4-Hydroxyazobenzene

198.22100

198.22

216-880-6

VX4306NSH1

3177

DTXSID3022160

YELLOW LEAVES FROM BENZENE, ORANGE PRISMS FROM ALC

29270000

44.95000

3.80760

Orange columnar solid

1.13g/cm3

155-157 °C

225 °C

233.646ºC

1.596

4.7 [ug/mL]|4.54e-04 M|INSOL IN WATER; VERY SOL IN ALC & ETHER; SOL IN BENZENE, CONCN SULFURIC ACID & DIL ALKALI (YELLOW)|Soluble in acetone, ethanol, benzene and ether|In water, 90 mg/l @ 20 °C

0mmHg at 25°C

pKa= 8.2 (conjugate acid)

3

R36/37/38

26-36

SM8300000

Xi

|Warning|H315 (100%): Causes skin irritation [Warning Skin corrosion/irritation]|P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P403+P233, P405, and P501|Aggregated GHS information provided by 44 companies from 4 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.

LD50 Mouse ip 75 mg/kg

4-Hydroxyazobenzene is not known to occur in nature(1).

4-Hydroxyazobenzene's production and use in the dye industry(1) may result in its release to the environment through various waste streams.

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 3200(SRC), determined from a structure estimation method(2), indicates that 4-hydroxyazobenzene is expected to have slight mobility in soil(SRC). The pKa of 4-hydroxyazobenzene is 8.2, indicating that the undissociated form will exist in neutral and acidic soils. In basic soils, the anion form will predominate and is expected to have higher mobility than the undissociated species. Volatilization of 4-hydroxyazobenzene from moist soil surfaces is not expected to be an important fate process(SRC) given an estimated Henry's Law constant of 6.7X10-10 atm-cu m/mole(SRC), derived from its vapor pressure, 2.31X10-7 mm Hg(3), and water solubility, 90 mg/l(4). 4- Hydroxyazobenzene is not expected to volatilize from dry soil surfaces(SRC) based on a vapor pressure of 2.31X10-7 mm Hg at 25 °C(3). 4-Hydroxyazobenzene persists in some wastewater treatment systems and degrades in others, which suggest that biodegradation may be an important fate process in soils(5).|AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 3200(SRC), determined from an estimation method(2), indicates that 4-hydroxyazobenzene is expected to adsorb to suspended solids and sediment in water(SRC). Volatilization from water surfaces is not expected(3) based upon an estimated Henry's Law constant of 6.7X10-10 atm-cu m/mole(SRC), derived from its vapor pressure, 2.31X10-7 mm Hg(4), and water solubility, 90 mg/l(5). The pKa of 8.2(6) indicates that this chemical will exist in the undissociated form in neutral and acidic environments, and as the anion in basic environments. According to a classification scheme(7), an estimated BCF of 10(SRC), derived from an estimated log Kow of 3.6(8), suggests the potential for bioconcentration in aquatic organisms is low. 4-Hydroxyazobenzene persists in some wastewater treatment systems and degrades in others(9), which suggest that biodegradation may be an important process in aquatic environments(SRC).|ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), 4-hydroxyazobenzene, which has a vapor pressure of 2.31X10-7 mm Hg at 25 °C(4), is expected to exist in vapor and particulate phases in the ambient atmosphere. Vapor-phase 4-hydroxyazobenzene is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be 27 hours(SRC), calculated from its rate constant of 1.4X10-11 cu cm/molecule-sec at 25 °C determined using a structure estimation method(3). Particulate-phase 4-hydroxyazobenzene may be removed from the air by wet and dry deposition(SRC).

The rate constant for the vapor-phase reaction of 4-hydroxyazobenzene with photochemically-produced hydroxyl radicals has been estimated as 1.4X10-11 cu cm/molecule-sec at 25 °C(SRC) using a structure estimation method(1). This corresponds to an atmospheric half-life of about 27 hours(SRC) at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(1). 4-Hydroxyazobenzene is not expected to undergo hydrolysis in the environment due to the lack of hydrolyzable functional groups(2). 4-Hydroxyazobenzene absorbs light at 347 nm(3) and may photolyze in the atmosphere due to absorption in the environmental UV spectrum (>290 nm)(SRC).

An estimated BCF of 10 was calculated for 4-hydroxyazobenzene(SRC), using an estimated log Kow of 3.6(1,SRC) and a regression-derived equation(2). According to a classification scheme(3), this BCF suggests the potential for bioconcentration in aquatic organisms is low.

The Koc of 4-hydroxyazobenzene was estimated as 3200(SRC), using an estimated low Kow of 3.6(1) and a regression-derived equation(2). The pKa of 4-hydroxyazobenzene is 8.2(4), indicating that the undissociated form of 4-hydroxyazobenzene will exist in neutral and acidic soils and the anionic form will exist in basic soils. The anionic forms are expected to have higher mobility than the neutral species(SRC). According to a classification scheme(3), the estimated Koc value suggests that the undissociated form of 4-hydroxyazobenzene will be relatively immobile in soils.

