CAS number：5392-40-5
molecular formula：C10H16O
molecular weight：152.23
EINECS number：226-394-6

English synonyms

2,6-Octadienal, 3,7-dimethyl-;2,6-Octadienal,3,7-dimethyl-;3,7-Dimethyl-1,2,6-octadienal;3,7-Dimethyll-2,6-octadienal;3,7-dimethyl-octa-2,6-dienal;linmengquan;6-Octadienal,3,7-dimethyl-2;cis,trans-Citral

Related categories

Aldehydes; Synthetic fragrances; Daily necessities; Spices and fragrances; Food fragrances; Flavors and fragrances; General reagents; Plant extracts; Carbonyl compounds; Other biochemical reagents; Plant growth hormones; Food additives; Edible fragrances (flavoring agents); Natural equivalent fragrances and artificial flavors; pharmaceutical raw materials; aldehydes; edible flavors; biochemical reagents; Chinese medicine reference substances; reference substances; natural plant essential oils; alcohols, aldehydes, ketones; food additives; daily chemical raw materials; medical raw materials; raw materials; standard products - Chinese medicine standards Products; Spices and Foods; Chemical Raw Materials; Organic Chemical Raw Materials; Chemical Solvents; Natural Flavor Oils; Monomer Fragrance; Daily Chemicals; General Biochemical Reagents-Natural Products; Spices; Aldehydes, Alcohols, Ketones; Chemical Reagents

Introduction

Colorless or slightly yellow liquid with strong lemon scent. No optical rotation. The boiling point of 228 ° C, the flash point of 92 ° C. There are cis and trans isomers. Treated with sodium bisulfite, the solubility of the cis form is very small, while the trans form is very large, so the two can be separated. Cis-citral: relative density (d200.8898, refractive index (nD20) 1.4891, boiling point 118-119°C (2666Pa). Trans-citral: relative density 0.8888, refractive index (nD20) 1.4891, boiling point 117-118°C ( 2666Pa).Soluble in non-volatile oil, volatile oil, propylene glycol and ethanol, insoluble in glycerol and water. Unstable in alkali and strong acid.
Natural products exist in lemongrass oil (70% to 80%), lichen seed oil (about 70%), lemon oil, white lemon oil, citrus leaf oil, etc.

Chemical properties

Colorless or slightly yellow liquid with strong lemon scent. No optical rotation. The boiling point of 228 ° C, the flash point of 92 ° C. There are cis and trans isomers. Treated with sodium bisulfite, the solubility of the cis form is very small, while the trans form is very large, so the two can be separated. Cis-citral: relative density (d200.8898, refractive index (nD20) 1.4891, boiling point 118-119°C (2666Pa). Trans-citral: relative density 0.8888, refractive index (nD20) 1.4891, boiling point 117-118°C ( 2666Pa).Soluble in non-volatile oil, volatile oil, propylene glycol and ethanol, insoluble in glycerol and water. Unstable in alkali and strong acid.
Natural products exist in lemongrass oil (70% to 80%), lichen seed oil (about 70%), lemon oil, white lemon oil, citrus leaf oil, etc. 

Use

●  GB 2760-96 stipulates that the edible spices are allowed to be used. It is mainly used to prepare lemon, citrus and assorted fruit flavors, and is also the main raw material for synthesizing ionone.
Used as a flavoring agent to prepare lemon flavor, and also used as a raw material for synthesizing ionone and vitamin A

●  Versatile and used in all areas where a lemony aroma is desired. It is an important spice of lemon type, deodorant wood type essence, artificially formulated lemon oil, bergamot oil and orange leaf oil. It is the raw material for the synthesis of ionones and methyl ionones. It can also be used to cover up the bad breath in industrial production. It can also be used in edible flavors such as ginger, lemon, white lemon, sweet orange, pomelo, apple, cherry, grape, strawberry and spice. It can also be used in wine flavors.

●  Citral is an edible flavor allowed by my country's regulations, and can be used to prepare fruit-type edible flavors such as strawberries, apples, apricots, sweet oranges, and lemons. The dosage is based on normal production needs, generally 1.70mg/kg in gum candy; 43mg/kg in baked food; 41mg/kg in candy; 23mg/kg in cold drinks; 9.2mg/kg in soft drinks.

●  It is used for the preparation of artificial lemon oil, citrus oil, and other citrus flavors, fruit flavors, cherry, coffee, plum and other food flavors. Citral is a raw material for synthesizing ionone, methyl ionone, damascone and other raw materials; as an organic raw material, it can be reduced to citronellol, nerol and geraniol; it can also be converted into citral. In the pharmaceutical industry, it is used to manufacture vitamins A and E, and is also the raw material of phytol.

●  Synthetic vitamin A. spices.

Production method

●  Naturally present in Lemongrass Oil, Lemon Oil, White Lemon Oil, Citrus Oil, Lime Seed Oil, Verbena Oil. It contains 70-80% of the natural essential oils of lemongrass oil and sage seed oil, which can be distilled from the essential oils. If it is necessary to prepare a fine product, it can be purified by the sodium bisulfite method and then distilled under reduced pressure. The industrial method for synthesizing citral is based on the synthesis of methyl heptenone, and 3,7-dimethylocten-6-yn-1-ol-3 (dehydrogenation) is prepared from methyl heptenone and acetylene. linalool). Then, dehydrolinalool is directly rearranged in an inert solvent at 140-150°C in the presence of a polymeric silicon sulfone catalyst. In addition, citral can be prepared from industrial geraniol (and nerol) by gas-phase dehydrogenation under reduced pressure with copper catalyst.

●  Citral is naturally present in fenugreek oil (about 80%), lemongrass oil (80%), clove basil oil (65%), tart lemon leaf oil (35%) and lemon oil, and can be industrially obtained from natural essential oils It is obtained from separation, and it can also be prepared by chemical synthesis.
Synthesized from methyl heptenone
Ethoxyacetylene magnesium bromide is condensed with methylheptenone to form 3,7-dimethyl-1-ethoxy-3-hydroxy-6-octene-1-yne, which is partially catalytically hydrogenated to obtain enol Ether, the latter is hydrolyzed and dehydrated with phosphoric acid to obtain citral, and the yield is 68% based on methyl heptenone. Dehydrolinalool can also be obtained by the condensation of acetylene and methyl heptenone, and then citral can be obtained by rearrangement at 140-150 ° C and inert solvent under the catalysis of condensed silicon sulfone. Separation from Radix japonica oil (this is the main method of producing citral in my country)
Add 30 kg of citral to 75% of citral to the mixed solution prepared by 18 kg of sodium bicarbonate, 38 kg of sodium sulfite and about 165 kg of clear water under full stirring, and stir for 5 to 6 hours at room temperature. After standing overnight, the layers were separated, and the lower layer of citral was precipitated in the form of an adduct. The adduct was washed with a small amount of toluene to remove oil and spun dry. Then add 10% sodium hydroxide solution, decompose citral at room temperature, and extract with benzene. The extract was first distilled under normal pressure (80-82°C) to recover benzene, and then distilled under reduced pressure to collect fractions at 110-111°C (1.47kPa) to obtain about 15-16kg of pure 98% citral.

●  It is obtained by separation of lemongrass oil or fenugreek oil by fractional distillation or bisulfite method.
It is obtained by the oxidation of geraniol, nerol or linalool under the catalysis of chromic acid.

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