Nitric acid oxidation PDF

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del tech orgo lab experiment 19...

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Alicia warner 10/15/2020 Chem 241

Title: Oxidation of Benzoin into Benzil Purpose: Prepare Benzil from Benzoin through Nitric Acid Oxidation Data/results: weight of Benzoin from previous lab was 1.851 grams Weight given by the professor 2.176 grams for a total of 4.027 grams of Benzoin Weight of glass and benzoin from previous lab 78.8709 Melting point of benzoic 132.0-133.4C After adding an initial 25 ml of NaOH an additional 10 mL needed to be added. Filter paper weight 0.094 grams Pre weighed on beaker 77.134 grams Beaker with crystals weight 112.942 Melting point of product 114.6C 4.027(1/212.24)(1/1)(210.23/1)=3.988 Theoretical yield: 3.988 grams (3.5808/3.988)(100)=89.789 Percent yield: 89.789% Percent error: 10.21% The product was a sharp needle like structure, that was a very faint yellow color and hard especially after the vacuum filtration. Procedure: To begin the experiment 4 grams of Benzoin from the previous lab must be weighed out and added to a 250 mL Erlenmeyer flask. This flask was then taken to a hood where if was combined slowly with 14 ml of nitric acid. When all 14 ml are added the flask is added to a boiling bath for about 10 or more minutes, when the time is completed the flask is removed from the boiling water, add 75 ml of water to the flask swirl until there is no longer any brown oxide fumes being released. After this was complete 25 ml of NaOH was added until the solution was above a ph of 10. To end the experiment put the mixture in an ice bath for a few minutes then collected through vacuum filtration. When the product is dry, find the melting point.

Alicia warner 10/15/2020 Chem 241

Post lab questions: 1. The difference between the benzoin and benzil would be that in benzoin oh is present and c=0 is absent on one of the carbons and it is in the reverse fir benzil. c=o is present and oh is absent. So the major difference would be the oh bond. In benzoin, due to the oh bond, there would be a peak at around 3400- 3500 in IR spectra, in the case of benzil there is no peak at 3400-3500 because of the lack of present oh bond. 2. A conjugated system is a system of connected p orbitals with delocalized electrons in molecules with alternating single and multiple bonds, which in general may lower the overall energy of the molecule and increase stability. Lone pairs, radicals, or carbenium ions may be part of the system. The compound may be cyclic, acyclic, linear, or mixed. 3. In benzoin, only 5 carbons are involved in extended conjugation, in benzil total 5 carbons are involved in extended conjugated from each phenyl ring, so a total of 10 carbons.

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Conclusion:

Alicia warner 10/15/2020 Chem 241

The purpose of the experiment was to be able to use nitric acid as an oxidizing agent to convert benzoin into benzil and determine a percent yield, and melting point from the product that was left behind. In the completion of the experiment and doing the calculations based off of the results that were observed the percent yield calculated was 89.789% the theoretical yield was 3.988 and the percent error was 10.20% The product that was left behind after vacuum filtration was a light yellow needle like crystalline structure that was very dry and hard. The melting point observed during the experiment for the benzil product was 114.6 C which is very high, when comparing to online sources of melting points of benzil which are around 94 to 95C this could be due to left over additives in the beakers that mixed with the product making it impure and causing the melting point to be higher than it normally should be. Although the percent yield that was calculated was noot extremely low there could have been potential errors that may have been avoided that would have made a better percent yield and a lower percent error such as in the case of, heating the ethanol and dissolving the clumps of crystals, some of the product that was not completely dissolved was lost and not calculated in the percent yield making a possibly small difference but a difference nonetheless. In the future to insure the most product is being used and analyzed i would ensure that all of the product is uniformly dissolved and properly vacuum filtered....