Glyoxylic Acid Vs Glycolic Acid | Detailed Comparison

Glyoxylic acid vs glycolic acid, although these two substances have similar names, they are quite different in many aspects. Glyoxylic acid is present in the synthetic flavors we use and the medicines we eat. Besides, it can also serve as a water quality stabilizer. Glycolic acid can produce water disinfectants, boiler descaling agents, etc. It is even an ingredient in the treatment of liver cancer.

Glyoxylic Acid Vs Glycolic Acid: What Are the Differences in Molecular Structure?

1.Glyoxylic Acid

It contains aldehyde groups, which are functional groups with strong reactivity. They can give glyoxylic acid some typical properties of aldehydes. For example, it can undergo silver mirror reactions and react with newly prepared copper hydroxide suspensions. It can be oxidized to carboxyl groups or reduced to hydroxyl groups under certain conditions.

The molecule also contains carboxyl groups. It makes glyoxylic acid and can undergo neutralization reactions with bases, esterification reactions with alcohols, etc. Besides, there can also be a series of reactions related to carboxyl groups, such as decarboxylation reactions.

2.Glycolic Acid

Its carboxyl group has acidity and can undergo acid-base neutralization reactions, reacting with bases to form salts and water. It can undergo an esterification reaction with alcohol to produce ester compounds. It can also undergo decarboxylation reactions, etc.

In its molecules, carboxyl groups give the molecule a certain acidity, which is slightly stronger than acetic acid. This is because the electron-withdrawing effect of hydroxyl groups makes it easier for carboxyl groups to ionize hydrogen ions.

Its hydroxyl group has the properties of an alcohol and can undergo an esterification reaction with carboxylic acids to produce corresponding esters. It can react with active metals to release hydrogen gas. Besides, it can undergo oxidation reactions and be oxidized to aldehyde or carboxyl groups under certain conditions.

Glyoxylic Acid Vs Glycolic Acid: What Are the Differences in Physical Features?

They have different colors and smells. Glyoxylic acid is generally white and has a less friendly smell. Meanwhile, glycolic acid has no color and smells like burnt candy. Although their boiling points are similar, their melting points are different. The former melts at 98℃, while the latter melts at 79℃.

Glyoxylic Acid Vs Glycolic Acid: What Are the Differences in Production?

1.Glyoxylic Acid

Below is the process of this substance by formaldehyde oxidation.

-Nitric Acid Oxidation Method

The first method is to use nitric acid oxidation. We use nitric acid as an oxidant. Firstly, set the reaction temperature at 30-50℃, adjust the concentration of nitric acid appropriately, and oxidize glyoxal to form glyoxylic acid. But this method has some drawbacks.

During the reaction process, many harmful gases, such as nitrogen oxides, are generated. Therefore, complex exhaust gas treatment equipment is required to treat these by-products. In addition, the reaction conditions are relatively harsh and require high corrosion resistance of the equipment.

-Hydrogen Peroxide for Oxidation Method

The second method is to use hydrogen peroxide as an oxidant. This reaction needs to be carried out in the presence of a catalyst.

Using tungstic acid or other transition metal compounds as catalysts, and controlling the reaction temperature and pressure within a certain range, glyoxal will undergo an oxidation reaction with hydrogen peroxide to produce glyoxylic acid. The biggest advantage of this method is that the main byproduct of the reaction is water. Therefore, it has minimal environmental harm.

2.Glycolic Acid

Below are the two methods for producing this substance.

-Formaldehyde And Carbon Monoxide Coupling Method

This method requires high temperature, high pressure, and a catalyst. We can use transition metal complexes as catalysts and set the reaction temperature to around 200℃. At pressures ranging from tens to hundreds of atmospheres, formaldehyde and carbon monoxide will react to produce glycolic acid.

This method has a very high utilization rate for atoms and is a method good for the environment. However, the reaction conditions are harsh every time. Due to the need for special high-pressure reaction equipment and efficient catalysts, the production cost will be very high.

-Biological Method

This method utilizes the catalytic action of microorganisms or enzymes to convert some organic compounds into glycolic acid. We can place certain bacteria in specific culture media and use sugars and other substrates to produce glycolic acid through metabolic pathways.

Firstly, we can screen microbial strains that can efficiently synthesize glycolic acid. Then, let the microorganisms ferment in the fermentation tank under appropriate fermentation conditions. The organisms utilize substrates for growth metabolism, converting substrates into glycolic acid during the fermentation process.

The reaction conditions of biological methods are mild and have minimal environmental harm. However, its product separation and purification process are relatively complex. Therefore, it has low production efficiency.

Conclusion

Glyoxylic acid vs glycolic acid, this article explains their differences in three aspects. They have different molecular structures, so they present different physical features. You can refer to the methods listed above if you want to produce them.