Benzaldehyde

Chembox new
Name = Benzaldehyde
IUPACName = Benzaldehyde
SystematicName = Benzenecarbaldehyde
ImageFileL1 = Benzaldehyde.png ImageSizeL1 = 100px
ImageNameL1 = Benzaldehyde
ImageFileR1 = Benzaldehyde-3D-vdW.png ImageSizeR1 = 120px
ImageNameR1 = Benzaldehyde
OtherNames = Phenylmethanal
Benzenecarboxaldehyde
Benzoic aldehyde
Section1 = Chembox Identifiers
SMILES = c1ccccc1C=O
CASNo = 100-52-7
ChemSpiderID = 235
Section2 = Chembox Properties
C=7|H=6|O=1
Appearance = colorless liquid
Density = 1.0415 g/ml, liquid
Solubility = Slightly soluble
(0.6 wt at 20 °C)
MeltingPt = −26 °C
BoilingPt = 178.1 °C
Viscosity = 1.4 cP at 25 °C
Section4 = Chembox Thermochemistry
DeltaHf = −86.8 kJ/mol
DeltaHc = −3525.1 kJ/mol
Entropy =
Section7 = Chembox Hazards
EUClass = Harmful (Xn)
RPhrases = R22
SPhrases = S2, S24
FlashPt = 63 C (Closed Cup)
NFPA-H = 2
NFPA-F = 2
NFPA-R =
ExternalMSDS = [http://www.jtbaker.com/msds/englishhtml/b0696.htm J. T. Baker]
Section8 = Chembox Related
Function = aldehydes
OtherFunctn = anisaldehyde
vanillin
OtherCpds = Benzyl alcohol
Benzoic acid

Benzaldehyde (C₆H₅CHO) is a chemical compound consisting of a benzene ring with an aldehyde substituent. It is the simplest representative of the aromatic aldehydes and one of the most industrially used members of this family of compounds. At room temperature it is a colorless liquid with a characteristic and pleasant almond-like odor: benzaldehyde is an important component of the scent of almonds, hence its typical odor. It is the primary component of bitter almond oil extract, and can be extracted from a number of other natural sources in which it occurs, such as apricot, cherry, and laurel leaves, peach seeds and, in a glycoside combined form (amygdalin), in certain nuts and kernels. Currently benzaldehyde is primarily made from toluene by a number of different processes.

Production

Benzaldehyde can be obtained by many processes. Currently liquid phase chlorination or oxidation of toluene are among the most used processes. There are also a number of discontinued applications such as partial oxidation of benzyl alcohol, alkali treating of benzal chloride and reaction between benzene and carbon monoxide.

Reactions

On oxidation, benzaldehyde is converted into the odorless benzoic acid. Benzyl alcohol can be formed from benzaldehyde by means of hydrogenation or by treating the compound with alcoholic potassium hydroxide thus undergoing a simultaneous oxidation and reduction which result in the production of potassium benzoate and benzyl alcohol. 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 can also undergo disproportionation in concentrated alkali (Cannizzaro's reaction): one molecule of the aldehyde is reduced to the corresponding alcohol and another molecule is simultaneously oxidized to the salt of a carboxylic acid. The speed of this reaction depends on the substituents present in the aromatic ring.

Uses

While it is commonly employed as a commercial food flavorant (almond flavor) or industrial solvent, benzaldehyde is used chiefly in the synthesis of other organic compounds, ranging from pharmaceuticals to plastic additives. It is also an important intermediate for the processing of perfume and flavoring compounds and in the preparation of certain aniline dyes.

The synthesis of mandelic acid starts from benzaldehyde:

First hydrocyanic acid is added to benzaldehyde and the resulting mandelic acid nitrile is subsequently hydrolysed to a racemic mixture of mandelic acid. (The scheme above depicts only one of the two formed enantiomers).

Glaciologists LaChapelle and Stillman reported in 1966 that benzaldeyde and N-heptaldehyde inhibit the recrystallization of snow and therefore the formation of depth hoar. This treatment may prevent avalanches caused by unstable depth hoar layers. However, the chemicals are not in widespread use because they damage vegetation and contaminate water supplies.Fact|date=February 2007

Biology

Almonds, apricots, apples and cherry kernels, contain significant amounts of amygdalin. This glycoside breaks up under enzyme catalysis into benzaldehyde, hydrocyanic acid and two molecules of glucose.

References

External links

* [http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc01/icsc0102.htm International Chemical Safety Card 0102]
* [http://ecb.jrc.it/ European Chemicals Bureau]
* [http://www.chemicalland21.com/arokorhi/specialtychem/perchem/BENZALDEHYDE.htm Benzaldehyde description at ChemicalLand21.com]