PROGRAMMED LEARNING IN CHEMISTRY

I-FIRST PRINCIPLES

By F. D. Gu~STONE, D.sc. , F.R .I.C . ancl R. B. MoYES, B.sc. , A.R.r.c.*

Department of Ghemist1·y , St Salvator's College , The Unive1'sity , St Ancl1·ews

During recent years interest in programmed learning has spread through the whole of the educational system and in this part of the article we explain and illustrate the principles involved. The technique has been used inde­pendently in all the university chemistry departments in Scotland. Part II gives an account of its experimental trial in Queen's College, Dundee.

Programmed learning is considered to be a more effective way of learning than the conventional procedures used by students in lecture rooms, libraries and studies. Because very little material has yet been published in the required form, interested teachers fre­quently prepare their own programmes, but to do this they need to understand the underlying principles. Two main types of programmes will be discussed: the so-called 'linear', or Skinnerian programmes, and 'branched' programmes.

LINEAR OR SKI NNERIAN PROGRAMMES

Linear programmes are based on three main principles first elaborated by Professor B. F. Skinner:

(i) information to be imparted is broken down into a large number of small logical steps which are presented to the learner in sequence; each unit of presentations is called a frame;

(ii) the student makes an overt response to the material presented;

(iii) correct responses are rewarded (rein­forced) immediately: the satisfaction of getting the correct answer is con­sidered to be a sufficient reward for a student.

It is an essential part of the linear pro­gramme that students should make the correct response to the question(s) presented in each frame, and programme writers usually

189

aim at an error rate not exceeding 5 per cent. If the error rate rises very much above this value at any point then the programme is at fault, and the writer should revise his material until the error rate is reduced to normal. Despite this, a case can be made for stiff linear programmes with lightly higher error rates for the highly motivated and highly selected groups of students to be found in centres of higher education.

A low error rate is achieved by careful attention to the following points:

(i) new material is presented in logical fashion;

(ii) each frame is carefully constructed so that there is no ambiguity in either the explanatory material or the question;

(iii) the step-size must be kept small, i.e. new ideas are introduced only at an appropriate rate and are linked, wheR­ever possible, with previous know· ledge;

(iv) a check is made that each item of new information is fully understood before proceeding to the next;

(v) the programme is continually revised in the light of students' responses;

(vi) cues or prompts are incorporated into the questions to assist the student. As the programme develops, however, these are gradually removed (faded) until the student is making the correct response without their assistance.

High error rates most often arise because the step-size is too large, or there is am­biguity in a frame, or the programme writer has assumed too much previous knowledge on the part of the student. As it is difficult

* Present address: Department of Chemistry, The University, Hull.

190 EDUCATION IN CHEMISTRY

to discover that a programme is too easy, it is useful to have a first draft that gives a high error rate and to reduce it in subsequent revisions.

Although linear programmes can be pre­sented on a simple machine, this is not necessary, and they are used mostly in book form or on sheets of paper. It is important that the student, having made his response to a question, should know immediately

G

Fig.

whether he is right or wrong, and this can be achieved by placing the answers im­mediately below each frame, which is covered until the response has been made. Once the student realizes that he is not being tested for examination purposes, cheating is not a serious problem. It is rather more important to be sure that there is no cheating when a programme is being tested.

Most of the chemistry programmes avail­able, whether published or privately circu­lated, are of the linear type. When writing a programme for the first time most teachers have found it helpful to begin with a small, coherent and not too complex topic. The final arbiters of the value of a programme are the students for whom it is written.

BRANCHED PROGRAMMES

Branched programmes are less common than the linear but are claimed by some to be more effective. Material is again presented in logical fashion in frames which normally contain a question and multiple-choice

answer. The student constructs his resporu and selects one of the answers. If he choose­correctly, the reasons for the correct answe_ will be explained-in case the right answer was obtained for the wrong reasons-and he then continues with the main programme. If the student selects a >vrong answer the error is explained, and he is returned to the main programme by a direct or indirect route. A possible scheme is illustrated in Fig. l.

