Lab+5+-+Electrophilic+Aromatic+Iodination

Electrophilic Aromatic Iodination __**﻿**__ __Introduction __ The experiment conducted, dealing with an electrophilic aromatic two step addition-elimination of 4'-Hydroxyacetophenone, implements Green Chemistry through use of greener regents and solvents. Green Chemistry provides many ways to reduce the amount and toxicity of by-products and solvents, the design of less hazardous chemical syntheses and includes implementation of safer reaction conditions. This experiment in particular offers more environmentally friendly reaction conditions by use of NaOCl instead of nitric acid as the oxidizing agent, and ethanol as a mild solvent. Also, the use of sodium iodide was considered over the use of either chlorine or bromine due to their hazardous nature.

During the electrophilic aromatic iodination of 4‘-hydroxyacetophenone, the reaction occurs as a two step elimination reaction pi bonded elections in the cyclic aromatic ring attack the electrophilic reagent (Vanillin being the aromatic ring and Sodium Iodide being the electrophilic reagent in this experiment) creating a Meisenheimer complex which is defined as the reaction between a benzine ring and an electrophile that generates a cation intermediate. This Meisenheimer complex then forms the substituted product. In this experiment the final substituted product was Iodovanillin.



__Procedure __

The procedure for this experiment can be found at University of Oregon's Greener Education Materials for Chemists.

Chemicals used in the lab:


 * Name: Vanillin
 * IUPAC Name: 4-Hydroxy-3-methodybenaldehyde
 * CAS #: 121-33-5
 * Molecular Formula: C 8 H ﻿ 8 O 3
 * Compound Formula: C 8 <span style="font-family: Verdana,Geneva,sans-serif;">H ﻿ 8 <span style="font-family: Verdana,Geneva,sans-serif;">O 3
 * <span style="font-family: Verdana,Geneva,sans-serif;">Structure:
 * <span style="font-family: Verdana,Geneva,sans-serif; font-size: 150%;">[[image:Vanillin.png width="127" height="157"]]


 * <span style="font-family: Verdana,Geneva,sans-serif;">Name: Sodium Iodide
 * <span style="font-family: Verdana,Geneva,sans-serif;">IUPAC Name: Sodium Iodide
 * <span style="font-family: Verdana,Geneva,sans-serif;">CAS #: 7681-82-5
 * <span style="font-family: Verdana,Geneva,sans-serif;">Molecular Formula: NaI
 * <span style="font-family: Verdana,Geneva,sans-serif;">Compound Formula: NaI
 * <span style="font-family: Verdana,Geneva,sans-serif;">Structure:
 * <span style="font-family: Verdana,Geneva,sans-serif; font-size: 150%;">[[image:SodiumIodide.gif width="40" height="28"]]


 * <span style="font-family: Verdana,Geneva,sans-serif;">Name: Ethanol
 * <span style="font-family: Verdana,Geneva,sans-serif;">IUPAC Name: Ethanol
 * <span style="font-family: Verdana,Geneva,sans-serif;">CAS #: 64-17-5
 * <span style="font-family: Verdana,Geneva,sans-serif;">Molecular Formula: C <span style="font-family: Verdana,Geneva,sans-serif; font-size: 10px; vertical-align: sub;">2 <span style="font-family: Verdana,Geneva,sans-serif;">H ﻿ 6 <span style="font-family: Verdana,Geneva,sans-serif;">O
 * <span style="font-family: Verdana,Geneva,sans-serif;">Compound Formula: C <span style="font-family: Verdana,Geneva,sans-serif; font-size: 10px; vertical-align: sub;">2 <span style="font-family: Verdana,Geneva,sans-serif;">H ﻿ 6 <span style="font-family: Verdana,Geneva,sans-serif;">O
 * <span style="font-family: Verdana,Geneva,sans-serif;">Structure:
 * [[image:Ethanol.png width="128" height="76"]]


