CID 2723872

C₆H₁₂O₆

Fructose

C 6
H 12
O 6

Ball-and-stick Stick Space-filling

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24 atoms, 24 single bonds.

IUPAC name: (3S,4R,5R)-2-(hydroxymethyl)oxane-2,3,4,5-tetrol
Molar mass: 180.156(20) g/mol
Atoms: 24
SMILES: C1C(C(C(C(O1)(CO)O)O)O)O
InChIKey: LKDRXBCSQODPBY-VRPWFDPXSA-N
PubChem CID: 2723872

Made of

C H O

Structural formula of fructose. Each unlabelled corner is a carbon atom, and the seven hydrogens on carbon are not drawn. Wedges come toward you, hashes go back. It shows which atoms are joined to which, not the shape. The model above shows the shape.

Fruit and honey both contain fructose, which the Merck Index, as quoted on PubChem, calls the sweetest of the sugars found in them. It is a monosaccharide, a sugar made of one unit rather than two joined together. Six carbon atoms, twelve hydrogen and six oxygen give it a molar mass of 180.16 g/mol.

Those counts are exactly the ones in glucose, and OpenStax Biology calls the pair structural isomers: one formula, C₆H₁₂O₆, with the atoms arranged differently. Glucose is an aldose, a sugar with its carbonyl (C=O) group at the end of the chain. Fructose is a ketose, whose ketone group, a carbon doubly bonded to oxygen, sits in the middle of the chain.

Bonded to glucose it forms sucrose, table sugar, and it is the sugar that gives high-fructose corn syrup its name. HSDB, the Hazardous Substances Data Bank, also uses the synonym levulose.

Structure and bonding

Fructose, as drawn, has 24 atoms and 24 bonds, all single, and one ring holds the eye. Five carbons and one oxygen close it, the six-membered form called a pyranose. Of the two carbons beside the ring oxygen, one, carbon 2 of the sugar’s chain, carries two groups: an OH and a CH₂OH arm. The other is a CH₂ with no OH. With Labels on, one OH shows on each of the remaining three ring carbons. Seen edge-on, the ring is not flat; its atoms step above and below a middle plane.

Stick strips the spheres and leaves that zigzag outline plain. Space-filling packs the atoms into one knobbly body dotted with hydrogens. An –OH group is enough for hydrogen bonding, OpenStax Chemistry says of ethanol, and the model shows fructose with five of them.

HSDB records pyranose-furanose interconversion: in solution this ring reopens and can close as a five-membered furanose. OpenStax Biology draws the five-membered ring and an open chain carrying the ketone C=O the model lacks. The IUPAC name, (3S,4R,5R)-2-(hydroxymethyl)oxane-2,3,4,5-tetrol, leaves carbon 2 unassigned, and OpenStax Biology notes that its groups lock into an α or β position as a ring closes.

Where it turns up

OpenStax Biology places fructose in fruit and inside sucrose, and the Merck Index adds honey. Factory fructose can begin as corn starch. HSDB describes starch broken down to glucose, then glucose isomerase, an enzyme drawn mainly from Streptomyces species, converting part of that glucose into fructose. The resulting high-fructose corn syrups hold 42, 55 or 90 per cent fructose on a dry-weight basis.

Honey and corn syrup also meet in the laboratory. PubChem’s carbon record notes that the ratio of carbon-13 to carbon-12 in honey is used to detect added high-fructose corn syrup, a check on adulteration.

Ice-cream makers add fructose to prevent sandiness, a gritty texture. Cosmetic formulas list it as a humectant, an ingredient that keeps moisture in the product, and PubChem’s consumer product data count 13 household and personal care items containing it.

Why it matters

Inside cells, a fructose unit sits at the hinge of glycolysis, the pathway that begins breaking down glucose for energy. In the second step an isomerase turns glucose-6-phosphate into fructose-6-phosphate. OpenStax Biology explains the switch: it allows the sugar to be split later into two three-carbon molecules. These are phosphate forms made from glucose inside the pathway, not fructose taken in with food.

Phosphofructokinase then adds a second phosphate, and this enzyme is rate-limiting, meaning it sets the pathway’s pace. It is active when ADP (adenosine diphosphate) runs high and less active when ADP runs low. The two added phosphates destabilise fructose-1,6-bisphosphate, and aldolase cleaves it into dihydroxyacetone phosphate and glyceraldehyde-3-phosphate.

Food makers value fructose for more than sweetness. The US Food and Drug Administration lists it as a flavouring agent, formulation aid, stabiliser, thickener and texturiser as well as a nutritive sweetener. HSDB calls crystalline fructose essentially pure, obtained by cooling a solution or by adding organic solvents to one. US production reported to the Environmental Protection Agency for 2023 fell between 50 and 100 million pounds.

Properties

Properties of fructose Molar mass summed from IUPAC/CIAAW 2024 standard atomic weights; formula, atom and bond counts and PubChem's molecular weight from PubChem CID 2723872.
Property	Value	Unit	Source
Molecular formula (Hill order)	C₆H₁₂O₆
Molar mass	180.156(20) g/mol	g/mol	IUPAC/CIAAW 2024
Carbon atoms	6
Hydrogen atoms	12
Oxygen atoms	6
Bonds	24
PubChem molecular weight	180.16 g/mol	g/mol	PubChem

Safety

As a food sugar, fructose is essentially harmless: all 172 company reports to the European Chemicals Agency under the Globally Harmonized System (GHS) find it meets no hazard criteria. The International Chemical Safety Card’s cautions concern the powder in workplaces, where fine dust may irritate mechanically and can explode when mixed with air. The PubChem Laboratory Chemical Safety Summary covers that setting.

Questions

Is fructose the same as glucose?

