G. Ross Robertson
University of California 10s Angeles
Cumulative Doctoral Examinations Experience and practice at UCLA
Dissatisfaction continues, in the United States a t least, with the classical scheme of conducting a single comprehensive examination for the PhD degree in chemistry. This statement does not, however, refer to the often-used "final oral" examination in which the candidate, in the manner of a press conference, faces a battery of questioners and "defends his thesis." Still on trial a t the moment, and in considerable favor, is the plan of dividing the period of examination into several "cumulative" efforts, scheduled a t convenient time intervals over many months. Northwestern University, one of the institutional pioneers in the new practice, published the first testimony on results.' I n this connection the Editor of THIS JOURNAL expressed his wish to report periodically additional examination schemes. With a similar background of experience in use of the cumulative device, now totaling about 15 years, UCLA's Chemistry Department has been asked to contribute a second report, herewith presented. Although there may have been some dividing of the classical comprehensive doctoral examination in earlier years, the original credit for a carefully-arranged cumulative system seems to belong to the staff in organic chemistry a t Harvard University, with inception about 20 years ago. In spite of nationwide interest, the Harvard scholars have published no article or other bill of claims for merit of the scheme. Originally of principal interest to organic chemists, the cumulative system spread rapidly to cover all of the so-called "divisions" of the subject-at least those of "pure" chemistry. All five of these groups a t UCLA, namely, analytical, biochemical, inorganic, organic, and physical use the cumulative plan. Rules of the Game
The general mechanism of the cumulative system has been reported by Frost and Hussey.' There are, however, optional procedures, and UCLA has already made a number of changes. The following is a condensed outline of current practice at Los Angeles. Before registration, new graduate students take orientation examinations which are designed to test the adequacy of undergraduate chemical training. Shortages revealed by the orientation examinations lead to required enrollment in certain fundamental courses a t once. If the shortage is in the field in This paper is contribution No. 1564 from the Department of Chemistry, UCLA. L F ~ ~ A. f i A., ~ , AND HUSSEY,A. (1958).
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which the student intends to work, he may not start the cumulative program until the shortage is remedied. Cumulative examinations occur approximately monthly. Papers are marked "passed" or "failed," with percentage marks, not A, B, C, etc. No grades are changed after original judgment of papers has been rendered. If the first term of the cumulative program occurs during the student's first year of residence, it is called a "free" semester. That is, passes are credited, but failures are not charged to the candidate. I n each subsequent term, successes and failures are both charged on the student's record. Seven passes, if attained a t frequency consistent with regulations cited below, complete the cumulative requirement. A single cumulative examination is supposed to be of length which a competent student can handle in one hour; hut actually two hours are allowed. The subject is normally in the field (referred to in this article as "division") selected by the candidate for his whole thesis period. Occasionally an examination covers two divisions, e.g., "physical-inorganic." Flat exceptions, in which a student writes an examination outside his division, are occasionally allowed by the Committee. Once per year a student may arbitrarily withhold his examination paper without penalty. Four consecutive failures, or six failures out of eight consecutive examinations, place the candidate on probation for some specified period; a letter of warning is then sent. Disqualification in the PhD program may result from seven consecutive failures, or for failure to pass seven in twenty attempted, or if work during a probation period is judged by the Committee as unsatisfactory. No cumulative examinations are held for the master's degree. Students not qualifying for the PhD may usually go on for the master's degree. A student originally seeking a master's degree may with proper qualifications change hi plan to the PhD program, whereupon he starts cumulative examinations at once. In such case he may have a "free semester" only if he is still in his first year of graduate residence. If a student changes his division after some of his cumulative examinations have already been passed, only two of these old examinations may he credited on his new cumulative program of seven passes required. Controversial Practices
The foregoing regulations a t the moment seem to be generally acceptable to the instructional staff. Others, while now in force, are subject to difference of opinion: Absolute secrecy is maintained before a cumulative examination as to authorship of coming questions or
as to the zone of a division in which a particular cumulative is to fall. For example, no advance notice is given whether a certain examination in physical chemistry is to stress quantum topics, thermodynamics, kinetics, or radiochemistry. The faculty author of a given examination may (if he can!) continue to withhold all identification indefinitely; or he may pass papers back to students, and invite discussion; or he may schedule a seminarlike conference, with all participants in that examination invited. One should realize, of course, that authorship of many of the questions will be selfevident to the candidates. A cumulative examination which is passed by .50% of the student writers is, on the average, considered to be about severe enough. This observation is not especially significant, however. For example, a t the present writing there is suspicion that the current cumulative scheme is slightly too lenient. Although the mere figure of 50% is sufficiently drastic, there still remains the possibility of examination questions which are too easy. Claims for Superiority of the Cumulative System
