO)2CHCO2H, described as the "monohydrate." This diol
exists in equilibrium with the dimeric hemiacetal in solution: Henry's law constant of glyoxylic acid is KH = 1.09 × 104 × exp[(40.0 × 103/R) × (1/T − 1/298)] .
with hot nitric acid
, the main side product being oxalic acid. Ozonolysis
of maleic acid
is also effective.
The conjugate base of gloxylic acid is known as glyoxylate and is the form that the compound exists in solution at neutral pH. Glyoxylate is an intermediate of the glyoxylate cycle
, which enables organism
s, such as bacteria, fungi, and plants to convert fatty acid
s into carbohydrate
s. Glyoxylate is the byproduct of the amidation process in biosynthesis of several amidated peptides.
of 4.7 × 10−4:2CHCOOH
(HO)2CHCO2− + H+
With base, glyoxylic acid disproportionates
:
Even though the aldehyde is a very minor component of its solutions, glyoxylic acid behaves as an aldehyde in its reactions. For example, it gives heterocycles upon condensation
with urea
and 1,2-diaminobenzene.
. This species reacts with ammonia to give hydroxyphenylglycine, a precursor to the drug amoxicillin
. Reduction of the 4-hydroxymandelic acid gives 4-hydroxyphenylacetic acid
, a precursor to the drug atenolol. Condensations with guaiacol
in place of phenol provides a route to vanillin
, a net formylation.
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
. Together with acetic acid, glycolic acid
Glycolic acid
Glycolic acid is the smallest α-hydroxy acid . This colorless, odorless, and hygroscopic crystalline solid is highly soluble in water. It is used in various skin-care products. Glycolic acid is found in some sugar-crops...
, and oxalic acid, glyoxylic acid is one of the C2 carboxylic acid
Carboxylic acid
Carboxylic acids are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group...
s. It is a colourless solid that occurs naturally and is useful industrially.
Structure and nomenclature
Glyoxylic acid is usually described with the chemical formulaChemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
OCHCO2H, i.e. containing an aldehyde
Aldehyde
An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....
functional group
Functional group
In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction regardless of the size of the molecule it is a part of...
(see image in upper right). In fact the aldehyde is not observed in solution or as a solid. In general aldehydes with electron-withdrawing substituents often exist mainly as their hydrate. Thus, the formula for glyoxylic acid is really (HO)2CHCO2H, described as the "monohydrate." This diol
Diol
A diol or glycol is a chemical compound containing two hydroxyl groups A geminal diol has two hydroxyl groups bonded to the same atom...
exists in equilibrium with the dimeric hemiacetal in solution: Henry's law constant of glyoxylic acid is KH = 1.09 × 104 × exp[(40.0 × 103/R) × (1/T − 1/298)] .
- 2 (HO)2CHCO2H
O[(HO)CHCO2H]2 + H2O
Preparation
The compound is formed by organic oxidation of glyoxalGlyoxal
Glyoxal is an organic compound with the formula OCHCHO. This yellow colored liquid is the smallest dialdehyde . Its tautomer acetylenediol is unstable.-Production:...
with hot nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
, the main side product being oxalic acid. Ozonolysis
Ozonolysis
Ozonolysis is the cleavage of an alkene or alkyne with ozone to form organic compounds in which the multiple carbon–carbon bond has been replaced by a double bond to oxygen...
of maleic acid
Maleic acid
Maleic acid is an organic compound that is a dicarboxylic acid, a molecule with two carboxyl groups. Maleic acid is the cis-isomer of butenedioic acid, whereas fumaric acid is the trans-isomer...
is also effective.
The conjugate base of gloxylic acid is known as glyoxylate and is the form that the compound exists in solution at neutral pH. Glyoxylate is an intermediate of the glyoxylate cycle
Glyoxylate cycle
The glyoxylate cycle, a variation of the Tricarboxylic Acid Cycle, is an anabolic metabolic pathway occurring in plants, bacteria, protists, fungi and several microorganisms, such as E. coli and yeast. The glyoxylate cycle centers on the conversion of acetyl-CoA to succinate for the synthesis of...
, which enables organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...
s, such as bacteria, fungi, and plants to convert fatty acid
Fatty acid
In chemistry, especially biochemistry, a fatty acid is a carboxylic acid with a long unbranched aliphatic tail , which is either saturated or unsaturated. Most naturally occurring fatty acids have a chain of an even number of carbon atoms, from 4 to 28. Fatty acids are usually derived from...
s into carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...
s. Glyoxylate is the byproduct of the amidation process in biosynthesis of several amidated peptides.
Reactions and uses
Glyoxylic acid is about 10x stronger acid than acetic acid, with an acid dissociation constantAcid dissociation constant
An acid dissociation constant, Ka, is a quantitative measure of the strength of an acid in solution. It is the equilibrium constant for a chemical reaction known as dissociation in the context of acid-base reactions...
of 4.7 × 10−4:2CHCOOH
(HO)2CHCO2− + H+With base, glyoxylic acid disproportionates
Disproportionation
Disproportionation, also known as dismutation is used to describe a specific type of redox reaction in which a species is simultaneously reduced and oxidized so as to form two different products....
:
- 2 OCHCOOH + H2O → HOCHCOOH + HOOC–COOH
Even though the aldehyde is a very minor component of its solutions, glyoxylic acid behaves as an aldehyde in its reactions. For example, it gives heterocycles upon condensation
Condensation reaction
A condensation reaction is a chemical reaction in which two molecules or moieties combine to form one single molecule, together with the loss of a small molecule. When this small molecule is water, it is known as a dehydration reaction; other possible small molecules lost are hydrogen chloride,...
with urea
Urea
Urea or carbamide is an organic compound with the chemical formula CO2. The molecule has two —NH2 groups joined by a carbonyl functional group....
and 1,2-diaminobenzene.
Phenol derivatives
Its condensation with phenols is versatile. The immediate product is 4-hydroxymandelic acidMandelic acid
Mandelic acid is an aromatic alpha hydroxy acid with the molecular formula C6H5CHCO2H. It is a white crystalline solid that is soluble in water and polar organic solvents. It is a useful precursor to various drugs...
. This species reacts with ammonia to give hydroxyphenylglycine, a precursor to the drug amoxicillin
Amoxicillin
Amoxicillin , formerly amoxycillin , and abbreviated amox, is a moderate-spectrum, bacteriolytic, β-lactam antibiotic used to treat bacterial infections caused by susceptible microorganisms. It is usually the drug of choice within the class because it is better absorbed, following oral...
. Reduction of the 4-hydroxymandelic acid gives 4-hydroxyphenylacetic acid
Phenylacetic acid
Phenylacetic acid is an organic compound containing a phenyl functional group and a carboxylic acid functional group. It is a white solid with a disagreeable odor...
, a precursor to the drug atenolol. Condensations with guaiacol
Guaiacol
Guaiacol is a naturally occurring organic compound with the formula C6H4. Although it is biosynthesized by a variety of organisms, this colorless aromatic oil is usually derived from guaiacum or wood creosote. Samples darken upon exposure to air and light. Guaiacol is present in wood smoke,...
in place of phenol provides a route to vanillin
Vanillin
Vanillin is a phenolic aldehyde, an organic compound with the molecular formula C8H8O3. Its functional groups include aldehyde, ether, and phenol. It is the primary component of the extract of the vanilla bean. It is also found in Leptotes bicolor, roasted coffee and the Chinese red pine...
, a net formylation.