Chemistry Everday for Everyone
Sherlock Holmes and the Nebulous Nitro Thomas G. Waddell and Thomas R. Rybolt Department of Chemistry, University of Tennessee at Chattanooga, Chattanooga, TN 37403 The following story describes a chemical mystery with an emphasis on knowledge in basic organic chemistry, scientific observation, and reasoning skills. This is the eighth article in a series presenting a scientific problem in mystery form in the context of the popular and beloved characters Sherlock Holmes and Dr. Watson (1– 7). There is a break in the story where the reader (students and teachers) can ponder and solve the mystery. Sherlock Holmes provides his solution in the paragraphs following this break. The Story Autumn in London had become my favorite time of the year. On this particular afternoon, one that would end with tragic news, I had been returning from a medical case on Vauxhall Bridge Road. Under the bluest of skies, I walked the last few blocks toward 221B Baker Street through crisp golden leaves. The subject of murder was furthest from my mind. As I entered our flat, ready to engage Sherlock Holmes in a vigorous discussion of the qualities of the season, I was met instead with the sound of Holmes’ voice and the sight of Inspector Lestrade reclined in my own chair before a crackling fire. Holmes held some manuscript rolled in his fist and tapped the chair with it as he spoke. “C. Loring Jackson is a Harvard graduate, Inspector. He studied with Bunsen at Heidelberg and with Hofmann at Berlin. I have read that he has carried out significant studies with substituted aromatic halogen compounds in which the halogens were readily replaceable by negative ions owing to strongly electron attracting groups.” “I am very sorry to have asked, Mr. Holmes,” returned the sallow Lestrade, shaking his head in bewilderment. “But surely that information is not relevant to the present situation.” “Perhaps not, Inspector,” Holmes replied, “but… Ah! Here is the faithful Watson! “Watson, join us here by the fire. I trust that you do not mind if Lestrade occupies your chair for the time being?” The rat-faced policeman looked up at me and blinked one eye feverishly. “I do not mind,” I replied coldly. Holmes’ tone suddenly became grim. “Watson,” he said, “Dr. Floyd Grounder has been murdered.” “Murdered? Grounder? That chemistry professor? Holmes, who would ever want to murder a chemistry professor?” “Hah!” ejaculated Lestrade. I had momentarily forgotten that he was present. As my initial recoil faded, I soon remembered the dishonored Professor Floyd Grounder. A few years ago, he had emerged as the guilty party in the unfortunate Fraudulent Ketone case (2) in which Holmes, by identifying the dishonest researcher, spared the reputations of Grounder’s innocent colleagues, the Chair of Natural Science, and one of the world’s greatest universities. Now Grounder had been murdered and Sherlock Holmes was once again in consultation with Scotland Yard, as he had been so many times in our years together.
“Lestrade,” Holmes said, “If you don’t mind, please run through the particulars of the case once more, for Watson’s benefit. In fact, I myself should like to review the salient events.” “Gladly, Mr. Holmes,” replied the Inspector. “Grounder was stabbed, Dr. Watson, in the back of the neck as he sat at his desk at the university. His back was toward the door and the door was unlocked but usually kept closed. So, anyone could have done it easily enough. We briefly considered that he was murdered by a colleague or administrator in retribution over that fraudulent research scandal. But that case is years old now and Grounder had worked in humiliation and isolation for so long. “And, moreover, here’s the kicker. We have many witnesses from his Organic Chemistry class who testify that after the last quiz he publicly and angrily accused one of the students of cheating…looking at another’s paper. He told the class that, later in the day, he would report that person to university authorities for instant expulsion. Professor Grounder was murdered in his office before any such report was filed.” Holmes’ chin rested on his chest and he made no response as Lestrade continued. “One more thing, Mr. Holmes. Dr. Grounder’s adjoining laboratory was vandalized at the time of the murder. There was much broken equipment, and his valuable research samples of natural products were smeared on the walls, as if in a violent fit of anger.” “Who was the accused student?” I inquired. “We have no way of knowing, Dr. Watson, since he did not reveal the name to his class or to anyone else. Of course, if we could identify that student, we would have ourselves a prime suspect with opportunity and motive.” Holmes, now tapping his cheek with the collection of rolled papers, remarked in a casual manner, “If luck is with us, there may be a way to discover the dishonest student, Lestrade.” “How can that be, Mr. Holmes?” Lestrade questioned. Holmes unrolled the manuscript and flattened the stack of papers on his lap. “Watson, these are the student quizzes from Dr. Grounder’s Organic Chemistry class. The inspector was thoughtful enough to bring them along this afternoon. They might prove informative.” Lestrade rocked forward in my chair. “They might, sir. But I don’t see how. There are 25 students in the class and there are 25 quiz papers. As I see it, there are, therefore, 25 suspects. A bit of a challenge even for you, Mr. Holmes!” “We shall see, Inspector, we shall see. Now, if you will excuse Watson and me, we will look into this little problem with pleasure. Perhaps in a day or two I shall ring you up at the Yard.” Lestrade stood up, and with a nod in my direction and with his coat under his arm, he departed, closing the door behind him none too softly it seemed to me. “Now, Watson,” Holmes said, rubbing his hands together. “Let us have a look at these quizzes.” He handed me the top paper and I read the single question:
Vol. 73 No. 12 December 1996 • Journal of Chemical Education
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Chemistry Everyday for Everyone
Write a balanced chemical equation illustrating one of the numerous aromatic substitution reactions recently studied by C. L. Jackson.
