#8

9 Tips
for Quality
Experimental
Write-Ups

#guide
27 August 2018

As we approach the dawn of a new academic year, my thoughts take me back to when I was a fresh-faced research student, arriving at my first research laboratory. It’s an exciting time and the learning curve is very steep.

One thing I stress to new research students is to think immediately about their data management. Yes, I know – what a dry subject – but it’s really important to understand from the off: (a) what data you need to collect; (b) how you should collect, store and interpret the data; (c) how to write-up your data properly for your project report, term paper or – hopefully – a journal article.

The answers to all three of these questions should come from your PI, but I often hear of students given little direction and advice. In this post, I share with you tips on how to write quality experimental reports on organic chemistry research (though some will apply to the other concentrations).

1. Keep on top of your experimental daily

You’ll hear this from me and probably many other researchers: write up your experimental as you go along. I can almost guarantee you won’t, or you will start to, but then quickly give up. Whilst typing up your experiment procedures and data isn’t exactly the definition of “fun”, doing it daily is good project management. If you don’t do it regularly, you’ll get to the end of your project and will need to write up tens/hundreds of experiments – that is the definition of “pain”.

Take 15 minutes a day, grab a coffee, and start typing. Write the experiment procedure, complete with masses and yields, and type up any initial data (i.e. the 1H NMR is a good starting point). Then, as the other data comes in at later dates, it’ll only take you a few minutes to add that data to your master document.

2. Past Tense, Passive Voice

It is important to write your experiments in the past tense, using the passive voice. It is very easy to slip into the present tense when writing about something you did recently, so make sure you check your tenses when proofreading.

3. The Procedure: It isn’t a recipe

I’ve found that the most common mistake when students start writing experiment procedures is poor structuring and an excess of trivial information. For example:

Compound A and compound B were dissolved in diethyl ether in a 250 mL round bottomed flask. The solution was heated to reflux for 90 minutes using an oil bath set to 50°C and a water condenser.

The origin of this behaviour is easily traceable: undergrad lab scripts. In a lab script, the procedure is spelt out so clearly, because lab work is a new concept. However, research projects or publication procedures should be written with the assumption that the reader is a trained chemist. All that is needed here is

A solution of compound A and compound B in diethyl ether was heated to reflux for 1.5 h.

4. “Then” is the devil

As well as not being a recipe, a procedure also is not a story. What really kills a well-written procedure is the overuse of the word “then”. The reader understands the natural progression of an experiment. For example:

Compound A was dissolved in diethyl ether, then compound B was added. The reaction was then heated to reflux for 24 h then cooled to room temperature. The solution was washed with water then brine then dried over MgSO4.

isn’t necessarily badly written, but how about:

To a solution of compound A in diethyl ether was added compound B and the reaction was heated to reflux for 24 h. After cooling to room temperature, the solution was washed with water (3 x 20 mL), brine (2 x 20 mL), then dried over MgSO4.

Which is easier to read? The one with five or one uses of the word “then”?

5. Use chemical formulas to improve legibility or for regional differences

Whilst it is good practice to write all chemical names in full, don’t be afraid to use chemical formulas for large inorganic complexes. For example, whilst it is correct to write

[1,1′-Bis(diphenylphosphino)ferrocene]dichloropalladium(II)

writing

Pd(dppf)Cl2

is just as informative and improves the legibility of the text. Also, regional differences like sulfur/sulphur can be avoided by giving the formula for common salts, i.e. MgSO4

6. Condense as much info into a “General Information” section

Any chemist should be able to reproduce your experiments from your experimental information. In order to do this, however, you need to provide a lot of additional information which is shared by every experiment. For example:

  • What grade of silica did you use for column chromatography?
  • What kind or brand of TLC plate did you use?
  • Did you purchase anhydrous solvent or dry and distill it yourself?
  • What is the full name/brand of each spectrometer you used?
  • etc.

This can all be covered in a section right at the start of your document called “General Information” (or something similar). So long as you are not the first student in your research group, a former member of your group will have already written this for their own work. So you can generally steal this from an old (but recent!) report or paper from your group (but obviously check it for quality and accuracy!).

7. Provide the correct amount of data

The amount of data you need to provide to support your experiment varies a lot based on PI ethos, research area and novelty of the work. If you are remaking a compound that has already been reported in the literature, some may say that you only need collect:

  • Proton (1H) NMR
  • Low-resolution Mass Spec (LRMS)

If the compound is novel, never before reported in the literature, you’ll need a lot more data:

  • Proton (1H) NMR
  • Carbon (13C) NMR
  • High-resolution Mass Spec (HRMS)
  • Low-resolution Mass Spec (HRMS)
  • Infra-red spectra (IR)
  • Elemental analysis (EA)
  • Melting/boiling points

If the material has a chiral center(s), you’ll need to report the specific rotation [α]. If the material was purified by column chromatography, as well as reporting the eluent you should also report the retention factor (Rf).

However, your PI might expect more (or less) from you. The above is just an example of what might be expected of you. You should find out what data you need to collect from your PI or a senior member of your research group.

8. Stick to a significant level of accuracy

It is important to think about accuracy when writing up experiments. Too frequently I read a report where:

5.0 g of X (5 mmol) and 4.68 mL (10 mmol) of Y were added

That researcher may have taken the time to measure exactly 4.68 mL of Y, but more often than not I would assume they probably just added 4.7 mL. If slightly more of a regent was added out of practicality, that is OK, but should be reported, even if it makes the molar ratios look less ideal:

5.0 g of X (5 mmol) and 4.7 mL (10.2 mmol) of Y were added

Similarly, carbon NMR data should be reported to one decimal place, but often I read student reports giving this data to 2 d.p. (a good guide for NMR data can be found by ACS here).

9. A (pretty) picture speaks a thousand words

Every experiment should be titled with the name of the compound being made. Whilst, informative, a picture speaks a thousand words. Make sure to include a figure of the chemical structure drawn in ChemDraw.

You should take some time to learn how to use ChemDraw properly. Instructions on doing that would be a whole guide in itself, but there’s a good amount of information available on this subject on Wikipedia (link).

At the very least, you should always draw your structures using the ACS Document 1996 settings. This has become the gold standard for bond length sizes, atom font sizes etc. The default settings in ChemDraw are horrible. Note, however, if you’re submitting a paper to a non-ACS journal (e.g. RSC), you might need to use that journal’s publisher’s settings for chemical structures.


I hope these tips will prove useful to students getting to grips with writing up their experiments. In a few months time, I will post a similar set of tips for writing quality reports. Stay tuned!

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July 2018