L-Menthol(CAS: 2216-51-5): Chemical Properties, Production Process, and Various Applications

What Is L-Menthol?

L-Menthol (also called Menthol Crystal or (-)-menthol), CAS 2216-51-5, is the naturally occurring levorotatory isomer of menthol – a cyclic monoterpene alcohol found in mint species such as Mentha piperita (peppermint) and Mentha arvensis (corn mint). It is a colourless, crystalline solid with a characteristic minty odour and a cooling sensory effect, and it is used across oral care, flavours and fragrances, cosmetics and personal care, and flavoured consumer products.

This guide covers the chemistry, specification, properties, production and applications of L-Menthol, its comparison with related cooling and flavour agents, dosage, quality and regulatory points, and supply. PolyBlueChem supplies L-Menthol crystals to the specification below in 25 kg fibre drums, with per-batch COA and SDS.

CAS number	2216-51-5
Chemical name	(1R,2S,5R)-2-Isopropyl-5-methylcyclohexanol (L-(-)-menthol)
Synonyms	L-Menthol; (-)-menthol; Menthol crystal; l-menthol
Molecular formula	C₁₀H₂₀O
Molecular weight	156.27 g/mol
Appearance	Colourless, needle-like crystals
Packing	25 kg net fibre drums

Chemistry and Structure

Menthol is a monoterpenoid alcohol: a cyclohexane ring carrying a hydroxyl group, an isopropyl group and a methyl group. The molecule has three chiral centres, so eight stereoisomers exist; the naturally dominant and most valued one is L-(-)-menthol. Its configuration gives it the strongest cooling effect and the “clean” mint profile.

The hydroxyl group (-OH) makes menthol an alcohol; it can be oxidised (to menthone), esterified (to menthyl esters) and reacted as a typical secondary alcohol.
The isopropyl and methyl groups make the molecule lipophilic and volatile, which is why menthol is a volatile, low-melting solid with a strong odour.
The stereochemistry is what distinguishes L-menthol from the D-isomer and the racemic (DL-) mixture – and is why the optical rotation is a key specification value.

Stereoisomer	Optical rotation	Note
L-(-)-Menthol	About -50°	The natural, most valued isomer (CAS 2216-51-5)
D-(+)-Menthol	About +50°	The mirror image (CAS 15356-60-2)
Racemic (DL-)-menthol	About 0°	Mixture of the two (CAS 89-78-1)

Specifications

L-Menthol crystals are supplied to the following specification:

Parameter	Specification
Appearance	Colourless crystals
Odour	Minty, cool
Melting point	41 – 44 °C
Optical rotation (25 °C)	-45° to -51°
Non-volatile matter	0.05% max
Residue on ignition	0.1% max
Heavy metals	10 ppm max
Arsenic (As)	3 ppm max
Purity	99% min

Parameter	What it controls
Optical rotation (-45° to -51°)	Confirms the L-(-)-isomer and its purity; a low value signals racemisation or a D-isomer blend
Melting point (41-44 °C)	Identity and purity of the crystalline product
Non-volatile matter (0.05% max)	Residue left after volatilisation; purity of the volatile fraction
Residue on ignition (0.1% max)	Inorganic residues
Heavy metals / arsenic	Toxic-metal limits for sensitive uses
Purity (99% min)	Active content of the crystals

A specification sheet and a per-batch certificate of analysis (COA) are available on request.

Physical and Chemical Properties

Property	Value / behaviour
Form	Colourless, needle-like crystals
Molecular weight	156.27 g/mol
Melting point	41 – 44 °C
Boiling point	About 212 °C at atmospheric pressure
Density	About 0.89 g/cm³ at 20 °C
Solubility	Sparingly soluble in water; freely soluble in alcohol, acetone and chloroform
Volatility	Volatile; responsible for the cooling, minty sensation
Reactivity	Oxidation (to menthone); esterification (to menthyl esters)

How L-Menthol Is Produced

L-Menthol is obtained either by extraction from mint oils or by synthetic routes. Both are used commercially; the choice depends on cost, volume and the purity/isomer required.

Route	Principle	Notes
Natural extraction	Steam distillation of mint oil, then crystallisation of menthol	Corn-mint (M. arvensis) oil is rich in menthol-free oil; the crystallised menthol is purified by recrystallisation
Synthetic (from menthone)	Hydrogenation of menthone or thymol-based routes	Gives control of purity and isomer profile; complements natural supply

Steam distillation – mint plant material is steam-distilled; the volatile oil (rich in menthol and menthone) is condensed and separated.
Crystallisation – the oil is cooled so that menthol crystallises out (menthol is a solid at room temperature, unlike many essential-oil components), and the crystals are separated.
Purification – the crystals are recrystallised (or distilled) to reach the required purity and optical rotation.

