Gas+Chromatograph+Lab

=Gas Chromatography Lab= =Introduction:= The purpose of this laboratory is to familiarize students with the form of Gas Chromatography, which is a method used by separation of substances. The process of gas chromatography is when a mixture is sent through the chromatography system and the different components in the mixture are then separated during this process.Another common use of this type of procedure is to identify purities of particular substances or it can be used to identify a compound.

Introduce the reaction here: the elimination, and what Zaitsev's rule predicts about products. If I read the conclusion that is what you are addressing there....but it's absent from your intro.

Procedure: The procedure for obtaining a gas chromatography analysis is very simple once the machine is warmed up and adjusted correctly. Simply draw up a sample of your material and inject it through the septum into the machine. The sample is swept up in a stream of an inert gas, in this case helium and then the gas is heated to the boiling point. The lower the boiling point of the individual samples the sooner they will be conveyed to the detector before exiting the machine. The data is then conveyed to a paper recording for later analysis.

Data:

Analysis: The graph showed two peeks that differentiating two different substances. The two substances were present in the sample material provided. The peaks represent the difference in boiling points of the two substances. The size of the peaks correlated to the volume of material present in the sample. The tracing was cut out and weighed. The two peaks were weighed individually and the percentage calculated. Nicely explained.

calculations okay--but you need to watch sig figs! Conclusion: The starting material for the elimination reaction performed by the professor was 2-Methyl-2-pentanol. First it is important to determine the type of elimination reaction to then predict the products. The only information given was the addition of heat and that hydronium was used. The other information derived from the starting sample. The leaving group in this reaction is a 3° carbon. The conjugate base of hydronium is water, a very poor base. Hydronium is a polar protic solvent. And hydroxyl is a very poor nucleophile. The information leads to the determination that the reaction is E1 elimination. Steric hindrance and a poor nucleophile are the most compelling evidence. Knowing the reaction method then leads to an understanding of the products. Two products are possible differentiated by the instantaneous stability of the carbocation and the potential energy of the product. 2-Methyl-2-Butene and 2-Methyl-1-Butene are both possible products. The first product is lower in PE and more stable in formation. //Zaitsev’s Rule// confirms that the product should be predominately 2-Methyl-2-Butene. There will however be a small portion of 2-Methyl-1-Butene produced and the data confirms this. In this chromatography experiment 6.67% was the lesser substituted product.
 * Substance Cutout ||= Weight (grams) ||= Percentage ||
 * Total Sample ||= 0.045 g ||= 100% ||
 * Large Peak ||= 0.003 g ||= 93.34% ||
 * Small Peak ||= 0.042 g ||= 6.67% ||

All the things you say here are true, but you have not told me HOW you know that the first peak is the 2-Methyl-1-butene. That's a critical piece of information.

Room for error can occur when inserting the substance in to the chromatography with the micro syringe possibly not inserting syringe completely may cause loss of inserted substance. Obvious error can be when weighing out the graph cutting out the peaks can vary the substance by a little error.

What might have occurred during the reaction, that could skew your results? =Post-lab Questions:= 1) Utilizing the Gas Chromatography is great for smaller components, but when is it useful to use factional distillation instead of the microscale? 2)When is it necessary to use other parameters such as altering the order or time of retention or the carrier gas flow rate, column length and the temperature? Or does it depend on the strength of the absorbent in components used. =Reference:= Higginbotham, Carol. Procedure: Gas Chromatography, Central Oregon Community College CH-242/335 Organic Chemistry II, Winter Term 2012