The key difference between glyceraldehyde and dihydroxyacetone is that glyceraldehyde is an aldehyde, whereas dihydroxyacetone is a ketone.
Both glyceraldehyde and dihydroxyacetone are simple carbohydrates. Both these compounds have the same chemical formula C3H6O3. But, their structures and functional groups are different from each other. Therefore, there is a difference between glyceraldehyde and dihydroxyacetone in terms of reactivity as well.
CONTENTS
1. Overview and Key Difference
2. What is Glyceraldehyde
3. What is Dihydroxyacetone
4. Similarities Between Glyceraldehyde and Dihydroxyacetone
5. Side by Side Comparison – Glyceraldehyde vs Dihydroxyacetone in Tabular Form
6. Summary
What is Glyceraldehyde?
Glyceraldehyde is a simple aldehyde which is a carbohydrate. It is a triose monosaccharide. That means; it has three carbon atoms (triose), and it is a basic unit of sugars (monosaccharide). Its chemical formula is C3H6O3. It is an aldose and the simplest among aldoses. An aldose is a monosaccharide having an aldehyde group at the end of the carbon chain. Since it is a monosaccharide, glyceraldehyde is sweet tasting.
Moreover, it is a colourless and crystalline solid. We can find it as an intermediate compound in carbohydrate metabolism. The name glyceraldehyde comes from the combination of two terms: glycerol + aldehyde. The molar mass of this compound is 90.07 g/mol. Moreover, its melting point and the boiling point are 145 °C and 150 °C, respectively.
Figure 01: Glyceraldehyde
There are two stereoisomers of glyceraldehyde because it has a chiral carbon atom. The two structures are named as enantiomers. In the laboratory, we can prepare this compound from the mild oxidation of glycerol. It will give both glyceraldehyde and dihydroxyacetone. For this oxidation, we can use hydrogen peroxide and a catalyst such as a ferrous salt.
What is Dihydroxyacetone?
Dihydroxyacetone is a simple ketone which is a carbohydrate. A synonym for this compound is glycerone. It is a triose, meaning it has three carbon atoms. The chemical formula is C3H6O3 while the molar mass is 90.07 g/mol. Its melting point can range from 89 to 91 °C. Further, this compound is hygroscopic and appears as a white crystalline powder. Dihydroxyacetone has a sweet, cooling taste. It also has a characteristic odour. Unlike glyceraldehyde, this compound does not have a chiral centre, therefore no enantiomers. This means it is optically-inactive. Usually, this compound exists in a dimer form.
Figure 02: Dihydroxyacetone
Furthermore, its monomer is highly water-soluble; it is also soluble in ethanol and acetone. The preparation method is the same as for glyceraldehyde because the mild oxidation of glycerol gives both glyceraldehyde and dihydroxyacetone. However, there is another method to prepare this compound using glycerol and cationic-palladium based catalysts in the presence of oxygen at room temperature. And, this method gives dihydroxyacetone more selectively, with a high yield.
What are the Similarities Between Glyceraldehyde and Dihydroxyacetone?
- Glyceraldehyde and dihydroxyacetone are simple carbohydrates.
- Both these compounds have the same chemical formula C3H6O3.
What is the Difference Between Glyceraldehyde and Dihydroxyacetone?
The key difference between glyceraldehyde and dihydroxyacetone is that glyceraldehyde is an aldehyde, whereas dihydroxyacetone is a ketone. When considering the structure of these compounds, glyceraldehyde contains three carbon atoms as a chain, two –OH groups and a double-bonded oxygen atom at the end of the carbon chain; in contrast, dihydroxyacetone contains three carbon atoms as a chain, two –OH groups and a double-bonded oxygen atom at the centre of the carbon chain.
Moreover, glyceraldehyde is a chiral compound, and it has two enantiomers, while dihydroxyacetone does not show chirality. Therefore, glyceraldehyde is optically active, whereas dihydroxyacetone is optically inactive. Furthermore, in the laboratory, we can prepare glyceraldehyde from the mild oxidation of glycerol in the presence of hydrogen peroxide and a catalyst such as a ferrous salt. We can prepare dihydroxyacetone using glycerol and cationic-palladium based catalysts in the presence of oxygen at room temperature. In addition to these, glyceraldehyde is non-hygroscopic whereas dihydroxyacetone hygroscopic.
The below infographic summarizes the difference between glyceraldehyde and dihydroxyacetone.
Summary – Glyceraldehyde vs Dihydroxyacetone
In summary, both glyceraldehyde and dihydroxyacetone are simple carbohydrates. However, the key difference between glyceraldehyde and dihydroxyacetone is that glyceraldehyde is an aldehyde, whereas dihydroxyacetone is a ketone.
Reference:
1.“Glyceraldehyde.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine, Available here.
2.“Dihydroxyacetone.” Wikipedia, Wikimedia Foundation, 9 Sept. 2019, Available here.
3. Zhang, Guoqiang, and Qinhong Wang. “Functional Carbohydrates.” Functional Carbohydrates, Feb. 2017, pp. 269–298., doi:10.1201/9781315371061-9.
Image Courtesy:
1. “Glyceraldehyde-2D-skeletal” (Public Domain) via Commons Wikimedia
2. “Dihydroxyacetone” By Edgar181 – Own work (Public Domain) via Commons Wikimedia
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