Structure elucidation is one of the most time-consuming parts of synthetic chemistry. You run an experiment, collect a spectrum, and then spend hours cross-referencing peaks against literature values, flipping through reference tables, or waiting for a colleague with more experience to take a look. For a compound you synthesized yourself the process should be confirmatory — yet in practice it rarely feels that way.
MID was built to change that.
MID is a free, browser-based computational toolset for molecular structure elucidation. There is nothing to install. You open the page, input your data, and get results. Everything runs server-side, so it works on any device with a browser — your lab computer, your laptop at home, or your phone while you are waiting for a column to run.
The problem MID solves
Most spectral assignment software falls into one of two camps: commercial packages that require institutional licenses and local installation, or academic tools that are powerful but assume you already know what you are doing. Neither is ideal for the day-to-day reality of a synthesis lab, where you need a fast, reliable answer without a learning curve.
MID sits in the middle. It is built for experimental chemists — people who run spectra constantly and need tools that are as quick to use as they are accurate. The interface is minimal by design. You do not need to read a manual. You put in your data and you get an answer.
What MID can do
¹H-NMR and ¹³C-NMR Peak Assignment
Paste your experimental chemical shifts into the tool, specify your solvent, and MID will return a ranked list of predicted assignments for each peak. The assignments are computed from first principles — not from a look-up table of average values — so they account for the actual electronic environment of each nucleus in your specific molecule.
This is most useful for confirmation after synthesis: you know what you made, you want to verify that the NMR is consistent with the proposed structure, and you want to do it quickly. MID gives you a clear, quantitative picture of which peaks correspond to which protons or carbons, including overlapping signals that simple look-up methods handle poorly.
NMR Spectrum Simulation — Including 2D
Draw a molecule or enter a SMILES string, and MID will generate a predicted NMR spectrum. This works for both ¹H and ¹³C, and the simulator supports 2D NMR experiments including COSY and HSQC — giving you predicted correlation maps that you can compare directly to your experimental data.
2D NMR is particularly powerful for larger or more complex molecules where 1D spectra alone are ambiguous. Being able to generate a predicted COSY or HSQC for a proposed structure — and overlay it mentally with your experimental spectrum — dramatically shortens the time between "I think this is the structure" and "I am confident this is the structure."
The predictions are grounded in quantum chemistry calculations rather than increment rules, which matters most for molecules with unusual substitution patterns or strained ring systems where empirical methods tend to underperform.
IR Spectrum Reader
Upload an IR spectrum file (JCAMP-DX format, as exported by most modern FTIR instruments) and MID will process it and identify the characteristic absorption bands. This is useful for quick functional group confirmation: you want to know whether that carbonyl stretch is where it should be, whether the broad O–H is consistent with your alcohol product, or whether you can rule out certain functional groups based on what is absent.
IR is often the fastest experiment in the lab, and having a tool that reads and interprets the output immediately — without manual peak picking — saves meaningful time across a synthesis campaign.
MS Spectrum Reader and Isotope Pattern Simulator
MID includes two mass spectrometry tools. The MS spectrum reader processes raw MS data and identifies molecular ion peaks, fragments, and adducts. The isotope pattern simulator takes a molecular formula and generates the expected isotope envelope — the pattern of M, M+1, M+2 peaks that is characteristic of a given elemental composition.
Isotope pattern matching is one of the most reliable ways to confirm a molecular formula from MS data, especially for compounds containing halogens, sulfur, or other elements with distinctive natural isotope distributions. MID computes the exact expected pattern so you can compare it side by side with your experimental spectrum.
Full Analysis Workflow
The full analysis tool brings all of this together. You can combine NMR, IR, and MS data in a single session and work through a complete structure elucidation from multiple spectral inputs at once. This is the workflow most closely aligned with how structure elucidation actually happens in practice: you collect several types of data, and the structure emerges from the convergence of evidence across all of them.
Who is it for?
MID is designed for experimental chemists: synthetic chemists, medicinal chemists, natural product researchers, and anyone who regularly uses NMR, IR, or MS as part of their workflow. It is equally useful for PhD students learning spectral interpretation and for experienced researchers who want to move faster.
It is also a genuine teaching tool. Predicted spectra give students a reference point to compare against their experimental data, and the assignment tools help build intuition about the relationship between structure and spectral features — intuition that is hard to develop from textbook examples alone.
The approach
Every prediction in MID is based on quantum chemical calculations rather than empirical increment rules. Increment rules work well for simple, well-represented structural types but deteriorate for unusual substitution patterns, strained geometries, or functional group combinations that are underrepresented in the databases they are built from.
Quantum chemical methods do not have this limitation in the same way — they compute properties from the electronic structure of the actual molecule, which means the accuracy is more consistent across structural space. The cost is computation time, which is why MID runs these calculations server-side on dedicated hardware rather than in the browser.
The result is a tool that is as easy to use as an increment-rule calculator, but with accuracy that holds up for the kinds of molecules that actually come out of synthesis labs.
Try it
MID is free to use. Register for an account to access the full toolset at moleculeidentifier.com.