Extended Essays 2021

Table #1: Modifications to the Methyl Synthesis & Refinement

Vogel’s methodology

Modifications in my methodology (Appendix #6)

Duration of reflux - kept constant at 5 hours Use of carbon tetrachloride to aid in separation of aqueous layer and methyl salicylate after the reflux Use of Bunsen burner to evaporate excess methanol after the reflux Power of the heating mantle not specified;

For an independent variable, duration of reflux was varied for one, two, three and four hours, as well as the original five. As carbon tetrachloride was inaccessible to a school laboratory, this step was ignored. Consequently, the use of sodium hydrogen carbonate (which would have ended the production of carbon dioxide from the carbon tetrachloride) and the distillation step to remove any excess the carbon tetrachloride after filtration was also removed. Ensuring the methanol would not be burnt during evaporation, the hot plate was used instead of the Bunsen burner. To reduce loss of methanol vapor or the breaking of the condenser f rom the ‘spitting’ of overheated liquid, porcelain chips were placed at the opening of the condenser and the power (voltage) of the heating mantle was kept low at 100V.

porcelain chips not placed in condenser

The method for determination of the ferric chloride calibration curve, published by the Journal

of Applied Pharmaceutical Science (Vol.4), was amended to suit the parameters of the experiment.

Table #2: Modifications to the Ferric Chloride & Methyl Salicylate Calibration Curve

Journal of Applied Pharmaceutical Science method

Modifications to the methodology (Appendix #4 & #7)

Concentration of methyl salicylate were 12, 24, 36, 48 60 & 72 / 3 from Volitra gel (10% of the compound) Preparation and use of 1% ferric chloride solution

As pure methyl salicylate was used in this experiment to produce the calibration curve, 10, 20, 30, 40 & 50% dilutions were created instead.

concentrations of methyl salicylate used in this experiment were higher than in the original method. Hence the concentration of the ferric chloride solution was reduced to 0.01% in aim to dilute the final purple color of the solution for clearer variation. Through trial and error, it was found that the polystyrene cuvettes would weaken and crack due to its high solubility in esters (methyl salicylate) and alcohols (ethanol) 16 . Hence, glass cuvettes were used.

Material of cuvette for absorbance measurement not specified

16 (Bangs Laboratories, Inc., 2015)

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