For synthetic material, the menthone route hydrogenates menthone to menthol under catalysis; the product is then purified and, where needed, the L-isomer is enriched. Because the buyer’s specification fixes the optical rotation, both natural and synthetic routes must deliver the correct stereochemistry and purity.

The Cooling Sensation: TRPM8 and Sensory Effect

Menthol is best known for the sensation of coolness it produces on skin and mucous membranes, without any actual drop in temperature. This is a sensory effect, not a change in heat:

Menthol activates the TRPM8 cold-sensing receptor, the same receptor that responds to cold temperatures.
Activation produces a perception of coolness – the basis for menthol’s use in products where a cooling, refreshing feel is wanted.
Because it is volatile and lipophilic, menthol reaches the receptors quickly and gives an immediate, intense sensory effect.

This cooling effect, combined with the minty odour and flavour, is why menthol is so widely used in oral care, confectionery, beverages, cosmetics and flavoured consumer products. (This section describes a sensory property of the ingredient; it is not medical advice.)

Product Forms and Grades

Form / grade	Description	Typical use
L-Menthol crystal	Large colourless crystals (this grade)	Where the natural L-isomer is required; general flavour/fragrance/oral care
Menthol powder / flakes	Milled or flaked forms	Faster dissolution/blending in some processes
DL- / racemic menthol	Mixture of L and D isomers	Cost-driven uses where the pure L-isomer is not essential
Mentha arvensis / piperita oil	Essential oils containing menthol	Where the full oil profile is wanted

Choosing the grade is largely a question of isomer and purity: L-menthol crystal for the natural-isomer profile, powder/flake forms for handling, and racemic menthol where cost dominates. Confirm the optical rotation your formulation requires.

Applications by Industry

Industry	Role of L-Menthol
Oral care	Minty flavour and cooling feel in toothpaste, mouthwash and gum
Confectionery and food	Mint flavour and cooling effect in candies, gum, desserts and beverages
Flavours and fragrances	A sharp, fresh mint note in flavour and fragrance compositions
Cosmetics and personal care	Cooling, refreshing sensory effect in skin, hair and shaving products
Topical and inhalation formulations	As a cooling, aromatic ingredient in topical and inhalation products
Other	Technical and sensory applications where a mint note or cooling effect is wanted

Oral care – menthol is one of the classic oral-care flavour ingredients, giving freshness and a cool mouthfeel.
Confectionery and beverages – the standard mint ingredient in chewing gum, hard candy, mints and mint-flavoured drinks.
Cosmetics and personal care – used for its refreshing, cooling sensory effect in skin care, hair care and shaving products.
Flavours and fragrances – a volatile top note that blends with citrus, herbaceous and woody accords.

L-Menthol vs Other Cooling and Flavour Agents

Agent	Type	Cooling strength	Typical use
L-Menthol	Natural monoterpene alcohol	Strong; natural	Oral care, flavours, personal care
DL- / racemic menthol	Synthetic/racemic	Weaker cooling (diluted by the D-isomer)	Cost-driven flavour use
WS-type coolants (menthyl/menthane derivatives)	Synthetic cooling agents	High, low odour	Where a strong cooling effect is wanted without a strong mint odour
Peppermint oil	Essential oil (menthol-rich)	Natural; broader profile	Where the full oil aroma is wanted

Guidance: choose L-menthol where the natural isomer and its odour are wanted; choose a synthetic coolant where a strong cooling effect with low odour is needed; use peppermint oil where the full essential-oil profile is desired.

Dosage and Formulation Notes

Application	Starting-point guidance
Oral care	A small fraction of a percent to a few percent, set by the flavour profile
Confectionery and gum	Set by the flavour; balanced against sweeteners and other flavours
Personal care	Very low levels, set by the cooling sensation and skin feel
Flavours/fragrances	Used as a top note at levels set by the perfumer/flavourist

Menthol is volatile and intensely odorous, so it is used at low levels and added late in the process where possible. Confirm the level by sensory evaluation and stability testing on your own formulation.

