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Heptyl p-hydroxybenzoate is an ester derivative of p-hydroxybenzoic acid (also known as parabens when in various alkyl ester forms).
It belongs to the family of parabens, which are commonly used as preservatives in cosmetics, pharmaceuticals, and food products due to their antimicrobial properties.
The “heptyl” part indicates that the esterifying alcohol is heptanol, a seven-carbon straight-chain alcohol, making it the heptyl ester of p-hydroxybenzoic acid.
CAS Number:
136-95-8
Synonyms:
Heptyl p-hydroxybenzoate,p-Hydroxybenzoic acid heptyl ester,Heptyl paraben,4-Hydroxybenzoic acid heptyl ester,Parahydroxybenzoic acid heptyl ester,p-Hydroxybenzoate heptyl ester
Introduction
Heptyl p-hydroxybenzoate, commonly referred to as Heptylparaben, is a member of the paraben family of esters derived from p-hydroxybenzoic acid.
It serves as a preservative and antimicrobial agent, widely used in food, cosmetic, and pharmaceutical formulations.
This compound’s extended alkyl chain compared to methylparaben or ethylparaben gives it unique properties including increased lipophilicity and stronger antimicrobial efficacy against fungi.
Structural and Molecular Properties
Heptylparaben consists of a para-substituted hydroxybenzoic acid esterified with a seven-carbon heptyl chain. The molecule features:
Aromatic ring with electron-donating hydroxyl group at para-position
Linear aliphatic heptyl ester, increasing hydrophobic character
Delocalized π-electron system contributing to chemical stability
Physical and Chemical Properties
Property Value
Appearance White to off-white powder
Melting Point 62–66 °C
Boiling Point 386.8 °C (estimated)
Solubility in Water Poor (0.002 g/100 mL)
Solubility in Alcohol Good
Log P (Partition Coefficient) ~4.7
pKa (phenolic OH) ~8.5
Synthesis and Production Methods
Esterification Route:
Heptylparaben is typically synthesized through the Fischer–Speier esterification of p-hydroxybenzoic acid with heptanol using an acid catalyst (e.g., sulfuric acid or p-toluenesulfonic acid).
General Reaction:
p-Hydroxybenzoic acid + Heptanol → Heptylparaben + H₂O
Alternative synthesis involves transesterification of methylparaben with heptanol under catalytic conditions.
Analytical Characterization Techniques
High-Performance Liquid Chromatography (HPLC) – quantitative analysis
Gas Chromatography–Mass Spectrometry (GC-MS) – trace detection
Infrared Spectroscopy (FTIR) – functional group confirmation
NMR Spectroscopy – structural confirmation (^1H and ^13C)
UV-Vis Spectrophotometry – for calibration in quality control
Applications in Industry
Cosmetics: Used in skin creams, lotions, and makeup for fungal resistance
Food Industry: Acts as a preservative for oils and lipid-based foods
Pharmaceuticals: Stabilizer in ointments, suspensions, and creams
Industrial Lubricants: Added to protect against microbial spoilage
Use in Food, Cosmetics, and Pharmaceuticals
Maximum allowable concentration: 0.3–0.4% w/w depending on application
E number (European Food Additive Code): Not currently assigned
Used in combination with other parabens for synergistic effect
Antimicrobial and Preservative Properties
Effective against:
Yeasts (e.g., Candida albicans)
Fungi (e.g., Aspergillus niger)
Mechanism:
Disruption of microbial cell membranes
Inhibition of enzymatic systems essential for replication
Mechanism of Action as a Preservative
Parabens, including heptylparaben, integrate into microbial lipid bilayers, disrupting membrane integrity and causing leakage of cellular contents, ultimately leading to cell death.
Pharmacokinetics and Metabolism
Absorption: Through dermal and oral routes
Distribution: Accumulates in adipose tissues
Metabolism: Hydrolyzed by esterases into p-hydroxybenzoic acid and heptanol
Excretion: Primarily via renal elimination
SAFETY INFORMATION ABOUT HEPTYL P-HYDROXYBENZOATE
First aid measures:
Description of first aid measures:
General advice:
Consult a physician.
Show this safety data sheet to the doctor in attendance.
Move out of dangerous area:
If inhaled:
If breathed in, move person into fresh air.
If not breathing, give artificial respiration.
Consult a physician.
In case of skin contact:
Take off contaminated clothing and shoes immediately.
Wash off with soap and plenty of water.
Consult a physician.
In case of eye contact:
Rinse thoroughly with plenty of water for at least 15 minutes and consult a physician.
Continue rinsing eyes during transport to hospital.
If swallowed:
Do NOT induce vomiting.
Never give anything by mouth to an unconscious person.
Rinse mouth with water.
Consult a physician.
Firefighting measures:
Extinguishing media:
Suitable extinguishing media:
Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide.
Special hazards arising from the substance or mixture
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas
Advice for firefighters:
Wear self-contained breathing apparatus for firefighting if necessary.
Accidental release measures:
Personal precautions, protective equipment and emergency procedures
Use personal protective equipment.
Avoid breathing vapours, mist or gas.
Evacuate personnel to safe areas.
Environmental precautions:
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Methods and materials for containment and cleaning up:
Soak up with inert absorbent material and dispose of as hazardous waste.
Keep in suitable, closed containers for disposal.
Handling and storage:
Precautions for safe handling:
Avoid inhalation of vapour or mist.
Conditions for safe storage, including any incompatibilities:
Keep container tightly closed in a dry and well-ventilated place.
Containers which are opened must be carefully resealed and kept upright to prevent leakage.
Storage class (TRGS 510): 8A: Combustible, corrosive hazardous materials
Exposure controls/personal protection:
Control parameters:
Components with workplace control parameters
Contains no substances with occupational exposure limit values.
Exposure controls:
Appropriate engineering controls:
Handle in accordance with good industrial hygiene and safety practice.
Wash hands before breaks and at the end of workday.
Personal protective equipment:
Eye/face protection:
Tightly fitting safety goggles.
Faceshield (8-inch minimum).
Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (US) or EN 166(EU).
Skin protection:
Handle with gloves.
Gloves must be inspected prior to use.
Use proper glove
removal technique (without touching glove's outer surface) to avoid skin contact with this product.
Dispose of contaminated gloves after use in accordance with applicable laws and good laboratory practices.
Wash and dry hands.
Full contact:
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
Splash contact
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
It should not be construed as offering an approval for any specific use scenario.
Body Protection:
Complete suit protecting against chemicals, The type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace.
Respiratory protection:
Where risk assessment shows air-purifying respirators are appropriate use a fullface respirator with multi-purpose combination (US) or type ABEK (EN 14387) respirator cartridges as a backup to engineering controls.
If the respirator is the sole means of protection, use a full-face supplied air respirator.
Use respirators and components tested and approved under appropriate government standards such as NIOSH (US) or CEN (EU).
Control of environmental exposure
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Stability and reactivity:
Chemical stability:
Stable under recommended storage conditions.
Incompatible materials:
Strong oxidizing agents:
Hazardous decomposition products:
Hazardous decomposition products formed under fire conditions.
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas.
Disposal considerations:
Waste treatment methods:
Product:
Offer surplus and non-recyclable solutions to a licensed disposal company.
Contact a licensed professional waste disposal service to dispose of this material.
Contaminated packaging:
Dispose of as unused product
