Iodination of Vanillin lab report

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Francis Marion University *

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Chemistry

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Feb 20, 2024

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1 Iodination of Vanillin Lab Report Introduction This lab involved a reaction called Electrophilic aromatic substitution. Electrophilic aromatic substitution reactions are when an electrophile reacts with an aromatic ring and substitutes for one of the hydrogens on the ring. This process occurs in two steps, through addition/elimination mechanisms. First, the electrophilic reagent attacks the pi bond electrons and adds to the ring forming a cationic intermediate. Next, the intermediate eliminates a group to form the substituted product. Where the substitution occurs depends on what’s already on the ring and this is known directing affect, as it “directs” the electrophilic group to its position. The three possible positions where the substituent can occur are ortho, meta, or para relative to the substituent already on the ring. Substituents can either be activating or deactivating. Ortho/para directors are activating groups and increases or speeds up the rate of the reaction. The unshared pairs of electrons add more density to the ring making the resonance effect stronger than the inductive effect and making the substituents strong activators. A meta director is a deactivating group and decreases or slows down the rate of the reaction. The deactivating groups work by using the inductive effect to withdraw electron density away from the ring. Vanillin is different when it comes to Electrophilic aromatic substitution due to the three functional groups that are attached to the ring. With there being three different groups attached (− OH , − OCH 3 , − CHO ) , it leaves only 2 positions that are available for the substituents. The three functional groups all influence the reaction and where they are placed. The -CHO is a deactivating group, -OH and − OCH 3 are both activating combining to make the reaction occur at a fast rate. The aldehyde is the meta-directing group, and it directs the Iodine cation two positions away on the ring. The remaining are ortho/para, and they direct the Iodine cation to positions that are adjacent or across the ring from them. With this information I predict that the iodine will be placed on position number two due to the fact that the activating groups and deactivating groups are working against each other, and the activating group would be the one directing the position due to the group being stronger. The experimental process was quite simple, and although the activating group did speed up the process, it wasn’t as fast as other experiments. Experimental To begin this experiment, we placed 0.50g of vanillin, 0.55g of potassium iodide, and 4 mL of distilled water in a 25 mL round-bottom flask. We then assemble the separatory setup. We placed the flask onto a hotplate and dissolved 1.05g of Oxone in 4 mL of distilled water that was added dropwise over a period of 5 minutes to the vanillin solution. The separatory funnel was

then replaced with the condenser and the heat of the hotplate was turned up to reflux for an hour. Once finished, the heat was turned off to cool the solution, and the condenser was rinsed with 10 mL of distilled water to rinse it. The solution was then tested with starch-iodine paper to test for the presence of the access oxidizing agent. If some was present, small amount of sodium bisulfate was added to get rid of the excess oxidizing agent, until none is present. We then performed suction filtration to dry the product, so that we could get the melting point. Once dried through suction filtration the product is then dried one last time using a towel to be sure that it is completely dry. We weighed the product and determined the melting point to identify the product. Results Table 1. Stoichiometry Vanillin KI Oxone (2, 5 ,or 6)-iodovanillin Structural formula C8H8O3 C8H7IO3 Molar mass 152.15 166.0 152 20 278.04 Grams 0.50g 0.55g Theoretical Yield in moles: 0.003mol Moles 0.003mol 0.0033mol Theoretical Yield in grams: 0.83g Calculations for theoretical yield: Ratio: 1/1 1 mol *0.003mol of vanillin = 0.003mol of Iodovanillin O .003 mol× 278.04 g / mol 1 mol = 0.834 g of 5 − iodovanillin Table 2.Summary of results Observed Melting Point Range (°C) Literature Melting Point Range (°C) Yield (g) Percent Yield (%) 179-181 183-185 0.83g 42.17% Percent yield calculations: ( 0.35 × 0.83 ) × 100 = 42.17% Discussion Figure 1. 5-Iodovanillin

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