Benzaldehyde

Benzaldehyde was first extracted in 1803 by the French pharmacist Martrès. His experiments focused on elucidating the nature of amygdalin, the poisonous compound found in bitter almonds, the fruit of Prunus dulcis.In 1803 C. Martrès published a manuscript on the oil of bitter almonds: "Recherches sur la nature et le siège de l'amertume et de l'odeur des amandes amères" (Research on the nature and location of the bitterness and the smell of bitter almonds). However, the memoir was largely ignored until an extract was published in 1819: Martrès fils (1819) [http://gallica.bnf.fr/ark:/12148/bpt6k78139n/f292.image.langEN "Sur les amandes amères,"] Journal de Pharmacie, vol. 5, pages 289–296. Further work on the oil by Pierre Robiquet and Antoine Boutron Charlard, two French chemists, produced benzaldehyde.Nouvelles expériences sur les amandes amères et sur l'huile volatile qu'elles fournissent Robiquet, Boutron-Charlard, Annales de chimie et de physique, 44 (1830), 352–382, In 1832, Friedrich Wöhler and Justus von Liebig first synthesized benzaldehyde.{{cite journal|author=Wöhler, Friedrich and Liebig, Justus von |year=1832|url=https://books.google.com/books?id=z-VAAAAAYAAJ&pg=249 |title=Untersuchungen über das Radikal der Benzoesäure|trans-title=Investigations of the radical of benzoic acid|journal=Annalen der Pharmacie|volume= 3|issue=3| pages= 249–282|doi=10.1002/jlac.18320030302|hdl=2027/hvd.hxdg3f|hdl-access=free}}

Benzaldehyde can be produced from both petroleum-based chemicals or plant-derived chemicals. Synthetic benzaldehyde is primarily produced using liquid phase chlorination and oxidation of toluene. Numerous other methods have been developed, such as the partial oxidation of benzyl alcohol, alkali hydrolysis of benzal chloride, and the carbonylation of benzene (the Gatterman-Koch reaction).{{cite book|doi=10.1002/14356007.a03_463.pub2 |chapter=Benzaldehyde |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2011 |last1=Brühne |first1=Friedrich |last2=Wright |first2=Elaine |isbn=978-3-527-30385-4 }}

Natural benzaldehyde is produced from cinnamaldehyde obtained from cassia oil by the retro-aldol reaction:{{Cite book |url=https://books.google.com/books?id=85yUennC-pUC&pg=PA87 |title=Innovation in food engineering : new techniques and products |date=2010 |publisher=CRC Press |others=Passos, Maria Laura., Ribeiro, Claudio P. |isbn=9781420086072 |location=Boca Raton, Florida |pages=87 |oclc=500683261}} the cinnamaldehyde is heated in an aqueous/alcoholic solution between 90 °C and 150 °C with a base (most commonly sodium carbonate or bicarbonate) for 5 to 80 hours,Wienes, Charles and Pittet, Alan O. (1985) {{US Patent|4617419}} Process for preparing natural benzaldehyde and acetaldehyde, natural benzaldehyde and acetaldehyde compositions, products produced thereby and organoleptic utilities therefor. followed by distillation of the formed benzaldehyde. This reaction also yields acetaldehyde. The natural status of benzaldehyde obtained in this way is controversial.

Benzaldehyde and similar chemicals occur naturally in many foods. Most of the benzaldehyde that people eat is from natural plant foods, such as almonds.{{Cite journal|title = The FEMA GRAS assessment of benzyl derivatives used as flavor ingredients|journal = Food and Chemical Toxicology|date = 2005-08-01|pmid = 15950815|pages = 1207–1240|volume = 43|issue = 8|doi = 10.1016/j.fct.2004.11.014|first1 = T. B.|last1 = Adams|first2 = S. M.|last2 = Cohen|first3 = J.|last3 = Doull|first4 = V. J.|last4 = Feron|first5 = J. I.|last5 = Goodman|first6 = L. J.|last6 = Marnett|first7 = I. C.|last7 = Munro|first8 = P. S.|last8 = Portoghese|first9 = R. L.|last9 = Smith}}

Almonds, apricot seeds, apple seeds, and cherry seed contain significant amounts of amygdalin. This glycoside breaks up under enzyme catalysis into benzaldehyde, hydrogen cyanide and two equivalents of glucose.

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{{Biochem reaction subunit|compound=Amygdalin|image=Amygdalin_structure.svg|class=skin-invert-image|imagesize=180px}}

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{{Biochem reaction subunit|compound=benzaldehyde|image=benzaldehyde.png|class=skin-invert-image|imagesize=50px}}

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Benzaldehyde contributes to the scent of oyster mushrooms (Pleurotus ostreatus).{{cite journal | doi = 10.1021/jf960876i | title = Volatile Compounds Secreted by the Oyster Mushroom (Pleurotus ostreatus) and Their Antibacterial Activities | year = 1997 | last1 = Beltran-Garcia | first1 = Miguel J. | last2 = Estarron-Espinosa | first2 = Mirna | last3 = Ogura | first3 = Tetsuya | journal = Journal of Agricultural and Food Chemistry | volume = 45 | pages = 4049 | issue = 10}}

Benzaldehyde is easily oxidized to benzoic acid in air at room temperature,{{cite journal |last1=Sankar |first1=Meenakshisundaram |title=The benzaldehyde oxidation paradox explained by the interception of peroxy radical by benzyl alcohol |journal=Nature Communications |volume=5 |pages=3332 |url=https://www.nature.com/articles/ncomms4332.pdf?origin=ppub|pmid=24567108 |year=2014 |doi=10.1038/ncomms4332 |bibcode=2014NatCo...5.3332S |doi-access=free}} causing a common impurity in laboratory samples. Since the boiling point of benzoic acid is much higher than that of benzaldehyde, it may be purified by distillation. Benzyl alcohol can be formed from benzaldehyde by means of hydrogenation. Reaction of benzaldehyde with anhydrous sodium acetate and acetic anhydride yields cinnamic acid, while alcoholic potassium cyanide can be used to catalyze the condensation of benzaldehyde to benzoin. Benzaldehyde undergoes disproportionation upon treatment with concentrated alkali (Cannizzaro reaction): one molecule of the aldehyde is reduced to the benzyl alcohol and another molecule is simultaneously oxidized to benzoic acid.

