|Preferred IUPAC name
|Systematic IUPAC name
3D model (JSmol)
CompTox Dashboard (EPA)
|Molar mass||106.124 g·mol−1|
|Appearance||colorless liquid |
|Density||1.044 g/mL, liquid|
|Melting point||−57.12 °C (−70.82 °F; 216.03 K)|
|Boiling point||178.1 °C (352.6 °F; 451.2 K)|
|6.95 g/L (25 °C)|
Refractive index (nD)
|Viscosity||1.321 cP (25 °C)|
Std enthalpy of
Std enthalpy of
|Safety data sheet||J. T. Baker|
|S-phrases (outdated)||(S2), S24|
|Flash point||64 °C (147 °F; 337 K)|
|192 °C (378 °F; 465 K)|
|Lethal dose or concentration (LD, LC):|
LD50 (median dose)
|1300 mg/kg (rat, oral)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
It is a colorless liquid with a characteristic almond-like odor. The primary component of bitter almond oil, benzaldehyde can be extracted from a number of other natural sources. Synthetic benzaldehyde is the flavoring agent in imitation almond extract, which is used to flavor cakes and other baked goods.
As of 1999, 7000 tonnes of synthetic and 100 tonnes of natural benzaldehyde were produced annually. Liquid phase chlorination and oxidation of toluene are the main routes. Numerous other methods have been developed, such as the partial oxidation of benzyl alcohol, alkali hydrolysis of benzal chloride, and the carbonylation of benzene.
A significant quantity of natural benzaldehyde is produced from cinnamaldehyde obtained from cassia oil by the retro-aldol reaction: 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, followed by distillation of the formed benzaldehyde. This reaction also yields acetaldehyde. The natural status of benzaldehyde obtained in this way is controversial.
Almonds, apricots, apples, and cherry kernels contain significant amounts of amygdalin. This glycoside breaks up under enzyme catalysis into benzaldehyde, hydrogen cyanide and two equivalents of glucose.
Benzaldehyde can be oxidized to benzoic acid, which is 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.
With diols, including many sugars, benzaldehyde condenses to form benzylidene acetals.
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:
Benzaldehyde is used as a bee repellent. 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. The beekeeper can then remove the honey frames from the bee hive with less risk to both bees and beekeeper.
Additionally, benzaldehyde is also used as a flavour chemical in JUUL e-cigarette pods, particularly the "Cool Mint", "Cool Cucumber", and "Fruit Medley" varieties. The concentration is relatively low, at ~10-3 mg/mL.
As used in food, cosmetics, pharmaceuticals, and soap, benzaldehyde is "generally regarded as safe" (GRAS) by the US FDA 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 carcinostatic (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. Benzaldehyde does not accumulate in human tissues. It is metabolized and then excreted in urine.
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