CID 5280795

C₂₇H₄₄O

Cholecalciferol

C 27
H 44
O 1

Ball-and-stick Stick Space-filling

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72 atoms, 74 bonds.

IUPAC name: (1S,3Z)-3-[(2E)-2-[(1R,3aS,7aR)-7a-methyl-1-[(2R)-6-methylheptan-2-yl]-2,3,3a,5,6,7-hexahydro-1H-inden-4-ylidene]ethylidene]-4-methylidenecyclohexan-1-ol
Molar mass: 384.648(64) g/mol
Atoms: 72
SMILES: CC(C)CCCC(C)C1CCC2C1(CCCC2=CC=C3CC(CCC3=C)O)C
InChIKey: QYSXJUFSXHHAJI-YRZJJWOYSA-N
PubChem CID: 5280795

Made of

C H O

Structural formula of cholecalciferol. Each unlabelled corner is a carbon atom, and the 29 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.

Human skin makes its own cholecalciferol, better known as vitamin D₃. Title 21 of the US Code of Federal Regulations describes it as produced when sunlight acts on 7-dehydrocholesterol in the skin. Ultraviolet rays break one bond of that compound, between carbons 9 and 10 of the steroid numbering, according to MeSH, the US National Library of Medicine’s subject headings. A ring opens, which makes the product a secosteroid: a steroid with a ring split.

Its 27 carbon, 44 hydrogen and one oxygen atoms come to 384.6 g/mol. Its crystals are fine and colourless, and melt at 84–85 °C. Moist air oxidises and inactivates it within a few days, the Hazardous Substances Data Bank (HSDB) reports, and it is sensitive to light. Vitamin D is fat soluble, so the vitamin taken in with food is packed into chylomicrons, particles described under cholesterol, and absorbed through the lymphatic system. Fat depots hold it for long periods.

Structure and bonding

Cholecalciferol has three rings of carbon atoms, one fewer than the four in the model of cholesterol. A five-membered ring and a six-membered ring share an edge; a second six-membered ring stands apart, joined to them by two CH carbons. Labels shows the molecule’s lone O on that separate ring, which also carries a =CH₂ group. An eight-carbon branched chain hangs from the five-membered ring.

The model draws three C=C double bonds, none inside a ring, alternating with single bonds; cholesterol’s model has one. CAMEO Chemicals, a US emergency-response database, files the compound under conjugated dienes. Chem1 names such an alternating run a conjugated system, its double-bond electrons delocalised, spread along the run; butadiene shows how. In Ball-and-stick, each double-bonded carbon holds its three bonds flat; the other 21 carbons point four single bonds at the corners of a tetrahedron.

Space-filling shows a hydrocarbon body about 15 Å long with a single O–H. Alcohols with a large hydrocarbon part dissolve little in water, a trend Chem1 sets out, and CAMEO lists this one as water insoluble. Stick thins the model to bonds alone, and the two-carbon bridge becomes easy to trace.

Where it turns up

Fish liver oils contain vitamin D₃, which is isolated from them. Few foods hold vitamin D naturally: MedlinePlus, the National Library of Medicine’s health site, names egg yolks, saltwater fish and liver. The NIH Office of Dietary Supplements (ODS) adds fatty fish and cheese; mushrooms carry vitamin D₂. Most people get their dietary vitamin D from fortified foods such as milk, cereal and yogurt, MedlinePlus notes. In July 2016 the US Food and Drug Administration (FDA) approved adding vitamin D to plant-based milk alternatives, naming D₂ for them and D₃ for milk.

Manufacture repeats the skin’s chemistry: ultraviolet irradiation of 7-dehydrocholesterol, itself produced from cholesterol, then purification by crystallisation. In the body the order runs the other way, MedlinePlus Genetics explains: an enzyme, 7-dehydrocholesterol reductase, converts 7-dehydrocholesterol to cholesterol.

Cholecalciferol is a therapeutic vitamin, a nutritional supplement and, with active US product registrations, a rodenticide. The World Health Organization includes it, as colecalciferol, in its Model List of Essential Medicines.

Why it matters

The drawn molecule is the inactive form of the vitamin, and ChEBI, a database of small biological molecules, traces its activation. The liver adds a hydroxyl (O–H) group to give calcidiol; the kidney adds another to give calcitriol, the active hormone. Low blood calcium and parathyroid hormone stimulate that last step, and calcitriol raises the gut’s absorption of calcium and of phosphate.

