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Para-tert-butylbenzoic acid (PTBBA; CAS 98-73-7) is a monosubstituted benzoic acid bearing a tert-butyl group at the para position.
It is a white crystalline solid with low water solubility and widespread use as an intermediate and additive in coatings, alkyd resins, corrosion-inhibiting formulations, and specialty chemicals.
CAS number: 98-73-7.
Other common synonyms / identifiers: 4-tert-Butylbenzoic acid; p-t-Butylbenzoic acid; Benzoic acid, 4-(1,1-dimethylethyl)-; TBBA; PTBBA; 4-t-Butylbenzoic acid.
This article reviews structural and nomenclature details, synthesis and production methods, physicochemical properties, analytical methods, reactivity and chemical behavior, industrial and niche applications, environmental fate, safety & handling, regulatory status, alternatives, and open areas for research.
Key practical data and representative experimental procedures are included to serve both academic and industrial readers.
CAS number: 98-73-7.
Other common synonyms / identifiers: 4-tert-Butylbenzoic acid; p-t-Butylbenzoic acid; Benzoic acid, 4-(1,1-dimethylethyl)-; TBBA; PTBBA; 4-t-Butylbenzoic acid.
Para-tert-butylbenzoic acid is one of the simplest para-substituted benzoic acids, obtained by substitution of a tert-butyl group at the 4-position of benzoic acid.
It emerged as a valuable specialty chemical because the bulky electron-donating tert-butyl moiety modifies the electronic and steric properties of the benzoic acid core — altering solubility, acidity and reactivity versus unsubstituted benzoic acid.
PTBBA has been produced and commercialized for many decades and is available from multiple chemical suppliers as a high-purity crystalline material used as an intermediate and additive in multiple formulations.
Nomenclature, identifiers, and structure
Preferred IUPAC name: 4-(tert-butyl)benzoic acid (IUPAC style: 4-(1,1-dimethylethyl)benzoic acid).
EC / EINECS number: 202-696-3
Structural remark: the tert-butyl group is para to the carboxylic acid, producing symmetrical substitution that influences melting point (higher than many alkyl-substituted benzoic acids) and steric shielding of the aromatic ring.
Physicochemical properties (summary table)
Key measured/consensus properties (representative values from supplier and database records):
Molecular formula: C₁₁H₁₄O₂.
Molecular weight: 178.23 g·mol⁻¹.
Appearance: white crystalline powder / crystals.
Melting point: ≈ 166–169 °C (typical supplier ranges: 164–169 °C).
Boiling point (literature/est.): reported high bp (~280 °C) under atmospheric conditions
Solubility: insoluble in water, soluble in alcohols, benzene and many organic solvents; reported pH ~3.9 for 1% aqueous suspension (indicative of carboxyl acidity in aqueous slurries).
LogP / partition coefficient: estimated XLogP ~3.9 (lipophilic).
Acid dissociation: as a benzoic acid derivative, the carboxyl group behaves as a weak acid (pKa typically near benzoic acid value; p-alkyl substitution modestly affects pKa).
Exact pKa values vary with measurement method; consult primary experimental sources for precise pKa.
Synthesis and industrial production routes
xidation of p-tert-butyltoluene (primary industrial method)
The most common and industrially scalable route to para-tert-butylbenzoic acid is the oxidation of p-tert-butyltoluene (para-tert-butylmethylbenzene) using molecular oxygen (air) with catalysts (heterogeneous or homogeneous) that facilitate the selective oxidation of the benzylic methyl group to the carboxylic acid.
Full oxidation of the methyl side chain to the acid is analogous to industrial oxidations of p-xylene to terephthalic acid or to the conversion of toluene derivatives to benzoic acids.
Typical oxidants: O₂ (air) often with cobalt, manganese or other transition metal catalysts and promoters under elevated temperature and pressure; solvent systems vary (acetic acid medium has historical precedent).
The reaction requires control of temperature, residence time and catalyst to limit over-oxidation or ring-side reactions.
Supplier literature and technical notes explicitly describe PTBBA production from p-tert-butyltoluene by air oxidation.
Alternative laboratory syntheses
In laboratory settings:
Direct Friedel–Crafts tert-butylation of benzoic acid is generally disfavored due to deactivating influence of the carboxyl group (it directs meta) — hence para selectivity requires different tactics (e.g., tert-butylation of an activated ring followed by oxidation of an alkyl side chain).
From 4-tert-butylbenzyl alcohol (oxidation of benzyl alcohol to acid) or from 4-tert-butylbenzaldehyde (oxidation of aldehyde) are feasible lab paths; these routes rely on available substituted benzyl derivatives.
Oxidative cleavage of sidechains or catalytic air oxidation remain practical routes at scale. Supplier/product pages reference oxidation of p-tert-butyltoluene as the standard industrial route.
Catalysts, process notes and byproducts
Industrial oxidation catalysts are chosen to favor benzylic oxidation with high selectivity.
Potential byproducts include partial oxidation intermediates (benzyl alcohol, benzaldehyde) and over-oxidation products (ring-oxidized species), which are minimized by optimized catalysts and process control.
Work-up often involves quench, filtration to remove catalyst residues, recrystallization and drying to yield the crystalline acid.
Chemical behavior and reactivity
Acidic behavior
The carboxylic acid group confers typical benzoic-acid reactivity: formation of salts (carboxylates), esters via Fischer or activated-acid methods, amides via activation (acid chloride, coupling reagents), and decarboxylation under forcing conditions.
Para tert-butyl substitution slightly alters electron density and steric environment, which modestly affects acidity and reactivity compared with benzoic acid.
Electrophilic aromatic substitution (EAS)
The tert-butyl group is electron donating via hyperconjugation and strongly activating for ortho/para substitution — but with the carboxyl group present (meta-directing), the existing para substitution locks regiochemistry; further substitution patterns are influenced by both substituents.
Nitration, sulfonation and halogenation reactions must consider the combined directing effects and steric hindrance of the tert-butyl group.
Esterification, amidation and derivatization
Standard esterification (acid + alcohol, with acid catalyst or via activated derivative) and amide coupling chemistry apply.
The bulky tert-butyl group frequently confers improved solubility in organic solvents to products derived from PTBBA and can affect polymerization behavior when used in monomers or as end-groups.
Thermal stability and decomposition
Melting point near ~167 °C; decomposition / decarboxylation typically occurs at higher temperatures. Supplier datasheets report decomposition/autoignition thresholds and thermal data for safe handling.
SAFETY INFORMATION ABOUT PARA TERTIARY BUTYL BENZOIC ACID
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
