Benzaldehyde
| Benzaldehyde | | |
| General |
|---|
| Other names | Phenylmethanal
Benzenecarboxaldehyde
Benzoic aldehyde
Benzene carbaldehyde |
| Molecular formula | C7H6O |
| SMILES | c1ccccc1C=O |
| Molar mass | 106.13 g/mol |
| Appearance | colorless liquid |
| CAS number | [100-52-7] |
| Properties |
|---|
| Density and phase | 1.0415 g/ml, liquid |
| Solubility in water | Slightly soluble
(0.6 wt at 20 °C) |
| Solubility in ethanol | Miscible |
| Melting point | −26 °C |
| Boiling point | 178.1 °C |
| Viscosity | 1.4 cP at 25 °C |
| Thermodynamic data |
|---|
Standard enthalpy
of formation Î"fH°liquid | −86.8 kJ/mol |
Standard enthalpy
of combustion Î"cH°liquid | −3525.1 kJ/mol |
Standard molar entropy
S°liquid | ? J.K−1.mol−1 |
| Hazards |
|---|
| EU classification | Harmful (Xn) |
| R-phrases | |
| S-phrases | , |
| NFPA 704 |  | Nfpa_h2.png |
 | Nfpa_f2.png |
 | Nfpa_r0.png |
|
| Supplementary data page |
|---|
Structure and
properties | n, εr, etc. |
Thermodynamic
data | Phase behaviour
Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Regulatory data | Flash point,
RTECS number, etc. |
| Related compounds |
|---|
| Related aldehydes | anisaldehyde
vanillin |
| Related compounds | Benzyl alcohol
Benzoic acid |
Except where noted otherwise, data are given for
materials in their standard state (at 25 °C, 100 kPa)
Infobox disclaimer and references |
|
Benzaldehyde (C
6H
5CHO) 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.
Benzaldehyde can be obtained by many process. Currently liquid phase
chlorination or
oxidation of toluene are among the most used processes. There is also a number of discontinued applications such as partial oxidation of
benzyl alcohol,
alkali treating of
benzal chloride and reaction between benzene and
carbon monoxideOn oxidation, benzaldehyde is converted into unpleasant smelling
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.
While it is commonly employed as a commercial food
flavourant (
almond flavour) 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 flavouring 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).
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.
*
International Chemical Safety Card 0102*
European Chemicals Bureau*
Benzaldehyde description at ChemicalLand21.com
