Textbook Errors, 132 Kenneth K. Andersen and David T. Bernstein University of New Hampshire Durham. 03824
I
1-Butanethiol and the Striped Skunk
The obnoxious odor of low molecular weight thiols is usually mentioned in elementarv organic chemistry textbooks. 1Huranvthml rn-hu~ylmerfapt&, is ofkn singled out and held resvonsihlr for the putrid udor ot'thr skunk's defensive sprav or musk.' Even t h ~ ; ~ we h recently (I) found no 1-hutanethiol in this secretion, some new textbooks maintain its presence. Tht major volatile components are actually 3-methyl-I-t~utanelhLd (isoamyl mercaptnni, /rans-2-butene-l-th1,11[crotyl mercantanr. and rrans-2-hutend methvl disulfide. We think it'inteiesting and useful to examine [he basis of the l-hutanethiol myth in hope that further spread of this error will cease. First, a definition of skunk is important, since the species is seldom described in organic texts, and, as will he seen, this omission is a cause of much confusion. The striped skunk (Mephitis mephitis), most abundant of the thiee genera found in the continental United States, is the animal most people associate with the word skunk (2). It ranges from southern Canada through most of the United States to k members of the mustelidae or northern Mexico (3).~ i k all weasel family, skunks have two anal scent sacs. When necessary, tht. skunk can discharge several ml of an amber-colored putrid-smelling oil from these sacs for distanres of nl)ou! ;I In. ~ ~ r e s s oare r s usuallv reoelled -of the mustelids, onl; the striped skunk, the SouthAmerican zorrino (Coneoatus suffocans) (4). the Philipnine teledu (Mydaus r n a r c h e j ~ u e t )(51, t h e ~ k e r i c a nmink (Mustela oison) (6). and the polecat (Mustela putorius) (6) have had their a n d s ~ ( ~ s c c r e t ichemically ~~ns inrt:s~igated.A look at rhe hiscors of chemical studies of skunk musk reveals the sources of the-1-hntanethiol myth. In 1862, F. Wohler reported on some 'hordamerihanischen stinhthiers" fluid that he had received from "freunde in Neuyorh" (7). Possibly for the obvious reason, the actual work was done hy a colleague identified as "Dr. Swarts aus Gent" who determined the per cent sulfur in the steam-volatile portion of the secretion.2 Wiihler also described the adverse effects of the musk on Dr. Swarts' health and mentions hut does not reference a contemporary study of Lassaigne, a then well-known chemist. In this context we note that a student rendered unconscious hv inhalatorv administration of skunk "perfume" recovered oiernight wi"thout ill effect except for a headache. Even so. the use of skunk musk as an anesthetic was not recommendkd (8). Further progress was slow. Dr. 0 . Loew collected samples during a trip through Texas in 1872, though in vain (9).ProSuggestions of material suitable for this column and columns suitable for publication directly should be sent with as many details as possible, and particularly with reference to modern textbooks, to W. H. Eberhardt, School of Chemistry, Georgia Institute of Technology, Atlanta, Georgis 30332. Since the purpose of this column is to prevent the spread and continuation of errors and not the evaluation of individual texts, the sources of errors discussed will not be cited. In order to be presented, an error must occur in at least two independent recent standard hooks. 'This anal sac secretion is sometimes called skunk scent. Skunk oil, on the other hand, is obtained from the fat of the skunk and contains no musk (16). 2Dr. Swart5 aus Gent was probably Th. Swarts, the only Swarts cited in Chem Centralblott in the years following 1862 and whose address was the Universitatslahoratorium, Gent.
Elemental Analyses of Supposed Butyl Mercaptides (Reported by T. B. Aldrich in 1896) Per Cent
Compound
Per
Cent Carbon
Hydrogen
Per Cent Metal
(RShPb Found8 Calcd. (R = C.H9) IR = C,HA
IRS)zHS Found'
Calcd. (R = C4H.) (R = CIHA
RSHgCl Founde Calcd. (R = C4Hs (R = C&) -
~.
