Isobutyl salicylate
[CAS# 87-19-4]

Identification

• Classification: Flavors and spices >> Synthetic spice >> Carboxylic acid and ester perfume >> Aromatic carboxylic acid ester
• Name: Isobutyl salicylate
• Synonyms: 2-Methylpropyl o-hydroxybenzoate; Isobutyl o-hydroxybenzoate; Salicylic acid isobutylester
• Molecular Formula: C₁₁H₁₄O₃
• Molecular Weight: 194.23
• CAS Registry Number: 87-19-4
• EC Number: 201-729-9
• FEMA: 2213
• SMILES: CC(C)COC(=O)C1=CC=CC=C1O

Properties

• Density: 1.1±0.1 g/cm³ Calc.^*
• Melting point: -6 °C (Expl.)
• Boiling point: 263.9±13.0 °C 760 mmHg (Calc.)^*, 267 °C (Expl.)
• Flash point: 103.4±12.6 °C (Calc.)^*
• Index of refraction: 1.524 (Calc.)^*, 1.509 (Expl.)

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H302
• Safety Statements: P264-P270-P301+P317-P330-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute toxicity	Acute Tox.	4	H302
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400
Chronic hazardous to the aquatic environment	Aquatic Chronic	2	H411
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315

Discovery and Applications

Isobutyl salicylate is an organic ester compound derived from the esterification of salicylic acid with isobutyl alcohol. Its molecular formula is C₁₁H₁₄O₃, and its structure features a salicylate core (2-hydroxybenzoate) in which the carboxylic acid group is replaced by an isobutyl ester group (–COOCH₂CH(CH₃)₂). The compound appears as a colorless to pale yellow liquid with a characteristic odor, often described as floral, sweet, or resembling wintergreen.

The compound was developed as part of ongoing investigations into esters of salicylic acid, a family of substances known for their fragrance, antiseptic properties, and pharmaceutical relevance. Isobutyl salicylate can be synthesized through a classical Fischer esterification reaction by refluxing salicylic acid with isobutyl alcohol in the presence of a strong acid catalyst, such as sulfuric acid or p-toluenesulfonic acid, under dehydrating conditions.

Isobutyl salicylate is primarily used in the fragrance and flavor industries. Its pleasant aromatic profile has led to its inclusion in a variety of perfumery applications, including fine fragrances, lotions, shampoos, and soaps. As an aromatic ester, it contributes to floral and fruity scent compositions, enhancing the overall complexity and longevity of fragrances. In the flavor industry, although less commonly than in perfumery, it may be used in trace amounts to provide sweet or spicy notes.

The structural features of isobutyl salicylate, especially the hydroxyl group ortho to the ester, enable it to participate in hydrogen bonding and influence its volatility and tenacity in fragrance formulations. This characteristic is shared with other salicylate esters such as methyl salicylate and amyl salicylate, which are also popular fragrance ingredients. Compared to methyl salicylate, which has a more penetrating and minty odor, isobutyl salicylate provides a softer, warmer note, making it better suited for floral or oriental compositions.

In cosmetic and topical formulations, salicylate esters including isobutyl salicylate may also serve as mild antiseptics or skin-conditioning agents, although their primary function remains aromatic. They are generally used in concentrations that are considered safe by regulatory authorities. The compound is listed in the International Fragrance Association (IFRA) guidelines, which recommend safe usage limits to prevent sensitization and irritation.

Analytical techniques used to characterize and verify the purity of isobutyl salicylate include gas chromatography (GC), often coupled with mass spectrometry (GC-MS), which can detect and quantify volatile organic compounds in fragrance formulations. Infrared (IR) spectroscopy can confirm the presence of ester and hydroxyl functional groups, and nuclear magnetic resonance (NMR) spectroscopy provides structural details through proton and carbon chemical shifts.

From a regulatory perspective, isobutyl salicylate is considered safe for use in consumer products when used within established concentration limits. However, like many fragrance ingredients, it may cause allergic reactions or skin sensitization in sensitive individuals, especially at higher concentrations or with repeated exposure. Safety evaluations are carried out based on data from in vitro and in vivo studies.

Although isobutyl salicylate is not widely used as a pharmaceutical active ingredient, it shares structural similarity with compounds used for analgesic and anti-inflammatory purposes, such as salicylic acid and its esters. Nonetheless, its primary domain remains olfactory and cosmetic applications, where its favorable sensory properties are most valuable.

In summary, isobutyl salicylate is a fragrance ester derived from salicylic acid and isobutyl alcohol. It is valued for its warm, sweet floral scent and is used in perfumes, toiletries, and other fragranced consumer goods. Its synthesis, stability, and safety profile have made it a reliable component in the formulation of aromatic products.

References

2023. RIFM fragrance ingredient safety assessment, isobutyl salicylate, CAS Registry Number 87-19-4. Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association, 181.
DOI: 10.1016/j.fct.2023.113909

2007. Fragrance material review on isobutyl salicylate. Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association, 45(1).
DOI: 10.1016/j.fct.2007.09.049

2008. Dielectric constant of isobutyl salicylate. Landolt-Börnstein - Group IV Physical Chemistry.
DOI: 10.1007/978-3-540-75506-7_300