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44 Chem. Educator 1999, 4, 44–50
© 1999 Springer-Verlag New York, Inc., S1430-4171(99)02286-8, 10.1007/s00897990286a, 420044ww.pdf
The History of Skunk Defensive Secretion Research
William F. Wood
Department of Chemistry, Humboldt State University Arcata, CA 95521, wfw2@axe.humboldt.edu
Abstract: The striped skunk (Mephitis mephitis) is widely known for the highly odoriferous defensive secretion
it uses to repel predators. Chemists have sporadically investigated the chemical composition of this secretion for
many years. In this research, a number of chemicals have been incorrectly attributed to this secretion and the
errors incorporated into the chemical literature. The major component in skunk spray was erroneously believed
to be 1-butanethiol, until it was later shown that the actual compound was (E)-2-butene-1-thiol. More recently,
two studies identified the third major compound in the secretion as either (E)-2-butenyl methyl disulfide or (E)-
2-butenyl propyl sulfide. These structural assignments were incorrect and the compound was later shown to be
(E)-2-butenyl thioacetate. Two investigations have reported chemicals that could not be confirmed in a later
study, so these compounds may have been artifacts produced during isolation or analysis. The striped skunk’s
secretion is similar to, but different from, the defensive secretions of two other skunk species, the spotted skunk
(Spilogale gracilis) and the hog-nosed skunk (Conepatus mesoleucus).
Folklore asserts that tomato juice will neutralize the odor of skunk spray, but human olfactory fatigue can
explain the apparent disappearance of the odor on sprayed pets. The odoriferous thiols in skunk spray can easily
be neutralized by oxidation to sulfonic acids.
Introduction
Skunks and their defensive secretion have both fascinated
and repelled natural product chemists. The chemicals secreted
by the members of the mephatinae, a New World subfamily of
the weasel family (Mustelidae), are so obnoxious that few
chemists have been willing to work with them. On the other
hand, once researchers published the identity of these
components, the purported identities were cited far and wide in
the popular and chemical literature. This led to several
incorrect structural identifications persisting in the literature
for years because few chemists were interested in
reinvestigating the chemicals in these secretions.
Six species of skunks are found in North America: the
striped skunk, Mephitis mephitis; the hooded skunk, M.
macroura; two species of hog-nosed skunks, Conepatus
mesoleucus and C. leuconotus; and two species of spotted
skunks, Spilogale putorius and S. gracilis. Spotted skunks
were previously considered one species (S. putorius), but have
recently been divided into two species, S. putorius in the
eastern United States and S. gracilis in the western U.S. All
skunk species are known for their potent means of chemical
defense: the spraying of a repulsive-smelling liquid from their
anal glands. Research on this secretion has been focused for
the most part on the most common member of this group, the
striped skunk (Figure 1). In this review, the term “skunk”
refers to this species, unless otherwise specified.
Skunk defensive secretion is frequently referred to as either
skunk spray or skunk musk. This secretion is stored in two
glands (anal sacs) leading to nipples situated just outside the
anal opening. When attacked or surprised, a skunk lifts its tail
and will eject this secretion a distance of up to about 3 meters
(Figure 2). At high concentrations it can cause nausea and
retching in humans and, like tear gas, it is a strong lachrymator
if it comes in contact with the eyes. At lower concentrations it
is highly repellant and can be detected by humans at extremely
low concentrations. In 1896, Aldrich showed it could be
detected at 10 ppb [1].
High concentrations of skunk spray can be toxic. Hydrogen
sulfide is very toxic to humans; methanethiol at concentrations
of 1 part per 100 in air will kill rats. In 1896, Aldrich made the
following speculation, indicating that the toxic properties of
compounds in skunk spray might result in death [1]: “The
substance is a powerful anaesthetic, and has also been used as
an antispasmodic. When inhaled without the admixture of a
large amount of air the victim loses consciousness, the
temperature falls, the pulse slackens, and, if the inhalation
were prolonged, the results would doubtless prove fatal.”
The anesthetic properties of the secretion referred to by
Aldrich above, stems from an 1881 report by W. B. Conway,
M.D. at the Virginia Agricultural and Mechanical College in
Blacksburg, Virginia [2].