 * <span style="font-family: Verdana,Geneva,sans-serif;">Name: Sodium Hypochlorite
 * <span style="font-family: Verdana,Geneva,sans-serif;">IUPAC Name: Sodium Hypochlorite
 * <span style="font-family: Verdana,Geneva,sans-serif;">CAS #: 7681-52-9
 * <span style="font-family: Verdana,Geneva,sans-serif;">Molecular Formula: CaClO
 * <span style="font-family: Verdana,Geneva,sans-serif;">Compound Formula: CaClO
 * <span style="font-family: Verdana,Geneva,sans-serif;">Structure:
 * [[image:Sodium_hypochlorite.gif width="126" height="77"]]


 * <span style="font-family: Verdana,Geneva,sans-serif;">Name: Sodium Thiosulfate
 * <span style="font-family: Verdana,Geneva,sans-serif;">IUPAC Name: Sodium Thiosulfate
 * <span style="font-family: Verdana,Geneva,sans-serif;">CAS #: 7772-98-7
 * <span style="font-family: Verdana,Geneva,sans-serif;">Molecular Formula: Na <span style="font-family: Verdana,Geneva,sans-serif; font-size: 10px; vertical-align: sub;">2 <span style="font-family: Verdana,Geneva,sans-serif;">S 2 <span style="font-family: Verdana,Geneva,sans-serif;">O 3
 * <span style="font-family: Verdana,Geneva,sans-serif;">Compound Formula: Na <span style="font-family: Verdana,Geneva,sans-serif; font-size: 10px; vertical-align: sub;">2 <span style="font-family: Verdana,Geneva,sans-serif;">S ﻿ 2 <span style="font-family: Verdana,Geneva,sans-serif;">O 3
 * <span style="font-family: Verdana,Geneva,sans-serif;">Structure:
 * <span style="font-family: Verdana,Geneva,sans-serif;">[[image:Sodium-thiosulfate.png width="130" height="102"]]

__<span style="font-family: Verdana,Geneva,sans-serif; font-size: 150%;">Data __
 * <span style="font-family: Verdana,Geneva,sans-serif;">Reagents
 * <span style="font-family: Verdana,Geneva,sans-serif;">Vanillin: 1.049 g
 * <span style="font-family: Verdana,Geneva,sans-serif;">Sodium iodide: 1.207 g
 * <span style="font-family: Verdana,Geneva,sans-serif;">Sodium hyperchlorite: 11 mL
 * <span style="font-family: Verdana,Geneva,sans-serif;">Ethanol: 20 mL <span style="color: #800000; font-family: Verdana,Geneva,sans-serif;"> put a decimal after the zero if you want to make it clear that it is a significant digit.
 * <span style="font-family: Verdana,Geneva,sans-serif;">Products
 * <span style="font-family: Verdana,Geneva,sans-serif;">Light tan crystals: 0.024 g
 * <span style="font-family: Verdana,Geneva,sans-serif;">Observations
 * <span style="font-family: Verdana,Geneva,sans-serif;">During the addition of sodium iodide, color slowly changed to a tawny pigment.
 * <span style="font-family: Verdana,Geneva,sans-serif;">The addition of sodium hypochlorite changed the color to a deep russet hue.
 * <span style="font-family: Verdana,Geneva,sans-serif;">The addition of HCl led to a chunky white precipitate in the solution.
 * <span style="font-family: Verdana,Geneva,sans-serif;">As HCl was added, color changed to an olive green and the liquid became more viscous.
 * <span style="font-family: Verdana,Geneva,sans-serif;">During the melting point test, the product turned dark brown and shriveled into a smaller bead at around 148°C, and stayed in that state until it melted.
 * <span style="font-family: Verdana,Geneva,sans-serif;">Melting Point
 * <span style="font-family: Verdana,Geneva,sans-serif;">Decomposition: 148°C
 * <span style="font-family: Verdana,Geneva,sans-serif;">Onset: 158°C
 * <span style="font-family: Verdana,Geneva,sans-serif;">Clear Point: 161°C

