Vitamin A (Retinol) (C₂₀H₃₀O) — Properties, Uses & Safety

Overview

Vitamin A, known chemically as retinol, has the molecular formula C20H30O and a molar mass of 286.45 g/mol. It appears as yellow crystals and belongs to the class of fat-soluble vitamins, meaning it dissolves in lipids and organic solvents rather than water and can be stored in the body's liver and fatty tissues. Retinol's structure features a cyclohexenyl ring (derived from beta-carotene) attached to a polyunsaturated side chain with four conjugated double bonds ending in a hydroxyl group. This extended conjugated system is responsible for retinol's ability to absorb light, which is directly linked to its critical role in vision. In the retina, retinol is converted to retinal (an aldehyde form), which combines with the protein opsin to form rhodopsin — the light-sensitive pigment in rod cells that enables vision in low-light conditions. Night blindness is one of the earliest symptoms of vitamin A deficiency. Beyond vision, vitamin A is essential for immune function, skin cell renewal, reproduction, and embryonic development. Dietary sources include liver, fish oils, eggs, and dairy products (as preformed retinol), and orange and green vegetables like carrots, sweet potatoes, and spinach (as provitamin A carotenoids like beta-carotene). GHS hazard codes include H302 (harmful if swallowed) and H361 (suspected of damaging fertility or the unborn child), as excessive intake can cause hypervitaminosis A with symptoms including nausea, headache, and liver damage. For chemistry students, vitamin A illustrates conjugated double bond systems, cis-trans isomerism (the 11-cis to all-trans isomerization of retinal is the molecular basis of vision), functional group transformations (alcohol to aldehyde to acid), and the biochemistry of fat-soluble molecules. It beautifully connects organic chemistry structure to biological function.

IUPAC Name

(1E,3E,5E,7E)-3,7-dimethyl-9-(2,6,6-trimethylcyclohex-1-en-1-yl)nona-1,3,5,7-tetraen-1-ol

CAS Number

68-26-8

PubChem CID

445354

Molecular Formula

C₂₀H₃₀O

Molar Mass

286.451 g/mol

State at STP

solid

Appearance

Yellow crystals