The following supposed virtues of the cumulative idea have been discussed in different institut.ions. Some are substantial, others based on mere notions. Each is followed herewith by a summary of local UCLA opinion: The system largely eliminates the nervous crisis characteristic of the single long examination. The overwhelming majority of the UCLA staff agrees. A minority considers that we have merely substituted a prolonged suspense for a single crisis of similar total nervous strain and interruption of student research. The system stimulates interest and attention to current chemical literature. This claim is not taken very seriously by local staff, in spite of the endeavor of question-writers to keep hot on the frontier. The "frontier" is simply too broad! Regardless of current literature, the system tends to stimulate continuous learning in the special z m e of the division in which the student works. Almost unanimously, yes. This conclusion raised the adjunct query: should the special zone of the next questions be revealed some time in advance of the cumulativeexamination date, as not done a t present? For example, should we announce that 'Lphysical-organic," or "structure-proof" is next due? Although favored by some staff members, others think that such a plan would merely touch off a cramming spree; or perhaps that it would just be useless. The cumulative system interferes less with student research than the single examination. Verdict 50-50, yes and no. Eliminates the incompetent graduate student in mini m u m time. Decidedly no. At UCLA such close attention is paid to "screening" of applicants for admission to the graduate school, and to the qualifying examination in chemistry before registration, that it is difficult for the incompetent student even to get a chance a t the cumulative program. I n fact, incompetents who persist may even spend more time fruitlessly under the cumulative scheme.
Gives early assistance in finding when the graduate student shouU be allvwed to start research. Unanimously no; but there might be a different point of view on another campus where it is the custom to delay research beyond the first year. Minimizes the "chore" duty of faculty members who have to compose the questions. Emphatically no. This verdict, however, merely reflects the fact that the (central) Graduate Council a t UCLA would require substitute examinations of some sort anyway. Questions Currently Under Debate
Should the staff, in divisional groups, meet a t the start of each semester, review past questions and lay out a program for the months immediately following? Closely related: How can we prevent the issuance of an excessive number of questions in one anne of a division, with hardship to the students in another zone; and conversely, how can we prevent individuals from slipping through with "blind spots," due to inadequate number of questions in the zone in which certain candidates do not work? Should questions be shorter, with four or even five parts of highly diverse character in each examination, forcing everybody to consider all zones before each test? Types of Questions Desirable in a Cumulative Examination
This topic is of special significance in organic chemistry, where in years of the distant past there has been a tendency to overstress memory questions. It is of course true that the doctoral candidate in this field must memorize an unusually large number of factsotherwise he probably does not belong in the profession of organic chemistry. The scholar proposing an organic cumulative examination, however, should strive to allow a diversity of chemical facts from which the student may draw out his solution. The following are general examples: Lahoratory data (titrations, UV, IR, NMR spectrograms, kmetic readings) are presented; the student is to draw conclusions as to molecular strncture. A "claim" or hypothesis from recent literature is quoted. The student is asked either to appraise this hypothesis on the basis of chemical knowledge already a t hand, or to propose an experiment which he thinks would be serviceable to give him the data needed for the job; and then to discuss critically. The candidate is asked to write a short but critical report on the proposals, claims, etc., made a t the public seminar given in the department by Professor X, distinguished visitor of last week. Copy of a recent journal article is presented as the first item of the examination question sheets. The article itself is open to criticism in more than one respect. For the purposes of the cumulativc cxamination, it is presumed to be a new manuscript just sent in by its author. The student is to imagine that he has been requested to serve as editorial referee for the paper, and is asked to write his report to Editor as the "answer" to the question. Short quotations are taken from current chemistry textbooks. All-or perhaps only the major fractionof these excerpts are in some respect fallacious. The Volume 41, Number 4, April 1964
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student is to select the erroneous items and discuss each critically. (Examiners wishing to use this idea may get valuable hints from the Karol Mysels "Textbook Errors" series in recent volumes of mis JOURNAL.) An organic compound C is to be prepared from raw material A (in some specified quantity at the start) B C. (Forthrough the synthetic sequence A mulas or names of A, B and C are given.) The student is to write exact directions, suitable for publication in a laboratory manual designed for undergraduates who have already had just one good laboratory semester course in organic synthesis. To save time, molar quantities may be used by the student to replace conventional metric measures; e.g., "Add, dropwise with stirring, concentrated sulfuric acid(l.1 mole)."
