Synthesis, three loadings, 18 runs plus three blanks

Chemistry research poster example

Three catalyst loadings for one ester synthesis, laid out as an A0 portrait board with the procedure running across the top as a five step chain. A synthetic chemistry poster is read for the method first, so the method is the first thing under the title.

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QU
Where the yield stops improving: three catalyst loadings for one ester synthesis
L. Fontaine ¹, D. Aruna ¹, H. Petrov ¹ ²
1 School of Chemistry, Quarryhill University · 2 Centre for Catalysis and Green Synthesis, Quarryhill University
Abstract
Undergraduate and small scale preparations of this ester routinely call for 2 mol % of the tin catalyst, a figure that appears to have been copied forward rather than measured. We ran the same esterification at 0.5, 1.0 and 2.0 mol %, six independent runs at each loading, with three catalyst free blanks, and measured isolated yield by gas chromatography against an internal standard. Mean yield was 71% at 0.5 mol %, 88% at 1.0 and 89% at 2.0, and the blanks returned 6%. The step from 0.5 to 1.0 is worth 17 points; the step from 1.0 to 2.0 is worth one, which is inside the run to run spread of either loading. Purity by GC area was 96.8%, 98.1% and 97.4%, so doubling the catalyst does not buy purity either. Time to constant water collection fell from beyond four hours at 0.5 mol % to 3 h 45 min at 1.0 and 3 h 20 min at 2.0, so the only thing the higher loading buys is twenty five minutes of reflux.
HOW THE STUDY RAN
1
Reagent prep
Acid and alcohol dried over sieves, 1.0 to 1.2 molar ratio, 25 mmol scale.
2
Catalyst loading
Tin catalyst weighed to 0.1 mg at 0.5, 1.0 or 2.0 mol % of the limiting acid.
3
Reflux 4 h
Toluene reflux with a Dean and Stark trap, water removed continuously.
4
Workup
Aqueous bicarbonate wash, dried, solvent removed under reduced pressure.
5
GC yield
Isolated mass then GC against dodecane as internal standard, duplicate injections.
%
0.5
1.0
2.0
0255075100
Figure 1. Mean isolated yield by catalyst loading in mol %, six runs each. Blanks returned 6%.
Source: 21 runs, GC against an internal standard, 2026.
Results and the numbers behind them
Mean isolated yield was 71% at 0.5 mol % with a standard deviation of 3.1 points across six runs, 88% at 1.0 mol % with a standard deviation of 1.9, and 89% at 2.0 mol % with a standard deviation of 2.2. Three catalyst free blanks gave 5%, 6% and 7%. The difference between 0.5 and 1.0 mol % is 17 points, far outside either spread; the difference between 1.0 and 2.0 is one point, well inside both. Purity measured as GC area percent was 96.8% at 0.5 mol %, 98.1% at 1.0 and 97.4% at 2.0, with the small fall at the highest loading coming from a single late eluting impurity that appears in four of the six runs at 2.0 mol % and in none of the runs below it. Nuclear magnetic resonance on one sample per loading agreed with the gas chromatography figures to within a point in all three cases, and no signal for residual acid was visible at 1.0 or 2.0 mol %. Reaction time to constant water collection was 3 h 20 min at 2.0 mol %, 3 h 45 min at 1.0 and beyond the 4 h window at 0.5, where two of the six runs were still collecting water when the reflux was stopped. Those two runs are included in the 0.5 mol % mean rather than excluded, which is part of why the spread at that loading is the widest of the three. Excluding them lifts the 0.5 mol % mean to 74% and narrows the gap to 1.0 mol % by three points, and it is reported here so a reader can decide which figure to carry forward.
REFERENCES
1.Aruna, D. and Fontaine, L. (2025) Catalyst loading conventions in undergraduate esterification. Journal of Chemical Education Practice, 61(2), 140 to 158.
2.Petrov, H. (2024) Internal standard selection for small scale GC yield measurement. Analytical Practice Letters, 19(3), 77 to 91.
3.Sorenson, K. (2026) Tin residues and workup burden in teaching laboratories. Quarryhill Chemistry Reports 2026-02.
What this means for the method
The practical result is that 1.0 mol % is the loading to write into the procedure. It reaches the same yield as 2.0 within a point, it gives the cleanest product of the three, and it halves the amount of a tin compound that has to be removed in the workup and disposed of afterwards. The case for 2.0 mol % reduces to twenty five minutes of reaction time, which matters in a teaching laboratory with a fixed session length and almost nowhere else. The case against 0.5 mol % is not the yield alone but the variance: the standard deviation is half as large again as at 1.0 mol %, and two of the six runs had not finished at four hours, so a class working to a timetable would see a wide spread of results for reasons that have nothing to do with technique. Three limits are worth stating. This is one ester on a 25 mmol scale in one solvent, and the loading that is flat here may not be flat for a hindered acid. Isolated yield and GC area are not the same as purity by nuclear magnetic resonance, which was run on one sample per loading and agreed to within a point. And the blanks confirm the reaction does not run usefully without catalyst, but they do not rule out a slow uncatalysed contribution at the longer times.
Conclusion
Yield rises 17 points between 0.5 and 1.0 mol % and one point between 1.0 and 2.0. One mol % gives the best combination of yield, purity and variance, and the customary 2 mol % buys nothing but a shorter reflux. It also doubles the tin that has to be washed out at workup and disposed of afterwards, which is the argument a teaching laboratory should weigh against twenty five minutes.
Yield 71%, 88% and 89% at 0.5, 1.0 and 2.0 mol %
Blanks returned 6%, so the reaction needs the catalyst
Purity best at 1.0 mol %, at 98.1% GC area
Doubling to 2.0 mol % saves 25 minutes and nothing else
Materials and instruments
All runs used the same batch of acid and alcohol, dried over 3 angstrom sieves, at a 1.0 to 1.2 molar ratio on a 25 mmol scale. Gas chromatography ran on a single instrument with dodecane as the internal standard and duplicate injections per run. Glassware and the Dean and Stark trap were dedicated to this series so that carryover between loadings could be ruled out. Nuclear magnetic resonance spectra were recorded on one sample from each loading at 400 MHz.

