the microscale techniques of reflux‚ crystallization‚ and melting-point determination were used. Utilizing these techniques a product yield of 93% for benzil and 57% for Benzilic acid was obtained‚ as well as a melting point range of 94.8 – 95.4oC for benzil and 152.0 – 153.9oC for Benzilic acid. With the literature melting-point value of benzil being 95oC ( Pavia‚ 2012)‚ the product was deemed of pure enough quality to be used in the preparation of Benzilic acid. The melting point of Benzilic acid
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Results: Limiting Reactant: Eq 1 Limiting reactant = Benzoin Theoretical yield of Benzil: Eq 2 Theoretical Yield Benzil | 0.296 g | Mass of Crude Benzil | 0.188 g | Mass of Final Benzil | 0.127 g | % Yield | 43% | % Recovery | 66% | Table 1: Mass of crude/final Benzil‚ % yield‚ and % recovery Percent Yield: % Yield = (Final product/Theoretical product) x 100 Eq 3 = (0.127 g/0.296 g) x 100 = 43% yield Percent Recovery
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NaOH was added until the solution turned yellow. After recrystallization‚ the product was benzoin. Step two was the oxidation of benzoin to benzil. Nitric acid was added to the benzoin and heated‚ this was followed by recrystallization to yield the benzil. In step three the benzil from step two was to be synthesized tetraphenylcyclopentadienone. The benzil and 1‚3-diphenylacetone were mixed with ethanol. After heating this‚ ethanoic KOH was added and the solution was left to reflux. The crystals
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forming hydronium. A carbonyl is formed as well as nitrogen dioxide gas. Simultaneously the oxygen separates itself from nitrogen dioxide by pushing its electrons onto the positively charged nitrogen. This forms benzil and nitrogen dioxide gas. The next series of reactions will occur using the benzil product formed and potassium hydroxide. Next‚ there is a nucleophilic
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benzoin. This requires a multistep synthesis with benzyl as an intermediate product. The first step required HNO3 as an oxidizing agent and the second step required KOH and HCl. The percentage yields of benzil and benzilic acid were 59.5% and 21.9% respectively. The calculated melting point of benzil was 90.1-91.6 which suggested some impurities‚ but the MP of benzilic acid was 149.3-151.5 which suggested a pure yield. The IR further confirmed the identity of benzylic acid with two OH peaks and the
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July 17th‚ 2012 Experimental Procedure and Observations: See Attached Pages Data/Results: Measured Weight of Product: 8.577 g benzil Theoretical Weight of Product: 15.765 g benzil Percent Yield: 8.577 g * 100% = 54.4% 15.765 g Melting Point of Intermediate (Benzoin) Melting Point of Product (Benzil) Trial 1 – 129-131°C Trial 2 – 133-135°C Trial 3 – 132-135°C Trial 1 – 92-93°C Trial 2 – 92-94°C Trial 3 – 93-95°C Average Melting
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Benzil is produced in the first step of this experiment’s multistep synthesis through the oxidation of benzoin. In order to produce the desired o-diketone‚ the alcohol on benzoin must be oxidized. Nitric acid was the oxidizing agent used in this experiment. As a result‚ the alcohol group on benzoin acted as the nucleophile and attacked the electrophilic nitrogen of nitric acid. As this step forms oxonium‚ excess water in the system deprotonated the oxonium to restore the neutral charge on oxygen
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The progress of the reaction was monitored in my case using two TLC plate. It first started off with the spotting of Standard benzoin and benzil which were provided in the lab and followed by the addition of the reaction mixture at once it starts changing colour/boiling‚ then at 10 and 20 mins into the reflux. Once all the necessary steps were spotted‚ the TLC plate was placed in in a beaker containing CH₂Cl₂(methylene chloride)‚ which was used as the developing solvent in this experiment. To check
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Preparation In a dry round bottom flask‚ 1.5mL of cyclohexanone was added with 5mL of methanol. The solution was cooled in an ice bath for 3 minutes after which 0.2g of sodium borohydride was measured and added to the solution. Upon mixing‚ a gas was formed (bubbles). The round bottom flask was removed from the ice bath and placed at room temperature. After 10 minutes at room temperature‚ 5.0mL of 3M NaOH and 2.0mL of distilled water was added to the solution. Isolation and Characterization The
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point 99 Grainy yellow Becoming all liquid 101 Clear 2nd trial Temperature (¡ÆC) Observation Unmelted Shiny light yellow crystal First liquid appear point 95 Grainy yellow Becoming all liquid 97 Clear C. Melting point of mixture (Unknown + Benzil) Temperature (¡ÆC) Observation Unmelted Shiny light yellow crystal First liquid appear point 95 Grainy yellow Becoming all liquid 97 Clear ¥±. Discussion of results Assessment of sample purity for a known substance. By comparing observed range
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