N

In frame A the reader chooses one of four possible answers. The correct answer leads to frame D ; incorrect answers lead to frame, B , C and E, where the error is explained. and the student then returns to frame A to try the question again. Frame D contains a question with three possible answers. The correct answer leads to frame H and incorrect answers to F and G. In frame F the error is explained before the student is returned to frame D. In frame G the error is explained and the reader is directed to frame I where a new question is asked. The correct answer to this question then leads back to frame D . the incorrect answers lead to frames J and K . In frame H the correct answer leads to frame M (not shown) on the main programme: a minor error leads to frame L , and a more serious error to frame N. Students arriving here are considered not to have understood the material in previous frames and are directed back to frame A to work through this section of the programme again. Such schemes are capable of wide variation.

PROGRAMMED LEARNING IN CHEl\iiSTRY 191

The answer serves a different purpose in -he two types of programme. In a linear programme it is primarily for reinforcement; in a branching programme it controls the route through the programme. In a branch­ing programme there is greater emphasis on correction, and error rates of up to 15 per cent are permitted. The step-size can there­fore be larger and this makes the programme le s tedious, particularly for the brighter student. The main disadvantage of branched programmes is that they are less convenient in book form and are best presented on expensive teaching machines.

ADVANTAGES OF PROGRAMMED LEARNING

Several benefits have been claimed for this technique by those who have devised pro­grammes and used them with groups of 'tudents.

(i) Programme writing helps the teacher to clarify his own ideas. Whilst this is true of any teaching operation faithfully done, it is particularly true of programme writing .with its insistent demand for logical development and clear presentation.

(ii) By examination of students' answers to a programme the writer quickly discovers those parts of the pro­gramme which are inadequate and what areas of the subject present students with greatest difficulty , and he has to find ways of circumventing these.

(iii) A student works through a programme at his own rate. It is found that slow students may take twice as long as their faster colleagues to complete a programme. A well-written pro­gramme can be used without outside help and so th~ student can choose his own times of working,. · ·

(iv) The mode of simple logical presenta­tion and of question and answer with low error rate is of particular value for below-average students who, per­haps for the first time, get a clear understanding of the subject material and gain confidence from repeatedly getting the right· answers. Such

students then derive · greater benefit from their normal diet of lectures' and tutorials and from textbooks.

(v) Though programmes take time to prepare they save time thereafter, since one demonstrator or supervisor can help a larger number of students without any loss of efficiency. Alter­natively, students can work through a programme without supe-rvision.

Programmes written so far are crude attempts to develop this technique. There is much to be learned about the best way to write, to present and to use linear pro­grammes, and the possibilities of branching programmes in this field of study are almost completely unexplored. But enough is known, in the opinion of some, to consider programme-learning as a useful and efficient procedure which merits further investigation and wider use in sixth forms, technical col­leges and universities.

In the bibliography there is a selected list . of programmes which have been prepared in various chemistry departments and circu­lated privately. These programmes have been well received by students who have frequently asked for further programmes on other topics, and although there has been no adequate test of the effectiveness of the programmes used, subjective expressions, based partly on the marking of degree examination scripts;· are favourable . Rec actions from teaching colleagues are more varied: some approve, but not always with enthusiasm; others think the technique unnecessary· and harmful.

SPECIMEN EXCERPT

An excerpt from a programme on 'Ethyl Acetoacetate and Related ;3-Keto Esters,' designed for second-year students,* is given below. This section of the programme is followed by others on the Claisen ester condensation, the hydrolysis of ;3-keto esters, ethyl acetoacetate as a ketone, ethyl aceto­acetate as an enol, reactions of the activated CH2 group, and a summary. Students take

* It must be remembered that Honours Cour£es in Chemistry in Scottish Universities are four years in length.

192 EDUCATION IN CHEMISTRY

2-4 hr to complete the programme. It is regretted that most of frame 3 has had to be omitted in t he interests of brevity.

to each frame, given between the broken and the full line, are covered until the frame has been read and the answer written down on a separate sheet of paper. When using such a programme the answers

PART I. THE PREPARATION OF ETHYL ACETOACETATE

l. The compound of structure CH3·CO·CH2·C0 2Et has the systematic name ethyl 3-oxo­butanoate but has long been known as ethyl acetoacetate or as acetoacetic ester. It is important in the study of organic chemistry for the following reasons:

(i) It is prepared by an important condensation reaction of wide application.

