Iodination+of+Vanillin

=Iodination of Vanillin=

Introduction:
This lab involves an electrophillic aromatic subtitution reaction. The mechanism carried out is a two-step Elimination (E1) mechanism, where the //pi// bond attacks the electrophile and creates a cationic aromatic ring. This allows the leaving group (hydrogen) to pop off, leaving behind it's electrons to reform the aromatic ring. To make this experiment possible, and safe, the reaction uses sodium iodide and NaOCl (bleach) in aqueous ethanol solution. I sure would like to see the reaction that is drawn below moved up here.

Procedure:
To begin add 1.0g of vanillin with 20ml of ethanol to a 100ml round bottom flask with a magnetic stir bar. Mix the solution until the vanillin is dissolved in the ethanol and then add 1.17g of sodium iodide. Mix the solution a bit and then place the flask into an ice bath for five minutes. Next gather 11ml of sodium hypochlorite in into a separatory funnel. Stir the mixture while adding the sodium hypochlorite dropwise for 10 min. After the addition allow the mixture to reach room temperature for about 10 min while continuing to stir. Once at room temperature 10ml of sodium thiosulfate is added and mixed into the mixture.The solution needs to be acidic so add HCl slowly while monitoring the pH with test strips and a precipitate should form on the bottom. Next remove the ethanol from the solution using a rotary evaporator. After about 5min of evaporation remove the solution and set it into a ice bath to cool down for 5min. Collect the precipitate using vacuum filtration. During the filtration wash the precipitate with some water and a small amount of cold ethanol. Scrape the crude product onto a dry filtration paper and sandwich it with another filtration paper to make sure that it is completely dry and weigh the crude product. Next add the crude product to a 150ml erlenmeyer flask. While heating and stirring use just enough 2-propanol to dissolve most of the crude product (about 20ml), then add water until the solution becomes cloudy (about 30ml) and then add enough 2-propanol to bring it back to clearish yellow (about 10ml). Let the solution cool for 5 minutes at room temperature and then let it sit in an ice bath for an additional 5min. Use vacuum filtration again to gather the final product. Measure the weight and the melting point of the final purified product.

Cite the source of this procedure--as the Doxsee and Hutchison book. A citation is required even when you paraphrase.

Data:

 * Reaction at hand**:
 * Starting Amount**: 2.17 grams Vanillin ( 1 gram 4-hydroxyacetophenone and 1.17 grams sodium iodide.) Sig figs! There should be another digit here!!


 * Observations:**
 * After sodium hypochlorite was added to the Vanillin, the solution in the flask turned a creamy, light brown color.
 * A milky precipitation occurred after the sodium thiosulfate and HCl was added to the solution:
 * During the recrystallization stage, the amount of 2-propanol and hot water used wasn't enough to dissolve the crude product. Once the crude product was partially dissolved and had a clear, yet colored appearance, it was given an ice bath and then filtrated.


 * Product Characteristics**: Off white, flaky substance. Slightly damp. Similar to a "bowl of tiny paint chips." An apt description! I saw them and I would agree.

Results:

 * Crude Product Mass:** From the first vacuum filtration, we received **3.36g** of crude aryl iodide.


 * Theoretical Yield:** 2.17g Vanillin X 1 mol/152 g (molecular weight) = 0.014 mol Vanillin

0.014 mol Vanillin X 278 g Mol. Weight IodoVanillin/ 1 mol = **3.96 gram (Theo. Yield)** Following the Sig Figs rules is required to get all the possible points for your lab. They're not too hard! You should talk with me if you are going to rewrite!
 * % Yield of Crude Product:** 3.36 gram Crude Product / 3.96 g (T.Y) X 100% = **84.8%**
 * Recovered Recrystallized Product: 0.57 g**
 * % Yield Of Pure Recrystallized Product:** 0.57 g Pure / 3.96 g (T.Y) X 100% = **14.4%**


 * % Recoveries:**


 * **Crude Product:** 3.36g/2.17g (start) X 100% = **155%**


 * **Pure Product**: 0.57g / 2.17 g X 100% = **26.3%**

**Melting Point:** 176.6-178.7 degrees Celsius

The purpose of this lab was to create a pure re-crystalized product of 5-iodovanillin by means of an electrophilic aromatic substitution reaction. The percent yield of the crude product was a solid 84.8%. The percent recovery was 155%. The reason that the percent recovery is above 100% is that iodine is added, and when the iodine reacts with the vanillin, it attaches itself to the ring, therefore making a much heavier substance. But wait! This is factored into the calculations, so it should not cause you to get over 100%. The percent yield of our final pure product was 14.4%, with a 26.3% recovery. Compared to the other groups in lab, these results were not horrible considering many of the groups were only able to get a tiny portion of the pure product, if any at all. Still, our percent yield was lower than it should be due to a few mistakes during the lab process (see errors). The melting point of our final product was 176.6-178.7 degrees Celsius. It was slightly lower than the literature values in the procedure (183-185). This is most likely due to a few impurities that still remained in the final product. Keep your language formal and impersonal. Avoid "our" and "their," etc.. Also, avoid judgments, like "these results were not horrible..."
 * Conclusion:**

Errors:
Not enough solvent was used to dissolve the crude product. The procedure said to add more solvent until the solution was colored, but clear. This step was rushed a bit, leading to not all of the crude product being dissolved. When scraping product off of the filtration paper, some of the paper would stick to the product as it got scraped off. We tried to get as much of the paper out as we could, but it still might have had an effect of the results. Also, there was always a bit of product that we were unable to scrape off of the paper.

Review the Guide to writing a good lab report (in Blackboard) if you want additional info on what I require, for style.