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Synthesis of Phenacetin from para-Acetamidophenol Essay

Experimental: Sodium metal was patted dry to remove any oil and was cat into small pieces. A dry 100cm3 round bottom flask was placed on a cork ring, on a balance and tarred sodium metal (0.6g) was placed into the flask. The flask was then attached to the dry reflux condenser and industrial methylated spirits (IMS, 15cm3) was added. Once all of the sodium has dissolved the solution was cooled to room temperature and the para-acetamidophenol (3.5g) was added. Ethyl iodine (3.0cm3) was slowly introduced to the mixture through the top of the condenser and the resulting in the mixture was boiled at reflux temperature for 20 minutes and was placed in a rotary evaporator to remove any excess solvent. Distilled water (40cm3) was added to the mixture and the flask was placed in ice until crystals were formed. The crude product was filtered using vacuum filtration the filtrates were washed with very little cold water and were left dry as much as possible.

The product was placed in a beaker, and enough aqueous methylated spirit (IMS) was added whilst the mixture was heated to dissolve the product. The mixture was then left to cool and was placed in ice to aid crystallization. The product was vacuum filtrated after a few minutes of standing in ice and the crystals were collected and dried in a vacuum oven at 40 degrees celsius. The mass of the crystals was calculated and the melting point was determined.

Discussion: The percentage yield obtained for the product was 84.33% which generally 65-85% yield is expected and the yield that was obtained for this product is within this range. When the product was filtered, the filtered liquid was still undergoing recrystallisation and this can affect the reduction of percentage yield. As well as that some of the product may remain soluble within the solvent and therefore may not crystallise this will effectively reduce recrystallisation. To ensure complete recrystallisation in the solvent and product the mixture may have to be left for a little longer.

The literal value for melting point of phenacetin is 134-137 degrees celsius. This means that the melting point measured for a product, which is moderately higher than its ranged stated by the literal value. The reason for this could be that there would be impurities within the product of the mixture and insufficient drying. Also in the stated melting point is within the range by 0.15%, which is a small indication of error. As a result it is unlikely this is caused by impurities rather than by inaccurate measurement. Furthermore impurities checks should be undertaken, for example if the product can be mixed with pure phenacetin and change in melting point can be noted and if there is no change. Then the product is pure.

Conclusion: Overall the final crude product weighing 3.50g of phenacetin from the para-acetamidophenol and having a melting point value range of 133.7-134.3 degrees celsius. As this a quite close to the literature value and this means that the product was pretty pure. Also it is a reasonable percentage yield.

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