, %ur calculations using 1973 atomic weighs ~
testing travel companions hindered his investigation. Later, colleaeues and students caused him to abandon the studv u (10). In 1896. Thomas B. Aldrich. subseauentlv known for his work on epinephrine, examined the secret& of Mephitis meohitis (10). He distilled the fluid into several fractions. ~ e r c u r ! and lead s a l t w r e prepared from the lvwer hoiling o Aldrirh based hiistructuralasfraction, a . ~ h 1~1(r-l10~C',. signmeit on their elemental analyses and the hp of l-butanethiol, h p 98°C. In his own words "The results of these analyses are sufficiently near the theoretical figures when considered together with the h p of a to convince, I think, the most sceptical that the greater part of this fraction contains one of the butyl mercaptans." His experimental results are given in the table together with the percentages calculated for hutyl and butenyl groups. Although the found and calculated percentages of lead and mercury agree more closely when R is butyl rather than buteuyl, the reverse is true for the amounts of carbon and hydrogen. A four carbon thiol is certainly suggested by these data, but the presence of unsaturation or verhaus a rine cannot he excluded. Aldrich also noted the similarity in odor and physical properties between his higher boiling fraction and 3-methyl-1-hutanethiol, the actual major musk component. Even though he never states that 1-hutanethiol is present. his work is nrohahlv the main source of the myth. Beckman, also in 1896,published an amusing article on the Philippine teledu (5).His coworker treated the distilled musk with 1-bromobutane and oxidizing the resulting sulfide to di-n-hutyl sulfone. If this old work is correct, 1-hutanethiol is present in teledu musk. Fester and Bertuzzi steam distilled the musk of the zorrino and concluded that the volatile material contained 2-hutene-1-thiol and its disulfide (4). Their carbon-hydrogen analysis differed from the theoretical by an unacceptable 2%. Possible isomers were neelected. Stevens examined striped skunk fluid, hut he ignored the volatile thiol fraction (11). He states "it remained for Aldrich odoriferous material is n-butyl to show that the rnercaptan" even though Aldrich never specifically said this. Volume 55, Number 3, March 1978 / 159
Recently, 2,2-dimethylthietane and 3,3-dimethyl-1,2-dithiolane were identified as components of mink and polecat musk (6, 12). Since most elementary textbooks omit references to the original literature, it's hard to know where their "facts" originate. Aldrich's work seems the most likely source of the 1butanethiol myth, but Beckmann's work also plays a part. In a 1919 edition of "Richter's Organic Chemistry," Beckmann's article on the "stink-badger of the Philippines," a literal translation of the German, is referenced (13). In 1943, a prominent American advanced organic treatise references Beckmann, but now the stink-badger is called a skunk (14). In the same year, an elementary text states without literature citation that the odor of skunk musk is "said to be due to butyl mercaptan" (15). Recall also Stevens' 1945 misleading reference to Aldrich's work. The 1968 Eighth edition of "The Merck Index" (16) states that n-hutyl mercaptan "occurs in skunk fluid" but cites Beckmann's article on the Philippine animal. Whether recent textbook authors were basing their statements on Aldrich's work or Beckmann's and confusing a teledu with a striped skunk or, more likely, simply repeating what they'd been taught, is hard to know, but the myth was obviously well established as part of the folklore of organic chemistry by the 1940's and maybe earlier. Perhaps it seems curious that no one challenged the 1butanethiol myth. After all, the odor of skunk musk is familiar
160 I Journal of Chemical Education
to most North American chemists and somewhat different from 1-butanethiol's stench, a smell also known to many. When we began our work we were not iconoclasts hut also true believers for such is the power of a myth. Acknowledgment
We thank Professor G. Kresze for providing us with a copy of reference (9). Literature Cited (11 Anderaen,K. K..andBernntein,D.T., J . Chrm. Ecol., 1,493 (l975). , of the Siore ~iologicolSurury of Kansas, No. 3, (21 ~ d m o n d s W. , T., ~ r . Rullelin 119741. (31 Verb. B. J.,"The Biology of the Striped Skunk." Universityaf Illinois Press. Chicago. 1967. l o Perter, G. A . and Bertuzzi, P. A , Reu. Foc. Quim Ind. Agr. llniv. Noc. lilorol. 5.85 (19371. 151 Beckmann,E..Pharrn. Zentrolholl+Dseh.. 37.557 11896). Chem.Int. 161 Schi1dkneekt.H.. Wilr,l.,Engmann,F.,G~und,N..andZiegler.M.,Angeiu. Edn. Enel.. 15,242. 1976. Chrm., 123.266 116621. I71 aus Gont.Dr.Swartr, JuaiusLisbi+!sAnn. !Sl Conwsv. w. R.. Virpinia Medical Monthly. 8,359 118811. "on Mlinehen," June. 1879, p. 252. 19) Loew, 0.. "Arrrlichrs lnlrlligr~n2bl~tl (101 A1drich.T. B., J E x p Med. 1.323 (18961. (111 Steuen~.P.G.,J. Amer Chem S o r . 67.407 119461. (121 Albene. E.,Chrm. Elit.. 13.92 (19771. !la1 Spielmann. P. E., "Richter's O~ganicChemistry,"P. Blakistonh Son and Co., Philadelphia. 1919,vol. 1 , p 143. I141 Connor. R..in "Organic Chemistry. An Advancod Treatise." (Editor: Gilman, H.1, John Wiley and Sons. London,2nd Ed., 1943, vol. 1,p. 839. 1151 Hill. G. A.. and Kelley, L.. "Organic Chomistry..IThe Blskisfon Co., Philsdelphis. 1943, p. 335. 1161 Sfecher. P. G., (Ediior), The Merek Inder.'8th Ed., Merck and Co.. he., Rahway.N.1.. 1968, p. 182. See also p. 952.
