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2-Aminonaphthalene-1-sulphonic acid is an aromatic amino sulfonic acid commonly known as Tobias acid.
2-Aminonaphthalene-1-sulphonic acid contains a diazotizable primary amino group and a strongly acidic sulfonic acid group on adjacent positions of a naphthalene ring.
2-Aminonaphthalene-1-sulphonic acid is used principally as an intermediate for azo lake pigments, organic pigments, direct and reactive dyes, printing-ink colorants, and further sulfonated dye intermediates.
CAS Number: 81-16-3
EC Number: 201-331-5
Molecular Formula: C₁₀H₉NO₃S
Molecular Weight: 223.25 g/mol
SYNONYMS
Tobias Acid, Tobias' Acid, Tobias Sulfonic Acid, 2-Amino-1-naphthalenesulfonic Acid, 2-Amino-1-naphthalenesulphonic Acid, 2-Aminonaphthalene-1-sulfonic Acid, 2-Aminonaphthalene-1-sulphonic Acid, 2-Naphthylamine-1-sulfonic Acid, 2-Naphthylamine-1-sulphonic Acid, β-Naphthylamine-1-sulfonic Acid, Beta-Naphthylamine-1-sulfonic Acid, β-Naphthylamine-1-sulphonic Acid, Beta-Naphthylamine-1-sulphonic Acid, 1-Sulfo-2-aminonaphthalene, 1-Sulpho-2-aminonaphthalene, 2-Amino-1-sulfonaphthalene, 2-Amino-1-sulphonaphthalene, 2-Amino-1-naphthalenesulfonate, Naphthalene-1-sulfonic Acid, 2-amino-, Naphthalene-1-sulphonic Acid, 2-amino-, 1-Naphthalenesulfonic Acid, 2-amino-, 1-Naphthalenesulphonic Acid, 2-amino-, 2-Aminonaphthalene-1-sulfonate, 2-Aminonaphthalene-o-sulfonic Acid, 2-Aminonaphthalene-o-sulphonic Acid, ortho-Aminonaphthalenesulfonic Acid, ortho-Aminonaphthalenesulphonic Acid, 2-Amino-1-naphthylsulfonic Acid, 2-Amino-1-naphthylsulphonic Acid, Naphthylamine Sulfonic Acid, Naphthylamine Sulphonic Acid, Aminonaphthalenesulfonic Acid, Aminonaphthalenesulphonic Acid, 2-Naphthylamine-1-sulfonate, Tobias Acid Free Acid, Tobias Acid Intermediate, Azo-Pigment Intermediate, Azo-Lake-Pigment Intermediate, Lithol-Red Intermediate, Naphthol-Pigment Intermediate, Diazotizable Naphthylamine Sulfonic Acid, Aromatic Amine Sulfonic Acid, Sulfonated Naphthylamine, Dye Intermediate 81-16-3, Pigment Intermediate 81-16-3, High-Purity Tobias Acid, Technical-Grade Tobias Acid, Pigment-Grade Tobias Acid, Dye-Grade Tobias Acid, Reagent-Grade Tobias Acid, Analytical-Grade Tobias Acid, Tobias Acid Analytical Standard, C₁₀H₉NO₃S, CAS 81-16-3, EC 201-331-5, PubChem CID 6670, DTXSID7020922, UNII F9QKW1FCE0, GWIAAIUASRVOIA-UHFFFAOYSA-N
APPLICATIONS
2-Aminonaphthalene-1-sulphonic acid serves as a major diazo component in the manufacture of azo lake pigments.
2-Aminonaphthalene-1-sulphonic acid undergoes controlled diazotization to form a reactive diazonium intermediate for coupling with suitable naphthol-based components.
2-Aminonaphthalene-1-sulphonic acid contributes a naphthalene ring that supports strong visible absorption and deep red pigment shades after coupling.
2-Aminonaphthalene-1-sulphonic acid enables pigment properties to be adjusted through coupler selection, laking metal, particle formation, and finishing conditions.
2-Aminonaphthalene-1-sulphonic acid functions as a traditional intermediate for producing lithol-type red pigments.
2-Aminonaphthalene-1-sulphonic acid provides the diazotized aromatic component used to construct the characteristic azo chromophore.
2-Aminonaphthalene-1-sulphonic acid supports formation of red lake pigments after coupling and conversion into an insoluble metal salt.
2-Aminonaphthalene-1-sulphonic acid requires high chemical purity to achieve consistent shade, strength, brightness, and dispersion behavior.
2-Aminonaphthalene-1-sulphonic acid serves as a diazo component for pigments based on 2-hydroxy-3-naphthoic acid coupling chemistry.