“Some time during the summer of 1879, two or three boys
[students at the above college], secured a two-ounce bottle
of the perfume from the skunk or pole-cat (Mephitis
Americanae), and concluded to play a trick upon one of
their school mates; entering his room, they held him, and
administered the above nauseous fluid (in its most
concentrated form), by inhalation. I could not ascertain
what amount was administered. However, when I reached
him I found the following symptoms: A total
unconsciousness, relaxation of the muscular system,
extremities cool, pupils natural, breathing normal, pulse 65,
temperature 94; in which condition he remained for one
hour.”
In the hour it took to revive the patient, the doctor
“administered small quantities of whisky at short intervals per
orem, with some difficulty getting him to swallow.” The
victim of this prank was reported to have a slight headache on
awakening that “passed off after a good night’s sleep.”
Many of the chemicals that have been identified in skunk
spray are thiols. In the older chemical literature these
compounds were called mercaptans, a name derived from the
The History of Skunk Defensive Secretion Research Chem. Educator, Vol. 4, No. 2, 1999 45
© 1999 Springer-Verlag New York, Inc., S1430-4171(99)02286-8, 10.1007/s00897990286a, 420044ww.pdf
Figure 1. The striped skunk, mephitis mephitis (photo by W. F.
Wood).
Figure 2. The striped skunk lifting its tail before spraying (photo by
W. F. Wood).
Figure 3. Sample of the defensive secretion from the striped skunk
(photo by W. F. Wood).
fact that these compounds form compounds with mercury. In
this review, modern chemical nomenclature terms are used
except in quotations of original literature. As an example, the
names “normal butyl mercaptan” or “n-butyl mercaptan” used
in the original literature are replaced with “1-butanethiol.” A
glossary of old and new names is included at the end of this
review.
Chemicals from the Striped Skunk (Mephitis mephitis)
The first report in the chemical literature on skunk spray was
in 1862 by a Dr. Swarts working with Wöhler in Germany [3].
They had obtained a sample of the secretion from a friend in
New York. Swarts analyzed the yellow oil and found that it
consisted of a colorless fraction boiling between 105 and 110
°C, a higher boiling yellow fraction boiling between 195 and
200 °C, and a nitrogenous basic compound in the residue after
distillation. In another experiment Swarts steam-distilled the
secretion and found the water-insoluble part of the distillate to
be rich in sulfur.
In 1879 another German, Dr. O. Löw next reported work on
skunk spray [4]. He confirmed Swarts’ findings that it
contained sulfur compounds and a nitrogenous base. His major
problem in completing the research was not his chemical
expertise, but the reactions of his companions and co-workers.
Löw’s experience was reported in a letter, part of which was
included in a later report on skunk spray by Aldrich [1].
“On an expedition through Texas in 1872 I had frequent
opportunity to collect a sufficient quantity of this secretion
to establish its chemical constitution, but all my
companions protested against it, declaring the odour which
clung to me to be unbearable. On my return to New York
City I started a few chemical tests, with the little I had
collected, when the whole college rose in revolt, shouting,
‘A skunk, a skunk is here!’ I had to abandon the
investigation.”
Thomas Aldrich, working in the Laboratory for
Physiological Chemistry at The Johns Hopkins University,
next investigated skunk secretion and reported his studies in
1896 and 1897 [1, 5]. He had a plentiful supply of skunk anal
sacs from sources primarily in Maine, and stated he received
some of these samples within 12 hours of collection. The
amount of secretion in these glands varied, with a maximum of
about 5 mL. He described it as follows, “the secretion is a
clear, limpid fluid, of golden-yellow or light- amber colour, of
a characteristic, penetrating, and most powerful odour, and
having a specific gravity, at ordinary temperature, less than
water (0.939).” See Figure 3.
In his first study, Aldrich distilled the secretion and found
two major volatile fractions, one boiling from 100 to 130 °C
and another from 130 to 150 °C [1]. The low boiling fraction
was further divided into fractions; most of the material
distilled between 100 and 110 °C. In order to identify the
thiol(s) in the low-boiling fraction, he looked at known thiols.
On the basis of their boiling points he excluded several low
molecular weight thiols: methanethiol (bp 6 °C), ethanethiol
(bp 36 °C), 1-propanethiol (bp 67 °C), and 2-propanethiol (bp
57–60 °C). As part of his study, Aldrich prepared 3-methyl-1-
butanethiol and determined its boiling range as 115–120 °C.