(ii) It furnishes a simple example of the phenomenon called tautomerism.

(iii) It is an important intermediate in the synthesis of many other compounds.

Ethyl acetoacetate is a ,8-keto ester. Examine the formula given belo-w and notice which carbon atoms are labelled a and ,8 and y.

y [3 " CH3·CO·CH2·C0 2Et

Write the structural formulae of the a- , ,8- andy- oxo esters based on ethyl butanoate.

2. Indicate whether t he following structures represent a- , ,8- or y- oxo esters. CH3 ·CO ·CH 2 ·C02Me (a) Et·CO·CHMe·C0 2Et (b) Pr·CO·[CH2] 2 ·C0 2Et (c) Ph·CO·C02Pr (d)

Ph·CO·CH2C0 2Me (e) Ph·CO·CH2·CH 2·C02Me (f)

(a) {3, (b) {3, (c) y, (d) o:, (e) {3, (j) y.

3. Ethyl acetoacetate is prepared by treating ethyl acetate, which usually contains necessary traces of ethanol, with sodium. The overall reaction is:

Na CH 3 ·C0 2Et + CH3 ·C02Et - -+ CH3 ·CO·CH2·C02Et

[The remainder of this longer-than-usual frame is an explanation of the mechanism of t his reaction and is not reproduced here. Many of the subsequent .frames reje1· back to this mater·ial. The frame ends in the following way.]

Putting these steps together we get the following (note that all steps are reversible): o-

6Et C'H,-CO,Et I CH3 ·C02Et , ' CH 2 ·C0 2Et , ' CH3·C·CH2·C02Et

I OEt

QJ;;t

<=, =~' CH 3 ·CO·CH2 ·C02 ·Et , ' CH3 ·CO·CH·C02Et

PROGRAMMED LEARNING IN CHEMISTRY

Continue with frame 4

4. To prepare ethyl acetoacetate, the ester are required.

ethyl acetat e sodium

193

. . .. ....... and the metal

5. Another necessary reactant, present in the ester in sufficient quantity to start the reaction, and produced as the reaction proceeds, is

ethanol

6. Complete the simplified equation for the overall reaction: Na

CH3 ·C0 2Et + CH3·C02Et - -+ EtOH + ...

7. The catalyst in this reaction is the basic

8. It is produced by the action of . ester.

sodium

ethoxide (OEt)

on

ethanol

ion.

.. . .. ...... initially present in the

9. Indicate the mechanism of this reaction by formulating each stage (take care to distinguish b etween reversible and non-reversible steps):

(i) Production of catalyst by reaction of sodium and ethanol.

194 EDUCATION IN CHEMISTRY

2Na + 2EtOH - --+ 2Na-'- + 20Et + H 2

10. (ii) Formation of an anion (carbanion) by interaction of ethyl acetate with the ba ic catalyst.

11. (iii) Reaction of this carbanion with a molecule of ethyl acetate (this step invoh·es addition of the carbanion to the electron-deficient carbon in the ester).

12. (iv ) Elimination of ethoxide ion to give ethyl acetoacetate which then loses a proton and remains as its anion until acidified at the end of the reaction.

13. Bearing in mind the meaning of words such as bibliophile and anglophile join the circled words to the appropriate boxed words.

electrophilic reagents react at

electron-deficient centres

electron-rich centres

electrophilic reagents react at electron-rich centres nucleophilic reagents react at electron-deficient centres

PROGRAMMED LEARNING IN CHEMISTRY

14. Complete the following reaction sequence by supplying the missing formula:

OEt CH,.CO,Et CH3 ·C0 2Et , ' ....................... ... , '

(anion)

--' -, -- .............................. .. --' ,-- ..

(intermediate)

(molecttle) (anion)

195

15. Both ethyl acetate and ethyl acetoacetate can form ions by giving up protons to a basic reagent. The anions are resonance hybrids. Formulate canonical structures for the anions from ethyl acetate (two) and ethyl acetoacetate (three).

