MLTIPLET for Windows

It was written by Dr. Bruce W. Tattershall, Lecturer in Chemistry at the University of Newcastle, England.

Platforms

Availability

Introduction

Mltiplet was written originally as an aid to learning about NMR multiplets in undergraduate chemistry courses.  It can be used to simulate the simplest multiplets, but it can equally show the most complex first-order multiplets interpreted in real chemical research.  It can handle up to nine coupled groups and up to 12 nuclei per group, but with the constraint that there must be no more than 600 transitions altogether in the multiplet.  (Nine single non-equivalent I = 1/2 nuclei would give 512 transitions.)

Mltiplet shows one multiplet at a time.  It knows nothing about the chemical shifts of other nuclei coupling to the one whose NMR absorption gives the multiplet shown, and it assumes that all these other nuclei have a nuclear spin quantum number I = 1/2. Typically they might be nuclei of 1 H, 19 F, or 31 P.

While the program generates quite realistic lineshapes, it assumes that the multiplet is completely first order, i.e. the intensities of the peaks are given by Pascal's triangle of binomial coefficients.  This is strictly true only if the multiplet is due to a different nuclear species from that of the nuclei coupling to it, e.g. the observed nuclei are 31 P and the coupling nuclei are 1 H, and the coupling nuclei, if of the same nuclear species as each other, do not couple to each other.  While this is rarely true in real chemistry, Mltiplet will still give simulations which are very similar to those seen in the observed spectra, provided that all of the couplings between the nuclei are much smaller than the chemical shift differences between them, when expressed in the same units (Hz).  This is why first order multiplets, as simulated by Mltiplet, are universally taught about in introductory courses in NMR, and many practising chemists never go further than this in their interpretation of observed multiplets.

The author has written or translated other software to make completely realistic simulations and fits to observed spectra, but use of this requires a knowledge of all the couplings and chemical shifts in the coupled system.  Many organic molecules may have spin systems which are too complex to be analysed rigorously in this way (though doing so is often more possible and necessary for more symmetrical inorganic molecules).  When all the information is not available for a completely rigorous simulation, Mltiplet can be useful in real research by showing what shape multiplet the researcher is looking for in a mass of observed peaks.  This is not always intuitively obvious, even to the author.

Use for Learning and Teaching

In our uses, at an introductory level, students could use Mltiplet to find out what happens to the appearance of multiplets as coupling constants are varied, and to understand the meaning of terms like 'triplet of doublets'.  In more advanced courses, our students have used it to confirm their hand analysis of presented real spectra, thus learning by trial and (usually some) error how to see complex multiplets and extract coupling constants from them.

Mltiplet for Windows is intended to be an 'intuitive' Windows program of the kind familiar to today's students, and hence easier for them to use without direct supervision.  It is envisaged that some students might wish to install it on their own PCs.  However, we intend to continue to use it in the drylab environment.

In England, some schools are teaching an introduction to NMR.  We feel that school teachers and their students could benefit from using Mltiplet as we do when the students come to the University of Newcastle.  Accordingly it is also offered for use at this level, according to the ingenuity of the teacher.

Built-in Help

I have taken the line of setting the help and built-in examples clearly at university level, but making it nevertheless self-contained, and therefore understandable by an intelligent school sixth-former, even though it is obviously meant to go beyond what they will have met already. I want to get away from the easy and boring and into the stimulating.

I have also tried to avoid giving away all the answers to questions which school teachers might want to ask students about their use of the program, though you might spot that some such questions are implied.

Disclaimer

The author makes no commitment to remedy reported bugs or make suggested improvements, but nevertheless would welcome comments from users.

Installation

The program assumes that you have a 300 dots per inch printer. If your Windows printer has a different resolution, e.g. 600 dpi, then instead of putting P on the command line, put e.g. P=600 (no spaces around the = sign) instead. If you do not put the L and P keywords on the command line, you will get the same program but without the ability to print the listing or the plot. This is designed to be useful in classroom situations where use of a printer is undesirable on grounds of running costs.

If you put the L keyword in the shortcut, you should make the Start in directory somewhere where scratch files can be created. The program will find the .dll files so long as they are in the same directory as itself: they do not need to be in the startup directory.

No further installation under Windows is required.  The software may be uninstalled simply by deleting mltpltw.exe and the two .dll files.

Feedback

Thanks very much.

Bruce Tattershall
Chemistry in the School of Natural and Environmental Sciences
University of Newcastle
Newcastle upon Tyne
England

Email:       Bruce.Tattershall@ncl.ac.uk
Website:   http://www.staff.ncl.ac.uk/bruce.tattershall/