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Hydroquinone, also known as benzene-1,4-diol or quinol, is an aromatic organic compound that is a type of phenol, a derivative of benzene, having the chemical formula C 6 H 4 (OH) 2. It has two hydroxyl groups bonded to a benzene ring in a para position.
Hydroquinone is used to reduce the activated silver ions to metallic silver. During this process, hydroquinone is oxidized to quinone. All silver halide not activated by light or reduced by hydroquinone is removed, leaving a negative by deposited silver where the film had been struck by light.
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Popular developing agents are metol (monomethyl-p-aminophenol hemisulfate), phenidone (1-phenyl-3-pyrazolidinone), dimezone (4,4-dimethyl-1-phenylpyrazolidin-3-one) and hydroquinone (benzene-1,4-diol). Dimezone is thought to resist oxidation in solution better than Phenidone A, but it is not as available as Phenidone A. Dimezone is also known ...
1,4-Benzoquinone, commonly known as para-quinone, is a chemical compound with the formula C 6 H 4 O 2.In a pure state, it forms bright-yellow crystals with a characteristic irritating odor, resembling that of chlorine, bleach, and hot plastic or formaldehyde.
Resonance structures of a semiquinone. Semiquinones (or ubisemiquinones, if their origin is ubiquinone) are free radicals resulting from the removal of one hydrogen atom with its electron during the process of dehydrogenation of a hydroquinone, such as hydroquinone itself or catechol, to a quinone or alternatively the addition of a single hydrogen atom with its electron to a quinone. [1]
The beetles' glands store enough hydroquinone and hydrogen peroxide to allow the beetle to release its chemical spray roughly 20 times. In some cases this is enough to kill a predator. [ 6 ] The main component of the beetle spray is 1,4-benzoquinone, an irritant to the eyes and the respiratory system of vertebrates.
Hydroquinone is the compound most frequently used in skin-whitening products. Due to concerns about its side effects, it was almost banned by the FDA in 2006, as medical issues of carcinogenicity and reports of disfiguring ochronosis existed. [10] In the European Union hydroquinone has been banned in cosmetic creams since 2000. [11]