Because the boiling range of this 5-carbon compound is higher
than that of the major fraction (100–110 °C), Aldrich focused
his study on the 4-carbon thiol, 1-butanethiol, which has a
46 Chem. Educator, Vol. 4, No. 2, 1999 Wood
© 1999 Springer-Verlag New York, Inc., S1430-4171(99)02286-8, 10.1007/s00897990286a, 420044ww.pdf
boiling point of 97 °C. He speculated that the fraction
distilling between 100 and 110 °C could possibly be 1-
butanethiol, if it were contaminated by a small quantity of a
higher-boiling compound.
Elemental analysis for sulfur in the lowest boiling fraction
gives results that are close to what would be expected for 1-
butanethiol (or an isomer). The calculated value for %S in
C4H9SH is 35.55%, and Aldrich found 35.37% and 34.98%,
values too low to make a positive identification of C4H9SH.
Aldrich was unable to perform carbon and hydrogen
elemental analyses directly on the lowest boiling fraction due
to decomposition of the thiol during the analysis. To overcome
this problem, he prepared lead and mercury derivatives of the
thiol in the lowest boiling fraction. Here too, the carbon and
hydrogen elemental analyses of these derivatives were slightly
different than would be expected for C4H9SH. In his report he
stated, “The results of these analyses are sufficiently near the
theoretical figures when considered with the boiling point to
convince, I think, the most skeptical that the greater part of this
fraction contains one of the butyl mercaptans.” There are three
other thiols with the same molecular formula as 1-butanethiol
(I): 2-butanethiol (II), 2-methyl-1-propanethiol (III) and 2-
methyl-2-propanethiol (IV). Of these compounds, Aldrich
attempted to synthesize 2-methyl-1-propanethiol, but did not
succeed.
CH3CH2CH2CH2SH CH3CHCH2CH2CH3
SH
CH3CHCH 2SH
CH3CH3CCH3
SH
CH3
III
III IV
Because Aldrich’s boiling point and elemental analysis
values were very close to expected values, he speculated that
an impurity could be responsible for the difference [1].
“Primary normal butyl mercaptan is given as boiling
at 97 °C. The boiling point of the fraction boiling between
100° and 110 °C could be easily explained if we assume the
presence in small quantity of some higher boiling body. This
assumption would also explain in general the analytical results.
I am inclined to believe in the presence of a higher mercaptan
(say amyl mercaptan [3-methyl-1-butanethiol]) rather than a
sulphide.”
In his explanation of the difference in elemental analysis of
his compound from that expected for 1-butanethiol, Aldrich
never indicated that he considered compounds with double
bonds or rings as a possibility.
The long-held belief that skunk secretion contains 1-
butanethiol (butyl mercaptan) certainly owes its source to
Aldrich’s 1896 publication [1]. Aldrich was very careful not to
claim a positive identification of 1-butanethiol, but did say the
compound could be 1-butanethiol or an isomer, if one took
into account impurities in his samples. He did, however, use
the following names to describe the elemental analysis of the
derivative of the thiol that boiled between 100 and 110 °C:
lead butyl mercaptide, (C4H9S)2Pb; and mercuric butyl
mercaptide, (C4H9S)2Hg. He then stated it was likely the
secretion “contained one of the butyl mercaptans.” He
reiterated this in his second publication on this secretion,
stating this part of the secretion “is a mixture of higher
mercaptans, containing among others (still undetermined)
normal butyl mercaptan” [5]. The many references to 1-
butanethiol in Aldrich’s articles certainly must have led others
into believing this compound had been positively identified in
skunk spray. This misconception was incorporated into the
chemical literature and persisted for many years. A 1978
review by Andersen and Bernstein on this topic describes the
myth that skunk spray is primarily 1-butanethiol as, “well
established as part of the folklore of organic chemistry by the
1940s and maybe earlier” [6]. For example, when Stevens
reported on an additional compound from skunk spray in 1945,
he stated that Aldrich showed “that the principal odoriferous
material is n-butyl mercaptan” [7]. The seventh edition of the
Merck Index (1960) under “n-butyl mercaptan” says it “occurs
in skunk fluid” and, in the entry, “Skunk Oil,” it cites Stevens’
work and reiterates that skunk spray contains n-butyl
mercaptan (1-butanethiol).
