Electrophilic Aromatic Iodination of Vanillin

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Electrophilic Aromatic Iodination of Vanillin


The purpose of this laboratory experiment is for an aromatic compound to undergo an electrophilic substitution reaction. To carry this out, our method combines sodium iodide and common bleach as the oxidizing agent in aqueous alcohol as the solvent.

Balanced Chemical Equations:

Physical Properties:

Name of ChemicalChemical StructureMolar Mass (g/mol)BP/MP (ºC)Density (g/mL)Mass/Vol. UsedPurpose 3-methoxy-4-hydroxybenzaldehyeC8H8O3152.1494MP=81-83, BP=285NA0.1gSolute EthanolCH3CH2OH46.0688MP=-114.1, BP=78.30.7892.0mLSolvent Sodium IodideNaI149.8943MP=661, BP=13003.6670.117gCatalyst BleachNaOCl74.4422MP=NA, BP=40dec1.2091.1mLOxidizing Agent Sodium ThiosulfateNa2O3S2158.0977NA1.6671.0mLExtraction Hydrochloric AcidHCl36.4609MP=-114.2, BP=-85.10.9090.6mLAcid Agent Limiting Reagent and Theoretical Yield:

(0.1g Vanillin/152g/mol) = 6.58 x 10^-4 mol Vanillin  Limiting Reagent

(0.117g NaI/150g/mol) = 7.8 x 10^-4 mol NaI

Theoretical Yield:
(6.58 x 10^-4 mol Vanillin/1)(279g/mol)  0.18g product


In an Erlenmeyer flask (or beaker), dissolve ~ 0.1 g of 3-methoxy-4-hydroxybenzaldehyde in 2.0 mL of ethanol. Cool the flask in an ice bath for a few minutes. To the ice-cold solution, add 0.117 g of sodium iodide. Over a period of 10 minutes, add 1.1 mL of Bleach (5.25% w/w NaOCl) dropwise to the cooled flask. The solution should turn a yellow color. Once the addition is complete, let the solution warm to room temperature and stir for about 10 minutes.

Stir the solution gently, and then add ~ 1 mL of sodium thiosulfate (10% w/w). The solution will turn a cloudy, grayish yellow. Acidify the solution with 3.2 M HCl, using pH paper to check the acidity of the solution (it will take approximately 0.6 mL of added HCl). Gently evaporate any excess ethanol. (Apply gentle heat only if necessary). Cool in an ice bath for about...
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