Terminology: Helping Students Cope with Name Reactions in Organic Chemistry Bruce Ganem Cornell University, Ithaca. NY 14853 The trepidation with which many college and university students approach the study of organic chemistry has become legendary. This is so in spite of gifted teachers who challenge students not to memorize isolated facts and stmctures but to think about chemical concepts and reaction mechanisms so that the intellectual elegance and beauty of organic chemistry can be appreciated. In spite of these exhortations, flocks of exhausted sophomores can still be found on examination's eve furiously leafing through piles of dog-eared 3 X 5 flash cards. The nroblem is narticularlv acute in the second semester when wide variety of reactions comprising much of the working vocabulary of orginic chemistry must be learned. Although different textbooks boast pedagogically different approaches to overall course structure, all must sooner or later confront the problem of "name" reactions and reagents. Name reactions are those processes that, for historical reasons or for convenience or ease of scientific discourse, bear the names of their inventors or discoverers. At least three monographs have appeared on this subject.'3 Moreover. the nonular series bv Fieser and Fieser entitled Refo; organic ~ y n t i e s i sconvincingly demonstrates that our obsession with keeoine - terminoloev -- short continues to propagate new name reactions, perhaps prematurely in many instances. A few years ago in the second semester of our "majors" organics class a t Comell, I tried an experiment that I hoped might ease the dilemma of learninglmemorizing name reactions. We were moving into the steamy thicket of carboxylic acids and their derivatives, where nomenclature alone terrifies most students. At the endof my first lecture on reactions of carboxylic acids with halogenating agents, I displayed the following short piece on an overhead transparency.
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On Dlstlngulshlng Two Name Reactions Three wise men named Hell, Volhatd and Zelinski,' Well-known to most students of chemistri, Studied several reactions To hrominate acids And elected to use PBra. Another chemist. Hunsdiecker." was elated when acids got decarhox;lated. Silver salts plus bromine Made alkyl halides real clean By a method now widely propagated. 'Nikoial 0.Zellnskl. 1861-1953: b. Russia (Tiraspoi):PhD University of Odessa.
"Clare Hunsdlecker, b.
1903 K i d .
Germany; PhD University of Cologne.
'
Swrey, A. A. Neme Reactions in Organic Chemsiry; Academic: New York. 1961. Krauch. H.: Kunz, W. OrganicNeme Reactions; Wiley: New York, 1964.
Mundy. 6. P.; Ellerd. M. G. Name Reactions and Reagents h Organic Synihesis: Wiley-Interscience: New York. 1988.
With apologies for the questionable humor, I suggested that thinking up such limericks might provide a welcome break from serious study, and I invited the class to submit contributions of their own. I promised to give brief biographies of the chemist-discoverers in class. The response was nothing short of phenomenal. Several limericks. a few noems in free verse. olus a ballad on acvl halides reached office in time for the next lecture. I reid a few to the class. includina an excentionallv well-researched piece, submitted anonymously, o n the pakial reduction of acid chlorides.
my
The Rosenmund Reduction Now Rosenmund"' knew to make aldehydes He should choose an OH that would oxidize. But hydrogenolyze Poisoned acid chlorides? That should easily win the Nobel Prize! "' Karl W. Rosenmund, b. 1884. Berlin; PhD University of Berlin. Rosenmund found that small amounts of a sulhn-qdnoline poison on the metal catalyst had little effect on the Initial reduction of the acid chloride, but p r c vented aldehyde hydrogenation. Three or four lectures later, by which time we were discussing carbonyl alkylation reactions, students began writing poems spontaneously during class. These verses were passed to the front row and placed on the lecturn whenever I turned my hack to write on the blackboard. The Clalsen Condensallon In his lab with some esters worked Claisen On occasion he tried putting base in. Ketoesters came out So you'd think he would shout, But he also got crossed condensation. -Tami Brenner, 1985 The fame of the Claisen reaction Brought its maker even greater satisfaction. When condensation took place With methoxide a s base, He knew enolates were part of the action. -Mark Baer, 1986 Many lecturers try to heighten interest in the historical development of organic chemistry by presenting brief sketches of major scientific figures while recounting their important discoveries. More often than not, students are too busv franticallv takine notes from the board to oav much attention to these anecdotes. As limerick writing mo;ed into higher gear at Cornell, I sensed that students were actually listening to my occasional background commentary. In a lecture on the Dieckmann condensation. for examole. I told the class how Adolph von Baeyer had first suggested this reaction t o young Dieckmann while he was still a student a t Munich. Apparently my remarks did not go unnoticed. Volume 67
Number I2 December 1990
1009
The Dleckmann Condensation Walter Dieckrnann look Haeyer's advice That arme way toclosr rings would he mre. Hy exposing d~rrters To base, he sequestered Ketoesters in yields that sufficed. -Andrew Phillips, 1985 Now Dieckmann took Baeyer's recommendation: Cvclize rines in a Claisen condensation. \iYithdiethyl adipare And the right amounr of base, His methud som became a sensation. -Michelle Felanne, 1985
By semester's end I had amassed dozens of poems and limericks featuring name reactions and reagents. At the request of several students, these rhymes were photocopied and circulated t o the entire class. In a questionnaire routinely used by our department to survey large lecture courses, many respondents noted that the writing exercises had measurably sharpened their learning skills and had added an unexpected element of creativity and spontaneity. Since then, I have regularly used this device as a teaching aid for organic chemistry, even in Cornell's "nonmajors" course. T h e results continue to shed new light on old reactions, to the pleasure of all involved.
The class learned how the Reformatsky reaction evolved from failed attempts to prepare Grign&d reagents of ahaloesters. The political implications of that finding were duly noted. The Reformatsky Reaction When Crignard was bn~ughtto the brink, Hriormarakg derided on zinc. Bromoesters, he could tell, Gave aldols quite well, So the Russians had forged a new link. -0laf Martinson, 1986
1010
Journal of Chemical Education
The Wohl Degradation There once was a chemist named Wohl Who bought an immense sugar howl. But it shrank when he cleaned With hydroaylamine And he was "short-chainged" on the whole. Matthew Richardson, 1989