2-Aminonaphthalene-1-sulphonic acid supports coupling with BONA-type components to generate strongly colored azo structures.
2-Aminonaphthalene-1-sulphonic acid contributes sulfonate functionality that permits subsequent laking with suitable polyvalent metal ions.
2-Aminonaphthalene-1-sulphonic acid enables the resulting pigment to combine low solubility with useful color strength and application stability.
2-Aminonaphthalene-1-sulphonic acid functions in the preparation of mixed-diazo pigment compositions.
2-Aminonaphthalene-1-sulphonic acid can be combined with diazonium components derived from substituted aminobenzenesulfonic acids.
2-Aminonaphthalene-1-sulphonic acid supports pigment systems in which multiple diazo components broaden shade and modify rheological performance.
2-Aminonaphthalene-1-sulphonic acid contributes to compositions designed for improved color development and dispersion in printing vehicles.
2-Aminonaphthalene-1-sulphonic acid serves as an intermediate for organic pigments used in offset printing inks.
2-Aminonaphthalene-1-sulphonic acid supports pigment structures capable of dispersing in resinous and oil-based printing vehicles after suitable surface treatment.
2-Aminonaphthalene-1-sulphonic acid contributes to pigments whose particle size and surface chemistry influence flow, gloss, transparency, and print strength.
2-Aminonaphthalene-1-sulphonic acid enables pigment manufacturers to modify ink rheology through coupling, laking, resin treatment, and particle conditioning.
2-Aminonaphthalene-1-sulphonic acid functions as an intermediate for pigments used in publication and packaging inks.
2-Aminonaphthalene-1-sulphonic acid supports production of red and related shades used in compatible printing systems.
2-Aminonaphthalene-1-sulphonic acid contributes to pigments that can be formulated for controlled viscosity, color strength, and transfer.
2-Aminonaphthalene-1-sulphonic acid requires final pigment testing for migration, bleed resistance, lightfastness, solvent resistance, and application-specific compliance.
2-Aminonaphthalene-1-sulphonic acid serves as an intermediate for pigments used in gravure and flexographic ink research.
2-Aminonaphthalene-1-sulphonic acid supports azo pigments capable of being dispersed in solventborne or waterborne resin systems after suitable finishing.
2-Aminonaphthalene-1-sulphonic acid contributes to colorants whose performance depends on particle size, surface polarity, binder compatibility, and milling conditions.
2-Aminonaphthalene-1-sulphonic acid enables formulation studies involving print density, transparency, drying, adhesion, and rub resistance.
2-Aminonaphthalene-1-sulphonic acid functions in the preparation of pigment compositions for water-based inkjet inks.
2-Aminonaphthalene-1-sulphonic acid supports azo lake pigments designed for fine particle dispersion in aqueous media.
2-Aminonaphthalene-1-sulphonic acid contributes ionic functionality that can be exploited during pigment synthesis or surface modification.
2-Aminonaphthalene-1-sulphonic acid enables investigation of dispersion stability, nozzle reliability, optical density, color gamut, and storage behavior.
2-Aminonaphthalene-1-sulphonic acid serves as an intermediate for pigments used in industrial coatings.
2-Aminonaphthalene-1-sulphonic acid supports formation of azo lake structures compatible with selected solventborne, waterborne, and powder-coating systems.
2-Aminonaphthalene-1-sulphonic acid contributes to pigments that provide decorative red shades and controlled hiding or transparency.
2-Aminonaphthalene-1-sulphonic acid requires finished coatings to be evaluated for weathering, heat stability, solvent resistance, migration, and overcoating behavior.
2-Aminonaphthalene-1-sulphonic acid functions as an intermediate for colorants used in plastics.
2-Aminonaphthalene-1-sulphonic acid supports production of insoluble azo pigments for compatible thermoplastic and thermosetting polymer systems.
2-Aminonaphthalene-1-sulphonic acid contributes to derived pigments whose heat stability and migration resistance depend on laking and crystal form.
2-Aminonaphthalene-1-sulphonic acid enables coloration studies involving polyolefins, vinyl polymers, engineering plastics, and masterbatch systems when the final pigment is suitable.
2-Aminonaphthalene-1-sulphonic acid serves as an intermediate for pigments used in rubber and elastomer coloration.
2-Aminonaphthalene-1-sulphonic acid supports production of red azo pigments capable of being dispersed through suitable rubber compounds.
2-Aminonaphthalene-1-sulphonic acid contributes to pigments whose surface treatment affects wetting, dispersion, cure interaction, and blooming.
