In NMR there are two maior effects for students t o eraso: chemical shift and spin coupiing. While a cognitive approach can be straightforward (e.g., "methyl resonances appear at low field"), effective teaching-getting an intuitive feeling for the quantities-can he much more rewardinz. Our first oroeram . prt:pnrrs the student fur the second, where a real opportunity for effective learninr is ~resentcd.Other workers have reached similar conclusions (12?and this, coupled with our experiences with student usage, underlies our enthusiasm for these programs. The first program, NMRSPEC, is based on experiences with the CALCHEM1 program "Interpretation of NMR Spectra" which systematically guides the student through the analysis of first-order proton NMR spectra. While the approach embodied in that program was sound, the lack of graphics and therefore its reliance on external diagrams was not desirable. In our program much use is made of Apple graphics in order to mikethe presentation clear and u&higuous so that the information is far more accessible to the user than in the CALCHEM version. A molecule is selected from a list of formulae (a modifiable data base of up to 20 spectra is displayed) and the lesson hegins. After a short introduction the student is conducted through the analysis of the spectrum, peak by peak. Starting with singlet peaks each proton-containing fragment is deduced using the integration line and approximate chemical shift (Fig. 5). The fragment's neighbors are then identified by considerine the chemical shift and the molecular formula in more detail ns in Figure 6. This figure illustrates one of the most important differences from the CAI.CHI?M version, in
Nuclear Magnetic Resonance Interpretationwith Graphics Penfold university of Canterbury Christchlrrch 1, New Zealand
R. D. Draper and 0. R.
Nuclear Magnetic Resonance (NMR) is now well established as one of the most commonly used techniques for a t Computer-Assisted Learning in CHEMISTRY, a project directed by P. B. Avscouah. Universih, of Leeds. least oreliminarv chemical structure evaluation. Now that NMR, a F ~ R T R A NIV program oy Ayscough et al.. (catalog number many undergraduates have direct accens to NMR facilities it CHM226F: Pipeline. fail 1982). is rsneciallv imnortant that thev have a clear understandine of basic principles. Our experience is, however, that in the early stages students are easily confused. T o aid initial understanding we have P r e s s (EPClCEI t o c o n t i n r ~ e written a suite of programs for the H e r e i s a list O f connon fragment5 Whlch nelghbovr to CH3 do r o u thank" I ' cw, z i C H ~3: CH +> ;a s > O H APPLE 11. The programs are highly in( The farnula i s C5Hs0O2 1 0 SU99eSt a fragment f o r peak 2 teractive with emphasis on graphics (note t h e number o f protons 3s 3)m techniques. The ~ ~ O L Ir Pe&s h~oodn s l b ~ IeS CH, Two of the programs in the suite are neighbow the subject of this article. Both are 1) CR, 1 1111111111 written in Apple UCSD Pascal and rely 2) CR2Z 1 1111111111111111 heavily upon the high resolution 3) @ 1111111111 graphics display for output. In addition 4' c=o 11111111111111 much effort has been made in order to 5) 0 1111111111111i 6) Y IIlillllllllllllllllllfllllll provide maximum convenience for the 8 c7h e 6n ~ c5 ashift ~4 3 O E2 c ~1 H 1, ~ 3o ~ 1 8 7 6 5 4 3 2 1 8 . user. The programs are intended for use 5. Screen display of N M R S P E C showing Figure by second- or t h i ~ d - ~organic ~ a r chemFigure 6. Screen display of correlation table in "~entidemification. NMRSPEC with deduction of neighboring group iiistry students particularly in the lahoiustrated. ratory, hut both have been found useful as lecture demonstration tools.
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P r e s s (SPRLE? to continue Choose the structure o f the c o n ~ o u n d '
Fragment NUMEER I
Fragments available a r e as follows. Just p r e s s the appropriate number. t e r a s e s fra9"e"ts; t o ..5 screen 2 1) CH ? > CHz 3) CH, 4 ) C0 s> o 6) @ 7) c i pagel
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the correct a n s w e r .
Figure 7. Screen display of the "final structure" in NMRSPEC.
Figwe 8. Screen dispiay in NMRSiMUL showing molecuie construction by number, list of previous inputs (top)and instructions(bottom).
Figure 9. NMRSIMUL screen dispiay with proton NMR spechum and integration line.
Volume 61 Number 9 September 1984
789
that the data for the program have been incorporated into the graphics display. Upon-reaching this point a guess may be made as to the actual structure, as illustrated in Figure 7. A similar course is followed first for the remaining singlets and then for the multiplets (with the addition that the neigboring proton-containing groups are identified). When all peaks have been studied the final structure is determined. In the second program, NMRSIMUL, the approach is complementary to that used in NMRSPEC. The student inp u i a molecul6, fragment by fragment, and the approximate proton NMR spectrum is displayed, allowing analysis (as learned in NMRSPEC). Seven molecular frarments. pach of them selectable by number, are displayed. ~ s e a c f;agment h is selected a "oseudo-molecule" is assembled at the too of the screen as in ~ i g u r 8. e For example to create isopropyl'acetate ((CH3)2CHOCOCH3) only the input 3 1 3 5 4 3 (the appropriate keys for each fragment) is required. Upon completion of the molecule its proton spectrum is displayed along with an integration line, see Figure 9. Each spectrum is displayed on a fixed scale in accordance with the desire that students be able to see relative shift values. A feature of NMRSIMUL is the use of the second bieh resolution era~hics - . screen. Bv this means spectra of two molecules can he compared easily and the value of the Dromam as a lecture demonstration tool is enhanced. (The ~ ~ forward d arrow e key allows the alternative screen to he viewed while asembling the molecule, while the back arrow key can be used to remove any errors). Qualitative student evaluation of these nrorrams indicate that, as an introduction to a systematic approach to solving first order proton NMR spectra, both are successful. Students rapidly pick up the hasic requirements in NMRSPEC and are quick to apply the ideas in the relative freedom of NMRSIMUL. NMRSIMUL and NMRSPEC are written in Apple-UCSD Pascal and therefore require a 48K Apple 11+ computer with a language card or 16K memory expansion card or alternatively an Apple IIe. One disk drive is required and a printer is optional. Copies of the programs including documentation may be obtained by sending (to the second author) a 5.25-in. diskette and a money order for $10 made out to Department of Chemistry, University of Canterhury, Christchurch 1,New Zealand. It is also available on Apple disk from Project SERAPHIM at a cost of $4 (make check payable to Project SERAPHIM).
Figure 10. Television screen display afler peaks have been across me recorder chart.
gradually moved
T h e C o l p o u n d t h a t e l u t e s l a s t is b e l i e v e d t o be t h e d r u g OPIPRIN
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a Figwe 11. interactive simulated prcgram--only me f o m peak Increases in height when students add a sample of pure drug to the mixture.
Chromatography: Use of a Microcomputer to Introduce Laboratory Techniques David K. Holdsworth University of Papua New Guinea University P. 0..Papua New Guinea Science students at the Universitv of Papua New Guinea are familiar with some uses of pape;chromatography. They have separated inks and colored plant components in their high school chemistry courses. They are unfamiliar with the chromatogtechniques of thin-layer, column and pas-liquid . raphy. The purchase of an inexpensive Sinclair Spectrum microcomputer enabled programs to be written to display colored, animated diagrams to introduce the three related topics. The microcompu
