Material guide · 160
Material guide: 7-methyl coumarin — its notes field reads None found, and its isomer is the one with the problem
· 16 min read
CAS 2445-83-2, 7 suppliers, C10H8O2. Its category field reads 'information only not used for fragrances or flavors', its cosmetic uses field reads 'not used anymore', and its notes field reads 'None found': the database tells you not to use it without saying why. Its isomer, 6-methyl coumarin, does say why. That record's notes field reads 'synthetic fragrance causing contact photoallergy', and it has 35 suppliers, four regulatory listings and continued use. This record also has two fields fighting each other. Its atmospheric boiling point reads 128 °C, the same number as the lower bound of its melting point at 128 to 130 °C, while its appearance field says pale white powder. Only 11 records in the database have identical boiling and melting point fields, and this is the only one where the boiling point is the broken half. Its strength field reads low while recommending evaluation at 1% or less; of 253 strength rank 1 materials, it is the only one that does, and rank 1's median recommendation is 10%.
About a 4 minute read.
The short version
- Name: 7-methyl coumarin, CAS 2445-83-2, C10H8O2, molecular weight 160.17, 7 suppliers
- Odour type tonka; odour: sweet, coumarinic, tonka, coconut, powdery
- Category:
information only not used for fragrances or flavors - Cosmetic uses:
not used anymore - Notes:
None found. It says don't use it and does not say why - Its atmospheric boiling point of 128 °C is the same number as its melting point, and the appearance field says powder
- Strength rank 1 (weak), yet it recommends evaluation at 1% or less. The only one of 253 rank-1 materials that does
The one with the problem is next door
I have just swept the 6,457 "information only" records and found that only 87 were ever fragrance materials, and that 86% give no reason for their withdrawal. This is one of the 75.
Its positional isomer does give one:
| 6-methyl coumarin | 7-methyl coumarin | |
|---|---|---|
| CAS | 92-48-8 | 2445-83-2 |
| Formula | C10H8O2 | C10H8O2 |
| Suppliers | 35 | 7 |
| Category | flavoring agents |
information only not used |
| Regulatory | JECFA, FEMA GRAS, CoE, FLAVIS | (empty) |
| Notes | "synthetic fragrance causing contact photoallergy" | None found |
What Kaidbey and Kligman published in Contact Dermatitis in 1978 was the photocontact allergy of 6-methylcoumarin (PMID 743874). When DeLeo and colleagues summarised New York photopatch testing from 1985 to 1990, 6-methylcoumarin was on that list too (PMID 1444508).
That is sunscreen history, and it has no direct bearing on this material.
And 6-methyl's category in this database is flavoring agents, not fragrance agents, which is
probably the database recording that it left cosmetics while keeping its food identity.
Why the 7-methyl record was removed has no answer here.
The boiling point field is broken
The bp and mp fields:
bp: 171.00 to 172.00 °C. @ 11.00 mm Hg | 128.00 °C. @ 760.00 mm Hg
mp: 128.00 to 130.00 °C. @ 760.00 mm Hg
The atmospheric boiling point of 128 °C is the same number as the melting point's lower bound.
I swept the database for this: 2,676 materials carry
both fields and only 11 have identical values. Which half is broken is settled by the
appearance field:
pale white powder (est)
A powder is solid at room temperature, so 128–130 °C is a real melting point. The boiling point field is the broken one.
Seven of the 11 are described as liquids, where the melting point is the broken half. This is the only powder, and the only one where the boiling point is the casualty.
There is a second piece of evidence in the same field: the other value is 171–172 °C at 11 mmHg. A solid melting at 128 °C cannot boil at 171 °C under 11 mmHg and at 128 °C at atmospheric pressure.
(For contrast: coumarin itself is mp 68–74, bp 297–301; 6-methyl is mp 73–79, bp 303. Both boil around 300 °C, so this 128 is plainly not a boiling point.)
The strength rank fights the evaluation recommendation
The odor_strength field reads:
low ,recommend smelling in a 1.00 % solution or less
Low strength, but dilute to 1% before smelling it.
Matching strength ranks against recommended concentrations across the database:
| Strength rank | With a recommendation | Median |
|---|---|---|
| 1 (weak) | 7 | 10.00% |
| 2 (medium) | 431 | 10.00% |
| 3 (strong) | 352 | 1.00% |
Recommending 1% or less is what rank 3 does. And of the 253 rank-1 materials in the database, this is the only one that recommends it.
Which to believe? I have measured how evaluation concentration relates to actual dose: the evaluation concentration predicts better (rho = 0.679) than the strength rank (rho = −0.592). The evaluation concentration is the more trustworthy field, so the "rank 1" is what to doubt.
(Incidentally, its isomer 6-methyl is rank 2 and also recommends 1%. The two recommendations agree; it is the ranks that do not.)
Read what comes after that 400 hours
The odor_substantivity field reads:
400 hour(s) at 20.00 % in dipropylene glycol
Measured at 20% in dipropylene glycol, not neat.
I have written that 400 hours is one of the database's buckets: it accounts for 16.5% of all substantivity values and means "very long" rather than "400". And the concentration marker decides whether two numbers can be compared. Two problems in one field.
Pharmacology in the solubility field
The solubility field is supposed to list solvents, but this record's contains a sentence:
7-methylcoumarin is a coumarin with strong hepatoprotective activity.
That is pharmacology, not solubility. It came in with the text of some supplier's catalogue entry.
I have collected several instances of this kind of field contamination;
the most common is a misplaced TSCA definition in the notes field. This time it is the solubility field.
What it smells like
Setting the field problems aside, the odour field is readable:
sweet, coumarinic, tonka, coconut, powdery
Against coumarin itself (sweet, hay, tonka, new mown hay), it gains coconut and powder and loses hay. And 6-methyl's odour field runs to ten words, beginning with coconut.
The three coumarins sit on one line: the parent leans hay, 6-methyl leans coconut, and 7-methyl falls between them.
What this doesn't establish
- I did not check 7-methyl coumarin's current status in any jurisdiction. This is all a comparison of database fields.
- Both papers are about 6-methyl. I cite them to show that the documented problem belongs to the record next door, not to imply this material shares it.
- The judgement that the boiling point is the broken half rests on the
appearancefield, which carries(est). - "Doubt the rank rather than the recommendation" rests on correlations I computed myself, which is a statistical preference rather than an outside authority.
- The
assayfield reads97.00 to 100.00, which is not the database's default template value (that is95.00 to 100.00), but neither does it tell you what your lot contains. - I do not know what those 7 suppliers sell. The solubility field lists 98% analytical grade, which reads more like research supply than perfumery supply.