Without enough vitamin D a child’s bones mineralise poorly and grow soft and weak, the disease rickets; adults get osteomalacia. Blood calcium falls, HSDB explains, more parathyroid hormone is released, and that hormone draws calcium out of the skeleton. Rickets can also follow from too little calcium or phosphorus, MedlinePlus adds, and one form is inherited.

Once thought infectious, rickets affected about 75 per cent of infants in New York City in 1921, the US Centers for Disease Control and Prevention (CDC) records. The CDC calls adding vitamin D to milk in the 1940s a critical step in controlling it, and it is now rare in the United States.

Properties

Properties of cholecalciferol Molar mass summed from IUPAC/CIAAW 2024 standard atomic weights; formula, atom and bond counts and PubChem's molecular weight from PubChem CID 5280795.
Property	Value	Unit	Source
Molecular formula (Hill order)	C₂₇H₄₄O
Molar mass	384.648(64) g/mol	g/mol	IUPAC/CIAAW 2024
Carbon atoms	27
Hydrogen atoms	44
Oxygen atoms	1
Bonds	74
Single bonds	71
Double bonds	3
PubChem molecular weight	384.6 g/mol	g/mol	PubChem

Safety

The European Union’s harmonised classification rates pure cholecalciferol as fatal if swallowed, in contact with skin or if inhaled. The same classification adds damage to organs from prolonged or repeated exposure; each hazard statement is listed in the PubChem Laboratory Chemical Safety Summary for cholecalciferol. In food it is a separate case: the FDA affirms it as generally recognised as safe (GRAS), within maximum levels that Title 21 sets food by food. Experts, ODS reports, do not believe excess sun causes vitamin D toxicity, because previtamin D₃, the vitamin’s forerunner, also yields other compounds that limit vitamin D₃ formation.

Questions

Is vitamin D₃ a steroid?

It is a secosteroid, a steroid with one ring broken open. MeSH, the US National Library of Medicine's subject headings, defines secosteroids as steroids in which one or more rings have split, a hydrogen atom added at each end of the break. ChEBI classes cholecalciferol as a hydroxy seco-steroid. The model shows it: three rings, 72 atoms and 74 bonds, where the model of cholesterol, C₂₇H₄₆O, has four rings, 74 atoms and 77 bonds.

How does skin make vitamin D₃?

Skin makes it from 7-dehydrocholesterol, a compound MeSH describes as a precursor of both cholesterol and vitamin D₃, when sunlight supplies ultraviolet light. The light first turns 7-dehydrocholesterol into previtamin D₃, which then becomes vitamin D₃, the NIH Office of Dietary Supplements (ODS) explains. Melanin, which darkens skin, competes with 7-dehydrocholesterol for ultraviolet light and so lowers the amount made, the CDC notes. The skin's capacity to make vitamin D falls with age, ODS reports.

What is the difference between vitamin D₂ and D₃?

D₃ differs from D₂, MeSH notes, in having a single bond between carbons 22 and 23 and no methyl group on carbon 24. D₂, ergocalciferol, is C₂₈H₄₄O, made by ultraviolet irradiation of ergosterol from yeast and related fungi. HSDB rates their vitamin activity as essentially equal; MedlinePlus says D₃ might raise blood vitamin D higher and for longer. In chicks D₂ is only 1 to 2 per cent as potent, so poultry feed is supplemented with D₃.

Is vitamin D₃ a vitamin or a hormone?

It carries both labels. MeSH defines vitamins as substances the human body cannot manufacture, while Title 21 of the US Code of Federal Regulations describes vitamin D₃ as produced in human skin. ChEBI calls it a steroid hormone. Its active form, calcitriol, attaches to a protein called the vitamin D receptor (VDR). Together with a second protein, the retinoid X receptor (RXR), it binds DNA and regulates vitamin D-responsive genes, MedlinePlus Genetics explains.

Is cholecalciferol dangerous?

As a pure substance it is. All 1,694 company reports to the European Chemicals Agency (ECHA) label it fatal if inhaled, and Japan's classification adds possible damage to fertility or the unborn child. In food it is another matter: the US Food and Drug Administration found adding vitamin D₃ to milk to be safe. Taking in too much is still harmful, the agency notes, raising calcium in the blood, a condition called hypercalcaemia.