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Examples of Questions from Cumulative Examinations
Although the student a t UCLA might normallv expect anexamination to be restricted to trhe designated division, it is occasionally the custom, without special warning, to merge questions from two divisions. Historically the physical-inorganic grouping was to he expected, but other combinations are pomihle. In such cases a t UCLA the compound examination is merely issued to the whole panel of candidates from two divisions. With special local interest in physical organic chemistry, we may expect in the future a few physical plus organic cumulatiVes. It will not he the intention, however, just to issue these to the special group engaged with theses in "physical-organic" chemistry. Each of the UCLA examples given below is in the range of 50 to 100% of the task assigned to one studeut on cumulative-examination day. Analytical Chemisl~y. Below are listed some recently developed analytical techniques which have been discussed in curnnt journal articles. Discuss three of these techniques with respect to the following points: a. Bash of the method. Include pertinent diagrams and indicate any special equipment required. b. Novelty of the technique. c. In what particular applications is thirr technique imnnrtant7 r-."-..".
(1) "Atomic Absorption Spectroscopy," Anal. Chem., 32, 898 (1960); also32,225(1960). (2) "Eleetrolytic Determination of Microgram Quantities of Water (not usine Karl Fischer reaeent)." Anal. Chem.. 31. "Use of ~embrrtnes'in Eieetrochemical Studies of Gases," Anal. Chem., 31,2,5(1959). "Use of Electron Capture Ionization Detectors in Ga. Chromatography," Anal. Chem., 33,171 (1961). "Stripping Voltametry with the Hanging Drop Mercury Electrode," Anal. Chem., 33,185,187 (1961). "Double Column Proerammed Tem~erature Gas Chmmatography," Anal. Chem., 33,523 (i961). TJse of Differential Reaction Rates to Analyze Mixtures," Anal. Chem., 33,896 (1961), and 34,606 (1962). Biochemistry. In a chapter by Kornberg in Halirons in Biochemistry, (Kasha and Pullmn, editors, ~ ~ press, d 1962, . p, 251), 14&word technical historical i,,troduotion to this question appears, and this was printed on the cumulative question sheet. Kornberg's "proposal" was then presented: ~
I propose, in this essay, to present and discuss the hypothesis that degradative pathways often involve phosphorolytic mechanisms and that biosynthetic sequences often rely on pyrophosphate release. Barring exceptions to this proposal,
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phosphorylases are therefore appropriately named; but reactions in whieh pyrophosphate is released, rather than pyro~hosnhorvlases.are better reesrded as "svnthetasen." s t & whet6er or'not you agree with theabove hypothesis and develop a clear argument giving reasons and examples which substantiate your position regarding this proposal. Inorganic Chemistry. ( a ) Many trtmsition-metal complexes undergo acid-hydrolysis (aquation) and base-hydrolysis reactions a t measurable rates. For example, Co(NHa)sC12+hydrolyzes in basic aqueous solution at a rate which is first order each in the concentrations of the complex and of hydroxide ion. Write the overall chemical equation and outline two separate plausible mechanisms which could account for this base hydrolysis. If you can, suggest experimental tette (be specific) which might he made to distinguish between your two types of mechanism for complexes of this general type. ( b ) Aqurttion of Pt(H20)C13-in aqueous solution follows the rate law, -d(complex)/dt = k(Pt(H9O)Cls~). Write the overall chemical equation and represent two separate plausible mechanisms for the aquation. ( e ) Radiochloride ion undergoes isotopic exchange with Pt(H.O)Cb- in agreement with the rate law, R = k'(Pt(HnO) C k ) . At 25-C. this rate of chloride exchange is must fader than the rate of aquation (k' > k), but is approximately the same as the rate of aquation of PtC142-. What do these facts imply about the mechanism of aquation of the trichloroaquo complex and its chloride exchange? (After the examination is past, see "Modern Coordination Chemistry," LEWISA N D WILKINS,Editors, Interscience Publishers, 1960, pp. 116,127,132-3; also "Mechatisms of Inorganic Wiley, 1958, pp, 1934.) Reactions," B a s o ~ AND o PEARSON, Organic chemistry. Treatment of the aziridme, denoted as (A) helow, with sodium iodide in acetone, gives an isomer (B), whereas an acid-catalyzed isomerieation of A gives a different isomer (C). Comment on the mechanisms of these reactions and deduce the structures of B and C.