In 1897, Aldrich and Jones published a second report on
skunk defensive secretion [5]. In this study they identified 2-
methylquinoline (V), a nitrogenous base that was presumably
the one that had previously been reported by Swarts [3] and
Löw [4]. Aldrich and Jones based their identification on a
number of derivatives prepared from the skunk’s compound
and compared them to the same derivatives of a synthetic
sample of 2-methylquinoline. Andersen, et al. [8] and
Wood [9] in later studies reconfirmed the presence of this
compound in skunk spray. Aldrich also detected a second
basic compound that was less volatile in the steam distillation
by which he isolated 2-methylquinoline. He did not identify
this second alkaloid, but did say, “It may be stated in passing
that the less volatile body differs from the more volatile in
containing sulphur.” Likely this was 2-quinolinemethanethiol
(VI), identified 93 years later by Wood [9].
NCH
3
VVI
NCH
2SH
In 1945, Stevens made a brief foray into the field of skunk
research while searching for new animal musks, specifically
large-ring ketones that could be used as perfume bases [7].
Animal musks have been an ingredient in high quality
perfumes for many years. About 20 years before Steven’s
study on skunk musk, Ruzicka had isolated and identified
muscone (VII) from the musk deer [10, 11] and civetone
(VIII) from the African civet [12, 13]. Both of these
compounds are large-ring ketones. Stevens failed to find any
large ring ketones, but did isolate bis[(E)-2-butenyl] sulfide
(IX).
O
VII VIII
O
CH3
The History of Skunk Defensive Secretion Research Chem. Educator, Vol. 4, No. 2, 1999 47
© 1999 Springer-Verlag New York, Inc., S1430-4171(99)02286-8, 10.1007/s00897990286a, 420044ww.pdf
H3CC
HCH
CH2SCH 2C
HCH
CH3
IX
Stevens noted that the secretion was “repulsive in odor,”
which may have kept him from working on it in a timely
fashion. The experimental procedure indicates that after
collection, the native secretion separated into two layers “after
several months” of storage. The sample was next treated for
several days with mercuric chloride to remove the thiols. After
removal of the mercury salts, the solution was stored for
“considerable time” before the solvent was removed. An initial
vacuum distillation was followed by extraction with 7% HCl
and 10% “alkali” to remove impurities. Finally, two successive
vacuum distillations were used to isolate the bis[(E)-2-butenyl]
sulfide. Stevens started with 210 g of secretion and isolated
4.5 g of the sulfide so, assuming none was lost, the initial
secretion should have contained at least 2% of this compound.
Later work on freshly collected skunk spray could not confirm
this compound even as a minor component [9]. The extensive
and harsh conditions used in Stevens’ isolation procedure may
have produced this compound.
In 1975, 79 years after Aldrich’s investigation, Kenneth
Andersen and David Bernstein at the University of New
Hampshire showed that 1-butanethiol (I) is not a major
component of skunk spray [14]. This study was done using the
volatile material obtained from a vacuum distillation of the
secretion. The major volatile compound is the unsaturated
(E)-2-butene-1-thiol (X). It was identified by comparison of IR
and 1H-NMR spectra of the skunk-produced compound to
those of a synthetic sample. Andersen and Bernstein later re-
examined Aldrich’s elemental analyses of derivatives prepared
from the lowest boiling fraction of skunk spray [6]. For many
of Aldrich’s derivatives, the percentages of carbon and
hydrogen are within the experimental values expected for (E)-
2-butene-1-thiol. Thus, Aldrich had certainly isolated a pure
sample of this compound.
CC
CH2SH
HCH3
H
X
Andersen and Bernstein similarly used IR and NMR
spectroscopy in their 1975 study to identify a second volatile
thiol from skunk spray, 3-methyl-1-butanethiol (XI).
Interestingly, in 1896 Aldrich had prepared 3-methyl-1-
butanethiol as part of his first study on skunk spray and
speculated it may have been a reason for the faulty elemental
analysis [1]. He said his synthetic compound had the same
boiling point, appearance, and odor of a fraction of skunk
secretion with the same boiling point. Alas, he never made a
positive identification of this compound by elemental analysis
or making derivatives.
CH3CHCH2CH2SH
CH3
XI
The third-most-abundant volatile compound Anderson and
Bernstein found in the secretion was identified as (E)-2-
butenyl methyl disulfide (XII) [14]. They synthesized this
compound from S-methyl thiophthalimide and (E)-2-butene-1-
thiol in refluxing benzene. This compound and the one from
skunk spray were reported to have identical NMR and IR
spectra; 15 years later, however, this structural assignment was
shown to be incorrect [9].
