Gas+Chromatography+Lab

Gas Chromatography is a separation method that separates a mixture, detects its components and records each component based on its boiling point. As the sample is injected into the machine, Helium gas carries it along the chromatography column, which is made of special material that allows the separation to initiate based on the different substance's boiling points. Those components with lower boiling points make it through the column quicker than those with a higher boiling point. Once the components make it through the column and pass the detector, they are recorded on a plot-curve by a strip-chart recorder. Gas Chromatography is used in a variety of ways on a large scale. It is used medically to separte and identify substances in blood and used to examine environmental substances, as well.
 * Introduction**:

All true: I would also like to have some discussion of Zaitsev's rule here, in the Introduction, and how it relates to the lab we are doing. While there are important lessons about gas chromatography this week there are also lessons about elimination reactions.

Each lab group will come in one by one, based on the order of the names on the chalk board. Once there, each group examine the Gas Chromatography machine and receive an overview of its functions by the professor. Then, using a syringe and needle, inject 2 microliters of the sample into the injection port. The Helium gas that is continually being pumped through the machine will carrry the sample and its components through the chromatography process. Once the sample has completely made it though, take the plot-curve that was drawn by the recorder. Cut from it the baseline of the graph, and the two curves that represent the Zaitsev and Hoffman products from the sample. Weigh each curve and record the weight. Also, weigh both curves together and record the total of the two. Take each individual curve weight and divide it by the total weight. Finally, identify which curve represents which product (Zaitsev or Hoffman) and find the percentage of each in the products. Compare results with others groups.
 * Procedure:**
 * Data/Observations:**

Thank you for including the reaction in your report. Note, however, that the second product you show (2-pentene) is not a product of this reaction.

Above is the reaction and the different products that were present in the sample used for this experiment. Zaitsv's product is the last one on the right. Yep, it is!

The product was injected into the injection port and the strip-recorder was turned on precisely at the same time.

The sample made it through the Gas Chromatographer machine in less than 5 minutes.

The curve drawn on the paper was a bit light and slightly difficult to identify. Each prodcut curve was cut slowly with precision. Only the initial (smaller) peak and the second (bigger) peak were cut out. The short stubby peaks that came after were just H2O, which was ignored.

Where is your chromatogram? I want to see it! It's important data.

First/Lowest Boiling Point Curve Weight: 0.008 g Second/Higher Boiling Point Weight: 0.049 g 0.008 / 0.057 x 100 = 14.0% 0.049 / 0.057 x 100 = 86.0%
 * Results:**
 * Total: 0.057g**

calculations are okay, although you have reported your percentages with too many digits (sig figs)

A higher proportion of the Zaitsev product was formed because it is the most favorable solution. This product is lower in potential energy, and is the most substituted alkene product in the mixture. To be exact, the Zaitsev product in this experiemnt (2-methylpropene) is tri-substituted while the other product (2-methyl-1-propene) is only mono-substituted. Zaitsev's rule says that in a reaction, the most substituted alkene product will dominate the product mixture. We know that is is a Zaitsev product (and not Hoffman) because E1 reactions always obey Zaitsev's rule. We know this is an E1 reaction because H3O+ is a weak base.
 * Discussion:**

There is a gap in your description. Please include the melting points of the two products that form in this reaction, with a citation to the source where you find those melting points. That information is necessary in order to draw the conclusion that the Zaitsev product is, in fact, the one that is present in greater quantity.

After the chromotography, we noticed our graph seemed to be missing some of the peak. The gas chromatogrpher's pen went dry for s couple of seconds and did not mark the whole peak. We were able to trace where we thought it had gone based on a very slight imprint from the pen, but it was not perfect. We most likely cut to small of a piece, which would lead to a skewed proportion. If the pen had not gone out, the proportion of the Zaitsev product would have been higher than 86.0%.
 * Error:**