ochem lab Column and Thin Layer Chromatography

Discussion the results for the first fraction were

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Discussion: The results for the first fraction were very good being that the percent error was only that 1.1%. The reason for the small error was that it was the first eluent to come through and the yellow band was distinctive when moving down the column. This allowed for the stopcock to be closed at the precise time. The results for the second fraction also had a small percent error of 4.3%. The small error was also most likely due to the precise closing of the stopcock. The last
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fraction’s results had an extremely high percent error, that being 88.0%. The high percent error could have been due to not closing the stopcock at the proper time or because extra 9:1 hexane/acetone solution was poured into the column to wash the excess of the spinach extract off of the sides. Also when the TLC plate was placed in the chamber it was put in a bit sideways which caused most of the dots to shift to the right. This is defiantly a source of error. The first of the eluents to leave the column first was that of the one containing the lowest polarity or nonpolar. The last eluent to leave the column is that of the one having the highest polarity. This is because the mobile phase first consisted of a nonpolar hexane/ acetone solution, and since the elution order is based upon the polarities of the eluent and the solvent matching the first two eluents can be assumed to be nonpolar. The opposite can be true for the third collected eluent. The solvent was switched to that of polar methanol, which was done to separate the last polar eluent due to the matching polarities. Evidence for supporting this conclusion can also be seen in the TLC part of the experiment. The backing for the TLC plate is that of silica gel (absorbent) which is a polar compound. The solvent which was used to develop the TLC chamber (30% ethylacetate in hexanes) was nonpolar. Since the solvent was nonpolar, the first two collected eluent samples will dissolve in the solvent due to the fact that they are also nonpolar and like dissolves like. This then causes the first two collected eluent samples not to absorb to the polar absorbent of silica gel, causing them to move further away from the origin line and farther up the plate. The last polar collected eluent will absorb to the stationary polar silica gel causing it to not move as far away from the origin line. Simply stated the less polar the dots are the farther up the plate they will move, and the more polar the dots the closer they will be to the origin line. Therefore when examining the TLC plate the above logic in the column
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chromatography is well supported by the movement of the dots. Also the observations of the different colored bands were due to different components being present in the spinach extract. Reference: 1 Huston, Ericka, and Chong Liu. Organic Chemistry 1 Laboratory Manual. Plymouth: Hayden McNeil, 2011. Print. Integrity Statement: I submit this lab report as an original document. I assert that all ideas and discussions of data contained herein is my own work, unless otherwise referenced.
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