The Henry's Law constant for 4-hydroxyazobenzene is estimated as 6.7X10-10 atm-cu m/mole(SRC) from its vapor pressure, 2.31X10-7 mm Hg(1), and water solubility, 90 mg/l(2). This Henry's Law constant indicates that 4-hydroxyazobenzene is expected to be essentially nonvolatile from water surfaces and moist soils(3). 4-Hydroxyazobenzene is not expected to volatilize from dry soil surfaces(SRC) based upon its vapor pressure of 2.31X10-7 mm Hg(1).

Occupational exposure to 4-hydroxyazobenzene may occur through inhalation and dermal contact with this compound at workplaces where 4-hydroxyazobenzene is produced or used, primarily in the dye industry(1).

DOSES OF 500 & 700 MG 4-HYDROXYAZOBENZENE, WHICH DID NOT PRODUCE TOXIC EFFECTS, WERE COMPLETELY ABSORBED FROM THE DIET OF RABBITS & WERE EXCRETED MAINLY IN THE URINE AS GLUCURONIDE.

THE URINE OF RABBITS GIVEN 4-HYDROXYAZOBENZENE CONTAINED 2-ACETAMIDOPHENOL, 4-ACETAMIDOPHENOL, CONJUGATED 4-AMINOPHENOL, CONJUGATED 2-AMINOPHENOL, & 4-HYDROXYAZOBENZENE GLUCURONIDE.|The azoreduction of phenylazo-2-naphthol (Sudan I), 5-(phenylazo)-6-hydroxynaphthalene-2-sulfonic acid (aniline subsidiary color of FD&C Yellow No. 6 (ANSC)), and phenylazophenol (Solvent Yellow 7 (SY7)) in skin during percutaneous absorption was measured and the contributions of cytosolic and microsomal reductions were characterized. By using a series of azo dyes with a common U-14C-labeled phenylazo moiety, percutaneous absorption and metabolism were measured in vitro in flow through diffusion cells with Sencar mouse, hairless guinea pig, and human skin. Azoreductase assays using subcellular fractions from skin of all species were used to examine intracellular rates and distribution for the series of dyes. The absorption of the lipophilic dyes Sudan I and SY7 from a finite surface dose of 5 ug/sq cm was extensive in all species. In mouse, 32.8 + or - 2.8% of the applied Sudan I Jose and 64.1 + or - 3.3% of the applied SY7 Jose were absorbed in 24 hr. In the hairless guinea pig, 57.6 + or - 5.9% of the applied Sudan I dose and 67.8 + or - 4.6% of the applied SY7 dose were absorbed in 24 hr. Human skin was least permeable, with 26.4 + or - 6.7% of the applied Sudan I Jose and 36.1 + or 4.5% of the applied SY7 dose absorbed in 24 hr. Sudan I and SY7 were extensively reduced in skin of all species during percutaneous absorption (29.5 and 26.5%, respectively, of the absorbed dose in human skin and greater than 50% of the applied Jose in other species). ANSC was the least absorbed, with 5% or less penetrating. SY7 was preferentially reduced in the skin cytosol of all species, whereas Sudan I was equally reduced in the skin cytosol and microsomal fractions. The site of azoreduction in the cell may affect the metabolic fate of the liberated arylamine. The extensive azoreduction observed during percutaneous absorption may modulate the toxicities of these compounds and must be considered when effective doses are determined for quantitative risk assessments from dermal exposures.|A study was made of the chemical structural requirements for binding to microsomal cytochrome p450 and enzymic reduction of the azo linkage in p-dimethylaminoazobenzene (DAB) and related azo dye carcinogens. Liver microsomes were prepared from male Wistar rats, some of which had been pretreated with microsomal enzyme inducers. Dimethylaminoazobenzene, its corresponding primary and secondary amines, and p-hydroxyazobenzene showed high substrate reactivity for reduction by microsomes. ... Active substrates showed type I (p-hydroxy derivative) or type 11 binding spectra, while inactive substrates showed only weak binding with microsomes. When two inactive compounds were incubated with microsomes under aerobic conditions, allowing preliminary hydroxylation to occur, there was marked facilitation of azoreduction. /It was/ concluded that p-substituted azobenzenes with electron donating groups facilitate azo dye reduction by rat liver microsomes, with good correlation between cytochrome p450 binding and substrate reactivity. Hydroxylation facilitates reduction of otherwise nonreactive compounds.|4-Phenylazophenol has known human metabolites that include (2S,3S,4S,5R)-3,4,5-trihydroxy-6-(4-phenyldiazenylphenoxy)oxane-2-carboxylic acid.

4-hydroxyazobenzene

Phenol, 4-(2-phenyldiazenyl)-: ACTIVE|It is not believed to be produced on a large-scale ... in either the US or Western Europe.|(1972) In Japan ... 2000 kg