Butylparaben
[CAS# 94-26-8]

Identification

• Classification: Chemical reagent >> Organic reagent >> Ester >> Butyl ester compound
• Name: Butylparaben
• Synonyms: p-Hydroxybenzoic acid butyl ester; 4-(Butoxycarbonyl)phenol; 4-Hydroxybenzoic acid butyl ester; Butoben; Butyl 4-hydroxybenzoate; Butyl p-hydroxybenzoate; Butyl parabens; n-Butyl 4-hydroxybenzoate; n-Butyl p-hydroxybenzoate; n-Butylparaben; 4-Hydroxybenzoic acid butyl ester
• Molecular Formula: C₁₁H₁₄O₃
• Molecular Weight: 194.23
• CAS Registry Number: 94-26-8
• EC Number: 202-318-7
• FEMA: 2203
• SMILES: CCCCOC(=O)C1=CC=C(C=C1)O

Properties

• Density: 1.1±0.1 g/cm³ Calc.^*
• Melting point: 67 - 70 °C (Expl.)
• Boiling point: 309.2±15.0 °C 760 mmHg (Calc.)^*, 368.5 - 370 °C (Expl.)
• Flash point: 129.2±13.2 °C (Calc.)^*
• Solubility: 0.207 mg/mL in H2O (20°C) (Expl.)
• Index of refraction: 1.526 (Calc.)^*

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

Safety Data

• Hazard Symbols: GHS05;GHS07 Danger
• Risk Statements: H315-H318-H319-H335-H412
• Safety Statements: P261-P264-P264+P265-P271-P273-P280-P302+P352-P304+P340-P305+P351+P338-P305+P354+P338-P317-P319-P321-P332+P317-P337+P317-P362+P364-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin irritation	Skin Irrit.	2	H315
Eye irritation	Eye Irrit.	2	H319
Specific target organ toxicity - single exposure	STOT SE	3	H335
Serious eye damage	Eye Dam.	1	H318
Chronic hazardous to the aquatic environment	Aquatic Chronic	3	H412
Skin sensitization	Skin Sens.	1	H317
Chronic hazardous to the aquatic environment	Aquatic Chronic	4	H413
Eye irritation	Eye Irrit.	2A	H319

Discovery and Applications

Butylparaben, chemically known as butyl 4-hydroxybenzoate, is a member of the paraben family, which are esters of p-hydroxybenzoic acid. It is widely used as a preservative in cosmetics, personal care products, pharmaceuticals, and some food items due to its antimicrobial and antifungal properties. The compound appears as a white, crystalline powder that is sparingly soluble in water but readily soluble in alcohol and organic solvents.

The history of butylparaben dates back to the early 20th century, coinciding with the development of synthetic preservatives to replace naturally derived agents. Parabens, including methylparaben, ethylparaben, propylparaben, and butylparaben, were synthesized and studied for their ability to prevent microbial growth in various formulations. Butylparaben was developed as one of the longer-chain esters, providing broader spectrum preservation and increased efficacy against yeasts and molds compared to its shorter-chain analogs.

In cosmetics and personal care applications, butylparaben is valued for its preservative capabilities. It is used to extend the shelf life of products by inhibiting the growth of bacteria, fungi, and molds. It is commonly found in creams, lotions, shampoos, conditioners, makeup, and deodorants. The inclusion of butylparaben in formulations helps maintain product integrity, especially in water-containing products that are more susceptible to microbial contamination.

Pharmaceutical applications of butylparaben include its use as an antimicrobial preservative in oral, topical, and injectable drug formulations. It ensures the stability and safety of medications over time, particularly those with aqueous components. Butylparaben is also used in ophthalmic and otic preparations to prevent microbial contamination during use.

In the food industry, butylparaben has been employed as a preservative, although its use is less common than that of other parabens. It is permitted in some regions for use in specific food categories and in accordance with maximum allowable limits. Its role in food preservation is similar to that in other products: preventing microbial spoilage and extending shelf life.

Butylparaben has been evaluated for safety by various health authorities. Toxicological studies have demonstrated that it is rapidly absorbed, metabolized, and excreted from the human body. It has a low potential for acute toxicity, and repeated-dose studies have not shown significant adverse effects at levels used in consumer products. However, its estrogenic activity, though significantly weaker than natural estrogens, has led to scrutiny regarding its potential endocrine-disrupting effects. Regulatory agencies such as the U.S. Food and Drug Administration and the European Scientific Committee on Consumer Safety have reviewed the available data and concluded that butylparaben is safe for use in cosmetics and personal care products at specified concentrations.

Environmental considerations have also emerged in recent years. Butylparaben and other parabens can be released into wastewater through product use and disposal. Although they are biodegradable to some extent, their presence in aquatic environments has raised concerns about potential effects on wildlife. Research continues into the environmental fate and ecological impact of parabens.

In industrial and laboratory settings, butylparaben is used in various analytical and preservation-related roles. Its stability and antimicrobial properties make it useful in the preparation of microbiological media and chemical standards. It is also included in diagnostic and laboratory reagents where preservation is required over prolonged storage periods.

The manufacture of butylparaben typically involves the esterification of p-hydroxybenzoic acid with butanol in the presence of an acid catalyst. The reaction yields butylparaben, which is then purified through crystallization or other separation techniques. Quality control measures ensure consistency in purity and performance for its various applications.

In conclusion, butylparaben is a versatile and widely used preservative with a long history of safe and effective use. Its broad-spectrum antimicrobial properties, chemical stability, and compatibility with a wide range of products have made it a common ingredient in cosmetics, pharmaceuticals, and some food products. Regulatory oversight and ongoing research continue to guide its use in response to evolving safety and environmental considerations.

References

2024. Temporal trends in exposure to parabens, benzophenones, triclosan, and triclocarban in adult females in Kyoto, Japan, from 1993 to 2016. Environmental science and pollution research international, 31(28).
DOI: 10.1007/s11356-024-33627-w

2024. Impact of butylparaben on growth dynamics and microcystin-LR production in Microcystis aeruginosa. Environmental Research, 257.
DOI: 10.1016/j.envres.2024.119291

2024. Estimation of suspected estrogenic transformation products generated during preservative butylparaben chlorination using a simplified effect-based analysis approach. Water Research, 267.
DOI: 10.1016/j.watres.2024.122414