CC
CH2SSCH 3
HCH3
H
XII
In 1982, Andersen and co-workers reported their continued
research on skunk defensive secretion using gas
chromatography–mass spectrometry (GC-MS) to identify many
new major and minor (less than 1%) constituents in skunk
spray [8]. This study confirmed the identifications of (E)-2-
butene-1-thiol and 3-methyl-1-butanethiol (66%, coeluted), but
was unable to confirm the third major component of their first
study, (E)-2-butenyl methyl disulfide. In this second study,
(E)-2-butenyl propyl sulfide (XIII) was reported as the third-
most-abundant compound (7%). This compound was
identified by analysis of its mass spectral fragmentation
pattern, however, like the third major compound of the
previous study, it too was an incorrect structural
assignment [9]. Other major compounds tentatively identified
from mass spectral fragmentation patterns were two disulfides
(7%) that coeluted, butyl (E)-2-butenyl disulfide (XIV) and
butyl 3-methylbutanyl disulfide (XV). These two disulfides
were not seen in later studies and may have been artifacts of
the analysis. Aldrich’s identification of 2-methylquinoline was
corroborated by comparison with an authentic sample, and a
new compound, S-3-methylbutanyl thioacetate (XVI), was
identified by comparison to a spectrum in the NBS mass
spectral library.
CH3CHCH2CH2SCCH3
CH3O
CC
H
CH3
CH2SCH2CH2CH3
H
CH3CH2CH2CH2SSCH2CH2CHCH3
CH3
CH3CH2CH2CH2SSCH2
C
HCCH3
H
XIII
XIV XV
XVI
In 1990, William Wood was the next player in skunk spray
research [9]. In his study, GC-MS analysis was done on native
48 Chem. Educator, Vol. 4, No. 2, 1999 Wood
© 1999 Springer-Verlag New York, Inc., S1430-4171(99)02286-8, 10.1007/s00897990286a, 420044ww.pdf
secretion and in several cases was done just minutes after
collection from skunks. The two major compounds of this
study were the two major thiols (X and XI) previously
identified by Andersen and co-workers. Since the third major
compound (XII and XIII) in each of the two Andersen studies
was different, both (E)-2-butenyl methyl disulfide and (E)-2-
butenyl propyl sulfide were prepared. Surprisingly, GC-MS
analysis showed neither of these synthetic compounds to be in
skunk spray. The third major compound of this 1990 study had
the same molecular weight (molecular ion) as (E)-2-butenyl
propyl sulfide, the compound identified in Andersen’s second
study, but it had a different mass spectral fragmentation
pattern. A possible candidate compound with the same
molecular weight, S-(E)-2-butenyl thioacetate (XVII), was
prepared. This thioacetate had identical properties by GC-MS
analysis as the compound in skunk spray. Furthermore, the 1H-
NMR spectra of S-(E)-2-butenyl thioacetate and (E)-2-butenyl
methyl disulfide (Andersen’s first study) are almost identical.
It is thus likely that both the (E)-2-butenyl methyl disulfide and
(E)-2-butenyl propyl sulfide reported by Andersen and co-
workers as the third major component in each of their reports
were actually S-(E)-2-butenyl thioacetate, XVII.
CC
H
CH3
CH2SCCH3
H
O
XVII
The incorrect assignments of these structures are easy to
explain. Identical NMR spectra are usually all that is needed to
assign the structure of a new simple compound. Andersen and
Bernstein had no reason to perform further tests in their first
study. In their second study, (E)-2-butenyl propyl sulfide was
identified by analysis of its MS fragmentation pattern. The
fragmentation patterns of this compound and S-(E)-2-butenyl
thioacetate have so many similar fragments that identification
without comparison to an authentic sample led to a wrong
structural assignment.
In this 1990 report, the presence of a number of compounds
identified in previous studies could not be confirmed,
including the two disulfides (XIV and XV) that coeluted in
Andersen’s second study [8], butyl (E)-2-butenyl disulfide and
butyl 3-methylbutanyl disulfide. Perhaps these two disulfides
were artifacts produced during the hour-long capillary GC-MS
analysis. Andersen and co-workers did suggest that some of
the compounds observed in their study might “arise from
thermally induced process[es].” Because, the bis[(E)-2-
butenyl] sulfide that Stevens found in his study [7] was not
detected, it too may be an artifact produced by the lengthy
isolation procedure.