Block by block

What each block on the board is for, in the order a reader walks it.

Title band, three authors and a QR code
The title states the finding as a question already answered: where the yield stops improving, across three catalyst loadings for one ester synthesis. Three authors carry superscripts over two affiliations, with the QR code at the right.
Abstract
A wide block giving the reason for the study, the customary 2 mol % figure that appears to have been copied forward, the three loadings tested, the mean yields of 71%, 88% and 89%, the 6% blanks, and the purity figures that show doubling the catalyst buys nothing.
How the study ran
Five numbered stages across the board: reagent preparation over sieves at a 1.0 to 1.2 molar ratio on 25 mmol scale, catalyst weighed to 0.1 milligram, four hours of toluene reflux with a Dean and Stark trap, an aqueous workup, and gas chromatography against dodecane.
Figure
Three bars for the three loadings at 71%, 88% and 89%, with the caption noting six runs at each and that the blanks returned 6%. The source line names the 21 runs and the internal standard method the numbers came from.
Results and the numbers behind them
Means with standard deviations of 3.1, 1.9 and 2.2 points, the three blank values, the gas chromatography purity figures, the late eluting impurity that appears only at 2.0 mol %, and the reaction times of 3 h 20 min, 3 h 45 min and beyond four hours.
What this means for the method
One mol % is the loading to write into the procedure: the same yield as 2.0 within a point, the cleanest product, and half the tin to remove at workup. The case for 2.0 reduces to twenty five minutes of reflux.
Conclusion, materials and references
A short conclusion, four checked points, a materials block covering the shared reagent batch and the dedicated glassware, and three numbered references. The board carries no separate key number block, so the headline yield sits in the conclusion and the figure instead.

What makes this board work

The procedure is a chain, not a paragraph

Five numbered stages run across the board under the title: reagent prep, catalyst loading, reflux, workup and gas chromatography yield. A chemist looking for whether they can repeat this reads the chain and stops.

Every yield carries its spread

71% with a standard deviation of 3.1, 88% with 1.9 and 89% with 2.2. That is what makes the 17 point step real and the one point step nothing, and it is the argument the whole board rests on.

The blanks are on the board

Three catalyst free runs returning 5%, 6% and 7% take about four words of space and remove the obvious objection that the reaction proceeds without catalyst. A poster with no blank invites the question at the worst possible moment.

Questions people ask

What goes on a chemistry research poster?

The reaction or system, the procedure in enough detail to be repeated, the conditions varied, the yields or measurements with their spread, a purity or characterisation read, and the blanks or controls. A yield with no standard deviation and no run count cannot be judged.

How do I show a procedure on a poster?

A numbered chain across the board works better than a paragraph because it gives each stage its own space and its own detail line. Keep it to five stages. A sixth stage is dropped silently by this component, so if your method needs six, group two of them.

Should the figure repeat the numbers in the text?

It should show the shape the text describes. Here the figure carries three bars for three loadings so the flat step from 1.0 to 2.0 is visible, while the standard deviations and the purity figures stay in the results text where there is room for them.

What type size does a chemistry poster need?

Body text on this A0 portrait board is near 24 pixels on the 1656 by 2340 canvas, about 12 millimetres printed, readable at a metre. Structures and schemes can be smaller, since a chemist steps in to read a structure, but conditions text should stay at body size.

Can I print this poster at 300 DPI?

The export doubles the working canvas, so an A0 portrait board leaves at 3312 by 4680 pixels, about 100 DPI at full size. That is the normal resolution for large format printing viewed from a metre, and there is no bleed, crop mark or CMYK option.

How do I adapt this to my own reaction?

Retype the title, authors and abstract, rewrite the five chain stages with your own conditions, change the figure categories and values, and edit the results text. The acknowledgements block has been retitled here as materials and instruments, which any section heading can be.

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