2-Aminonaphthalene-1-sulphonic acid requires the final colorant to be evaluated for heat resistance, sulfur-curing compatibility, extraction, and migration.
2-Aminonaphthalene-1-sulphonic acid functions as a building block for direct dyes.
2-Aminonaphthalene-1-sulphonic acid provides a diazotizable amino group for constructing monoazo, disazo, and polyazo structures.
2-Aminonaphthalene-1-sulphonic acid contributes a sulfonic acid group that increases the water compatibility of many derived dyes.
2-Aminonaphthalene-1-sulphonic acid enables dye affinity, shade, solubility, and leveling behavior to be modified through coupling-component selection.
2-Aminonaphthalene-1-sulphonic acid serves as an intermediate for reactive dyes used on cellulose.
2-Aminonaphthalene-1-sulphonic acid supports incorporation of naphthalene-based azo units into molecules containing fiber-reactive groups.
2-Aminonaphthalene-1-sulphonic acid contributes to dyes capable of producing clear bluish-red shades on cotton under suitable application conditions.
2-Aminonaphthalene-1-sulphonic acid enables water solubility and fiber reactivity to be combined within a single derived colorant structure.
2-Aminonaphthalene-1-sulphonic acid functions as a diazo component in asymmetrical polyazo dye synthesis.
2-Aminonaphthalene-1-sulphonic acid provides an ionic naphthalene unit capable of modifying color, solubility, and molecular aggregation.
2-Aminonaphthalene-1-sulphonic acid supports preparation of multi-chromophore colorants for inks, coatings, textiles, and functional materials.
2-Aminonaphthalene-1-sulphonic acid enables the position and number of ionic groups to be varied in advanced dye structures.
2-Aminonaphthalene-1-sulphonic acid serves as an intermediate for dyes applied to cotton and regenerated cellulose.
2-Aminonaphthalene-1-sulphonic acid supports water-soluble colorants capable of interacting with cellulose through ionic, hydrogen-bonding, and planar aromatic interactions.
2-Aminonaphthalene-1-sulphonic acid contributes to dye structures designed for exhaust, padding, printing, or reactive application processes.
2-Aminonaphthalene-1-sulphonic acid requires the finished dye to be assessed for fixation, wash-off, shade reproducibility, fastness, and wastewater behavior.
2-Aminonaphthalene-1-sulphonic acid functions as an intermediate for dyes used in paper coloration.
2-Aminonaphthalene-1-sulphonic acid supports preparation of sulfonated azo dyes compatible with aqueous paper-processing systems.
2-Aminonaphthalene-1-sulphonic acid contributes to colorants capable of being added to pulp, surface-size mixtures, or coating formulations.
2-Aminonaphthalene-1-sulphonic acid enables paper-dye performance to be adjusted for affinity, bleed resistance, shade, brightness, and process-water retention.
2-Aminonaphthalene-1-sulphonic acid serves as an intermediate for leather and specialty-fiber dyes.
2-Aminonaphthalene-1-sulphonic acid provides a water-compatible aromatic diazo component for producing acid and direct-type colorants.
2-Aminonaphthalene-1-sulphonic acid supports dyes whose performance can be tailored through additional sulfonate, metal-binding, or reactive substituents.
2-Aminonaphthalene-1-sulphonic acid requires final dye evaluation for penetration, leveling, fixation, rubbing fastness, and wastewater treatability.
2-Aminonaphthalene-1-sulphonic acid functions as a starting material for pigment compositions containing resin or rosin derivatives.
2-Aminonaphthalene-1-sulphonic acid supports coupling processes performed in the presence of modified resinous materials.
2-Aminonaphthalene-1-sulphonic acid contributes to pigments whose surfaces are conditioned during synthesis to improve dispersion in ink varnishes.
2-Aminonaphthalene-1-sulphonic acid enables improvements in flow, gloss, transparency, flocculation resistance, and color development.
2-Aminonaphthalene-1-sulphonic acid serves as a precursor for surface-modified carbonaceous pigments.
2-Aminonaphthalene-1-sulphonic acid can be diazotized and reacted with suitable pigment surfaces to introduce sulfonated aromatic groups.
2-Aminonaphthalene-1-sulphonic acid supports modification of pigment dispersibility and surface charge in aqueous systems.
2-Aminonaphthalene-1-sulphonic acid enables preparation of modified black pigments for inks, coatings, and related dispersion applications.
2-Aminonaphthalene-1-sulphonic acid functions as a colorant intermediate in color-filter research.
