Material guide: Calone (watermelon ketone) — one of the highest longevity records in the database, and the number carries a greater-than sign

Start with this material's longevity field, because it is the highest figure in sixty-six material guides:

> 600 hours at 10% in DPG

Three things are crowded into that one line: six hundred hours, a greater-than sign, and a tenfold dilution.

Counting the database: of the 2,027 materials carrying a longevity record, only 17 exceed 400 hours, and only 8 reach 600 or more. This one is in the top 0.84%.

And that was measured at a tenfold dilution.

The greater-than sign deserves its own section

We have written about the 400-hour ceiling: 13.3% of materials pile up at the top of the scale, and a reader cannot tell that those mean "at least 400" rather than "exactly 400".

This material demonstrates the same problem written a different way.

Counting across the database: 206 longevity records carry a ">" sign, which is 10.2% of the 2,027.

A tenth of those records are not measurements; they are lower bounds. They say "it had not disappeared when we stopped watching", not "it disappeared at hour 600".

This is more honest than the 400-hour ceiling — at least the greater-than sign tells you it was censored. But drop it into a spreadsheet as a number and sort on it, and that information is gone.

The short version

• Longevity > 600 hours at 10% in DPG, putting it in the top 0.84% of 2,027 records.
• 206 records across the database carry a greater-than sign; those are lower bounds, not measurements.
• It is white powder crystals, melting point 38–41 °C. Like omega-pentadecalactone, a solid at room temperature that melts near body temperature.
• Flash point 166.67 °C, the highest in this series.
• It is not found in nature, and real watermelon aroma comes principally from C6 and C9 aldehydes and alcohols — structurally unrelated to it.
• A 2008 study mapped structure against odour: the 7-alkyl group is what maintains the marine character, and removing the carbonyl weakens the marine note while introducing aldehydic and floral-fruity ones.
• Corpus: 31 formulas, median dose 0.91%. Someone reported buying 50 g — that is 1,099 five-gram trials.

The basics

Database name	watermelon ketone
Trade names	Calone, Calone 1951 (Firmenich)
CAS	28940-11-6
Chemical name	7-methyl-2H-1,5-benzodioxepin-3(4H)-one
Formula	C₁₀H₁₀O₃
Molecular weight	178.19
Odour	Fresh, watery, clean, melon, green, marine, ozone, phenolic
Odour family	melon
Strength	High (evaluate at 10% or below)
Longevity	> 600 hours at 10% in DPG (a lower bound, not a measurement)
Appearance	White powder crystals
Melting point	38–41 °C
Boiling point	158 °C @ 760 mmHg
Flash point	166.67 °C
Vapour pressure	0.001 mmHg @ 25 °C (est)
logP	1.90 (est)
Natural occurrence	Not found in nature
Storage	36 months or longer
Regulatory listings	(blank)
Suppliers	58
Corpus position	31 formulas, median dose 0.91%

The watermelon in the name has nothing to do with watermelon

It is called watermelon ketone, and its natural occurrence field reads not found in nature.

So what does real watermelon smell of? That has been measured.

Tripodi and colleagues, in the Journal of the Science of Food and Agriculture in 2020, studied the aroma compounds of mini-watermelon fruits from different grafting combinations, using solid-phase microextraction gas chromatography-mass spectrometry.

The result: the most represented compounds were C6 and C9 aldehydes and alcohols, which characterise the fruit aroma of the Cucurbitaceae family. Specifically, (Z)-2-nonenal, (E,Z)-2,6-nonadienal, (Z)-3-nonen-1-ol and (Z,Z)-3,6-nonadien-1-ol were prevalent. Quantities differed between rootstocks, with RS841 best at maintaining yield, quality parameters, sensory characteristics and volatile aroma compounds together.

On one side, straight-chain nine-carbon aldehydes and alcohols. On the other, a seven-membered heterocyclic ketone fused to a benzene ring. They are structurally unrelated.

So "watermelon ketone" describes what it reminds you of, not what it is. That is the pattern from heliotropin, cyclamen aldehyde and helional — with an extra layer here: the "watermelon" it reminds you of is closer to water and sea than to the fruit.

The odour field bears that out: fresh, watery, clean, melon, green, marine, ozone, phenolic. One of eight descriptors is melon.

(If you actually want watermelon, the route is the C6 green-leaf family like cis-3-hexenol plus C9 dienals. That is a different road.)

That methyl group at position 7

This material has a good structure-odour study behind it.

