Vitamin D3 (Cholecalciferol) (C₂₇H₄₄O) — Properties, Uses & Safety

Overview

Vitamin D3, also called cholecalciferol, has the molecular formula C27H44O and a molar mass of 384.64 g/mol. It is a fat-soluble secosteroid — a steroid molecule in which one of the rings has been broken open — that appears as a white crystalline solid. Vitamin D3 is unique among vitamins because the human body can synthesize it: when ultraviolet B (UVB) radiation from sunlight strikes the skin, it converts 7-dehydrocholesterol (a cholesterol derivative) into previtamin D3, which then thermally isomerizes to vitamin D3. This photochemical reaction is a remarkable example of how light energy drives chemical transformations in biological systems. Once formed or ingested from dietary sources such as fatty fish, egg yolks, and fortified milk, vitamin D3 undergoes two hydroxylation reactions — first in the liver to form 25-hydroxyvitamin D3 (calcidiol), then in the kidneys to produce the active hormone 1,25-dihydroxyvitamin D3 (calcitriol). Calcitriol's primary function is regulating calcium and phosphorus absorption in the intestines, which is essential for building and maintaining strong bones and teeth. Vitamin D deficiency leads to rickets in children and osteomalacia in adults. GHS hazard codes include H300 (fatal if swallowed in concentrated form), H310 (fatal in contact with skin), and H410 (very toxic to aquatic life with long-lasting effects), though these apply to pure concentrated forms, not dietary supplements. For chemistry students, vitamin D3 is a treasure trove of concepts: photochemistry and UV-induced reactions, steroid ring structure and nomenclature, thermal isomerization, hydroxylation reactions, enzyme catalysis, and the conversion of a simple lipid into a potent hormone. It demonstrates how chemistry, biology, and physics intersect in human health.

IUPAC Name

(1S,3Z)-3-[(2E)-2-[(1R,3aS,7aR)-1-[(2R)-6-methylheptan-2-yl]-7a-methyl-2,3,3a,5,6,7-hexahydro-1H-inden-4-ylidene]ethylidene]-4-methylidenecyclohexan-1-ol

CAS Number

67-97-0

PubChem CID

5280795

Molecular Formula

C₂₇H₄₄O

Molar Mass

384.637 g/mol

State at STP

solid

Appearance

White crystalline solid