New natural products identified in this 1990 report were S-
(E)-2-butenyl thioacetate, 2-quinolinemethanethiol, and S-2-
quinolinemethyl thioacetate (XVIII). The 2-methylquinoline
identified by Aldrich and Jones in 1897 [5] and the S-3-
methylbutanyl thioacetate identified by Andersen and co-
workers in 1982 [8] were reconfirmed. To summarize, this
later research showed the striped skunk spray to have 7 volatile
components in greater than 1% abundance. Three are thiols
(VI, X, and XI), three are thioacetate derivatives of these
thiols (XVI, XVII and XVIII), and the final compound is an
alkaloid, 2-methylquinoline, (V).
NCH
2SCCH3
O
XVIII
Many dog owners have anecdotal tales of their pets having a
faint “skunky” odor recur on damp evenings long after the
odor from an encounter with a skunk had vanished. The
thioacetate derivatives of (E)-2-buten-1-thiol and 3-methyl-1-
butanethiol may be responsible for this observation. These
compounds are not as volatile or odoriferous as the thiols, but
are easily converted to the more potent thiols on water
hydrolysis. Thus, damp conditions may lead to conversion of
thioacetates trapped in animal hair to the mephitic thiols.
CC
H
H
CH2SSCH 2
CH3CC
HCH
3
H
CH3CC
HCH
2SSCH 2CH2CHCH3
HCH3CH3CHCH2CH2SSCH 2CH2CHCH 3
CH3CH3
CH2SH
XX
XXI
XXII XXIII
CH2CH2SH
XIX
Chemicals from the Spotted Skunk (Spilogale gracilis)
In 1991, after finishing the work on the striped skunk, Wood
examined the secretion from the spotted skunk. Unfortunately,
after publication of this study, Spilogale putorius was divided
into two species, S. putorius in the eastern part of the United
States and S. gracilis in the western part. Thus, because the
skunks were collected in California, the species of skunk
investigated was S. gracilis even though the publication
purports to describe S. putorius. The defensive secretion of the
spotted skunk differs from that of the striped skunk in that it
contains only thiols; it contains none of the thioacetates found
in striped skunk secretion [15]. The two major thiols of the
striped skunk, (E)-2-butene-1-thiol and 3-methyl-1-butanethiol
are also the major components in the secretion of the spotted
skunk. A third thiol, 2-phenylethanethiol (XIX), was present at
moderate concentration in this smaller skunk. A number of
minor compounds were identified from this species. These
include phenylmethanethiol (XX) that Andersen et al. had
found in the striped skunk [8]. Also present were the
disulfides, bis[(E)-2-butenyl] disulfide (XXI), (E)-2-butenyl 3-
methylbutyl disulfide (XXII), and bis(3-methylbutyl) disulfide
(XXIII), compounds that would be expected to form by air
oxidation of the major thiols of this secretion.
The History of Skunk Defensive Secretion Research Chem. Educator, Vol. 4, No. 2, 1999 49
© 1999 Springer-Verlag New York, Inc., S1430-4171(99)02286-8, 10.1007/s00897990286a, 420044ww.pdf
Table 1. Composition of the Major Volatile Components (>1%) in Anal Sac Secretion from Three Species of North American Skunks (ND = None
Detected)
Compound Striped Skunka Spotted Skunkb Hog nosed Skunkc
(E)-2-butene-1-thiol (X) 38–40% 30–36% 71%
3-methyl-1-butanethiol (XI) 18–26% 48–66% ND
S-(E)-2-butenyl thioacetate (XVII) 12–18% ND 17%
S-3-methylbutanyl thioacetate (XVI) 2–3% ND ND
2-phenylethanethiol (XIX) trace 2–5% ND
2-methylquinoline (V) 4–11% trace 2%
2-quinolinemethanethiol (VI) 4–12% trace 0.5%
S-2-quinolinemethyl thioacetate (XVIII) 1–4% ND ND
aRange of data from 4 striped skunks. bRange of data from 2 spotted skunks. cDetermined from a single hog-nosed skunk.
Chemicals from the Hog-nosed Skunk (Conepatus
mesoleucus)
In 1937, Fester and Bertuzzi investigated an Argentinean
species of the hog-nosed skunk (Conepatus suffocans) [16].
These researchers had only 4 mL of secretion and were able to
isolate 0.42 g of a yellow liquid with a mercaptan-like odor.
