Citral

Not to be confused with Geraniol.

Citral is an acyclic monoterpene aldehyde. Being a monoterpene, it is made of two isoprene units. Citral is a collective term which covers two geometric isomers that have their own separate names; the E-isomer is named geranial (trans-citral; α-citral^[2]) or citral A. The Z-isomer is named neral (cis-citral; β-citral^[2]) or citral B. These stereoisomers occur as a mixture, often not in equal proportions; e.g. in essential oil of Australian ginger, the neral to geranial ratio is 0.61.^[3]

Citral^[1]

Geranial
Neral
Names
IUPAC name 3,7-dimethylocta-2,6-dienal
Other names citral geranialdehyde
Identifiers
CAS Number	5392-40-5 Y
3D model (JSmol)	Interactive image Interactive image
ChEBI	CHEBI:16980 Y
ChEMBL	ChEMBL1080997 Y
ChemSpider	553578 Y
ECHA InfoCard	100.023.994
EC Number	226-394-6
IUPHAR/BPS	6327
KEGG	C01499 Y
PubChem CID	638011
RTECS number	RG5075000
UNII	T7EU0O9VPP Y
UN number	2810
CompTox Dashboard (EPA)	DTXSID6024836
InChI InChI=1S/C10H16O/c1-9(2)5-4-6-10(3)7-8-11/h5,7-8H,4,6H2,1-3H3/b10-7+ Y Key: WTEVQBCEXWBHNA-JXMROGBWSA-N Y InChI=1/C10H16O/c1-9(2)5-4-6-10(3)7-8-11/h5,7-8H,4,6H2,1-3H3/b10-7+ Key: WTEVQBCEXWBHNA-JXMROGBWBB
SMILES O=CC=C(C)CCC=C(C)C O=C/C=C(/CC/C=C(/C)C)C
Properties
Chemical formula	C10H16O
Molar mass	152.24 g/mol
Appearance	Pale yellow liquid
Odor	Lemon like
Density	0.893 g/cm3
Boiling point	229 °C (444 °F; 502 K)
Vapor pressure	0.22 mmHg (20 °C)
Magnetic susceptibility (χ)	−98.9×10−6 cm3/mol
Hazards
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H315, H317
Precautionary statements	P261, P264, P272, P280, P302+P352, P321, P332+P313, P333+P313, P362, P363, P501
NFPA 704 (fire diamond)	0 1 0
Flash point	91 °C (196 °F; 364 K)
Related compounds
Related alkenals	Citronellal Methacrolein trans-2-Methyl-2-butenal
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Natural Occurrence

Citral is present in the volatile oils of several plants:^[4][5][6]

• lemon myrtle (90–98%)
• Litsea citrata (90%)
• Litsea cubeba (70–85%)
• lemongrass (65–85%)
• lemon tea-tree (70–80%)
• Ocimum gratissimum (66.5%)
• Lindera citriodora (about 65%)
• Calypranthes parriculata (about 62%)
• petitgrain (36%)
• lemon verbena (30–35%)
• lemon ironbark (26%)
• lemon balm (11%)
• lime (6–9%)
• lemon (2–5%)
• orange

Further, in the lipid fraction (essential oil) of Australian ginger (51–71%)^[3] Of the many sources of citral, the Australian myrtaceous tree, lemon myrtle, Backhousia citriodora F. Muell. (of the family Myrtaceae), is considered superior.^[7]

Uses

Citral is a precursor in the industrial production of vitamin A, vitamin E, vitamin K.

Citral is also precursor to lycopene, ionone and methylionone.

Fragrances

Citral has a strong lemon (citrus) scent and is used as an aroma compound in perfumery. It is used to fortify lemon oil. (Nerol, another perfumery compound, has a less intense but sweeter lemon note.) The aldehydes citronellal and citral are considered key components responsible for the lemon note with citral preferred.^[7]

It also has pheromonal effects in acari and insects.^[8][9]

The herb Cymbopogon citratus has shown promising insecticidal and antifungal activity against storage pests.^[10]

Food additive

Citral is commonly used as a food additive ingredient.^[11]

It has been tested (2016) in vitro against the food-borne pathogen Cronobacter sakazakii.^[12]

See also

• Citronellal
• Geraniol
• Limonene
• Nerol
• Vaporizer