1-Naphthol
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1-Naphthol, or α-naphthol, is an
organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...
with the formula . It is a fluorescent white solid. 1-Naphthol differs from its isomer 2-naphthol by the location of the hydroxyl group on the
naphthalene Naphthalene is an organic compound with formula . It is the simplest polycyclic aromatic hydrocarbon, and is a white Crystal, crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 Parts-per notation ...
ring. The naphthols are naphthalene homologues of
phenol Phenol (also known as carbolic acid, phenolic acid, or benzenol) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile and can catch fire. The molecule consists of a phenyl group () ...
. Both isomers are soluble in simple organic solvents. They are precursors to a variety of useful compounds.


Production

1-Naphthol is prepared by two main routes. In one method, naphthalene is nitrated to give 1-nitronaphthalene, which is hydrogenated to the amine followed by hydrolysis: : : : Alternatively, naphthalene is hydrogenated to tetralin, which is oxidized to 1-tetralone, which undergoes dehydrogenation.


Reactions

Some reactions of 1-naphthol are explicable with reference to its tautomerism, which produces a small amount of the keto tautomer. : One consequence of this tautomerism is the Bucherer reaction, the ammonolysis of 1-naphthol to give 1-aminonaphthalene. 1-Naphthol biodegrades via formation of 1-naphthol-3,4-oxide, which converts to 1,4-naphthoquinone. The 4-position of 1-naphthol is susceptible to electrophilic attack. This regioselective reaction is exploited in the preparation of diazo dyes, which are form using diazonium salts. Reduction of the diazo derivatives gives 4-amino-1-naphthol. Partial reduction of 1-naphthol gives the tetrahydro derivative, leaving intact the phenol ring. Full hydrogenation is catalyzed by rhodium.


Applications and occurrence

1-Naphthol is a precursor to a variety of insecticides including carbaryl and pharmaceuticals including nadolol as well as for the
antidepressant Antidepressants are a class of medications used to treat major depressive disorder, anxiety disorders, chronic pain, and addiction. Common side effects of antidepressants include Xerostomia, dry mouth, weight gain, dizziness, headaches, akathi ...
sertraline and the anti-protozoan therapeutic atovaquone. It undergoes azo coupling to give various azo dyes, but these are generally less useful than those derived from 2-naphthol.
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/ref> 1-Naphthol is a metabolite of the insecticide carbaryl and
naphthalene Naphthalene is an organic compound with formula . It is the simplest polycyclic aromatic hydrocarbon, and is a white Crystal, crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 Parts-per notation ...
. Along with TCPy, it has been shown to decrease testosterone levels in adult men.


Other uses

1-Naphthol is used in each of the following chemical tests, which predate the use of spectroscopic and chromatographic methods: *
Molisch's test Molisch's test is a sensitive chemical test, named after Austrian botanist Hans Molisch, for the presence of carbohydrates, based on the dehydration of the carbohydrate by sulfuric acid or hydrochloric acid to produce an aldehyde, which condenses ...
gives a red- or purple-colored compound to indicate the presence of carbohydrate. * rapid furfural test turns purple quickly (<30s) if fructose is present, distinguishing it from glucose. * Sakaguchi test turns red to indicate the presence of
arginine Arginine is the amino acid with the formula (H2N)(HN)CN(H)(CH2)3CH(NH2)CO2H. The molecule features a guanidinium, guanidino group appended to a standard amino acid framework. At physiological pH, the carboxylic acid is deprotonated (−CO2−) a ...
in proteins. * Voges–Proskauer test changes color from yellow to red to indicate that
glucose Glucose is a sugar with the Chemical formula#Molecular formula, molecular formula , which is often abbreviated as Glc. It is overall the most abundant monosaccharide, a subcategory of carbohydrates. It is mainly made by plants and most algae d ...
is being broken down into acetoin which is used by bacteria for external energy storage.


Safety

1-Naphthol has been described as "moderately toxic".


References


External links


NIST Chemistry WebBook 1-Naphthalenol
* {{DEFAULTSORT:Naphthol, 1- 1-Naphthyl compounds