NMR spectroscopy is used to look at the chemical environments of a selected nucleus (typically 1H) on a molecular level. Our NMR services are designed to streamline the most common analyses (routine 1H characterizations) while having the capability to run complex experiments. Our machine is a Bruker 400 MHz spectrometer.
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1-Dimensional NMR experiments:
¹H NMR: Routine chemical characterization of synthetic organic compounds. We almost always start by acquiring a 1H NMR to get a rough idea of the concentration and purity of the sample.
13C, 19F, 31P, 15N, 35Cl, 11B, etc.: We have a tunable broadband probe which can be set to virtually any nucleus. To date, we’ve done carbon, fluorine, phosphorus, chlorine-35, boron, and nitrogen, but we have the capability to do others.
2-Dimensional NMR experiments:
Correlation Spectroscopy (COSY): ¹H- ¹H through-bond correlations. While some of this information can be gleaned from the coupling constants of a 1-dimensional 1H NMR spectrum, this 2-dimensional method unambiguously determines the hydrogens which are three bonds apart.
Nuclear Overhauser Effect Spectroscopy (NOESY): ¹H- ¹H through-space correlations. This is often used in differentiating stereoisomers and regioisomers which cannot be unambiguously identified by 1-dimensional techniques. For molecules in the 800-1500 amu range, we also offer the rotational-frame parallel (ROESY).
Heteronuclear Single Quantum Coherence (HSQC): 1H-X (typically 1H-13C) 1-bond correlations. This is often used to assign a 13C NMR spectrum when the 1H NMR spectrum is already assigned. Although uncommon, we can also do 1H-31P HSQC and 19F-13C HSQC.
Heteronuclear Multiple Bond Correlation (HMBC): ¹H-X (typically 1H-¹³C) multiple bond correlations. Typically, 3-bond correlations show up the strongest, while 2- and 4-bond correlations show weakly. This is often used in conjunction with HSQC to map a molecule from hydrogen to carbon. Although uncommon, we can also do 1H-31P HMBC (see our blog post on identifying the location of a phosphate group on a sugar).
Diffusion-Oriented Spectroscopy (DOSY): This is a 2-dimensional technique where the second axis is not another nucleus, but the diffusion constant of the molecule. This can be used for a variety of purposes – we’ve used it to measure dimerization of a molecule (the dimer has a lower diffusion constant than the monomer), and to identify which peaks in a 1H NMR spectrum are from monomer and which are from polymer.
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