Proton HNMR Spectra Technique
Proton HNMR Spectra Technique CHEM 225
Popular in Organic chemistry 2
Popular in Chemistry
This 2 page Class Notes was uploaded by MelLem on Monday May 16, 2016. The Class Notes belongs to CHEM 225 at Simmons College taught by Professor gurney in Spring 2016. Since its upload, it has received 14 views. For similar materials see Organic chemistry 2 in Chemistry at Simmons College.
Reviews for Proton HNMR Spectra Technique
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 05/16/16
Melanie LeMay CHEM 224L01 H NMR – Proton Nuclear Resonance Spectroscopy Purpose: The purpose of H NMR also commonly known Proton NMR is to deduce the structure of the molecule using peaks containing multiplicity. Theory: NMR is an analytical tool used to help deduce the structure of organic molecules. It uses the chemical shift, integration, and multiplicity of neighboring protons to help determine which structure is best. NMR can be used for this reason due to the spin state of the nuclei of the proton. HNMR detects the carbonhydrogen framework of an organic compound. The machine works by applying a magnetic field that orientates the atomic nucleus. There are two possible spin states for the H atom, when performing the HNMR, one can gain the knowledge of how many different H signals are present, the location from the type of protons, the integration given to you from the area under each signal that shows as a peak, and by gaining the shape or the multiplicity, one is able to know the amount of neighboring protons. Procedure: Creating A Solution: 1. The solution must be diluted, 420 mg of the sample may be used. The sample can be placed in a small clear vial, eppindorf or testtube. 2. Add 0.50.7 mL of the appropriate deuterated solvent. 3. Agitate the mixture in the vial. Ensure that the solution is homogenous. If there are any solids, they can be filtered with a glass wool plug. 4. Using a Pasteur pipet, transfer the sample to the NMR tube, if the level in the tubing is not adequate enough, solvent can be added to bring it to the correct level that is needed. The solution should be above the point where the read is taken in the calibrated device used to put the collar on. 5. Cap the NMR tube, and wipe the outside of the tube to remove any material, that may impede the smooth spinning of the tubing in the machine, or affect the read, such as finger prints. Taking the Read of a Solution: 1. Remove and dispose of gloves before entering the NMR room, the powder from the gloves can affect the NMR machine. 2. Sign into the machine 3. Remove the blank from the machine by slowly depressing the valve, this will start a flow of air and raise the NMR tubing that is already inside. 4. Put the collar on the sample, wipe off the NMR tube with a kimwipe to remove finger prints. 5. While still depressing the valve, place the NMR tube with the solution you want to have a scan of into the NMR machine, Slowly release the valve to lower it into the scanning position. Ensure that the NMR tubing and the collar are spinning, this can be done by using the light to see if the black dot on the collar is visible. If it is not remove the tube and try again. 6. Move to the computer and using 2 computer programs, take the spectrum of the sample that you wish to have an HNMR scan of. Follow the procedure printed on the table at the computer. Print the scan following the use of the computer. Liquid 1. 57 drops of unknown in about in about 34 ml of solvent 2. place in NMR tubing and Run NMR. Clean Up: 1. Dispose of the solution in the NMR tubing in the appropriate waste area. 2. Clean the NMR tubing with acetone. If the acetone does not remove the solvent from the NMR tube, water can be used to clean it, it is important to clean the tubing with acetone after the use of water to ensure that no residue is left, for this can cause unwanted residual peaks to show in another scan. 3. Leave the tubing to dry overnight, for the acetone takes a while to dry and it is important to have a clean and dry NMR tube for all scans. Points of Confusion: If the solution is too concentrated, the peaks on the spectrum may not appear as clear as they should, broad peaks that are not easy to interpret may show if the solution is too concentrated. A diluted solution I required when taking the scan. If the NMR tube with the collar is not spinning in the NMR machine, the solution may also have peaks due to the solution not spinning. The spinning of the NMR tube while its in the machine makes the solution more homogenous. If the NMR tubing is not cleaned following the procedure, the solvent may cause a sticky residue to form inside the tube, this is difficult to clean and if not fully removed can cause errors and residual peaks from the other solutions. TMS – tetramethylsilane, is used as a standard in calibrating the machine, its beak shows at 0, and should not be used in deducing a structure. When taking the scan, ensure that the receiver gain is not too high, monitor the process of the scans and make sure the screen has yellow on it, not red. This red indicates that the receiver gain is too high and should be lowered. The scan must be restarted at this point, using the command (zg) enter. Deuterated Solvents Commonly Used: Deuterated chloroform D 2 H NMR “Buckets” in ppm:
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'