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Crystal Menthol typically appears as clear or white, needle-like crystals.
It is derived from peppermint oil or synthesized from thymol.
It acts as a cooling agent, providing a soothing effect on the skin, mucous membranes, or taste receptors.
CAS Number: 89-78-1
Synonyms:
(−)-Menthol,L-Menthol,DL-Menthol (when racemic),5-Methyl-2-(1-methylethyl)cyclohexanol Peppermint camphor,Hexahydrothymol
Introduction
Crystal menthol, also known simply as menthol, is a naturally occurring organic compound derived mainly from the oils of cornmint, peppermint, and other mint plants.
It is widely recognized for its distinctive minty aroma and cooling sensation when applied to the skin or mucous membranes.
Menthol exists as a cyclic terpene alcohol and can be found in solid crystalline form under standard room temperature.
Historically, menthol has been used for centuries in traditional medicine to treat various ailments such as headaches, nasal congestion, and minor pain.
It became popular in modern pharmaceutical formulations in the early 20th century due to advancements in extraction and crystallization processes.
Today, crystal menthol is used extensively across multiple industries, including pharmaceuticals, food, cosmetics, and aromatherapy.
Chemical Structure and Properties
Molecular Formula and Structure
The molecular formula of menthol is C10H20O, and its IUPAC name is (1R,2S,5R)-2-isopropyl-5-methylcyclohexanol.
It is a monoterpenoid alcohol with a cyclohexane ring structure that features three chiral centers, giving rise to eight stereoisomers.
Physical Properties
Appearance: Colorless or white crystalline solid
Melting Point: 41–44 °C
Boiling Point: ~212 °C
Density: 0.890 g/cm³
Solubility: Soluble in ethanol and ether, slightly soluble in water
Optical Isomerism
Menthol exhibits optical isomerism, with (-)-menthol (levomenthol) being the most biologically active isomer.
It naturally occurs in mint essential oils and provides the well-known cooling sensation.
Racemic and synthetic forms contain mixtures of isomers with reduced biological activity.
Extraction and Synthesis
Natural Sources
The primary botanical sources of menthol are:
Mentha arvensis (cornmint)
Mentha piperita (peppermint)
Menthol content in these plants ranges between 30% and 70% depending on the species and extraction method.
Extraction Process
Steam Distillation: Mint leaves are distilled to produce essential oil.
Fractional Distillation: The oil is refined to isolate menthol.
Crystallization: Menthol is crystallized out by cooling the oil.
Synthetic Production
Menthol can be synthesized via the hydrogenation of thymol or through asymmetric synthesis processes. Synthetic menthol is used when natural production cannot meet demand.
Crystallization Process
Menthol is typically crystallized from its oil using one of the following methods:
Cooling Techniques
Gradual cooling of menthol-rich oil from 45 °C to 5 °C over 12–24 hours yields high-purity crystals.
Solvent Systems
Solvents like ethanol or hexane may be used to aid in purification.
Recrystallization enhances purity (>99%).
Quality Control
Parameters such as crystal morphology, melting point, and purity are strictly monitored using standardized tests to ensure consistency and safety.
Analytical Methods
The quality and purity of crystal menthol are determined using various analytical techniques:
Gas Chromatography (GC)
Used to quantify the menthol content and identify impurities.
High-Performance Liquid Chromatography (HPLC)
Separates and identifies menthol isomers.
Spectroscopy
Infrared (IR): Identifies characteristic -OH and C-H stretching.
Nuclear Magnetic Resonance (NMR): Provides structural confirmation.
Mass Spectrometry (MS): Confirms molecular weight and fragmentation.
Standards
Quality benchmarks are set by the USP (United States Pharmacopeia), BP (British Pharmacopoeia), and JP (Japanese Pharmacopoeia).
SAFETY INFORMATION ABOUT CRYSTAL MENTHOL
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
