Heptanal

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Heptanal[1]
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Template:Longitem C7H14O
Molar mass 114.18
Appearance Clear liquid
Density 0.80902 at 30 °C
Melting point Template:Chembox CalcTemperatures
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Template:Longitem −81.02·10−6 cm3/mol
Template:Longitem Hexanal

Octanal

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Heptanal or heptanaldehyde is an alkyl aldehyde. It is a colourless liquid with a strong fruity odor, which is used as precursor to components in perfumes and lubricants.[2]

Production

The formation of heptanal in the fractional distillation of castor oil[3] was already described in 1878. The large-scale production is based on the pyrolytic cleavage of ricinoleic acid[4] (Arkema method) and on the hydroformylation of 1-hexene with rhodium 2-ethylhexanoate as a catalyst upon addition of some 2-ethylhexanoic acid (Oxea method):[2][5]

Hydroformylation of 1-Hexene

Heptanal naturally occurs in the essential oils of ylang-ylang (Cananga odorata), clary sage (Salvia sclarea), lemon (Citrus x limon), bitter orange (Citrus x aurantium), rose (Rosa) and hyacinth (Hyacinthus).[6]

Properties

Heptanal is a flammable, slightly volatile colorless liquid of pervasive fruity to oily-greasy odor,[7] which is miscible with alcohols[6] and practically insoluble in water.[8] Because of its sensitivity to oxidation, heptanal is filled under nitrogen and stabilized with 100 ppm hydroquinone.[9]

Heptanal forms flammable vapor-air mixtures. The compound has a flash point of 39.5 °C.[8] The explosion range is between 1.1% by volume as the lower explosion limit (LEL) and 5.2% by volume as the upper explosion limit.[8] Its ignition temperature is 205 °C.[8]

Uses

Heptanal can be used for the production of 1-heptanol via hydrogenation:

Synthese von 1-Heptanol

The oxidation of heptanal with oxygen in the presence of a rhodium catalysts leads at 50 °C to heptanoic acid in 95% yield.[10] Heptanal reacts with benzaldehyde in a Knoevenagel reaction under basic catalysis with high yield and selectivity (> 90%) to jasminaldehyde,[11][2] which is mostly used in fragrances for its jasmine-like aroma as a cis/trans isomer mixture.[12]

α-pentylcinnamal (jasminal) by aldol condensation of benzaldehyde with heptanal

A by-product of the given reaction is the unpleasant rancid smelling (Z)-2-pentyl-2-nonenal.[13] Nevertheless, heptanal can be converted into (Z)-2-pentyl-2-nonenal virtually quantitatively in the presence of aqueous boric acid upon azeotropic removal of water.[14]

2-Pentyl-2-nonenal by self-condensation of heptanal

Full hydrogenation provides the branched primary alcohol 2-pentylnonan-1-ol, also accessible from the Guerbet reaction from heptanol.[15]

References

  1. ↑ Merck Index, 11th Edition, 4578.
  2. ↑ a b c Template:Ullmann
  3. ↑ F. Krafft, Distillation of castor oil, under reduced pressure, Analyst, 3, 329a (1878).
  4. ↑ A. Chauvel, G. Lefebvre, Petrochemical Processes: Technical and Economic Characteristics, vol. 2, p. 277, Editions Technip, Paris, 1989, Template:ISBN.
  5. ↑ A. Fischbach et al on behalf of Oxea Deutschland GmbH (20 May 2009). Verfahren zur Herstellung von Aldehyden, German patent DE 102007053385.
  6. ↑ a b G. A. Burdock, Fenaroli's Handbook of Flavor Ingredients, Fifth Edition, 2005, CRC Press, Boca Raton, Fl., Template:ISBN.
  7. ↑ Script error: No such module "Citation/CS1".
  8. ↑ a b c d Record in the GESTIS Substance Database of the Institute for Occupational Safety and HealthScript error: No such module "TemplatePar". Script error: No such module "TemplatePar".
  9. ↑ Acros Organics (rev. 19 Nov 2012). Heptaldehyde, stabilized (safety data sheet).
  10. ↑ H. Springer and P. Lappe, on behalf of Celanese Chem Europe GmbH (3 May 2001). Verfahren zur Herstellung aliphatischer Carbonsäuren aus Aldehyden, German patent DE 10010771.
  11. ↑ Script error: No such module "Citation/CS1".
  12. ↑ alpha-Amylzimtaldehyd (rev. 4 Aug 2000) at the Riechstofflexikon [Odorant Dictionary], vol. A.
  13. ↑ J. M. Hornback, Organic Chemistry, 2nd edition, p. 886, Thomson Brooks/Cole, 2006, Template:ISBN.
  14. ↑ Script error: No such module "Citation/CS1".
  15. ↑ G.H. Knothe: Lipid Chemistry, Guerbet Compounds Template:Webarchive, AOCS Lipid Library, 22 December 2011.
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