Glucose Molecular Formula and Facts

The molecular formula for glucose is C₆H₁₂O₆ or H-(C=O)-(CHOH)₅-H. Its empirical or simplest formula is CH₂O, which indicates there are two hydrogen atoms for each carbon and oxygen atom in the molecule. Glucose is the sugar that is produced by plants during photosynthesis and that circulates in the blood of people and other animals as an energy source. Glucose is also known as dextrose, blood sugar, corn sugar, grape sugar, or by its IUPAC systematic name (2R,3S,4R,5R)-2,3,4,5,6-Pentahydroxyhexanal.

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What Is the Chemical Formula of Sugar?

By Anne Marie Helmenstine, Ph.D.

Key Glucose Facts

• The name "glucose" comes from the French and Greek words for "sweet", in reference to must, which is the sweet first press of grapes when they are used to make wine. The -ose ending in glucose indicates the molecule is a carbohydrate.
• Because glucose has 6 carbon atoms, it is classified as a hexose. Specifically, it is an example of an aldohexose. It is a type of monosaccharide or simple sugar. It may be found in either linear form or cyclic form (most common). In linear form, it has a 6-carbon backbone, with no branches. The C-1 carbon is the one bearing the aldehyde group, while the other five carbon each bear a hydroxyl group.
• The hydrogen and -OH groups are able to rotate around the carbon atoms in glucose, leading to isomerization. The D-isomer, D-glucose, is found in nature and is used for cellular respiration in plants and animals. The L-isomer, L-glucose, is not common in nature, although it may be prepared in a lab.
• Pure glucose is a white or crystalline powder with a molar mass of 180.16 grams per mole and density of 1.54 grams per cubic centimeter. The melting point of the solid depends on whether it is in the alpha or beta conformation. The melting point of α-D-glucose is 146 °C (295 °F; 419 K). The melting point of β-D-glucose is 150 °C (302 °F; 423 K).
• Why do organisms use glucose for respiration and fermentation rather than another carbohydrate? The reason is probably that glucose is less likely to react with the amine groups of proteins. The reaction between carbohydrates and proteins, called glycation, is a natural part of aging and consequence of some diseases (e.g., diabetes) that impairs the functioning of proteins. In contrast, glucose may be enzymatically added to proteins and lipids via the process of glycosylation, which forms active glycolipids and glycoproteins.
• In the human body, glucose supplies about 3.75 kilocalories of energy per gram. It is metabolized into carbon dioxide and water, producing energy in chemical form as ATP. While it's needed for many functions, glucose is particularly important because it supplies nearly all the energy for the human brain.
• Glucose has the most stable cyclic form of all the aldohexoses because nearly all of its hydroxy group (-OH) are in the equatorial position. The exception is the hydroxy group on the anomeric carbon.
• Glucose is soluble in water, where it forms a colorless solution. It also dissolves in acetic acid, but only slightly in alcohol.
• The glucose molecule was first isolated in 1747 by the German chemist Andreas Marggraf, who obtained it from raisins. Emil Fischer investigated the structure and properties of the molecule, earning the 1902 Nobel Prize in Chemistry for his work. In the Fischer projection, glucose is drawn in a specific configuration. The hydroxyls on C-2, C-4, and C-5 is on the right side of the backbone, while the C-3 hydroxyl is on the left side of the carbon backbone.

Sources

• Robyt, John F. (2012). Essentials of Carbohydrate Chemistry. Springer Science & Business Media. ISBN:978-1-461-21622-3.
• Rosanoff, M. A. (1906). "On Fischer's Classification of Stereo-Isomers." Journal of the American Chemical Society. 28: 114–121. doi:10.1021/ja01967a014
• Schenck, Fred W. (2006). "Glucose and Glucose-Containing Syrups." Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a12_457.pub2