Quality, Standards and Regulatory

Point	Note
Identity/purity	Confirmed by melting point, optical rotation and purity on the COA
Pharmacopoeial use	Menthol is described in major pharmacopoeias; confirm the monograph and grade for your use
Flavour/fragrance use	Where it is used as a flavouring or fragrance ingredient, confirm the permitted use for your market
Toxic metals	Heavy metals (10 ppm max) and arsenic (3 ppm max) control purity for sensitive uses

Always confirm the grade and the permitted use for your application and market before ordering.

Safety, Handling and Storage

Low hazard – menthol is of low acute toxicity, but it is a potent sensory active and can irritate eyes and mucous membranes in high concentration.
Dust/vapour – handle with ventilation; avoid breathing concentrated vapour.
Storage – keep sealed, cool and dry, away from heat and strong odours; menthol is volatile and will sublime/lose weight if left open or warm.
Segregation – store away from other strongly odorous materials to avoid odour transfer.

Packaging, Logistics and Supply

Item	Standard options
Packaging	25 kg net fibre drums (as specified)
Documentation	Per-batch COA and SDS
Incoterms	FOB and CIF
Storage	Sealed, cool and dry, away from odours

Menthol price tracks the mint harvest (a weather-sensitive agricultural feedstock) and the energy and logistics of crystallisation/purification. The market is seasonal: supply is tightest between crops and eases after a good harvest. Buying on committed tonnage and planning around the harvest cycle gives the best terms.

Menthol in Oral Care and Confectionery

Oral care and confectionery are the classic homes of menthol, because the same two properties – a minty flavour and a cooling sensation – are exactly what consumers expect there.

Product	Why menthol is used
Toothpaste	Mint flavour and a fresh, cool mouthfeel
Mouthwash	Aromatic freshness and a cooling rinse
Chewing gum	Long-lasting mint flavour with a cooling effect
Hard candy and mints	Strong mint taste and a cooling finish
Mint-flavoured beverages	A refreshing mint note

In these products menthol is a flavouring and sensory ingredient: it delivers the mint note and the perceived coolness. Because it is volatile and intense, it is used at low levels and is often combined with other mint or flavour components to build a rounded profile. L-Menthol crystal is the preferred isomer where the full natural mint character and cooling intensity are wanted.

Menthol in Personal Care and Cosmetics

Category	Role of menthol
Skin care	Cooling, refreshing sensory effect
Shaving products	Cooling feel after shaving
Hair care	Invigorating, cooling scalp sensation
Body and bath	Refreshing coolness in washes and lotions
Deodorants	Fresh, clean sensory profile

In personal care, menthol is used for the cooling, refreshing sensation it gives, and for its clean, minty odour. Levels are kept low because the effect is potent, and the ingredient is typically balanced with other sensates, humectants or soothing agents to give the intended skin feel. As with all sensory actives, the level is confirmed by sensory panel and stability testing.

Market, Seasonality and Supply

Menthol is unusual among industrial ingredients because a large share of supply begins as an agricultural crop. That shapes the market.

Harvest-driven supply – natural menthol starts with the mint harvest (notably corn mint), so supply and price swing with weather, planted area and yield.
Seasonal pricing – prices are usually tightest between crops and ease after a good harvest; synthetic menthol and coolant prices track their own feedstocks.
Isomer and grade – the market distinguishes L-menthol crystal, powder/flake forms, racemic menthol and mint oils; the buyer’s optical-rotation requirement is a real cost driver.
Volatility risk – because menthol sublimes, packaging and storage affect the delivered weight and quality; good drum packaging matters.

For buyers, the practical planning points are to buy around the harvest cycle, confirm the isomer/specification precisely, and allow for the seasonal price curve in long-term contracts.

Frequently Asked Questions about L-Menthol

What is L-Menthol?

L-Menthol (CAS 2216-51-5) is the natural levorotatory isomer of menthol, a monoterpene alcohol with a minty odour and a cooling sensory effect.

What is the CAS number of menthol crystal?

2216-51-5 for L-(-)-menthol; racemic DL-menthol is CAS 89-78-1 and D-menthol is CAS 15356-60-2.

Why does the optical rotation matter?

It confirms the L-(-)-isomer and its purity; a low rotation indicates racemisation or a blend with the D-isomer, which weakens the cooling effect.

What is the melting point of L-menthol?

41 – 44 °C for the grade supplied here.

Is menthol natural or synthetic?

Both: it is extracted from mint oils and also produced synthetically (for example from menthone). The specified optical rotation is what matters.

How should menthol be stored?

Sealed, cool and dry, away from heat and strong odours – it is volatile.

What is the packing?

25 kg net fibre drums.