“C. L. Jackson, Holmes? That name is familiar to me.” “Indeed it should be, Watson. I was telling Lestrade about him when you came in. I had a brief look at the papers before you arrived and Lestrade was asking about him then. Actually, I met C. L. Jackson on the Continent some years ago and had the opportunity to be of service to him in a professional manner…before your time, Watson. But for now, my friend, with the accompaniment of my favorite briar, I shall attempt to track down a murderer amongst all these formulae and equations.” During the next hour, the air of our flat became dense with the fumes from Holmes’ acrid pipe, as he repeatedly studied a page then flipped furiously through the student papers. I occupied myself well enough with the Times, knowing that with patience (and luck, as Holmes had said), any clues present in the examinations would be revealed. “Look at this, Watson,” Holmes remarked suddenly. He had removed two pages and smoothed them out on the coffee table between us. It is necessary at this point to reproduce exactly the quiz papers which I saw before me:
and I could not help but notice the familiar smile on his face and the gleam in his eye. “Mrs. Hudson will contact the street urchin Wiggins of our troop of Baker Street Irregulars, and he will in turn track down Effie Gaboriau and John Mincing at the University. That should not be too difficult and I predict that at 9:00 tomorrow morning we shall be chatting with these two students before this very hearth.” We had our supper early and for the remainder of the evening Holmes happily worked in his laboratory corner, pursuing his current researches into the identification of animal saliva, while I labored diligently through a long and depressing Russian novel. At the appointed time the next morning, Mrs. Hudson knocked and escorted into our lodgings the two students from Dr. Grounder’s organic chemistry class who had attracted the attention and scrutiny of Sherlock Holmes. Effie Gaboriau was clothed in an attire of carnival quality, smelling (albeit faintly) of a strange perfume, undoubtedly inexpensive. She was a girl of small stature, with long black hair and short blunted fingers. Her face projected a foul mood. Holmes, in an uncharacteristic manner, stooped to kiss her hand, affecting a brief bow in the process. Effie’s companion, John Mincing, a dashing young man, dressed smartly in the latest fashion, took the chair offered by Holmes and introduced himself with an air of confidence. “We are at a loss as to why we are here, Mr. Holmes. But, of course, quite curious. Can you enlighten us?” “I frankly do not have time for this,” added Miss Gaboriau in an irate tone that matched her expression. “My class work takes all my time. What is the meaning of this summons?” Holmes replied in his most gracious manner. “Believe me, Miss Gaboriau, when I tell you that your visit is a matter of great importance. Dr. Watson and I thank you for your cooperation in coming to see us and we assure you that it will take very little time. I have only one question to ask each of you and then you may instantly return to your University.” “Proceed, Mr. Holmes,” replied Mincing. “Miss Gaboriau,” asked Holmes, “What is the symbol for the element sodium?” “What!” cried Effie. “You bring me here to ask chemistry questions!” “Answer, please,” Holmes replied courteously. “N.....a,” she said, spelling the elemental symbol. Holmes turned to Mincing. “Mr. Mincing, what is a substitution reaction?” “Well, I’ve had some difficulties with that concept, Mr. Holmes. But generally I think that in those cases some negative unit displaces a Cl on some carbon atom.” Holmes stood up immediately. “Thank you again for coming, Miss Gaboriau, Mr. Mincing. I pray that your future at the University will be most successful.” The students, without disguising their astonishment, left 221B without a word. I closed the door after them and returned to Holmes’ side. “Holmes, are you mad? I thought that you were investigating a case of cheating and homicide!” “My good fellow!” he countered. “Lestrade will be delighted that we have cleared this up. Perhaps some promotion in rank will be his reward for our perseverance in this matter.
