Hexanal

Description

Hexanal has a characteristic fruity odor and taste (on dilution). May be prepared from the calcium salt of caproic acid and formic acid.

Description

Hexanal, once commonly called caproic aldehyde, is a six-carbon straight-chain aldehyde. It is a clear liquid with an atmospheric-pressure boiling point of 131 oC. P. Bagard published the first synthesis of hexanal in 1907. It is found in foods ranging from olive oil to pears to Hass avocados. Its fruity flavor makes it a useful additive in the flavor industry.
In 2014, Y. Takeuchi and co-workers at the University of Tokyo studied hexanal in another context: They discovered that it and its isomer 4-methylpentanal act as pheromones in rats. They found that exposing rats to these chemicals in combination causes the rodents to display increasingly anxious behavior. Neither compound alone produces similar results.
Stressed-out rats also release the aldehyde mixture. In so doing, they increase the anxiety levels of other rats.

Chemical properties

Colorless liquid; sharp aldehyde odor.Immiscible with water.

Chemical properties

Hexanal occurs, for example, in apple and strawberry aromas as well as in orange and lemon oil. It is a colorless liquid with a fatty, green odor and, in low concentration, is reminiscent of unripe fruit.
Hexanal is used in fruit flavors and, when highly diluted, in perfumery for obtaining fruity notes.

Chemical properties

Hexanal has a fatty, green, grassy, powerful, penetrating characteristic fruity odor and taste (on dilution).

Occurrence

Reported found in some natural aromas of apple, strawberry, camphor oil, tea extracts, tobacco leaves, Eucalyptus globulus, dwarf pine, bitter orange and coffee. Also reported found in nearly 300 natural sources including apple, apricot, banana, sweet and sour cherry, citrus peel oils and juices, berries, guava, melon, raisins, peach, pear, papaya, pineapple, asparagus, cabbage, celery, carrot, lettuce, shallots, onion, leek, ginger, parsley, bread, cheeses, butter, milk, fish, meats, cocoa, coffee, tea, nuts, popcorn, potato chips, oat products, honey, soybean, plum, cauliflower, beetroot, celery root, figs, cardamom, coriander seed and leaf, brussel sprouts, rice, quince, radish, lovage, corn oil, laurel and malt

The Uses of Hexanal

Hexanal is used in the flavor industry to prepare fruity flavors. It is utilized as a flavoring agent in the food industry. It is also used in Witting and aldol reactions.

The Uses of Hexanal

Analgesic; antidepressant.

The Uses of Hexanal

Hexanal occurs naturally inmany foods, such as in ripening fruits, or because of addition as a flavorant; it has an apple taste. It can also be produced in foods because of lipid peroxidation during cooking. It is mainly used as a food flavorant, in fragrances, and in the manufacture of dyes, plasticizers, synthetic resins, and pesticides. It is released to air and water during production or use for the manufacture of other products or during the use of these products themselves. It undergoes oxidation and polymerization readily.
Feron et al. identified hexanal in about 80 different types of food.

Definition

ChEBI: A fatty aldehyde that is hexane in which one of the terminal methyl group has been mono-oxygenated to form the corresponding aldehyde.

Preparation

Prepared from the calcium salt of caproic acid and formic acid

Aroma threshold values

Detection: 4.1 to 22.8 ppb; recognition: 400 ppb; aroma characteristics at 2.0%: green, fatty, leafy, vegetative, fruity and clean with a woody nuance

Taste threshold values

Taste characteristics at 2.5 ppm: green, woody, vegetative, apple, grassy, citrus and orange with a fresh, lingering aftertaste

Synthesis Reference(s)

Journal of the American Chemical Society, 93, p. 1693, 1971 DOI: 10.1021/ja00736a021

General Description

A clear colorless liquid with a pungent odor. Flash point 90°F. Less dense than water and insoluble in water. Vapors heavier than air.

Air & Water Reactions

Highly flammable. Insoluble in water.

Reactivity Profile

Caproaldehyde is an aldehyde. Aldehydes are frequently involved in self-condensation or polymerization reactions. These reactions are exothermic; they are often catalyzed by acid. Aldehydes are readily oxidized to give carboxylic acids. Flammable and/or toxic gases are generated by the combination of aldehydes with azo, diazo compounds, dithiocarbamates, nitrides, and strong reducing agents. Aldehydes can react with air to give first peroxo acids, and ultimately carboxylic acids. These autoxidation reactions are activated by light, catalyzed by salts of transition metals, and are autocatalytic (catalyzed by the products of the reaction). The addition of stabilizers (antioxidants) to shipments of aldehydes retards autoxidation. May attack some forms of plastics [USCG, 1999].

Hazard

Flammable, moderate fire risk.

Health Hazard

Ingestion causes irritation of mouth and stomach. Contact with vapor or liquid irritates eyes. Liquid irritates skin.

Fire Hazard

Behavior in Fire: Vapor is heavier than air and may travel to a source of ignition and flash back.

Chemical Reactivity

Reactivity with Water No reaction; Reactivity with Common Materials: May attack some plastics; Stability During Transport: Stable; Neutralizing Agents for Acids and Caustics: Not pertinent; Polymerization: Not pertinent; Inhibitor of Polymerization: Not pertinent.