> See also: > - [[Spectroscopy]] > - [[Mass Spectrometry]] > # Determining Molecular Structures The structure of a molecule is what determines its properties. There are a variety of techniques that can be used to analyze these properties in order to deduce the structure of the molecule under investigation ## Experimental Determination ### IR/NMR Spectroscopy + Mass Spectrometry The techniques of [[Infrared Spectroscopy]], [[Nuclear Magnetic Resonance (NMR) Spectroscopy]], and [[Mass Spectrometry]] can be combined to determine the molecular structure of organic molecules. Below is a suggested procedure to use when analyzing the data from these techniques: > [!todo] Analyzing Spectroscopy/Spectrometry Data > 1. Start with [[Mass Spectrometry]] > - The molecular formula is often provided in data set > - If not, you can use the relative abundance of isotopes (M+ vs M+1 vs M+2) to determine amount of specific atoms present > - Determine **degrees of unsaturation** > 2. Look at [[Infrared Spectroscopy]] > - Analyze potential functional groups > - Match **degrees of unsaturation** (from step 1) to the identified functional groups until all are accounted for > 3. Look at [[Nuclear Magnetic Resonance (NMR) Spectroscopy|1H NMR]] > - Double check all current structure possibilities using **[[integration]] values** (ratio of protons for each signal) > - Use location of fragmentation signals (from MS) along with signal splitting patterns to determine the structure of the carbon skeleton > - Double check using coupling/splitting of signals > 1. Look at [[Nuclear Magnetic Resonance (NMR) Spectroscopy|13C NMR]] > - If all prior steps have been done correctly, the 13C NMR data should perfectly line up with prediction > - If the molecule lacks symmetry, there will likely be a single 13C NMR signal for each carbon atom within the molecule > > > [!warning]- Verify Molecular Weight > > Regularly check to make sure molecular weight of your possible structures aligns with the Mass Spectroscopy data > > If you are still left with multiple possible structures after these steps then you can look at the **chemical shifts** of the NMR signals to determine the layout of **electronegative atoms** and possibility of **aromatic structures** **Cryo-Electron Microscopy (CryoEM)** - [[CryoEM]] **X-Ray Crystallography** - [[Protein Crystallization]] ## Computational Determination - Machine Learning (Neural Networks) -> AlphaFold & The CASP Competition