2-Aminonaphthalene-1-sulphonic acid supports preparation of dyes or pigment derivatives containing an ionic naphthalene-based chromophoric component.
2-Aminonaphthalene-1-sulphonic acid contributes to formulations investigated for controlled spectral transmission and color purity.
2-Aminonaphthalene-1-sulphonic acid requires final color-filter materials to be evaluated for heat resistance, light stability, solubility, patterning, and electrical performance.
2-Aminonaphthalene-1-sulphonic acid serves as the starting material for producing Amino G Acid.
2-Aminonaphthalene-1-sulphonic acid undergoes rearrangement and additional sulfonation to form 2-amino-6,8-naphthalenedisulfonic acid.
2-Aminonaphthalene-1-sulphonic acid supports manufacture of a more highly sulfonated intermediate used in dye production.
2-Aminonaphthalene-1-sulphonic acid enables the Amino G Acid yield to be influenced through reaction temperature and residence-time control.
2-Aminonaphthalene-1-sulphonic acid functions as the starting material for producing Amino J Acid.
2-Aminonaphthalene-1-sulphonic acid can be converted through sulfonation and hydrolysis into 2-amino-5,7-naphthalenedisulfonic acid.
2-Aminonaphthalene-1-sulphonic acid supports production of an important intermediate for water-soluble dyes.
2-Aminonaphthalene-1-sulphonic acid enables the ratio of Amino J Acid to Amino G Acid to be adjusted through process-temperature selection.
2-Aminonaphthalene-1-sulphonic acid serves as a precursor for aminonaphthalenedisulfonic and aminonaphthalenetrisulfonic acid derivatives.
2-Aminonaphthalene-1-sulphonic acid provides a defined substitution pattern from which additional sulfonic acid groups can be introduced.
2-Aminonaphthalene-1-sulphonic acid supports preparation of intermediates having higher aqueous solubility and altered dye-substrate affinity.
2-Aminonaphthalene-1-sulphonic acid enables development of direct, reactive, acid, and specialty dyes through further functionalization.
2-Aminonaphthalene-1-sulphonic acid functions as a substrate in controlled diazotization-process development.
2-Aminonaphthalene-1-sulphonic acid forms a sparingly soluble diazonium product whose crystal characteristics influence subsequent pigment quality.
2-Aminonaphthalene-1-sulphonic acid supports investigation of dispersants and protective colloids that promote fine diazonium-particle formation.
2-Aminonaphthalene-1-sulphonic acid enables improved pigment strength, shade, brightness, and reproducibility when diazotization is properly controlled.
2-Aminonaphthalene-1-sulphonic acid serves as a model aromatic amine for azo-coupling kinetics.
2-Aminonaphthalene-1-sulphonic acid supports investigation of diazotization rate, diazonium stability, coupling pH, particle nucleation, and reaction completion.
2-Aminonaphthalene-1-sulphonic acid provides an ionic aromatic structure suitable for monitoring by chromatography and ultraviolet spectroscopy.
2-Aminonaphthalene-1-sulphonic acid enables process variables to be correlated with pigment yield, impurity formation, shade, and filtration behavior.
2-Aminonaphthalene-1-sulphonic acid functions as an analytical reference material for dye-intermediate quality control.
2-Aminonaphthalene-1-sulphonic acid supports calibration of liquid-chromatographic, capillary-electrophoretic, ultraviolet, and mass-spectrometric methods.
2-Aminonaphthalene-1-sulphonic acid enables measurement of residual starting material in pigments, dyes, process liquors, and wastewater.
2-Aminonaphthalene-1-sulphonic acid requires characterized assay, moisture, salt content, isomer profile, and impurity data for quantitative analysis.
2-Aminonaphthalene-1-sulphonic acid serves as a reference for detecting positional aminonaphthalenesulfonic acid isomers.
2-Aminonaphthalene-1-sulphonic acid supports chromatographic differentiation from aniline, aminobenzenesulfonic acids, and other aminonaphthalenesulfonic acids.
2-Aminonaphthalene-1-sulphonic acid enables manufacturers to identify isomeric contamination that can change dye shade and coupling behavior.
2-Aminonaphthalene-1-sulphonic acid contributes to method validation through retention, spectral, mass, and purity comparisons.
2-Aminonaphthalene-1-sulphonic acid functions as a quality-control standard for monitoring 2-aminonaphthalene contamination.
2-Aminonaphthalene-1-sulphonic acid production can generate small quantities of 2-aminonaphthalene as a side product.
2-Aminonaphthalene-1-sulphonic acid requires stringent purification because 2-aminonaphthalene is a recognized carcinogenic impurity.