:Image:Benzaldehyd-chemical-Cannizzaro.png

With diols, including many sugars, benzaldehyde condenses to form benzylidene acetals.{{Citation needed|date=April 2025}}

Benzaldehyde is commonly employed to confer almond flavor to foods and scented products, including e-cigarette liquids. It is sometimes used in cosmetics products.{{Cite journal|title = Final report on the safety assessment of benzaldehyde|journal = International Journal of Toxicology|date = 2006-01-01|pmid = 16835129|pages = 11–27|volume = 25|doi = 10.1080/10915810600716612|first = Alan|last = Andersen| issue=Suppl 1 |s2cid = 32177208|doi-access = free}}

In industrial settings, benzaldehyde is used chiefly as a precursor to other organic compounds, ranging from pharmaceuticals to plastic additives. The aniline dye malachite green is prepared from benzaldehyde and dimethylaniline. Benzaldehyde is also a precursor to certain acridine dyes. Via aldol condensations, benzaldehyde is converted into derivatives of cinnamaldehyde and styrene. The synthesis of mandelic acid starts with the addition of hydrocyanic acid to benzaldehyde:

:Image:Benzaldehyde-chemical-mandelicacid.png

The resulting cyanohydrin is hydrolysed to mandelic acid. (The scheme above depicts only one of the two formed enantiomers).

Benzaldehyde is used as a bee repellent.{{Cite book|title = Why Do Bees Buzz?: Why Do Bees Buzz? Fascinating Answers to Questions about Bees|url = https://books.google.com/books?id=xzQ4NWlIrHwC&pg=PA177|publisher = Rutgers University Press|date = 2010-02-09|isbn = 9780813549200|language = en|first1 = Elizabeth|last1 = Evans|first2 = Carol|last2 = Butler|pages = 177–178}} A small amount of benzaldehyde solution is placed on a fume board near the honeycombs. The bees then move away from the honey combs to avoid the fumes.{{Cite book|title = Storey's Guide to Keeping Honey Bees: Honey Production, Pollination, Bee Health|url = https://books.google.com/books?id=cos5WSDNKrEC&pg=PA167|publisher = Storey Publishing|date = 2010-01-01|isbn = 9781603425506|language = en|first1 = Malcolm T.|last1 = Sanford|first2 = Richard E.|last2 = Bonney|page = 167}} The beekeeper can then remove the honey frames from the bee hive with less risk to both bees and beekeeper.

Benzaldehyde reacts with nitroethane in the presence of a catalyst to produce phenyl-2-nitropropene, a precursor to amphetamine and other chemicals.{{cite web |url=https://erowid.org/archive/rhodium/chemistry/phenyl-2-nitropropene.html |title=Synthesis of Phenyl-2-Nitropropene |author= |website=Erowid |access-date=October 7, 2023}}

As used in food, cosmetics, pharmaceuticals, and soap, benzaldehyde is "generally regarded as safe" (GRAS) by the US FDA{{citation | author=Friedrich Brühne | author2=Elaine Wright | contribution=Benzaldehyde | title=Ullmann's Encyclopedia of Industrial Chemistry | edition=7th | publisher=Wiley | year=2007 | page=11| title-link=Ullmann's Encyclopedia of Industrial Chemistry }} and FEMA. This status was reaffirmed after a review in 2005. It is accepted in the European Union as a flavoring agent. Toxicology studies indicate that it is safe and non-carcinogenic in the concentrations used for foods and cosmetics, and may even have anti-carcinogenic (anti-cancer) properties.

For a 70 kg human, the lethal dose is estimated at 50 ml. An acceptable daily intake of 15 mg/day has been identified for benzaldehyde by the United States Environmental Protection Agency.{{Cite web|url=https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=41551 |title=Health and Environmental Effects Profile for Benzaldehyde |last=Assessment|first=US EPA National Center for Environmental|website=cfpub.epa.gov|access-date=2017-09-16}} Benzaldehyde does not accumulate in human tissues. It is metabolized [by what?] and then excreted in urine.

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{{Commons category|Benzaldehyde}}

• {{ICSC|0102|02}}
• {{SIDS|name=benzaldehyde| id=100527}} [https://web.archive.org/web/20181009042751/http://www.inchem.org/documents/sids/sids/100527.pdf Archived]
• [https://archive.today/20121209073221/http://www.chemicalland21.com/arokorhi/specialtychem/perchem/BENZALDEHYDE.htm Benzaldehyde description at ChemicalLand21.com]
• [http://chemsub.online.fr/id_number/CSOID0000000560.html ChemSub Online: Benzaldéhyde.]
• [http://toxnet.nlm.nih.gov/cpdb/chempages/BENZALDEHYDE.html Carcinogenicity Potency Project]

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Category:Flavors

Category:Solvents

Category:Phenyl compounds

Category:Substances discovered in the 19th century