Made of the same elements

C₂₇H₄₆O Cholesterol 74 atoms, 77 bonds.
C₁₈H₃₄O₂ Oleic acid 54 atoms, 53 bonds.
C₂₁H₃₀O₂ Progesterone 53 atoms, 56 bonds.
C₂₁H₃₀O₅ Cortisol 56 atoms, 59 bonds.
C₁₆H₃₂O₂ Palmitic acid 50 atoms, 49 bonds.
C₁₉H₂₈O₂ Testosterone 49 atoms, 52 bonds.
C₁₈H₂₄O₂ Estradiol 44 atoms, 47 bonds.
C₂₀H₁₄O₄ Phenolphthalein 38 atoms, 41 bonds.

All 51 compounds made of carbon, hydrogen and oxygen

C₁₅H₁₆O₂ Bisphenol A 33 atoms, 34 bonds.
C₁₃H₁₈O₂ Ibuprofen 33 atoms, 33 bonds.
C₁₀H₂₀O Menthol 31 atoms, 31 single bonds.
C₁₄H₁₄O₃ Naproxen 31 atoms, 32 bonds.
C₁₂H₂₂O₁₁ Lactose 45 atoms, 46 single bonds.
C₁₂H₂₂O₁₁ Sucrose 45 atoms, 46 single bonds.
C₄H₉OH 1-Butanol 15 atoms, 14 single bonds.
C₉H₈O₄ Aspirin 21 atoms, 21 bonds.
C₂H₅OC₂H₅ Diethyl ether 15 atoms, 14 single bonds.
C₈H₈O₃ Methyl salicylate 19 atoms, 19 bonds.
C₈H₈O₃ Vanillin 19 atoms, 19 bonds.
C₆H₅CHO Benzaldehyde 14 atoms, 14 bonds.
C₆H₁₂O₆ Fructose 24 atoms, 24 single bonds.
C₆H₁₂O₆ Glucose 24 atoms, 24 single bonds.
C₆H₅COOH Benzoic acid 15 atoms, 15 bonds.
C₄H₈O Butanone 13 atoms, 12 bonds.
C₆H₅OH Phenol 13 atoms, 13 bonds.
C₃H₇OH 1-Propanol 12 atoms, 11 single bonds.
C₃H₇COOH Butyric acid 14 atoms, 13 bonds.
CH₃COOC₂H₅ Ethyl acetate 14 atoms, 13 bonds.
C₃H₈O Isopropyl alcohol 12 atoms, 11 single bonds.
C₇H₆O₃ Salicylic acid 16 atoms, 16 bonds.
C₃H₈O₂ Propylene glycol 13 atoms, 12 single bonds.
C₃H₆O Acetone 10 atoms, 9 bonds.
C₆H₈O₆ Ascorbic acid 20 atoms, 20 bonds.
C₃H₈O₃ Glycerol 14 atoms, 13 single bonds.
C₆H₈O₇ Citric acid 21 atoms, 20 bonds.
CH₃OCH₃ Dimethyl ether 9 atoms, 8 single bonds.
C₂H₅OH Ethanol 9 atoms, 8 single bonds.
C₂H₅COOH Propionic acid 11 atoms, 10 bonds.
C₂H₆O₂ Ethylene glycol 10 atoms, 9 single bonds.
C₃H₆O₃ Lactic acid 12 atoms, 11 bonds.
CH₃CHO Acetaldehyde 7 atoms, 6 bonds.
C₂H₄O Ethylene oxide 7 atoms, 7 single bonds.
C₄H₆O₅ Malic acid 15 atoms, 14 bonds.
CH₃COOH Acetic acid 8 atoms, 7 bonds.
CH₃OH Methanol 6 atoms, 5 single bonds.
C₄H₆O₆ Tartaric acid 16 atoms, 15 bonds.
C₂H₄O₃ Glycolic acid 9 atoms, 8 bonds.
CH₂O Formaldehyde 4 atoms, 3 bonds.
HCOOH Formic acid 5 atoms, 4 bonds.
H₂CO₃ Carbonic acid 6 atoms, 5 bonds.
H₂C₂O₄ Oxalic acid 8 atoms, 7 bonds.