Nucleophilic Aromatic Substitution of 2,4-Dinitrochlorobenze

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Experiment #1

Nucleophilic Aromatic Substitution of 2,4-dinitrochlorobenze

Name: Anouk Deck-Leger
Student I.D: 9380868
Date performed: September 13th, 2010
Due Date: September 20th, 2010
Introduction:
The company DNCB produces large amounts of 2,4-dinitrochlorobenzene and they sell this product to treat against warts and severe and chronic hair loss. It can also be used as an alternative treatment for HIV. The supervisor notices an excess amount of m-aminobenzoic acid stored away which is currently not being used for anything. This reactant can be used in certain reactions to produce valuable solutions for ophthalmologists. This product is going to waste, and our objective is to see if we can obtain a usable end product when reacting m-aminobenzoic acid with 2,4-dinitrochlorobenzene. In order for this reaction to take place, we must verify that we can obtain a product through the following nucleophilic aromatic substitution reaction:

When electron withdrawing groups are present on a benzene ring, the ring can more easily undergo a nucleophilic attack. In this reaction we are dealing with a halogen (Cl) placed on the benzene ring, and when the electron withdrawing group is present either in ortho or para positions the nucleophilic attack will attack with more ease than if the EWG is positioned on meta carbon or when there are no EWG's present at all. Both reactants, the m-aminobenzoic acid and the 1-chloro-2,4-dinitrobenzene, were mixed together and were dissolved using dimethylformamide. The resultant solution was heated, mixed with deionized H2O and vacuum filtrated in order to separate our formed product form the solvent. This technique was further repeated after our product was washed with heated ethanol. The final product was m-(2,4-dinitroanilino) benzoic acid. The reaction mechanism for the overall reaction in question is as follows:

Results & Observations:
Mass of 2,4-dinitrochlorobenzene = 1.012g
Mass of m-aminobenzoic acid = 0.686g
Mass of m-(2,4-dinitroanilino) benzoic acid = 0.045g

Boil both masses with DMF for 1 hour

When above solution was added to 100mL deionized H2O:
-the solution turned bright yellow
-Opaque
-The solution was cloudy.

The solution began to precipitate upon settling at room temperature.

Final solution:
-Dark yellow
-Solution was clear
-Bright yellow precipitate formed at the bottom of flask

Vacuum filtration was performed.
Solid was bright yellow in colour.

This bright yellow solid was then added to heated ethanol:
-Solution became orange
as we added H2O, the solution turned bright yellow again and remained cloudy. Our lab manual states that this solution should have been clear and not opaque!

Second Vacuum Filtration was performed and the final solid product was pasty and bright yellow.

Calculations:
* mass of 5mmol of 1-chloro-2,4-dinitrobenzene:
5.0mmol x (1mol/1000mol) x (202.6 g/mol)
mass= 1.013g

* Mass of 5mmol m-aminobenzoic acid:
5.0mmol x (1mol/1000mol) x (137.1g/mol)
mass = 0.6855g

* Theoretical Yield m-(2,4-dinitroanilino) benzoic acid:
5mmol x (303.2g/mol) x ( 1mol/1000mol)
Theoretical Yield = 1.516g

* % Yield:
Actual yield / theoretical yield
% yield = 0.450g / 1.516g
% Yield = 29.68%

Answer to Questions:
1) The reason that DMF is used as a solvent in this experiment versus the use of water as a solvent is because we need the nucleophile to be strong in its solution for the reaction to proceed. For this to happen the reaction must take place in a nonpolar solvent, this way there is no ion-dipole interactions between the ion and the nonpolar solvent. The problem is that ionic compounds are insoluble in most nonpolar solvents. We use DMF because these compounds can dissolve in aprotic polar solvents. Thus, DMF will not contribute a hydrogen bond. 2) When chlorobenzene is reacted with NaOH using water as a solvent, the chief products are phenol and diphenyl ether.3
C6H5–Cl  + ...
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