chemsample-lab2-discussion

Conducted by: Student A + B
 *  __Diels-Alder Reaction of 2,3-dimethyl-1,3-butadiene & Maleimide (Double Quant)__ **

 Applying double the amounts of protocol reagents, we were able to obtain a significant yield of product for both samples one & two (3.6584g and 3.409g, respectively). In contrast to our counterparts running the reaction at regular (called for) quantities, the yield our reactions obtained were quite significant. The samples were prepared cleanly, and in the proper manner, and run through the Mars-microwave for the proper allotted amount of time. The vessels were cooled properly, filtered properly, & transferred for weighing in accordance with the lab manual’s protocol. However, looking at the results (specifically the melting points of the two samples … irrespective of the yield weights – as they are essentially similar), we noticed a significant difference between our two samples ~

 Sample One, //Dry Weight//: 3.6584g  Sample Two, //Dry Weight// 3.409g  (Notice that these yields are very close to one another)

 Sample One: //MPR// = 105 – 109.4 deg/c *124.5-128.5 and 124.5-127.9 (//Additional melting point ranges from 2/25)//  Sample Two: //MPR// = 123.3 – 127.7 deg/c *120.8-126.8 and N/A

We have yet to actually compare our melting point ranges to literature values in order to get an idea of our samples chemical structure, however, it is clear by the deviation between the two samples that a significant contrast does exist. It is very likely that sample one, the lesser of the two MPR’s, contains significant impurities (as this is what would occur if impurities were present – MP would change … dramatically, if large amounts of impurity existed). To rectify this situation, it is important that we put both products through Infrared analysis to get an idea of the chemical structure for each - doing this will give us a clear indication as to which sample is pure, and which is not. On 2/25, we learned that our melting point was not too far from literature values. To validate that we didn't have a product with any impurities we took two additional melting points for each of our samples. For sample one, once again the melting points were good - showing that there were none, or very little impurities in our product. For sample two, similiar results could have been indicated due to the exceptional melting point. However, the second melting point of the two had to be disregarded due to the 30 degree range in the melting point. It was speculated that condensation from another sample could have contributed to the 30 degree difference, rather than the presence of impurities.

**__Diels-Alder Reaction of 2,3-dimethyl-1,3-butadiene & Maleimide (Regular Quant)__** run by Student C + D

We did not get a percent yield because the person writing this results did not remember to do so. However, we did run a melting point check three times. The first time the machine was broken and which we figured out when it reached 150 degrees and nothing had melted. I used the old timey mel temp to take a reading of two tubes. In both tubes, the melting started for one part of the product around 63 degrees. There was a distinctly different second part that started melting at 88 degrees and was completely melted at 98 degrees. This means that most likely the product was not a pure Diels-Alder product. However, it also means that it was not a homolous solution of two things either. This is because the melting temperature did not lower and there were TWO distinctly different parts melting in the capillary tube. It seems that letting the reactants sit in the microwave vessels over the course of a week may have had an effect on the formation of the product. Perhaps the stir bar was not fully able to mix the two layers that formed while being microwaved. Further tests will be run in a future lab to determine the purity of the product.

**__Diels-Alder Reaction of Fumarate & 2,3-dimethyl-1,3-butadiene__** Conducted by Student E + F The total yield of our product came out to 26.34%. Aside from having a low yield, we also encountered some issues testing our product. First, we had a difficult time testing the melting point of our Diels Alder product. It came to our attention that the melting point was exceedingly high, and was taking up a lot of time (unlike previous boiling points where it was rare to go beyond 150o). Then we arrived at our first conclusion that our product was wet and it needed time to dry into a powder. Thus, we placed it in a plastic boat, covered it with plastic wrap, and pierced it with holes. Once it dried we started the test again to find the same melting point of 300 degrees Celsius. Then my partner and I hypothesized: what could be the reason for the high melting point, and what can we do to get rid of this compound? Finally we concluded that there was NaCl in our sample. Unfortunately this meant our sample was impure. Thus, we decided to use the nonpolar solvent, Methylene Chloride to separate the Sodium Chloride out of our product. Then we took this over to the rotary evaporator once more to hopefully separate out the solvents. Since our product was liquid, we moved onto the IR portion of testing and used the AgCl plate test. It came to no surprise that our product showed little peak intensity, this was rather disappointing. But after realizing our mistakes, it came to no surprise that the product appeared to be very concentrated on the graph. Another important detail that shouldn’t be left out is there was too much product put on the plates which no only affected our IR graph, but left us with no more product for the TLC plating. Although, thankfully there was a group who did allow us to try it with theirs so we didn’t miss out!

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