is Ricinoleic acid, CH3(CH9)GHOHCHd2H=CH(CHz),CO~H, pyrolyzed in the vapor state at approximately 500DC under nitrogen in a well-known method for synthesis of heptaldehyde and undecylenic acid, (CHF=CH(CH&~O~H). Yields are high. This reaction has been generalized to compounds such as CH&HOHC6Hlr and CsHaCH=CHCH2COH(C1H& A B 3-Cyclohexen-1-01, however, fails to give the reaction. (a) Write equations for this reaction with (A) and (B), respectively, as starting materials. (6) Propose a reasonable mechanism for this reaction and discuss it.
(d) Explain carefully what experiments you would carry out to prove or disprove the validity of the mechanism you have proposed. Explain what you would hope to prove by each experiment. ( e ) Write equations for as many practical syntheses for B as you can. Be sure to begin with readily available starting materials; comment on side products and difficulties which you might expect to encounter in this synthesis. This general synthesis has been modified to give a. convenient method for extending a carbon chain by 5 or 6 carbons. ( ~ exn tension by 7 carbons also works well although one of the stmting materials is less readily available.) Write equations showing how this could be done. Use of special techniques. A. C. Cope and co-workers (J. Am. Chem. Sac., 84, 4843 (1962)) have described the preparation of the two epimeric bicyclo[5.1.0loctan-3~ls. One of the pure e~imeric alcohols (A) was obtained by treatment of the AJ-cyeloheptenol with methylene iodide and zinc-copper couple.
Oxidation of A to [he kvtmr and rrduvti~mof rhc lxtrer with scrdlum IwnJtydridc KBVP H mixture of :,h.uhoIs eonr:!ining 3 0 5 uf .I : ~ n d70(:- of :IS i.ionlet 8. '1'11e mixluw could IM: ~clnrared by vapor-phase chromatography or by elution chromatography from alumina. Equilibration of the two epimers under Meerwein-Ponndorf conditions gave rise to an equilibrium mixture containine ea. 80% of A and m.20% of B. Show how the above information and conformational'&alysis of the bicycla[5.1.0]octane ring system lead to a configurational assignment to epimers A and B.
a
Ph?/siealehemistvy. For each of the following pmperties, state with brief reasoning whether a calculation using classical statistical mechanics would be likely to yield a quantitatively correct result:
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(a) the equation of state of gaseous xenon from 100 to
~ , n A-. n~u --"
( b ) the heat capacity of liquid helium from 1 to SOX, a t 1 atm. ( e ) the critical point of ammonia. (d) the meltinenoint of ice a t 1 atm. (ej the equation of state of astellarinterior. (f) the rotational heat capacity of CL gas a t 273'K and 1 atm. (g) the pressure of black-body radiation a t 273'K. ( h ) the statistic dielectric constant of ice a t 273'K and 1 atm. ( i ) the modulus of elasticity of rubber.
