Heptanal or heptanaldehyde is an

alkyl In organic chemistry, an alkyl group is an alkane missing one hydrogen. The term ''alkyl'' is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula of . A cycloalkyl is derived from a cycloalk ...

aldehyde In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl grou ...

. It is a colourless liquid with a strong fruity odor, which is used as precursor to components in perfumes and lubricants.

Production

The formation of heptanal in the fractional distillation of

castor oil Castor oil is a vegetable oil pressed from castor beans. It is a colourless or pale yellow liquid with a distinct taste and odor. Its boiling point is and its density is 0.961 g/cm3. It includes a mixture of triglycerides in which about ...

was already described in 1878. The large-scale production is based on the pyrolytic cleavage of

ricinoleic acid Ricinoleic acid, formally called 12-hydroxy-9-''cis''-octadecenoic acid is a fatty acid. It is an unsaturated omega-9 fatty acid and a hydroxy acid. It is a major component of the seed oil obtained from mature castor plant (''Ricinus communis'' ...

(Arkema method) and on the

hydroformylation Hydroformylation, also known as oxo synthesis or oxo process, is an industrial process for the production of aldehydes from alkenes. This chemical reaction entails the net addition of a formyl group (CHO) and a hydrogen atom to a carbon-carbon d ...

of 1-hexene with rhodium 2-ethylhexanoate as a catalyst upon addition of some

2-ethylhexanoic acid 2-Ethylhexanoic acid is the organic compound with the formula CH3(CH2)3CH(C2H5)CO2H. It is a carboxylic acid that is widely used to prepare lipophilic metal derivatives that are soluble in nonpolar organic solvents. 2-Ethylhexanoic acid is a colo ...

(Oxea method): Hydroformylierung von 1-Hexen IS

Heptanal naturally occurs in the

essential oil An essential oil is a concentrated hydrophobic liquid containing volatile (easily evaporated at normal temperatures) chemical compounds from plants. Essential oils are also known as volatile oils, ethereal oils, aetheroleum, or simply as the o ...

s of ylang-ylang (''

Cananga odorata ''Cananga odorata'', known as ylang-ylang ( ) or cananga tree, is a tropical tree that is native to the Philippines, Malaysia, Indonesia, New Guinea, the Solomon Islands, and Queensland, Australia. It is also native to parts of Thailand and Viet ...

''), clary sage (''

Salvia sclarea ''Salvia sclarea'', the clary or clary sage, is a biennial or short-lived herbaceous perennial in the genus ''Salvia''. It is native to the northern Mediterranean Basin, along with some areas in north Africa and Central Asia. The plant has a leng ...

''), lemon ('' Citrus x limon''), bitter orange ('' Citrus x aurantium''), rose ( ''Rosa'') and hyacinth ( ''Hyacinthus'').G. A. Burdock, ''Fenaroli’s Handbook of Flavor Ingredients, Fifth Edition'', 2005, CRC Press, Boca Raton, Fl., .

Properties

Heptanal is a flammable, slightly volatile colorless liquid of pervasive fruity to oily-greasy odor, which is

miscible Miscibility () is the property of two substances to mix in all proportions (that is, to fully dissolve in each other at any concentration), forming a homogeneous mixture (a solution). The term is most often applied to liquids but also applies ...

with

alcohols In chemistry, an alcohol is a type of organic compound that carries at least one hydroxyl () functional group bound to a saturated carbon atom. The term ''alcohol'' originally referred to the primary alcohol ethanol (ethyl alcohol), which is ...

and practically insoluble in water. Because of its sensitivity to oxidation, heptanal is filled under

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

and stabilized with 100 ppm

hydroquinone Hydroquinone, also known as benzene-1,4-diol or quinol, is an aromatic organic compound that is a type of phenol, a derivative of benzene, having the chemical formula C6H4(OH)2. It has two hydroxyl groups bonded to a benzene ring in a ''para'' ...

. Heptanal forms flammable vapor-air mixtures. The compound has a

flash point The flash point of a material is the "lowest liquid temperature at which, under certain standardized conditions, a liquid gives off vapours in a quantity such as to be capable of forming an ignitable vapour/air mixture". (EN 60079-10-1) The fl ...

of 39.5 °C. The explosion range is between 1.1% by volume as the

lower explosion limit Mixtures of dispersed combustible materials (such as gaseous or vaporised fuels, and some dusts) and oxygen in the air will burn only if the fuel concentration lies within well-defined lower and upper bounds determined experimentally, referred to a ...

(LEL) and 5.2% by volume as the upper explosion limit. Its ignition temperature is 205 °C.

Uses

Heptanal can be used for the production of

1-heptanol 1-Heptanol is an alcohol with a seven carbon chain and the structural formula of CH3(CH2)6OH. It is a clear colorless liquid that is very slightly soluble in water, but miscible with ether and ethanol. Overview There are three other isomers of h ...

via

hydrogenation Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a Catalysis, catalyst such as nickel, palladium or platinum. The process is commonly employed to redox, reduce or S ...

The oxidation of heptanal with

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

in the presence of a rhodium catalysts leads at 50 °C to

heptanoic acid Enanthic acid, also called heptanoic acid, is an organic compound composed of a seven-carbon chain terminating in a carboxylic acid functional group. It is a colorless oily liquid with an unpleasant, rancid odor. It contributes to the odor of som ...

in 95% yield. Heptanal reacts with benzaldehyde in a Knoevenagel reaction under basic catalysis with high yield and selectivity (> 90%) to

jasminaldehyde Jasminaldehyde (also known as jasmine aldehyde and α-pentylcinnamaldehyde) is a fine chemical used as an aroma compound in perfumes. It is responsible for jasmine's characteristic scent. Synthesis Jasminaldehyde used in industry is commonly de ...

, which is mostly used in fragrances for its

jasmine Jasmine ( taxonomic name: ''Jasminum''; , ) is a genus of shrubs and vines in the olive family (Oleaceae). It contains around 200 species native to tropical and warm temperate regions of Eurasia, Africa, and Oceania. Jasmines are widely cultiva ...

-like aroma as a ''cis''/''trans'' isomer mixture. Jasminaldehyd 2 IS

A by-product of the given reaction is the unpleasant rancid smelling (''Z'')-2-pentyl-2-nonenal. When good reasons are given, heptanal can be converted into (''Z'')-2-pentyl-2-nonenal virtually quantitatively in the presence of aqueous boric acid upon azeotropic removal of water. 2-Pentyl-2-nonenal IS

Full hydrogenation provides the branched

primary alcohol A primary alcohol is an alcohol in which the hydroxy group is bonded to a primary carbon atom. It can also be defined as a molecule containing a “–CH2OH” group. In contrast, a secondary alcohol has a formula “–CHROH” and a tertiary ...

2-pentylnonan-1-ol, also accessible from the

Guerbet reaction The Guerbet reaction, named after Marcel Guerbet (1861–1938), is an organic reaction that converts a primary Alcohol (chemistry), alcohol into its β-alkylated Dimer (chemistry), dimer Alcohol (chemistry), alcohol with loss of one equivalent of wa ...

from heptanol.G.H. Knothe
''Lipid Chemistry, Guerbet Compounds''
{{Webarchive, url=https://web.archive.org/web/20160521114621/http://lipidlibrary.aocs.org/OilsFats/content.cfm?ItemNumber=39194 , date=2016-05-21, AOCS Lipid Library, 22 December 2011.

References

Alkanals