4-Nitrophenol
Encyclopedia
4-Nitrophenol is a phenolic
compound that has a nitro group at the opposite position of hydroxy group on the benzene ring.
s in the crystalline state. The alpha-form is colorless pillars, unstable at room temperature, and stable toward sunlight. The beta-form is yellow pillars, stable at room temperature, and gradually turns red upon irradiation of sunlight. Usually 4-nitrophenol exists as a mixture of these two forms.
In solution, 4-nitrophenol has a dissociation constant
(pKa) of 7.08 at 22 °C. Solution of 4-nitrophenol alone appears colorless or pale yellow, whereas its phenolic salts tend to develop a bright yellow color. This color-changing property makes this compound useful as a pH indicator
.
. It is reduced to 4-aminophenol, then acetylated with acetic anhydride
.
4-Nitrophenol is used as the precursor for the preparation of phenetidine and acetophenetidine, indicators, and raw materials for fungicides. Bioaccumulation
of this compound rarely occurs.
In peptide synthesis
, carboxylate ester
derivatives of 4-nitrophenol may serve as activated components for construction of amide
moieties.
4-Nitrophenol is a product of the enzymatic cleavage of several substrates. Amounts of 4-nitrophenol produced by a particular enzyme
in the presence of its corresponding substrate can be measured with a spectrophotometer at or around 400 nm and used as a proxy measurement for the amount of the enzyme in the sample.
which is responsible for methemoglobinemia
, potentially causing cyanosis, confusion, and unconsciousness. When ingested, it causes abdominal pain and vomiting. Prolonged contact with skin may cause allergic response. Genotoxicity and carcinogenicity of 4-nitrophenol are not known. LD50: mouse, p.o. 282 mg/kg; rat, p.o. 202 mg/kg.
Phenols
In organic chemistry, phenols, sometimes called phenolics, are a class of chemical compounds consisting of a hydroxyl group bonded directly to an aromatic hydrocarbon group...
compound that has a nitro group at the opposite position of hydroxy group on the benzene ring.
Properties
4-Nitrophenol shows two polymorphPolymorphism (materials science)
Polymorphism in materials science is the ability of a solid material to exist in more than one form or crystal structure. Polymorphism can potentially be found in any crystalline material including polymers, minerals, and metals, and is related to allotropy, which refers to chemical elements...
s in the crystalline state. The alpha-form is colorless pillars, unstable at room temperature, and stable toward sunlight. The beta-form is yellow pillars, stable at room temperature, and gradually turns red upon irradiation of sunlight. Usually 4-nitrophenol exists as a mixture of these two forms.
In solution, 4-nitrophenol has a dissociation constant
Dissociation constant
In chemistry, biochemistry, and pharmacology, a dissociation constant is a specific type of equilibrium constant that measures the propensity of a larger object to separate reversibly into smaller components, as when a complex falls apart into its component molecules, or when a salt splits up into...
(pKa) of 7.08 at 22 °C. Solution of 4-nitrophenol alone appears colorless or pale yellow, whereas its phenolic salts tend to develop a bright yellow color. This color-changing property makes this compound useful as a pH indicator
PH indicator
A pH indicator is a halochromic chemical compound that is added in small amounts to a solution so that the pH of the solution can be determined visually. Hence a pH indicator is a chemical detector for hydronium ions or hydrogen ions in the Arrhenius model. Normally, the indicator causes the...
.
Uses
4-Nitrophenol is an intermediate in the synthesis of paracetamolParacetamol
Paracetamol INN , or acetaminophen USAN , is a widely used over-the-counter analgesic and antipyretic . It is commonly used for the relief of headaches and other minor aches and pains and is a major ingredient in numerous cold and flu remedies...
. It is reduced to 4-aminophenol, then acetylated with acetic anhydride
Acetic anhydride
Acetic anhydride, or ethanoic anhydride, is the chemical compound with the formula 2O. Commonly abbreviated Ac2O, it is the simplest isolatable acid anhydride and is a widely used reagent in organic synthesis...
.
4-Nitrophenol is used as the precursor for the preparation of phenetidine and acetophenetidine, indicators, and raw materials for fungicides. Bioaccumulation
Bioaccumulation
Bioaccumulation refers to the accumulation of substances, such as pesticides, or other organic chemicals in an organism. Bioaccumulation occurs when an organism absorbs a toxic substance at a rate greater than that at which the substance is lost...
of this compound rarely occurs.
In peptide synthesis
Peptide synthesis
In organic chemistry, peptide synthesis is the production of peptides, which are organic compounds in which multiple amino acids are linked via amide bonds which are also known as peptide bonds...
, carboxylate ester
Carboxylate ester
A carboxylate ester is a carboxylic acid ester.Typically, the term "ester" refers to a carboxylate ester, but technically, the parent acid of an ester can be any acid.For example, methyl formate is a carboxylate ester....
derivatives of 4-nitrophenol may serve as activated components for construction of amide
Amide
In chemistry, an amide is an organic compound that contains the functional group consisting of a carbonyl group linked to a nitrogen atom . The term refers both to a class of compounds and a functional group within those compounds. The term amide also refers to deprotonated form of ammonia or an...
moieties.
4-Nitrophenol is a product of the enzymatic cleavage of several substrates. Amounts of 4-nitrophenol produced by a particular enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
in the presence of its corresponding substrate can be measured with a spectrophotometer at or around 400 nm and used as a proxy measurement for the amount of the enzyme in the sample.
Toxicity
4-Nitrophenol irritates the eyes, skin, and respiratory tract. It may also cause inflammation of those parts. It has a delayed interaction with blood and forms methaemoglobinMethaemoglobin
Methemoglobin is a form of the oxygen-carrying metalloprotein hemoglobin, in which the iron in the heme group is in the Fe3+ state, not the Fe2+ of normal hemoglobin. Methemoglobin cannot release bound oxygen, unlike oxyhemoglobin. It is a bluish chocolate-brown in color...
which is responsible for methemoglobinemia
Methemoglobinemia
Methemoglobinemia is a disorder characterized by the presence of a higher than normal level of methemoglobin in the blood. Methemoglobin is an oxidized form of hemoglobin that has an increased affinity for oxygen, resulting in a reduced ability to release oxygen to tissues. The oxygen–hemoglobin...
, potentially causing cyanosis, confusion, and unconsciousness. When ingested, it causes abdominal pain and vomiting. Prolonged contact with skin may cause allergic response. Genotoxicity and carcinogenicity of 4-nitrophenol are not known. LD50: mouse, p.o. 282 mg/kg; rat, p.o. 202 mg/kg.