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| Names | |||
|---|---|---|---|
| IUPAC name Benzenecarbaldehyde | |||
| Preferred IUPAC name Benzaldehyde[1] | |||
| Other names Benzenecarboxaldehyde Phenylmethanal Benzoic aldehyde | |||
| Identifiers | |||
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3D model (JSmol) | |||
| ChEBI | |||
| ChEMBL | |||
| ChemSpider |
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| ECHA InfoCard | 100.002.601 | ||
| EC Number |
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| KEGG |
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| RTECS number |
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| UNII | |||
| UN number | 1990 | ||
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| Properties | |||
| C7H6O | |||
| Molar mass | 106.124 g·mol−1 | ||
| Appearance | colorless liquid strongly refractive | ||
| Odor | almond-like | ||
| Density | 1.044 g/mL, liquid | ||
| Melting point | −57.12[2] °C (−70.82 °F; 216.03 K) | ||
| Boiling point | 178.1 °C (352.6 °F; 451.2 K) | ||
| 6.95 g/L (25 °C)[3] | |||
| logP | 1.64[4] | ||
| −60.78·10−6 cm3/mol | |||
Refractive index (nD) | 1.5456 | ||
| Viscosity | 1.321cP (25 °C) | ||
| Thermochemistry | |||
Std enthalpy of formation(ΔfH⦵298) | −36.8 kJ/mol | ||
Std enthalpy of combustion(ΔcH⦵298) | −3525.1 kJ/mol | ||
| Hazards | |||
| GHS labelling: | |||
 | |||
| Warning | |||
| H302 | |||
| P264,P270,P301+P312,P330,P501 | |||
| NFPA 704 (fire diamond) | |||
| Flash point | 64 °C (147 °F; 337 K) | ||
| 192 °C (378 °F; 465 K) | |||
| Explosive limits | 1.4–8.5% | ||
| Lethal dose or concentration (LD, LC): | |||
LD50 (median dose) | 1300 mg/kg (rat, oral) | ||
| Safety data sheet (SDS) | J. T. Baker | ||
| Related compounds | |||
Related compounds | Benzyl alcohol Benzoic acid Benzaldehyde oxime | ||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Benzaldehyde (C6H5CHO) is anorganic compound consisting of abenzene ring with aformyl substituent. It is among the simplestaromaticaldehydes and one of the most industrially useful.
It is a colorless liquid with a characteristicodor similar to that ofbitter almonds andcherry, and is commonly used in cherry-flavoredsodas.[5] A component of bitter almond oil, benzaldehyde can be extracted from a number of other natural sources.[6] Synthetic benzaldehyde is the flavoring agent in imitation almond extract, which is used to flavor cakes and other baked goods.[7]
Benzaldehyde was first extracted in 1803 by the French pharmacist Martrès. His experiments focused on elucidating the nature ofamygdalin, the poisonous compound found inbitter almonds, the fruit ofPrunus dulcis.[8] Further work on the oil byPierre Robiquet and Antoine Boutron Charlard, two French chemists, produced benzaldehyde.[9] In 1832,Friedrich Wöhler andJustus von Liebig first synthesized benzaldehyde.[10]
Benzaldehyde can be produced from both petroleum-based chemicals or plant-derived chemicals. Synthetic benzaldehyde is primarily produced using liquid phasechlorination andoxidation oftoluene. Numerous other methods have been developed, such as the partialoxidation ofbenzyl alcohol,alkali hydrolysis ofbenzal chloride, and thecarbonylation of benzene (theGatterman-Koch reaction).[6]
Natural benzaldehyde is produced fromcinnamaldehyde obtained fromcassia oil by the retro-aldol reaction:[11] the cinnamaldehyde is heated in anaqueous/alcoholic solution between 90 °C and 150 °C with abase (most commonlysodium carbonate orbicarbonate) for 5 to 80 hours,[12] followed by distillation of the formed benzaldehyde. This reaction also yieldsacetaldehyde. Thenatural status of benzaldehyde obtained in this way is controversial.[11]
Benzaldehyde and similar chemicals occur naturally in many foods. Most of the benzaldehyde that people eat is from natural plant foods, such asalmonds.[13]
Almonds,apricot seeds,apple seeds, andcherryseed contain significant amounts ofamygdalin. Thisglycoside breaks up under enzyme catalysis into benzaldehyde,hydrogen cyanide and two equivalents ofglucose.
Benzaldehyde contributes to the scent ofoyster mushrooms (Pleurotus ostreatus).[14]
Benzaldehyde is easily oxidized tobenzoic acid in air at room temperature,[15] 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 bydistillation.Benzyl alcohol can be formed from benzaldehyde by means ofhydrogenation. Reaction of benzaldehyde with anhydroussodium acetate andacetic anhydride yieldscinnamic acid, while alcoholicpotassium cyanide can be used tocatalyze the condensation of benzaldehyde tobenzoin. Benzaldehyde undergoesdisproportionation upon treatment with concentrated alkali (Cannizzaro reaction): one molecule of the aldehyde is reduced to thebenzyl alcohol and another molecule is simultaneously oxidized tobenzoic acid.
With diols, including many sugars, benzaldehyde condenses to formbenzylidene acetals.[citation needed]
Benzaldehyde is commonly employed to conferalmond flavor to foods and scented products, including e-cigarette liquids. It is sometimes used in cosmetics products.[16]
In industrial settings, benzaldehyde is used chiefly as a precursor to other organic compounds, ranging from pharmaceuticals to plastic additives. Theaniline dyemalachite green is prepared from benzaldehyde anddimethylaniline. Benzaldehyde is also a precursor to certainacridine dyes. Viaaldol condensations, benzaldehyde is converted into derivatives ofcinnamaldehyde andstyrene. The synthesis ofmandelic acid starts with the addition ofhydrocyanic acid to benzaldehyde:
The resultingcyanohydrin ishydrolysed tomandelic acid. (The scheme above depicts only one of the two formedenantiomers).
Benzaldehyde is used as abee repellent.[17] 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.[18] Thebeekeeper can then remove thehoney frames from the bee hive with less risk to both bees and beekeeper.
Benzaldehyde reacts withnitroethane in the presence of a catalyst to producephenyl-2-nitropropene, a precursor toamphetamine and other chemicals.[19]
As used in food, cosmetics, pharmaceuticals, and soap, benzaldehyde is "generally regarded as safe" (GRAS) by theUS FDA[20] andFEMA.[13] This status was reaffirmed after a review in 2005.[13] It is accepted in the European Union as a flavoring agent.[16] Toxicology studies indicate that it is safe and non-carcinogenic in the concentrations used for foods and cosmetics,[16] and may even haveanti-carcinogenic (anti-cancer) properties.[16]
For a 70 kg human, the lethal dose is estimated at 50 ml.[6] Anacceptable daily intake of 15 mg/day has been identified for benzaldehyde by theUnited States Environmental Protection Agency.[21] Benzaldehyde does not accumulate in human tissues.[16] It is metabolized[by what?] and then excreted in urine.[16]
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