2-Aminonaphthalene-1-sulphonic acid supports safer pigment and dye manufacture when impurity extraction and sensitive analytical limits are applied.
2-Aminonaphthalene-1-sulphonic acid serves as a process-performance reference during the Bucherer amination reaction.
2-Aminonaphthalene-1-sulphonic acid supports measurement of conversion from 2-hydroxynaphthalene-1-sulfonic acid into the corresponding amino compound.
2-Aminonaphthalene-1-sulphonic acid enables evaluation of ammonia concentration, sulfur-dioxide donor, temperature, pressure, and reaction time.
2-Aminonaphthalene-1-sulphonic acid contributes to optimization of yield while suppressing residual naphthol and carcinogenic 2-aminonaphthalene impurities.
2-Aminonaphthalene-1-sulphonic acid functions as a target product in sulfonation–amination process studies.
2-Aminonaphthalene-1-sulphonic acid supports evaluation of chlorosulfonic-acid addition, low-temperature sulfonation, neutralization, extraction, and precipitation.
2-Aminonaphthalene-1-sulphonic acid enables process engineers to correlate reaction conditions with isomer purity, yield, color, and filterability.
2-Aminonaphthalene-1-sulphonic acid requires closed corrosion-resistant equipment and controlled acid, ammonia, and sulfur-dioxide handling.
2-Aminonaphthalene-1-sulphonic acid serves as a target substance in industrial-wastewater recovery.
2-Aminonaphthalene-1-sulphonic acid can be recovered from suitable process liquors through extraction, adsorption, ion exchange, membrane treatment, or controlled precipitation.
2-Aminonaphthalene-1-sulphonic acid recovery supports reduced raw-material loss and lower color and organic loading in wastewater.
2-Aminonaphthalene-1-sulphonic acid enables circular process improvements when recovered material meets impurity and performance specifications.
2-Aminonaphthalene-1-sulphonic acid functions as a target analyte in environmental monitoring of dye-manufacturing discharges.
2-Aminonaphthalene-1-sulphonic acid supports assessment of wastewater-treatment efficiency, sediment association, photolysis, and biological removal.
2-Aminonaphthalene-1-sulphonic acid enables laboratories to distinguish the parent intermediate from downstream dyes and transformation products.
2-Aminonaphthalene-1-sulphonic acid requires prevention of uncontrolled release despite its relatively low measured bioaccumulation potential.
2-Aminonaphthalene-1-sulphonic acid serves as a model ionic aromatic amine in environmental-fate research.
2-Aminonaphthalene-1-sulphonic acid supports investigation of anionic mobility, adsorption to suspended solids, and irreversible binding to humic materials.
2-Aminonaphthalene-1-sulphonic acid enables comparison of low-volatility sulfonated compounds with nonsulfonated aromatic amines.
2-Aminonaphthalene-1-sulphonic acid contributes to understanding how pH, ionic form, organic matter, and sunlight influence environmental behavior.
2-Aminonaphthalene-1-sulphonic acid functions as a model compound in activated-sludge and biodegradation studies.
2-Aminonaphthalene-1-sulphonic acid supports evaluation of biological adaptation to sulfonated aromatic dye intermediates.
2-Aminonaphthalene-1-sulphonic acid enables monitoring of parent-compound disappearance and formation of aromatic transformation products.
2-Aminonaphthalene-1-sulphonic acid requires analytical confirmation because physical adsorption can be mistaken for complete biodegradation.
2-Aminonaphthalene-1-sulphonic acid serves as a laboratory reagent in research on aromatic sulfonic-acid chemistry.
2-Aminonaphthalene-1-sulphonic acid provides both electrophile-directing sulfonic functionality and a derivatizable amino group.
2-Aminonaphthalene-1-sulphonic acid supports diazotization, acylation, sulfonylation, halogenation, oxidation, reduction, and further sulfonation studies.
2-Aminonaphthalene-1-sulphonic acid enables preparation of symmetrical and asymmetrical naphthalene derivatives for colorant and materials research.
2-Aminonaphthalene-1-sulphonic acid functions as a precursor for amino-group-protected naphthalene sulfonic acid derivatives.
2-Aminonaphthalene-1-sulphonic acid can undergo acetylation or other temporary protection before controlled ring substitution.
2-Aminonaphthalene-1-sulphonic acid supports preparation of halogenated or otherwise substituted intermediates while limiting unwanted amino-group reactions.
2-Aminonaphthalene-1-sulphonic acid enables sequential synthesis of functional dye and pigment building blocks.
2-Aminonaphthalene-1-sulphonic acid serves as a source of 2-aminonaphthalene under controlled desulfonation research conditions.