No, although the two share one formula, C₆H₁₂O₆, and one molar mass. OpenStax Biology calls them structural isomers: the same atoms in a different arrangement. Glucose is an aldose and fructose a ketose, its open chain carrying a ketone group partway along. In ring form they differ again: OpenStax Biology gives glucose a six-membered ring and fructose a five-membered one, though the Hazardous Substances Data Bank records fructose switching between five- and six-membered rings.

Why does the fructose model show a six-membered ring?

The ring drawn is the pyranose form of D-fructose, five carbons and one oxygen, with every bond single. It is one snapshot. HSDB, the Hazardous Substances Data Bank, records pyranose-furanose interconversion in solution, so the same molecule also closes into a five-membered ring, the form OpenStax Biology describes. It also exists in equilibrium with an open chain carrying a C=O group that the drawing does not include, as OpenStax Biology notes for such sugars.

Where does fructose come from?

Plants make it: OpenStax Biology finds it in fruit and as half of every sucrose molecule, and the Merck Index adds honey. Industry obtains it from several starting points, HSDB lists, among them beet sugar and other sucrose split into its two halves, and inulin. High-fructose corn syrup starts as corn starch, which is turned into glucose and then partly into fructose by the enzyme glucose isomerase.

Is fructose a carbohydrate?

Yes. Its six carbons, twelve hydrogens and six oxygens keep the 1:2:1 ratio OpenStax Biology gives for carbohydrates, and the word itself comes from carbon plus the components of water. As a single sugar unit it is a monosaccharide, and with six carbons a hexose. OpenStax Biology puts the energy in a gram of carbohydrate at 4.3 kcal, a figure for the class as a whole.

Made of the same elements

C₆H₁₂O₆ Glucose 24 atoms, 24 single bonds.
C₆H₈O₆ Ascorbic acid 20 atoms, 20 bonds.
C₆H₈O₇ Citric acid 21 atoms, 20 bonds.
C₄H₆O₆ Tartaric acid 16 atoms, 15 bonds.
C₄H₉OH 1-Butanol 15 atoms, 14 single bonds.
C₉H₈O₄ Aspirin 21 atoms, 21 bonds.
C₂H₅OC₂H₅ Diethyl ether 15 atoms, 14 single bonds.
C₄H₆O₅ Malic acid 15 atoms, 14 bonds.

All 51 compounds made of carbon, hydrogen and oxygen

C₈H₈O₃ Methyl salicylate 19 atoms, 19 bonds.
C₈H₈O₃ Vanillin 19 atoms, 19 bonds.
C₃H₇COOH Butyric acid 14 atoms, 13 bonds.
CH₃COOC₂H₅ Ethyl acetate 14 atoms, 13 bonds.
C₃H₈O₃ Glycerol 14 atoms, 13 single bonds.
C₇H₆O₃ Salicylic acid 16 atoms, 16 bonds.
C₆H₅COOH Benzoic acid 15 atoms, 15 bonds.
C₄H₈O Butanone 13 atoms, 12 bonds.
C₆H₅OH Phenol 13 atoms, 13 bonds.
C₃H₈O₂ Propylene glycol 13 atoms, 12 single bonds.
C₃H₇OH 1-Propanol 12 atoms, 11 single bonds.
C₆H₅CHO Benzaldehyde 14 atoms, 14 bonds.
C₃H₈O Isopropyl alcohol 12 atoms, 11 single bonds.
C₃H₆O₃ Lactic acid 12 atoms, 11 bonds.
C₁₄H₁₄O₃ Naproxen 31 atoms, 32 bonds.
C₂H₅COOH Propionic acid 11 atoms, 10 bonds.
C₃H₆O Acetone 10 atoms, 9 bonds.
C₂H₆O₂ Ethylene glycol 10 atoms, 9 single bonds.
CH₃OCH₃ Dimethyl ether 9 atoms, 8 single bonds.
C₂H₅OH Ethanol 9 atoms, 8 single bonds.
C₂H₄O₃ Glycolic acid 9 atoms, 8 bonds.
CH₃COOH Acetic acid 8 atoms, 7 bonds.
H₂C₂O₄ Oxalic acid 8 atoms, 7 bonds.
CH₃CHO Acetaldehyde 7 atoms, 6 bonds.
C₁₅H₁₆O₂ Bisphenol A 33 atoms, 34 bonds.
C₂H₄O Ethylene oxide 7 atoms, 7 single bonds.
C₁₃H₁₈O₂ Ibuprofen 33 atoms, 33 bonds.
C₁₀H₂₀O Menthol 31 atoms, 31 single bonds.
H₂CO₃ Carbonic acid 6 atoms, 5 bonds.
CH₃OH Methanol 6 atoms, 5 single bonds.
C₂₀H₁₄O₄ Phenolphthalein 38 atoms, 41 bonds.
HCOOH Formic acid 5 atoms, 4 bonds.
CH₂O Formaldehyde 4 atoms, 3 bonds.
C₁₂H₂₂O₁₁ Lactose 45 atoms, 46 single bonds.
C₁₂H₂₂O₁₁ Sucrose 45 atoms, 46 single bonds.
C₁₈H₂₄O₂ Estradiol 44 atoms, 47 bonds.
C₁₉H₂₈O₂ Testosterone 49 atoms, 52 bonds.
C₂₁H₃₀O₅ Cortisol 56 atoms, 59 bonds.
C₁₆H₃₂O₂ Palmitic acid 50 atoms, 49 bonds.
C₂₁H₃₀O₂ Progesterone 53 atoms, 56 bonds.
C₁₈H₃₄O₂ Oleic acid 54 atoms, 53 bonds.
C₂₇H₄₄O Cholecalciferol 72 atoms, 74 bonds.
C₂₇H₄₆O Cholesterol 74 atoms, 77 bonds.