As I looked down upon them without a glimmer of understanding, Holmes rang for Mrs. Hudson. Upon her arrival at our door he whispered a message in her ear
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Stop Here and Solve the Mystery
Chemistry Everday for Everyone
Holmes and Lestrade are correct in their assumption that the cheater and the murderer are the same person. This mystery can be solved with sound reasoning and with the application of correct organic chemistry principles. Some knowledge of the previous Fraudulent Ketone case could be helpful but is not essential. 1. Why was the attention of Sherlock Holmes drawn to the quiz papers of those two students? 2. What did Holmes learn from examining their answers? 3. Who cheated on the quiz and murdered Professor Grounder?
The following paragraphs contain Holmes’ chemical solution to this mystery. Compare your solution with his. The Solution “I am sorry, Holmes. It certainly would be less frustrating to me if I could follow your reasoning on some occasion.” “My good fellow,” said Holmes with an affectionate smile. “You have always been my Boswell and shall remain so. You have seen these two student quizzes. What remains to be clarified?” “Well, first of all,” I suggested in an injured tone, “how did you select Miss Gaboriau and Mr. Mincing from twenty-five papers?” “Excellent question!” roared Holmes with what I thought was undue enthusiasm. “Watson, the quiz question clearly implies that there were numerous examples from which to select an answer. Now, Miss Gaboriau and Mr. Mincing selected the same equation to present. This in itself is not suspicious, but coupled to the fact that identical (and rather foolish) mistakes were made by both students leads me to the inescapable conclusion that one student, our murderer, copied from the other, a presumed innocent.” “What foolish mistakes are you referring to, Holmes?” I asked, as I held the two test papers closer to the light of our gas lamp. “First of all, Watson, a nitro unit is not –NO3 but –NO2. This mistake appears in no other paper in the class. Secondly, in a reactant line, the (COOCH)2 should be (COOCH 3)2 as was written correctly in the product line. This mistake appears in no other paper, only these two. Moreover, both students placed the respective formulae at the same positions on the page. Neither do I find this feature in any other paper. There had to have been collaboration on this answer.” “I see that now, Holmes. Indeed, it is sound reasoning. But you cannot tell who copied the answer from whom!”
“Indeed I can, Watson,” Holmes cried. “Did you observe that Effie knew the symbol for sodium?” “Yes,” I replied tentatively. “Then, in the first line of her answer, why did she foolishly write N2+ instead of Na+?” I looked at the papers again, carefully focusing my attention, and finally saw it. “ From a distance she thought that Mincing’s ‘a’ was a ‘2’.” Holmes answered in a quiet voice. “Excellent, Watson, excellent,” and with his kind words the warmest feeling I can remember washed my soul. Holmes rose from his chair and went to the mantle above the fireplace for a plug of shag tobacco. “There is a bit more, Watson. Mincing had difficulty with the concept of a substitution reaction, but answered my question to him in an awkward but correct manner. His quiz answer is consistent. What he crossed out of his product structure is a Cl, which he did at the end when he realized that the negative unit must displace the Cl. Effie had undoubtedly copied the Cl, then later, failing to realize that Mincing had crossed it out, left it in place. Her answer makes no sense at all for a substitution reaction.” “Holmes, could not these symbols tell a different story. Might we not interpret the quiz papers in a different way?” “No, Watson, the tale is clear. But…”—he smiled playfully at this point—“did you notice how smartly I kissed Effie’s hand upon her introduction? Yes? Well, Watson, I was only confirming the faint odor of a terpene on her presence. Grounder’s precious research chemicals from the soapwort spider-flower, remaining after her violent outburst of murder and vandalism. Terpenes, Watson, like the oil of lemon, often have intense and characteristic aromas. Remember the Fraudulent Ketone case, my good fellow!” So I knew then what had happened. “Effie Gaboriau, Holmes, a cheat and a murderer. She would have had no trouble stabbing the professor, with no witnesses. Do you still insist upon giving Lestrade credit for your successful resolution of his case?” Holmes was solemn. “Oh yes, Watson. There is a passage, older than England, from the Tao Te Ching by Lao Tzu, which I like to remember.” The secret waits for the insight Of eyes unclouded by longing. Those who are bound by desire See only the outward container.
Literature Cited 1. 2. 3. 4. 5. 6. 7.
Waddell, T. G.; Rybolt, T. R. J. Chem. Educ. 1989, 66, 981–982. Waddell, T. G.; Rybolt, T. R. J. Chem. Educ. 1990, 67, 1006–1008. Waddell, T. G.; Rybolt, T. R. J. Chem. Educ. 1991, 68, 1023–1024. Waddell, T. G.; Rybolt, T. R. J. Chem. Educ. 1992, 69, 999–1001. Waddell, T. G.; Rybolt, T. R. J. Chem. Educ. 1993, 70, 1003–1005. Waddell, T. G.; Rybolt, T. R. J. Chem. Educ. 1994, 71, 1049–1051 Rybolt, T. R.; Waddell, T. G. J. Chem. Educ. 1995, 72, 1090–1092.
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