Hügel and colleagues published "Marine fragrance chemistry" in Chemistry & Biodiversity in 2008. Their opening sentence settles its status: the main marine message in perfumery is projected by Calone 1951 (7-methyl-2H-1,5-benzodioxepin-3(4H)-one).

They note that Kraft (Givaudan) and Gaudin (Firmenich) further expanded the marine molecular family by extending the carbon chain of the 7-methyl group.

Their own research targeted the polar group of the parent benzodioxepinone. The finding: analogues prepared by chemical modification or removal of the carbonyl group introduced aldehydic, sweet and floral-fruity notes, with a diluted or diminished potency of the marine odour.

To analyse benzodioxepinones with a range of aromatic ring substituents they developed a new synthesis route, and reached the key conclusion:

A 7-alkyl group in Calone 1951 is essential for maintaining the significant marine odour characteristic.

Their work supports the concept that the odorant structure occupying the hydrophobic binding pocket adjacent to the aromatic ring-binding site of the olfactory receptor is pivotal in designing more potent and characteristic marine fragrances.

What that means at the bench: the differences within this family are not about whether there is a marine character, but about what hangs off position 7. So if you own several marine or ozonic materials and they smell like versions of the same thing, that reading is correct — they are substituted variants of one skeleton.

(Which loops back to one per slot: several members of one family may just be several versions of one material.)

It is a powder, and it is hard to set alight

Two handling details.

One: white powder crystals, melting point 38–41 °C. Like omega-pentadecalactone, solid at room temperature and melting near body temperature. Weighing means making a stock first; solids handling is in the cinnamic alcohol article.

Two: flash point 166.67 °C, the highest in this series. Against cineole's 50 °C and benzaldehyde's 62.8 °C. No fire concerns in storage, which is a rare bit of ease on a palette.

Shelf life is 36 months or longer, also longer than most — of the 1,303 database materials with a stated shelf life, only 8.5% state 36 months or more.

Those three facts together make it look easy to buy. Which is exactly why someone bought 50 g.

How long 50 g lasts

In the last article's thread, someone wrote:

"50gm of calone… I have literally no idea why I bought that much at the time but it was relatively cheap so who cares."

In the corpus it appears in 31 formulas at a median dose of 0.91%.

50 g ÷ (0.91% × 5 g) = 1,099 five-gram trials.

At three a week, that is seven years. The shelf life is 36 months.

"Relatively cheap" is accurate and "who cares" is honest. But that bottle passes its shelf life long before it empties, and an aged material does not merely weaken.

Smelling it and using it

• Start between 0.5% and 1%. The corpus median is 0.91%, and the strength field says high, evaluate at 10% or below.
• It covers things. That ozonic-marine signal is assertive and dominates a formula's impression from low concentrations.
• Note the word "phenolic". It is the last descriptor in the odour field. At higher concentrations a disinfectant or plastic register emerges, and that is why many people dislike it.
• Smell it beside helional. Both carry watery and ozone, but helional adds hay and cyclamen while Calone adds melon and phenolic.
• It stays to the end. Over 600 hours at a 10% dilution. The wateriness you smell on day two is probably this.

Buying and storage

Fifty-eight suppliers. Buy on CAS 28940-11-6. The names Calone, Calone 1951 and watermelon ketone all point at the same thing.

Buy small. At a 0.91% dose, 10 g is 220 five-gram trials, which is already several years for most people.

Shelf life 36 months or longer; cool, dry, sealed, away from light. It is a solid, so keeping moisture out is enough.

Regulatory and safety

One GHS statement: H302, harmful if swallowed.

But the acute toxicity figure is not high: oral rat LD50 1,556 mg/kg. Against cyclamen aldehyde's 3,810 and omega-pentadecalactone's above 5,000, that is noticeably lower.

"One GHS statement" and "low toxicity" are not the same claim — that field carries data for only 369 of 42,225 records, and this material's toxicity field does carry a figure. Read both columns together.

Check current IFRA Standards for the limit — here is how.

→ Watermelon ketone in the database: full physical data, 58 suppliers and suggested blends. → Search by odour: try "marine watery ozone".

References

H. M. Hügel, B. Drevermann, A. R. Lingham, P. J. Marriott, Marine fragrance chemistry, Chemistry & Biodiversity, 5(6), 1034–1044 (2008). PMID 18618392. doi:10.1002/cbdv.200890083

G. Tripodi, C. Condurso, F. Cincotta, M. Merlino, A. Verzera, Aroma compounds in mini-watermelon fruits from different grafting combinations, Journal of the Science of Food and Agriculture, 100(3), 1328–1335 (2020). PMID 31743449. doi:10.1002/jsfa.10149