2-Aminonaphthalene-1-sulphonic acid can undergo hydrolytic removal of the sulfonic acid group under sufficiently severe acidic conditions.
2-Aminonaphthalene-1-sulphonic acid supports historical studies of sulfonation reversibility and naphthylamine recovery.
2-Aminonaphthalene-1-sulphonic acid requires exceptional containment in this context because the resulting 2-aminonaphthalene is carcinogenic.
2-Aminonaphthalene-1-sulphonic acid functions as a process-control reference in acid precipitation.
2-Aminonaphthalene-1-sulphonic acid can be isolated from soluble sodium or ammonium salts by controlled reduction of pH.
2-Aminonaphthalene-1-sulphonic acid supports evaluation of precipitation temperature, crystal size, washing efficiency, filtration rate, and residual salt.
2-Aminonaphthalene-1-sulphonic acid enables production of free-acid material suitable for high-quality pigment manufacture when precipitation is properly controlled.
2-Aminonaphthalene-1-sulphonic acid serves as a benchmark intermediate in historical and modern dye-chemistry education.
2-Aminonaphthalene-1-sulphonic acid demonstrates the relationship between diazotization, azo coupling, sulfonate solubility, and lake-pigment formation.
2-Aminonaphthalene-1-sulphonic acid supports instruction in positional isomerism among aminonaphthalenesulfonic acids.
2-Aminonaphthalene-1-sulphonic acid requires professional laboratory controls because aromatic-amine dust and carcinogenic impurities must be minimized.
DESCRIPTION
2-Aminonaphthalene-1-sulphonic acid is the chemical commonly known as Tobias acid and is identified by CAS Number 81-16-3 and EC Number 201-331-5.
2-Aminonaphthalene-1-sulphonic acid has the molecular formula C₁₀H₉NO₃S and a molecular weight of approximately 223.25 g/mol.
2-Aminonaphthalene-1-sulphonic acid contains a primary amino group at position 2 and a sulfonic acid group at position 1 of the naphthalene ring.
2-Aminonaphthalene-1-sulphonic acid normally exists as a zwitterionic or ionic solid rather than as a volatile neutral aromatic amine.
2-Aminonaphthalene-1-sulphonic acid appears as white needles, scales, or a white to light-orange crystalline powder.
2-Aminonaphthalene-1-sulphonic acid is slightly soluble in cold water, more soluble in hot water, and only very slightly soluble in alcohol or ether.
2-Aminonaphthalene-1-sulphonic acid has a reported water solubility near 4.1 g/L at 20°C and a reported pKa near 2.35.
2-Aminonaphthalene-1-sulphonic acid has negligible vapor pressure and presents occupational exposure mainly through dust and direct contact.
2-Aminonaphthalene-1-sulphonic acid is commonly produced by sulfonating 2-naphthol to form oxy-Tobias acid and converting the hydroxy group into an amino group through a Bucherer reaction.
2-Aminonaphthalene-1-sulphonic acid is isolated by extraction of organic impurities followed by acidification, precipitation, filtration, washing, and drying.
2-Aminonaphthalene-1-sulphonic acid quality control commonly includes assay, moisture, acidity, ash, color, residual 2-naphthol, positional isomers, and 2-aminonaphthalene.
2-Aminonaphthalene-1-sulphonic acid requires especially strict control of 2-aminonaphthalene because that process impurity is carcinogenic and can impair pigment quality.
2-Aminonaphthalene-1-sulphonic acid has relatively low reported acute oral toxicity but can cause serious eye irritation according to some notified classifications.
2-Aminonaphthalene-1-sulphonic acid may irritate the skin and respiratory tract when dust is generated, although published classifications are not fully uniform.
2-Aminonaphthalene-1-sulphonic acid emits toxic nitrogen-oxide and sulfur-oxide fumes when strongly heated to decomposition.
2-Aminonaphthalene-1-sulphonic acid should be handled with dust containment, local exhaust ventilation, protective gloves, protective clothing, and chemical eye protection.