From this small quantity they were not able to make a positive
identification of any compounds, but did state it was very
similar, but not identical, to 1-butanethiol. They speculated
that the secretion contained (E)-2-butene-1-thiol and that, after
exposure to air, their sample was mostly the oxidized form of
this thiol, bis[(E)-2-butenyl] disulfide. However,
theirexperimental elemental analyses for this disulfide are
unacceptable when compared to the calculated values, a 2.33%
difference for C, a 0.44% difference for H, and a 1.99%
difference for S.
GC-MS analysis of the secretion from a North American
hog-nosed skunk shows a different composition from the
secretions of the spotted skunk and the striped skunk [17].
Like the secretion from the striped skunk, it does contain
thioacetate derivatives of the thiols in the secretion. However,
a major component of the striped and spotted skunks’
secretion, 3-methyl-1-butanethiol, is missing. The major
components from this skunk’s secretion are (E)-2-butene-1-
thiol and S-(E)-2-butenyl thioacetate. The minor compounds
from this species are phenylmethanethiol, 2-methylquinoline,
2-quinolinemethanethiol, and bis[(E)-2-butenyl] disulfide.
Since the hog-nosed skunk’s secretion contains a thioacetate
derivative of the major thiol and does not contain any 2-
phenylethanethiol, it is more like the secretion of the striped
than of the spotted skunk. This may indicate that the hog-
nosed skunk and striped skunk are more closely related to each
other than either is to the spotted skunk. A comparison of the
major volatile components from these three species of skunks
is presented in Table 1.
Recent taxonomic research indicates that the two species of
hog-nosed skunks, Conepatus leuconotus and C. mesoleucus,
reported to occur on the southern border of the United States
are likely the same species. Thus, according to the rules of
zoological nomenclature, the one that was described first has
priority. If they are shown to be the same species, the name C.
leuconotus will be used [18].
Deodorizing Skunk Spray
There are many different recipes for the removal of skunk
spray from pets and other sprayed objects. The most common
is the use of tomato juice. Bathing an animal in tomato juice
seems to work because at high doses of skunk spray the human
nose quits smelling the odor (olfactory fatigue). When this
happens, the odor of tomato juice can easily be detected. A
person suffering olfactory fatigue to skunk spray will swear
that the skunk odor is gone, apparently neutralized by the
tomato juice. Another person coming on the scene at this point
will readily confirm that the skunk spray has not been
neutralized by the tomat juice (personal observation by WFW).
To get rid of the odor of skunk spray, it is necessary to change
the thiols into compounds that have little or no odor. Oxidizing
the thiols to sulfonic acids can easily do this.
CC
H
CH3
CH2SH
HCC
H
CH3
CH2SOH
H
O
O
O
Many oxidizing agents can effect this change. For pets, Paul
Krebaum of Lisle, Illinois developed one of the best home
remedies, an adaptation of a laboratory method he used to
destroy hydrogen sulfide and thiols [19].
• Bathe the animal in a mixture of 1 quart of 3% hydrogen
peroxide (from drug store), 1/4 cup of baking soda
(sodium bicarbonate), and a teaspoon of liquid detergent.
• After 5 minutes rinse the animal with water.
• Repeat if necessary.
• The mixture must be used after mixing and will not work
if it is stored for any length of time. Since it releases
oxygen, it cannot be stored in a closed container. For
inanimate objects one cup of sodium hypochlorite
solutions (liquid laundry bleach) in a gallon of water is
cheap and effective.
Glossary of Names and Terms
The nomenclature of chemicals in this review uses the
current rules codified by the International Union of Pure and
Applied Chemistry (IUPAC). Much of the older literature uses
different nomenclature systems reflecting usage at that time. A
major shift in chemical names has been to replace the term
mercaptan by thiol for the R-SH functional group.
Designations of the spatial orientation of groups attached to a
double bond has also changed. The terms cis and trans have
been replaced with the prefixes (Z) and (E) to indicate the
orientation of substituents on a double bond. These prefixes
use different nomenclature rules to describe the orientation of
substituents, so there is no way to directly translate the use of
these prefixes from one system to another. In many cases,
50 Chem. Educator, Vol. 4, No. 2, 1999 Wood
© 1999 Springer-Verlag New York, Inc., S1430-4171(99)02286-8, 10.1007/s00897990286a, 420044ww.pdf
however, the use of the prefix trans will coincide with the
prefix (E). Finally, the prefixes S- and (S)- are different and
should not be confused. S- is used to indicate a point of
attachment to sulfur (e.g., S-3-methylbutanyl thioacetate),
while (S)- denotes the spatial orientation of substituents on a
stereogenic center.
