Solvent Orange 3, also known as 2,4-Diaminoazobenzene, is a synthetic azo dye with the chemical formula C12H12N4. It is used primarily in industrial applications for coloring plastics, oils, waxes, and sometimes inks. The dye imparts a bright orange hue, but its use in consumer products has been largely restricted or banned due to its potential health risks. Solvent Orange 3 is considered toxicologically equivalent to Basic Orange 2, a dye that has been assessed for its carcinogenic potential in a screening by Environment Canada and Health Canada in 2014, where it was found to have carcinogenic properties. Given its toxic profile, Solvent Orange 3 is classified as hazardous, especially in terms of its carcinogenicity.

Chemical Composition and Structure

Solvent Orange 3 consists of an azo group (-N=N-) linking two aromatic rings, with two amino groups (-NH2) positioned at the 2- and 4-positions of one of the rings.The azo bond is responsible for the vibrant orange color, and the presence of amino groups contributes to the reactivity of the compound, raising concerns about its potential to degrade into harmful aromatic amines, which are known to pose significant health risks.

Physical Properties

Solvent Orange 3 typically appears as a bright orange crystalline powder. It is insoluble in water but highly soluble in organic solvents such as oils, waxes, and hydrocarbons. The dye is known for its thermal and light stability, which makes it suitable for industrial applications requiring long-lasting color retention in non-aqueous environments.

Production Process

Solvent Orange 3 is produced via a diazotization reaction, in which aromatic amines are treated with nitrous acid to form a diazonium salt, which is then coupled with another aromatic amine to form the characteristic azo bond (-N=N-). The production of Solvent Orange 3 requires strict control to prevent the release of hazardous by-products, particularly aromatic amines, which are carcinogenic.

Applications

• Industrial Use: Solvent Orange 3 is primarily used in the following sectors:

  • Plastics and Waxes: It is used to color plastics, waxes, and other materials where its bright orange color and solubility in organic solvents are advantageous.
  • Lubricants and Oils: Solvent Orange 3 is used in lubricants and oils, where its stability ensures that the color remains intact in harsh conditions.
  • Inks and Coatings: The dye is also used in certain industrial inks and coatings that require vibrant, long-lasting color.

• Historical Use in Consumer Products: In the past, Solvent Orange 3 was used in cosmetics, textile dyes, and personal care products. However, due to its carcinogenic potential, its use in these products has been largely phased out or banned.

Health and Safety Concerns

Carcinogenicity

Solvent Orange 3 is toxicologically equivalent to Basic Orange 2, which has been identified as having carcinogenic potential in a screening conducted by Environment Canada and Health Canada in 2014. Both dyes are considered hazardous due to their potential to degrade into aromatic amines, which are known carcinogens. Although direct studies on Solvent Orange 3’s carcinogenicity are limited, its structural similarity to Basic Orange 2 raises significant concerns. Aromatic amines, released upon degradation of azo dyes like Solvent Orange 3, are linked to cancer, particularly bladder cancer. For this reason, its use is restricted or banned in many consumer applications.

Toxicity

In addition to its potential carcinogenicity, Solvent Orange 3 can cause acute toxicity if ingested, inhaled, or absorbed through the skin. Prolonged exposure may lead to respiratory issues, skin irritation, and a heightened risk of cancer. Due to its toxicological profile, it requires careful handling in industrial settings, with strict safety protocols in place to minimize worker exposure.

Environmental and Safety Considerations

Solvent Orange 3 is not biodegradable and can persist in the environment, particularly in aquatic ecosystems. Its ability to degrade into hazardous aromatic amines adds to its environmental risk. Regulatory bodies have imposed strict guidelines for the disposal and handling of products containing Solvent Orange 3 to prevent environmental contamination. In many regions, industries using this dye must adhere to strict waste management protocols to ensure that it does not pollute water sources or accumulate in the ecosystem.

Regulatory Status

Due to its toxic and potentially carcinogenic nature, Solvent Orange 3 is heavily regulated. In many countries, it is banned from use in cosmetics, textiles, and personal care products. In industrial settings, its use is restricted and subject to stringent safety guidelines. Environment Canada and Health Canada have highlighted its carcinogenic potential, aligning with global efforts to phase out or restrict harmful azo dyes in consumer products.

Applications Under Strict Control

• Industrial settings: Despite its toxic profile, Solvent Orange 3 continues to be used in certain industrial applications, particularly where its bright color and stability are required.
• Research and Analytical Use: The dye may still be used in research contexts under controlled conditions, where strict protocols minimize exposure.

Safety

 The problem with azo dyes (monoazo or diazo) is photocatalytic degradation leading to oxidation and the subsequent formation of impurities such as aromatic amines, some of which have carcinogenic activity. (Chung KT, Stevens SE Jr, Cerniglia CE. The reduction of azo dyes by the intestinal microflora. Crit Rev Microbiol. 1992;18(3):175-90. doi: 10.3109/10408419209114557. )

Molecular Formula  C₁₂H₁₂N₄

Molecular Weight  212.25 g/mol

CAS     495-54-5

UNII    IP3X2567YP

EC Number  207-803-7

DTXSID4043856

CHEMBL1623562

Synonyms:

Solvent Orange 3

2,4-Diaminoazobenzene

Chrysoidine Base

References__________________________________________________________________________

Screening Assessment Aromatic Azo and Benzidine-based Substance GroupingCertain Azo Solvent Dyes. Environment and Climate Change Canada Health Canada May 2016

Synopsis. Pursuant to sections 68 or 74 of the Canadian Environmental Protection Act, 1999 (CEPA 1999), the Ministers of the Environment and of Health have conducted a screening assessment on 22 Azo Solvent Dyes. These substances constitute a subgroup of the Aromatic Azo and Benzidine-based Substance Grouping being assessed as part of the Groupings Initiative of Canada’s Chemicals Management Plan (CMP) based on structural similarity and applications. Substances in this grouping were identified as priorities for assessment as they met the categorization criteria under subsection 73(1) of CEPA 1999 and/or were considered as a priority based on other human health concerns. The Chemical Abstracts Service Registry Number (CAS RN)1, Domestic Substances List (DSL) name, and Colour Index (C.I) name or common name of the 22 substances are presented in the following table.....