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1,4-benzoquinone

1,4-Benzoquinone
Skeletal formula
Space-filling model
Para-Benzoquinone needles.jpg
Names
Preferred IUPAC name
Cyclohexa-2,5-diene-1,4-dione
Other names
1,4-Benzoquinone
Benzoquinone
p-Benzoquinone
p-Quinone
Identifiers
106-51-4 YesY
3D model (Jmol) Interactive image
Interactive image
ChEBI CHEBI:16509 YesY
ChEMBL ChEMBL8320 YesY
ChemSpider 4489 YesY
ECHA InfoCard 100.003.097
6307
KEGG C00472 YesY
PubChem 4650
RTECS number DK2625000
UNII 3T006GV98U YesY
Properties
C6H4O2
Molar mass 108.10 g·mol−1
Appearance Yellow solid
Odor Acrid, chlorine-like
Density 1.318 g/cm3 at 20 °C
Melting point 115 °C (239 °F; 388 K)
Boiling point Sublimes
Slightly soluble
Solubility Slightly soluble in petroleum ether; soluble in acetone; very soluble in ethanol, benzene, diethyl ether
Vapor pressure 0.1 mmHg (25°C)
-38.4·10−6 cm3/mol
Hazards
Main hazards Toxic
R-phrases R23/25 R36/37/38 R50
S-phrases S26 S28 S45 S61
Flash point 38 to 93 °C; 100 to 200 °F; 311 to 366 K
Lethal dose or concentration (LD, LC):
LD50 (median dose)
296 mg/kg (mammal, subcutaneous)
93.8 mg/kg (mouse, subcutaneous)
8.5 mg/kg (mouse, IP)
5.6 mg/kg (rat)
130 mg/kg (rat, oral)
25 mg/kg (rat, IV)
US health exposure limits (NIOSH):
PEL (Permissible)
TWA 0.4 mg/m3 (0.1 ppm)
REL (Recommended)
TWA 0.4 mg/m3 (0.1 ppm)
IDLH (Immediate danger)
100 mg/m3
Related compounds
Related compounds
1,2-Benzoquinone
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YesYN ?)
Infobox references

1,4-Benzoquinone, commonly known as para-quinone, is a chemical compound with the formula C6H4O2. In a pure state, it forms bright-yellow crystals with a characteristic irritating odor, resembling that of chlorine, bleach, and hot plastic. This six-membered ring compound is the oxidized derivative of 1,4-hydroquinone. The molecule is multifunctional: it exhibits properties of a ketone, forming an oxime; an oxidant, forming the dihydroxy derivative; and an alkene, undergoing addition reactions, especially those typical for α,β-unsaturated ketones. 1,4-Benzoquinone is sensitive toward both strong mineral acids and alkali, which cause condensation and decomposition of the compound.

1,4-Benzoquinone is prepared by oxidation of diisopropylbenzene via a reaction related to the Hock rearrangement:

The reaction proceeds via the bis(hydroperoxide). Acetone is a coproduct.

Another major process involves the direct hydroxylation of phenol by acidic hydrogen peroxide: C6H5OH + H2O2 → C6H4(OH)2 + H2O Both hydroquinone and catechol are produced. Subsequent oxidation of the hydroquinone gives the quinone.

Quinone was originally prepared industrially by oxidation of aniline, for example by manganese dioxide. This method is mainly practiced in PRC where environmental regulations are more relaxed.

The oxidation of hydroquinone is rapid and convenient and therefore desirable for the laboratory. 1,4-Benzoquinone can be prepared from hydroquinone via a number of oxidation methods. One such method makes use of hydrogen peroxide as the oxidizer and iodine or an iodine salt as a catalyst for the oxidation occurring in a polar solvent; e.g. isopropyl alcohol.


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Wikipedia

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