Retinaldehyde

All-trans-retinal

Names
IUPAC name (2E,4E,6E,8E)-3,7-Dimethyl-9-(2,6,6-trimethylcyclohexen-1-yl)nona-2,4,6,8-tetraenal
Other names retinene; retinaldehyde; vitamin A aldehyde; RAL
Identifiers
CAS Number	116-31-4 Y
3D model (Jmol)	Interactive image
ChemSpider	553582
ECHA InfoCard	100.003.760
PubChem CID	638015
UNII	RR725D715M Y
InChI InChI=1S/C20H28O/c1-16(8-6-9-17(2)13-15-21)11-12-19-18(3)10-7-14-20(19,4)5/h6,8-9,11-13,15H,7,10,14H2,1-5H3/b9-6+,12-11+,16-8+,17-13+ Key: NCYCYZXNIZJOKI-OVSJKPMPSA-N
SMILES CC1=C(C(CCC1)(C)C)/C=C/C(=C/C=C/C(=C/C=O)/C)/C
Properties
Chemical formula	C20H28O
Molar mass	284.44 g·mol−1
Appearance	Orange crystals from petroleum ether
Melting point	61 to 64 °C (142 to 147 °F; 334 to 337 K)
Solubility in water	Nearly insoluble
Solubility in fat	Soluble
Related compounds
Related compounds	retinol; retinoic acid; beta-carotene; dehydroretinal; 3-hydroxyretinal; 4-hydroxyretinal
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y  (what is YN ?)
Infobox references

Retinal is also known as retinaldehyde. It was originally called retinene, and renamed after it was discovered to be vitamin A aldehyde. Retinal is one of the many forms of vitamin A (the number of which varies from species to species). Retinal is a polyene chromophore, bound to proteins called opsins, and is the chemical basis of animal vision. Retinal allows certain microorganisms to convert light into metabolic energy.

Vertebrate animals ingest retinal directly from meat, or they produce retinal from carotenoids, either from one of two carotenes (α-carotene, β-carotene) or from β-cryptoxanthin, a type of xanthophyll. These carotenoids must be obtained from plants or other photosynthetic organisms. No other carotenoids can be converted by animals to retinal, and some carnivores cannot convert any carotenoids at all. The other main forms of vitamin A, retinol, and a partially active form, retinoic acid, may both be produced from retinal.

Invertebrates such as insects and squid use hydroxylated forms of retinal in their visual systems, which derive from conversion from other xanthophylls.

Living organisms produce retinal (RAL) by irreversible oxidative cleavage of carotenoids. For example,

catalyzed by a beta-carotene 15,15'-monooxygenase or a beta-carotene 15,15'-dioxygenase. Just as carotenoids are the precursors of retinal, retinal is the precursor of the other forms of vitamin A. Retinal is interconvertible with retinol (ROL), the transport and storage form of vitamin A

catalyzed by retinol dehydrogenases (RDHs) and alcohol dehydrogenases (ADHs). Retinol is called vitamin A alcohol, or more often, simply vitamin A. Retinal can also be oxidized to retinoic acid (RA)