PROPERTIES
Chemical Name: 2-Aminonaphthalene-1-sulphonic acid
Common Name: Tobias acid
Alternative Common Name: 2-Naphthylamine-1-sulphonic acid
Preferred IUPAC Name: 2-Aminonaphthalene-1-sulfonic acid
Registry Name: 1-Naphthalenesulfonic acid, 2-amino-
CAS Number: 81-16-3
EC Number: 201-331-5
PubChem CID: 6670
DSSTox Identifier: DTXSID7020922
UNII: F9QKW1FCE0
Molecular Formula: C₁₀H₉NO₃S
Molecular Weight: 223.25 g/mol
Exact Molecular Weight: Approximately 223.0303 Da
InChIKey: GWIAAIUASRVOIA-UHFFFAOYSA-N
Chemical Family: Aminonaphthalenesulfonic acids
Chemical Classification: Aromatic amine sulfonic acid
Functional Groups: Primary aromatic amino group and sulfonic acid group
Amino-Group Position: 2-position
Sulfonic-Acid Position: 1-position
Physical State: Crystalline solid
Appearance: White needles, white scales, or white to light-orange crystalline powder
Odor: No strong characteristic odor expected
Water Solubility at 20°C: Approximately 4.1 g/L
Cold-Water Solubility: Slight
Hot-Water Solubility: Greater than in cold water
Alcohol Solubility: Very slight
Ether Solubility: Very slight
Reported Log Kow: Approximately −1.16
Reported pKa: Approximately 2.35
Vapor Pressure at 25°C: Estimated near 5.3 × 10⁻¹⁰ mmHg
Volatility: Negligible
Primary Airborne Exposure Form: Dust
Primary Industrial Function: Dye and pigment intermediate
Primary Pigment Application: Azo lake and lithol-type red pigments
Primary Dye Applications: Direct, reactive, polyazo, paper, textile, and specialty dyes
Primary Diazo Function: Aromatic diazonium-component precursor
Important Coupling Component: 2-Hydroxy-3-naphthoic acid and related derivatives
Downstream Intermediates: Amino G Acid, Amino J Acid, and other more highly sulfonated aminonaphthalenes
Primary Manufacturing Starting Material: 2-Naphthol
Primary Manufacturing Intermediate: 2-Hydroxynaphthalene-1-sulfonic acid
Primary Conversion Reaction: Bucherer amination
Common Commercial Forms: Free acid, wet cake, sodium salt, ammonium salt, or process solution
Important Process Impurity: 2-Aminonaphthalene
Additional Process Impurities: Residual 2-naphthol, positional isomers, inorganic salts, sulfur-containing residues, and colored by-products
Hazard-Classification Consistency: Published notifications are not uniform
Frequently Reported Hazard: Serious eye irritation
Reported Acute Oral LD50 in Rat: Approximately 14,200 mg/kg
Skin Hazard: Dust or prolonged contact may cause irritation
Eye Hazard: May cause serious irritation
Respiratory Hazard: Dust may irritate the nose, throat, and respiratory tract
Carcinogenicity of Main Substance: No harmonized carcinogenic classification identified in the cited data
Carcinogenic Impurity Concern: 2-Aminonaphthalene must be strictly controlled
Combustibility: Organic solid capable of burning under severe fire conditions
Thermal Decomposition Products: Nitrogen oxides, sulfur oxides, carbon monoxide, carbon dioxide, smoke, and irritating organic fumes
Environmental Ionic Form: Predominantly anionic under ordinary environmental conditions
Estimated Soil Mobility: Moderate
Estimated Soil-Adsorption Coefficient: Approximately 220
Measured Fish Bioconcentration Factor: 6 or lower
Bioaccumulation Potential: Low
Biodegradation: Expected to occur slowly in screening conditions
Volatilization from Water: Not expected to be significant
Environmental Binding: Aromatic amino group may bind strongly to humic material
Recommended Storage: Cool, dry, tightly closed, clean, and well ventilated
Environmental Precaution: Prevent concentrated release to drains, soil, groundwater, sediment, and surface water
Quality-Control Parameters: Appearance, assay, water, acidity, ash, color, residual 2-naphthol, positional isomers, inorganic salts, and 2-aminonaphthalene
Current Data Requirement: Confirm grade-specific purity, impurity limits, hazard classification, packaging, storage conditions, and shelf life from current documentation.
FIRST AID
Inhalation:
Move the affected person to fresh air.
Keep the person at rest in a position comfortable for breathing.
Avoid further exposure to 2-Aminonaphthalene-1-sulphonic acid dust, smoke, or thermal-decomposition fumes.
Obtain medical attention if coughing, sore throat, wheezing, breathing discomfort, headache, nausea, or other symptoms develop.
Provide respiratory support only through trained personnel using suitable protective equipment.
Skin Contact:
Remove contaminated clothing, footwear, watches, and accessories.
Brush away loose powder carefully without generating airborne dust.
Wash the affected skin thoroughly with soap and plenty of water.
Obtain medical attention if redness, irritation, itching, pain, or other symptoms persist.
Wash contaminated clothing before reuse.
