chemsample-infraredspectroscopy-methods

Conducted by: Student A + B
 * __TECH 0710: Identifying an Unknown Compound by Infrared Spectroscopy__ **

For this experiment you need to weigh out 100 mg of potassium bromide and 2 mg of benzoic acid. Then, you will place the two powders into a mortar and mix it into an even finer powder using a pestle. After this process is done you will quickly cover it in order to keep moisture from getting into your sample. You will be putting your sample into the metal compartment shown below. You are going to open the KBr trap in the middle where the crease is ~ its kind of hard, so Be Careful ... and //dont drop it//! There are two small circular metal pieces inside this metal trap; Note, that the one with the 'circular engraved' side goes first.


 * Note**: circle side goes up.



Place a paper pellet that is provided by your instructor inside the collar along with your sample. Take the other metal piece in along with the piece next to the trap. This can be used to push the pellet down. Now put the compartment back together and place it into the compression machine - which will compress the sample into what is called a //KBr pellet//. **Note**: looks like it has plastic over it where as before it was just a hole inside the paper pellet. Now its time to use the machine, because the dying process is complete.

Open the plastic door to the machine. Place the pellet in the middle, close the door. Make sure its tightly secured in its position by twisting the knob on the bottom and twisting the handle located on top. Now you will compress the two anvils together by pumping the lever on the right with the blue handel until it reaches 5000 N. Note: this can be difficult so make sure someone can help if its needed.

Wait and then slowly relase the pressure using the bottom knob, then remove the compartment from the machine. Remove the KBr pellet with tweezers and place into the sample holder. Place into the machine on the bottom and test your sample and recognize the peaks shown. When done place pellet into a watchglass.

**__Preparing a sample of p-Anisaldehyde: Using NaCl plates__** Take the solution p-Anisaldehyde and place a drop of it on one of the NaCl plates.

Place the other plate on top of it to eliminate air bubbles and work as a trap for the solution. After this process is complete place the plates into the sample holder in the machine shown above. Obtain the IR graph and look at the peaks within the compound (s).

Conducted by: Student C + D
 * __TECH 0710: Identifying an Unknown Compound by Infrared Spectroscopy__ **

Determining IR spectra within our Chem Kid //sub-group// (:p!) broke down as follows: One **known solid**IR spectra, One **known liquid** IR spectra, & One **unknown liquid** IR spectra. Methods were similar for each, however, for sake of convenience & clarity they are listed individually below ~

//Known Solid// (//KBr, Vanillin//) //prep// ~ 100 mg (0.1 g) of KBr was weighed & mixed in with a precise 2.0 mg amount of Vanillin - both mixed within a 50 mL beaker,... and cover wrapped (to attempt) to ensure dryness of the sample (both solids hold water absorbing properties - which, if occurs, will ruin the sample). The sample was then crushed into a fine powder (via mortar & pestle), compressed in the compression unit shown above, & readied for the IR Spectrophotometer. The sample was then placed into the IR Photometer & absorption values were displayed across the screen (for your viewing pleasure). Evaluation of the graph was then the final process!

//Known Liquid// (//Acetophenone//) //prep// ~ After obtaining the NaCl plates and rinsing them with dichloromethane, they were then placed in the IR Spectrophotometer to obtain a background. When the background of the clean salt plates was complete, we then, using a pasteur pipette, placed two drops of Acetophenone on one of the salt plates. Next we placed the other salt plate on top of the liquid and applied pressure to be sure the liquid had been evenly distributed across the entire salt plate and that no air bubbles was present.The salt plates were once again placed in the IR Spectrophotometer, this time with the known liquid between the salt plates, and the IR Spectra was produced on the computer screen.

//Unkown Liquid// (//Sample # 3//) //prep// ~ Once again, after cleaning the NaCl plates with dichloromethane, they were then placed in the IR Spectrophotometer to obtain a background. When the background of the clean salt plates was complete, we then, using a pasteur pipette, placed two drops of our Unknown Liquid #3 on one of the salt plates. Next we placed the other salt plate on top of the liquid and applied pressure to be sure the liquid had been evenly distributed across the entire salt plate and that no air bubbles was present.The salt plates were then placed in the IR Spectrophotometer, this time with the Unknown Liquid #3 between the salt plates, and the IR Spectra was produced.


 * Note** - that the pictures above are good references for a visual understanding of what happened!

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