IUPAC Names Compared to Common Names Used in
Previous Reports
a) bis[(E)-2-butenyl] disulfide = dicrotyl disulfide
b) bis[(E)-2-butenyl] sulfide = dicrotyl sulfide
c) 1-butanethiol = butyl mercaptan, normal-butyl mercaptan,
n-butyl mercaptan
d) (E)-2-butene-1-thiol = trans-2-butene-1-thiol, crotyl
mercaptan
e) (E)-2-butenyl methyl disulfide = trans-2-butenyl methyl
disulfide
f) (E)-2-butenyl propyl sulfide = trans-2-butenyl propyl
sulfide
g) butyl (E)-2-butenyl disulfide = n-butyl crotyl disulfide
h) butyl 3-methylbutanyl disulfide = n-butyl isoamyl
disulfide
i) 3-methyl-1-butanethiol = iso-amyl mercaptan, isoamyl
mercaptan
j) 2-methylquinoline = α-methyl-quinoline
Acknowledgment. I thank Professor Kenneth K. Andersen
of the University of New Hampshire for supplying copies of
the report on Löw’s work and a translation of Fester and
Bertuzzi’s study.
References and Notes
1. Aldrich, T. B. “A Chemical Study of the Secretion of the Anal
Glands of Mephitis mephitica (Common Skunk), with Remarks on
the Physiological Properties of this Secretion” J. Exp. Med. 1896, 1,
323.
2. Conway, W. B. “A New Anaesthetic” Virginia Med. Month. 1881, 8,
259.
3. Swarts. “Über das Öl des Stinkthiers” Justus Liebigs Ann. Chem.
1862, 123, 266.
4. Löw, O. “Notizen über das Stinkthier (Mephitis texana)” Ärtzliches
Intelligensblatt von München. 1879, (June), 252.
5. Aldrich, T. B.; Jones, W. “α-Methyl-quinoline as a Constituent of
the Secretion of the Anal Glands of Mephitis mephitica” J. Exp.
Med. 1897, 2, 439.
6. Andersen, K. K.; Bernstein, D. T. “1-Butanethiol and the Striped
Skunk” J. Chem. Educ. 1978, 55, 159.
7. Stevens, P. G. “American Musk III. The Scent of the Common
Skunk” J. Am. Chem. Soc. 1945, 67, 407.
8. Andersen, K. K.; Bernstein, D. T.; Caret, R. L.; Romanczyk, Jr., L. J.
“Chemical Constituents of the Defensive Secretion of the Striped
Skunk (Mephitis mephitis)” Tetrahedron 1982, 38, 1965.
9. Wood, W. F. “New components in defensive secretion of the striped
skunk, Mephitis mephitis” J. Chem. Ecol. 1990, 16, 2057.
10. Ruzicka, L. “Constitution of Muscone” Helv. Chim. Acta 1926, 9,
715.
11. Ruzicka, L. “Further Consideration on the Constitution of Muscone”
Helv. Chim. Acta 1926, 9, 1008.
12. Ruzicka, L. “Constitution of Civetone” Helv. Chim. Acta 1926, 9,
230.
13. Ruzicka, L.; Schinz, H.; Ceidel, C. F. “Constitution of Civetone,
Civetol and Civetane” Helv. Chim. Acta 1927, 10, 695.
14. Andersen, K. K.; Bernstein, D. T. “Some Chemical Constituents of
the Scent of the Striped Skunk (Mephitis mephitis)” J. Chem. Ecol.
1975, 1, 493.
15. Wood, W. F.; Morgan C. G.; Miller, A. “Volatile Components in
Defensive Spray of the Spotted Skunk, Spilogale putorius” J. Chem.
Ecol. 1991, 17, 1415.
16. Fester, G. A.; Bertuzzi, F. A. “La Secrecion del Zorrino” Rev. Fac.
Quim. Ind. Agric., Univ. Nac. Litoral 1937, 5, 85.
17. Wood, W. F.; Fisher, C. O; Graham, G. A. “Volatile Components in
Defensive Spray of the Hog-nosed Skunk, Conepatus mesoleucus” J.
Chem. Ecol. 1993, 19, 837.
18. Dragoo, Jerry University of New Mexico, jdragoo@unm.edu.
Personal communication.
19. Reese, K. M. “Skunk reagent too strong” Chem. Eng. News 1994, 72
(June 20), 88.
