FlavScents AInsights Entry for (E)-2-buten-1-al (CAS: 123-73-9)

1. Identity & Chemical Information

• Common Name(s): Crotonaldehyde
• IUPAC Name: (E)-but-2-enal
• CAS Number: 123-73-9
• FEMA Number: 2331
• Other Identifiers: FL No. 02.013
• Molecular Formula: C4H6O
• Molecular Weight: 70.09 g/mol
• Functional Groups and Structure–Odor Relevance: (E)-2-buten-1-al is an α,β-unsaturated aldehyde, which contributes to its reactivity and characteristic pungent odor. The presence of the aldehyde group is crucial for its sensory properties, often imparting a sharp, acrid aroma.

Citation hooks: FlavScents; PubChem; FEMA

2. Sensory Profile

(E)-2-buten-1-al is characterized by a pungent, acrid odor with a sharp, penetrating quality. It is often described as having a green, grassy note with a hint of citrus. The compound's intensity is high, and it can dominate a blend if not used judiciously. Its odor threshold is relatively low, making it effective as an impact note in formulations.

Citation hooks: FlavScents; peer-reviewed sensory literature

3. Natural Occurrence & Formation

(E)-2-buten-1-al is not commonly found in nature but can be formed through the oxidative degradation of lipids, particularly in the presence of oxygen and heat. It is also a byproduct of the Maillard reaction, contributing to the aroma of cooked foods. Its formation in natural products is limited, affecting its designation as a "natural flavor."

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

4. Use in Flavors

(E)-2-buten-1-al is used in flavor formulations to impart a fresh, green note. It is commonly found in citrus, herbal, and green flavor profiles. Typical use levels in finished food products range from 0.1 to 5 ppm, with higher concentrations potentially leading to an overpowering aroma. It is relatively stable under acidic conditions but can degrade under high heat or prolonged storage.

Citation hooks: FlavScents; FEMA GRAS documentation; formulation literature

5. Use in Fragrances

In fragrance applications, (E)-2-buten-1-al is used to add a fresh, green, and slightly citrusy note. It is often employed in fine fragrances, personal care products, and household items. Its volatility makes it a top note, contributing to the initial impression of a fragrance. Typical concentrations range from trace amounts to 0.5% in the final product.

Citation hooks: FlavScents; IFRA; fragrance chemistry texts

6. Regulatory Status (Regional Overview)

• United States: Recognized as GRAS by FEMA for flavor use.
• European Union: Listed under Regulation (EC) No 1334/2008 with FL No. 02.013.
• United Kingdom: Aligns with EU regulations post-Brexit.
• Asia: Approved for use in Japan and China, with specific restrictions varying by country.
• Latin America: Generally accepted, but specific regulations may vary by country.

Citation hooks: FEMA; EFSA; national authority publications

7. Toxicology, Safety & Exposure Considerations

• Oral Exposure: Considered safe at low concentrations typical in food applications. No specific ADI established, but use is guided by FEMA GRAS status.
• Dermal Exposure: Can cause irritation and sensitization; IFRA standards should be consulted for safe use levels in fragrances.
• Inhalation Exposure: High volatility requires caution in occupational settings to prevent respiratory irritation.

Citation hooks: EFSA; FEMA; PubChem; toxicology literature

8. Practical Insights for Formulators

(E)-2-buten-1-al is valued for its ability to impart a fresh, green note, enhancing the realism of citrus and herbal profiles. It synergizes well with other aldehydes and green notes but can be overpowering if overused. Formulators should be cautious of its reactivity and potential to cause irritation.

Citation hooks: FlavScents; industry practice

9. Confidence & Data Quality Notes

Data on (E)-2-buten-1-al is well-documented, particularly in terms of its sensory properties and regulatory status. However, specific toxicological data may be limited, necessitating reliance on industry standards and guidelines.

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 2026-04-22 18:58:01 GMT (p2)