Electrophilic Aromatic Iodination Of Vanillin
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Electrophilic Aromatic Iodination of Vanillin
Purpose:
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 Chemical
Chemical Structure
Molar Mass (g/mol)
BP/MP (ÐÑ”C)
Density (g/mL)
Mass/Vol. Used
Purpose
3-methoxy-4-hydroxybenzaldehye
C8H8O3
152.1494
MP=81-83, BP=285
Solute
Ethanol
CH3CH2OH
46.0688
MP=-114.1, BP=78.3
0.789
2.0mL
Solvent
Sodium Iodide
149.8943
MP=661, BP=1300
3.667
0.117g
Catalyst
Bleach
NaOCl
74.4422
MP=NA, BP=40dec
1.209
1.1mL
Oxidizing Agent
Sodium Thiosulfate
Na2O3S2
158.0977
1.667
1.0mL
Extraction
Hydrochloric Acid
36.4609
MP=-114.2, BP=-85.1
0.909
0.6mL
Acid 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
Procedure:
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 10 minutes, and then collect the precipitate by vacuum filtration. Wash the crystals well with ice-cold water. Recrystallize the crude aryl iodide from isopropanol. Place in an ice bath and collect the crystals by vacuum filtration.
Determine the weight of your crystals, determine the melting point, and take an IR spectrum. As always, analyze your data by comparing your values to literature values.
Cleaning Up: Place all waste in the appropriate waste container.
Results:
After the addition of hydrochloric acid, the solution solidified slightly to a thick, white, slushy material. This material was then cooled in an ice bath for approximately ten minutes, and then the crystals were collected via vacuum filtration. Once the crystals were collected, the product was recrystallized from isopropanol. This process required the heating of the crystals with isopropanol as the solvent, cooling to room temperature, sit in an ice bath for a few minutes, and collect the final crystals through vacuum filtration once again. This final product is the wanted iodovanillin.
Wt. of Vanillin
Wt. of Sodium Iodide
Wt. of Iodovanillin crystals
MP of Iodovanillin
pH after HCl addition
0.1035g
0.1171g
0.061g
183.8ÐÑ”C
Calculations:
Theoretical Yield: (See above for limiting reagent info.)
(6.58