__<span style="font-family: Verdana,Geneva,sans-serif; font-size: 150%;">Analysis __




 * <span style="font-family: Arial,Helvetica,sans-serif;">Name: Iodovanillin
 * <span style="font-family: Arial,Helvetica,sans-serif;">Alternate Name: 5-iodovanillin
 * <span style="font-family: Arial,Helvetica,sans-serif;">IUPAC Name: 4-Hydroxy-5-iodo-3-methoxybenzaldehyde semicarbazone
 * <span style="font-family: Arial,Helvetica,sans-serif;">CAS #:5438-36-8 (unlisted)
 * <span style="font-family: Arial,Helvetica,sans-serif;">Molecular Formula: <span style="font-family: Verdana,Geneva,sans-serif;">C <span style="font-family: Verdana,Geneva,sans-serif; font-size: 10px; vertical-align: sub;">8 <span style="font-family: Verdana,Geneva,sans-serif;">H ﻿ 7 <span style="font-family: Verdana,Geneva,sans-serif;">IO 3
 * <span style="font-family: Arial,Helvetica,sans-serif;">Compound Formula: <span style="font-family: Verdana,Geneva,sans-serif;">C <span style="font-family: Verdana,Geneva,sans-serif; font-size: 10px; vertical-align: sub;">8 <span style="font-family: Verdana,Geneva,sans-serif;">H ﻿ 7 <span style="font-family: Verdana,Geneva,sans-serif;">IO 3
 * <span style="font-family: Arial,Helvetica,sans-serif;">Structure:



__<span style="font-family: Verdana,Geneva,sans-serif; font-size: 150%;">Discussion __ The extremely low yield for this lab was due to many factors. The rotary evaporator took a visually significant chunk of product as a toll for its convenience and proficiency in the evaporative arts. Every other container transfer also lessened the final return sample. The largest hit, however, came during the crystallization procedure; during which the product was over-saturated with ethanol. This diluting the solution too much, severely hampered crystal formation and heralded a paltry yield. Many groups lost a bunch of their product at this stage. We (the royal "we") need to optimize the conditions for the recrystallization. I think the procedure could be improved.

The melting point of the final product was 161ºC which is considerably lower than the literary value melting point for Iodovanillin, which is 183-185ºC. Also, t<span style="font-family: Arial,Helvetica,sans-serif;">he product decomposed first, implying a chemical reaction instead of the phase change of a pure compound. A foreign substance or could have easily caused the depression in melting point and could relate a presence or abundance of an impurity. Supplementary melting points could have been taken in order to show further trends.

The solvent (ethanol) was polar and therefore upon the addition of HCl a precipitate was formed due to the change in pH causing it to go from basic to acidic and therefore reducing solubility.

__<span style="font-family: Verdana,Geneva,sans-serif; font-size: 150%;">﻿Conclusion __ While the procedure in itself had an unsuccessful yield, avoid any judgements. For all you know, this is the highest yield anyone has ever seen with this procedure. the practicalities of the application are clear and concise. Aromatic rings do not usually work well with Iodine but the other options are far more detrimental and do not fall within the realms of green chemistry and that is why a good oxidizing agent (hypochlorite) is used for this procedure. The reagents used in the process are by far more green than those used previously for this experiment and the final product Iodovanillin (5-Iodovanillin) was obatined successfully, even though in lower quantities than were desired.


 * Post Lab Question:**


 * Q.** <span style="font-family: Arial,Helvetica,sans-serif;">Calculate the atom economy for this reaction. Atom economy is defined on Wikipedia, but essentially is the mass of the desired product divided by the mass of all reactants (don’t include catalysts or solvents in our reaction).


 * <span style="font-family: Arial,Helvetica,sans-serif;">A. **Atom economy = The mass of the desired product is 279.05g for Iodovanillin and the reactants are Vanillin (152.148g), Sodium Iodide (149.89g) and Sodium Hypochlorite (74.44g) so the calculated atom economy is (279.05 ÷ 376.48) × 100 = 74.121% It can be assumed that all of the reactants were consumed in the reaction since no other information was given otherwise.

This report earned the following scores for: format (2/2) style (2/2) commendable!! data (3/3) quality of result (1/1) quality of reported data (1/1) conclusion (2/2) error (1/1) post-lab Q (1/1) for a total of 14. Well done. A parenthetical note about Wolfram Alpha: I have found glaring mistakes there before. Use it only with caution.

__<span style="font-family: Verdana,Geneva,sans-serif; font-size: 150%;">Notes __ The chemical structures, formulas, and vital statistics of each compound was researched using [|Wolfram Alpha computational knowledge engine] and confirmed using the [|CRC Handbook of Chemistry and Physics [90th Edition.]]