Eye Contact:
Rinse the eyes immediately with plenty of clean, gently flowing water.
Hold the eyelids open and move the eyes in all directions during irrigation.
Remove contact lenses when present and easy to do, then continue rinsing.
Continue irrigation for at least 15 to 20 minutes.
Obtain prompt medical attention because serious eye irritation may occur.
Ingestion:
Rinse the mouth thoroughly with water.
Do not induce vomiting unless directed by qualified medical personnel or a poison center.
Give water only when the affected person is fully conscious and able to swallow safely.
Never give anything by mouth to an unconscious, drowsy, or convulsing person.
Obtain medical advice following significant ingestion or if symptoms develop.
Note to Physicians:
No substance-specific antidote should be assumed.
Provide supportive care and treat according to the patient’s symptoms and clinical condition.
Assess the eyes, skin, respiratory tract, gastrointestinal tract, liver, kidneys, and neurological condition after substantial exposure.
Consider possible exposure to carcinogenic 2-aminonaphthalene when the purity or source of the material is uncertain.
Use current poison-center guidance and grade-specific safety documentation as the primary medical references.
HANDLING AND STORAGE
Handling:
Handle 2-Aminonaphthalene-1-sulphonic acid in accordance with good industrial-hygiene and aromatic-amine procedures.
Review current technical and safety documentation before opening, sampling, weighing, transferring, diazotizing, or processing the material.
Avoid all unnecessary contact with the skin, eyes, and clothing.
Do not breathe dust, aerosol, smoke, or thermal-decomposition fumes.
Use enclosed weighing, charging, conveying, reaction, filtration, drying, and packaging systems wherever reasonably practicable.
Avoid pouring, grinding, sweeping, or pneumatic-transfer methods that generate uncontrolled airborne dust.
Ventilation:
Provide effective general ventilation in storage and processing areas.
Use local exhaust ventilation at weighing stations, bag-emptying points, mixers, reactors, filters, centrifuges, dryers, mills, and packaging equipment.
Capture dust at the source rather than allowing it to spread through occupied areas.
Use enclosed powder-transfer systems for repeated or large-scale operations.
Use suitable dust-collection equipment for dry conveying, milling, and packaging.
Prevent recirculation of contaminated air unless it has been adequately filtered.
Use particulate respiratory protection when engineering controls cannot adequately limit exposure.
Storage:
Store 2-Aminonaphthalene-1-sulphonic acid in tightly closed and correctly labeled containers.
Keep the material in a cool, dry, clean, secure, and well-ventilated location.
Protect 2-Aminonaphthalene-1-sulphonic acid from moisture, excessive heat, intense light, contamination, and physical damage.
Keep 2-Aminonaphthalene-1-sulphonic acid separated from strong oxidizing agents, nitrites, strong acids, strong bases, and incompatible reactive chemicals.
Store the material away from food, feed, pharmaceuticals, cosmetics, and consumer-product raw materials.
Use first-in, first-out stock rotation within the applicable shelf life.
Inspect stored material for discoloration, caking, moisture uptake, damaged packaging, contamination, or unusual odor.
Maintain lot segregation because positional-isomer and 2-aminonaphthalene content can affect downstream quality and safety.
Store analytical and high-purity grades separately from bulk technical material.
Retain impurity and certificate-of-analysis records for each lot.
Spill and Leak Procedures:
Restrict access to the affected area and remove unnecessary personnel.
Eliminate ignition sources when this can be done safely.
Provide effective ventilation before beginning recovery operations.
Wear suitable gloves, protective clothing, chemical eye protection, and particulate respiratory protection.
Avoid dry sweeping, compressed-air cleaning, or other methods that disperse powder.
Collect spilled material with a suitable hazardous-dust vacuum or another low-dust recovery method.
Dampen small quantities carefully only when the recovery and disposal procedure permits water use.
Use clean chemically compatible tools for manual recovery.
Handling Precautions:
Wear chemical-resistant gloves selected from documented compatibility and permeation information.
Use tightly fitting chemical goggles.
Wear a face shield in addition to goggles where slurry, solution, or reaction-mixture splashing is reasonably foreseeable.
Use protective clothing and closed chemical-resistant footwear.
Provide accessible eyewash and emergency-shower equipment near major handling locations.
Use suitable particulate respiratory protection during dusty operations.
Inspect containers, liners, hoses, transfer devices, filters, ventilation systems, and dust collectors before use.
Prevent accumulation of powder on floors, ledges, equipment, structural surfaces, and ventilation ducts.
Minimize manual handling and use closed transfer whenever practicable.