CH.·C = 0 - I

I OEt

16. Ethyl acetoacetate (structure condensation of

OEt

-«------+ CH 2 = C - 0 I

I OEt

OEt

I OEt

is prepared by self­...... under the influence of sodium.

ethyl acetate

17. Condensation requires the basic catalyst produced in this reaction The catalyst converts the ester into its from. .. .. .. ...... .. and ..

ethoxide ion (OEt), sodium (ethanol), ethanol (sodimn), anion (or carbanion), CH2·C0 2Et

196

18.

EDUCATION IN CHEMISTRY

This nu ..... . .. . . . . .. ..ic reagent is a with a second molecule of structure

.. ...... hybrid. The anion reacts to form a reaction intermediate of

o-1

nucleophilic, resonance, ethyl acetate, CH3 ·C·CH2 ·CO·Et

19. This splits out OEt to give the anion of structure

I OEt

which passes immediately to m the presence of the base .

ethyl acetoacetate, CH3·CO·CH·C02Et, OEt

BIBLIOGRAPHY

The following is a list of the more important books on the general subject of programmed learning and includes four published programmes on chemical subjects.

A. A. Lumsdaine and R. Glaser, Teaching Machines and Programmed Lea1·ning, Nat. Educ. Assoc. of America, 1960.

J. G. Holland and B. F. Skinner, The Analysis of Behaviour, McGraw-Hill Publishing Co. Ltd, 1961.

R. Goodman, Programmed Learning and Teaching 1\llachines, English Universities Press Ltd, 2nd Ed., 1963.

W. I. Smith and J. W. Moore, Progmmmed Lem·ning, D. Van Nostrand Co. Ltd, 1962.

E. J. Green, The Learning Process and P1·ogrammed Instruction, Holt, Rinehart and Winston, 1962.

C. A. Thomas, I. K. Davies, D. Openshaw and J. B. Bird, Prog1·ammed Lea1·ning in Perspective, City Publicity Services Ltd., 1963.

K. Austwick, Teaching Machinery and Programming, Pergamon Press, 1964.

J.A. Young, et. al., J. chem. Educ., 1963, 40, 11-28. L. M. Stolurow, Teaching by Machine, U.S. Dept. of

Health, Education and Welfare, OE34010 Co­operative research monograph No. 6 (1963).

G. M. Barrow, M. E. Kenney, J. D. Lassila, R. L . Litle and W. E. Thompson, Programmed Supple­ment for General Chemistry (2 vols), IV. A. Ben­jamin Inc., 1963, approx. 83.95 each.

H. N. Christensen, pH and Dissociation, W . B. Saunders Co. Ltd, 1963, 12s.

P. H. Carnell and R. N. Reusch, Molecular Equili­brium, W. B. Saunders Co. Ltd, 1963, 17s. 6d.

L. Sacerdote, General Chemistry: A Programmed Review, John Wiley & Sons Inc., 1963, 36s.

The following have been privately circulated:

A practical course in aqueous solution chemistry (H. F. W. Taylor, Aberdeen. First-year students).

Chemical equilibria. Dissociation constants. pH. Titrations. Solubility. Conductivity. Elec­trolysis. Thermochemistry. Kinetics (D. E. Hoare, Queen's College, Dundee. Medical and Dental students).

Organic nomenclature. Carbonyl compounds. Substitution of benzene derivatives. Stereoiso­merism (G. R. Inglis, Queen's College, Dundee. Medical and Dental students).

Classification of Reagents. Electrophilic addition reactions. Electrophilic aromatic substitution. Organic synthesis. Aromatic synthesis (A. R.. Forrester, D. R . Hogg and R.. H. Thomson, Aberdeen. Seond-year students).

Nomenclature of aliphatic compounds. Ethyl acetoacetate and related fl-keto esters. Olefins and acetylenes (F. D. Gunstone, St Salvator's College, St Andrews. Second-year students).

Nomenclature (P. J. Sykes, Edinburgh. Second ­year students).