Material guide: dodecanal (aldehyde C-12 lauric) — vapour pressure lines up neatly along the carbon chain, the longevity column refuses to

CAS 112-54-9, 53 suppliers, C12H24O. Line up the straight-chain aldehydes from C-8 to C-14 and vapour pressure falls monotonically, spanning 345-fold, a textbook staircase. Longevity won't queue: 7, 276, 224, 72, 368, 400 hours, with C-11 five times shorter than C-12. Digging in, the tidy column turns out to be six estimated values, while the messy one is what people actually smelled on blotters. Its natural occurrence is counterintuitive too: the first word in its odor field is soapy, citrus peel oils carry only 0.002 to 0.055%, and the richest natural source is coriander leaf oil at 4.96 to 10.30%. Two more things: the database notes field recommends pairing it with lilyall for a clean fresh accord, a material banned in the EU since 2022; and a University of Tokyo team found it in the wrist-gland secretions of ring-tailed lemurs, rising with testosterone in the breeding season.

About a 4 minute read.

Too long, didn't read

Name: dodecanal, trade name aldehyde C-12 lauric (lauric aldehyde), CAS 112-54-9
C12H24O, MW 184.32, 53 suppliers; FEMA 2615, listed in all four regulatory indexes
Odor family aldehydic; descriptors: soapy, waxy, aldehydic, citrus, green, floral, orange rind
Longevity 368 hours @100%, strength high, evaluate at 10% or less
Melting point 3–8 °C, so it solidifies in cold weather; shelf life listed at just 10 months, store under nitrogen away from light
Richest natural source is coriander leaf oil (4.96–10.30%); citrus peel oils hold 0.002–0.055%
GHS: H315 skin irritation, H411 aquatic toxicity

The straight-chain family tree: one column lines up, one doesn't

Take the database's straight-chain fatty aldehydes from C-8 to C-14:

Material	Carbons	Vapour pressure, mmHg	Longevity (hr @100%)	Suppliers
octanal (C-8)	8	2.068	7	73
nonanal (C-9)	9	0.532	276	63
decanal (C-10)	10	0.207	224	92
undecanal (C-11)	11	0.083	72	35
dodecanal (C-12)	12	0.034	368	53
tetradecanal (C-14)	14	0.006	400	13

The vapour pressure column is textbook material: each added carbon drops it a step, 345-fold from top to bottom, no exceptions.

The longevity column is a mess. C-9 outlasts C-10, and C-11 suddenly drops to 72 hours, a fifth of its neighbour C-12. All six entries carry the same "@100%" notation, yet no order emerges.

I had planned to write "longer chain, longer lasting" and had to retract it once the table existed. Then I checked the raw vapour pressure fields: all six values carry the (est) marker — they are calculated from boiling points. Boiling points in a homologous series rise monotonically with carbon count by nature, so anything computed from them comes out monotonic. Longevity is what individual suppliers smelled on blotters and reported, each their own way.

The tidy column is the calculated one; the messy column is the measured one. What the est marker actually tells you and why agreeing estimates aren't evidence covered this before; this table is the third instalment of the same lesson.

One aside: there are two C-12s — this straight-chain one, and the branched 2-methyl undecanal (MNA). MNA lists 388 hours, but its vapour pressure of 1.428 was estimated from a boiling point that article showed to be wrong, so I've kept it out of the table.

A soapy citrus aldehyde whose biggest source is coriander

The first descriptor in its odor field is soapy, followed by waxy, aldehydic, citrus and orange rind. The occurrence field lists a parade of citrus: bergamot oil at 0.002–0.055%, blood orange around 0.03–0.043%, grapefruit 0.02%. All fractions of a tenth of a percent.

The real quantities sit elsewhere: coriander leaf oil at 4.96–10.30%, betel leaf oil at 4.23%. Two orders of magnitude above citrus peel. "Cilantro tastes like soap" is a famous argument, and one of the main constituents of cilantro leaf oil has soap as the first word in its odor field. Hard not to connect those two facts, but I haven't checked the causation — it's in the closing list.

The University of Tokyo found it on lemur wrists

In 2020 the Touhara lab at the University of Tokyo published a ring-tailed lemur study in Current Biology (Shirasu et al., PMID 32302584). Male lemurs rub secretions from their wrist glands onto their tails and wave them at females. Tracking the secretions by GC-MS, the team found three C12 and C14 aldehydes rising significantly in the breeding season, testosterone-dependent: dodecanal, 12-methyltridecanal and tetradecanal.

The behavioural details deserve exact reporting: tested singly, the two that held female attention longer were the other two aldehydes; dodecanal earned its place as part of the three-component mixture that attracted females. The authors call these "putative" lemur pheromones and go no further.

That bottom row of the table, tetradecanal, is one of the three — 13 suppliers carry it, longevity 400 hours. The lemurs' materials are commercially available to you.

In Kinokuni mandarins but not Satsumas

The other paper is from T. Hasegawa's research institute in 2010 (Miyazawa et al., PMID 20378969). Using aroma extract dilution analysis (AEDA), they compared Japan's native Kinokuni mandarin with the mainstream Satsuma. The key odorants shared by both were decanal, linalool and a few others; seven compounds contributed significantly only in Kinokuni, and dodecanal is one of them, alongside octanal, geraniol and thymol.

Same genus, one aldehyde apart, and the aroma profiles part ways. It also explains why perfumery citrus accords add C-12 back in deliberately: peel oil has it, just not enough of it.

The pairing the notes field recommends is now banned

The database notes field reads:

clean fresh accord - aldehyde C-12 10% and lilyall

Ten percent C-12 with lilyall for a clean, fresh accord. The problem: lilyall is Lilial, CMR-classified for reproductive toxicity and banned from EU cosmetics since March 2022. When that line entered the database it described a legal formula. Follow it today and the result can't be sold in the EU.

Catalogue data doesn't show its age. Regulatory fields get updated; formula advice buried in a notes field does not.

Buying and storing

53 suppliers, no sourcing problem. Three practical notes:

Shelf life is listed at 10 months, short for this series (most materials say 24), with nitrogen blanketing and light protection specified. The oxidation path of fatty aldehydes into acids is the same story told in the benzaldehyde guide.
Melting point 3–8 °C. A solidified bottle in winter is physics, not spoilage; warm it back up.
Strength says high with a 10%-or-less evaluation dilution. C-10 and C-11 in the same series say 1% or less — a tenfold spread hiding under one adjective. Before smelling, read the number, not the word.

Its public demo-formula links number 4, a low profile in the corpus.

What this article has not established

That cilantro's soapiness comes from dodecanal — not checked. I listed two database facts: coriander leaf oil contains 4.96–10.30% of it, and soapy is the first word in its odor field. The causal link would need sensory studies.
The lemur paper does not show dodecanal attracts on its own. The singly significant aldehydes were the other two; this one is a mixture member, and the authors say "putative".
For the scrambled longevity column I offered one explanation (suppliers measuring independently) without ruling out genuine non-monotonicity.
All six vapour pressures are estimates. The 345-fold span is the output of an estimation formula, not six measurements.