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U-M CHEM 216 - Lecture Note

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Notes on using the Bruker AC-200- TECMAG 200MHz NMR Precautions: WARNING!!!! Remove your wallet, watches, etc. before approaching the magnet! Never bring any ferromagnetic items into the magnet room. Be careful with metal objects in the room. Avoid taking your credit or ATM cards too close to the magnet (approx. 2 feet). No loose staples or paper clips allowed. People with medical implants should not approach the magnet. People with pacemakers are not allowed in the room. You must be trained either by the class instructor or by an NMR staff member. This instrument is also known as the Bruker AC200. It has a Tecmag DSPect hardware-computer interface module. The NTNMR software is run under Windows-NT. The magnet strength is 4.7 Tesla with a 1H larmor frequency of 200MHz. Sample Preparation in the NMR room: At the NMR console you will find the spinner (a plastic collar) that fits snugly over the NMR tube. Slide the spinner over the NMR tube to the appropriate place using the depth gauge (also located near the console). (Note: Be careful not to get oil from your fingertips on the NMR tube or spinner. Use a Chemwipe to clean the outside of the tube before inserting into the magnet.) Insert the sample tube in the spinner, use the depth gauge to adjust the depth of the NMR tube in the spinner Use a depth gauge to determine where the spinner should be. Approximate height of spinner on an NMR tube. Note that the person is not touching the spinner. Spinner on an NMR tube. The placement is too high. No signal would be seen. Collecting the Data:The instrument is in room 2407. There are 7 parts you should be able to identify before acquiring your data. There are two monitors. The one on the right is connected to the computer. The one on the left is connected to the instrument console and will be used to monitor the deuterium lock signal. There are two keyboards. There is a standard QWERTY keyboard to operate the software. The other is to the right and is used to insert the sample and to lock and shim your samples. It will be referred to as the SCM keyboard. The monitors and keyboards are on the instrument console. While it looks like a big metal box, it contains all the electronics (amplifiers, receiver, etc.) for the instrument. On the front, left-hand side of the console, there is a small black button. It is used to stop spinning of the sample at the end of your acquisitions. Finally, the magnet is the big silver object in the back of the room. (If you want to know more about the constituent parts of the magnet, check out this part of the JEOL website: http://www.jeol.com/nmr/mag_view/magnet_destruction.html) On the computer keyboard, press Ctrl-Alt-Del simultaneously, then login.  On the computer keyboard, press Ctrl-Alt-Del simultaneously, then login.  On the SCM (NMR) keyboard , press the orange button, then press the Lift button to turn the lift air on. Put the sample on the column of air on top of the magnet. Press the Lift off button to lower the sample into the magnet. Inserting the sampleOnce the sample has been properly inserted into the magnet the normal procedure is to perform three steps to achieve optimum magnet homogeneity 1) spinning the NMR tube, 2) set the deuterium lock parameters, 3) optimize the shims currents  Press Spin button to spin the sample. The light on the Spin button should turn on.  On the NTNMR software window click on the Console button to open the Console Toolbar window, Click on load, select standard.shm file, then Click Open.  This will load the standard shim set on the SCM keyboard.  Look at the computer screen on the left. A deuterium signal should appear in the center of the screen. If not, press Lock Power on the SCM keyboard and set the value between 30 and 35 by turning the knob on the keyboard. (The range of 30-35 is appropriate for CDCl3 solvent; for Acetone-d6 use 10-15).  Press Lock Gain and adjust the value between 100-104.  Press the Lock Phase button and adjust the value to 253 (This value may change in the future; look for a note on the computer with the current value).  Press Field and adjust the field value till the deuterium signal appears in the middle of the window. (January 17, 2003: Field = 4200 for CDCl3, Field = 4010 for Acetone-d6).  Press Lock (the deuterium signal will disappear and the light on the Sweep OFF button will turn on). The Lock button light will blink.  If the lock light is blinking, Press Field and slowly adjust the field until the lock light stops blinking. (Generally, for a solid lock the line should be over one grid line above the center).  Now shim the magnet. Shimming Procedure: Check to make sure that the Fine button has a green light indicating it is engaged. As when locking, try to maximize the lock signal level by selecting a shim key (see below) and very slowly adjusting the knob at the bottom of the SCM keyboard.  If you have difficulty shimming, try reading the latest stored shim file (ask GSI).  If the lock level disappears off the top of the screen, Press Lock Power and lower the current value until the lock level is one to two grids below the top.  Press Z and adjust the value in whichever direction increases the lock level. Once the Z value is optimized (i.e. the lock level is maximized in the window) press Z2 and repeat the procedure. DO NOT adjust the Z3 or Z4. Doing so may cause the 1H signal to be lost.  After optimizing Z2, go back to Z and re-optimize it. Repeat this procedure until the lock level is completely maximized in the window.  Press Lock Phase and adjust to maximize lock level  Press Standby 1H NMR ACQUISITION:  On the NTNMR software click on the File menu. Select Open. Click on small inverted triangle then Click on NTNMR, then double Click on Data. Select the H1_CDCl3.tnt file (for Acetone-d6 solvent select H1_Acetone.tnt file) and Click the Open button. It will load the standard proton parameters.  Click on the Dashboard button to check the parameters and make necessary changes (e.g.number of scans (NS), spectral width (SW), etc.).  Begin with the RG (receiver gain) set at 2. It may be increased at values of 2n where n is an integer.  Click on ZG in the Acquisition Toolbar and wait for the acquisition to finish.  During acquisition, check to make sure the receiver is not saturated. If


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