Nucleophilic aromatic permutation occurs when an negatron rich nucleophile onslaughts an negatron deficient species on an aromatic ring. The substituent on the aromatic ring is replaced with another substituent given that the former is a good departure group. And a good departure group would be a substituent which can suit more negative charge or is more stable due to distribution of charges or resonance. The substituent on the benzine ring has an consequence on the responsiveness of the aromatic ring. Effectss such as inductive consequence wherein the electronegativity of the substituent attached is greater which hence pulls the negatron denseness towards itself. For illustration, Nitrogen, Oxygen and halogens are more negatively charged than the Carbon on the ring hence, it pulls the negatron denseness towards itself and hence deactivating the ring. Deactivation of the ring implies that the reaction would be slower and triping the aromatic ring on the other manus means that the reaction would be faster. Another thing to see in nucleophilic aromatic permutation is the site of where nucleophilic onslaught takes topographic point. There are different orientation of reaction depending how substituted the ring is. It could be ortho, meta or parity to the substituent ( if it ‘s monosubstituted ) . So when these two factors that are taken into consideration are combined, it will so state us the responsiveness and where the nucleophile will attack/or direct the new substituent and besides tell us which of the merchandise will organize in bulk.
Experimental
To transport out this experiment a mixture of the followers was obtained in a 125 milliliter Erlenmeyer flask: 1.010g of 2,4-dinitrochlorobenzene ; 0.6800g of m-aminobenzoic acid ; and in conclusion 25 milliliters Dimethylformamide ( DMF ) . Upon fade outing the solids to the liquid DMF, it became a clear xanthous brown homogeneous liquid solution. The solution was heated in a H2O bath for one hr with occasional swirling of the flask. The solution 100mL of deionized H2O was added, and the solution became an opaque xanthous mustard colored homogeneous liquid solution. The solution was run through a vacuity filter to obtain the xanthous brown pastelike precipitate. The precipitate was so removed from the filter paper and was assorted ab initio with 25mL 95 % ethyl alcohol and heated in an Erlenmeyer flask. The xanthous brown precipitate so suspends in the liquid ethyl alcohol and more ethyl alcohol was added until all the precipitate was dissolved and the solution turned into a clear xanthous brown liquid. The solution was removed from the hot home base and deionized H2O was added until the solution became a mustard yellow cloudy opaque solution. The solution was cooled to room temperature and was run through vacuity filtration. The dark mustard xanthous brown precipitate formed was so obtained in a pre-weighed ticker glass and air dried.
Datas and consequences:
Calculations:
Mass of 2,4-dinitrochlorobenzene ( DNCB ) = Required # of moles x M.W. of ( DNCB )
=0.005mol x 202.6g/mol = 1.013g DNCB
Mass of m-aminobenzoic acid ( MABA ) = Required # of moles x M.W. of ( MABA )
=0.005mol x 137.1g/mol = 0.6855g MABA
Theoretical Output =
Percentage Yield=
Percentage Mistake =
Table 1. Properties of Reactants and Merchandises
Compound
Molecular Weight
g/mol
Melting Point
A°C
Boiling point
A°C
Density g/mL
Hazards
Appearance
2,4-dinitrochlorobenzene
202.6
53-54
315
314*
Toxic thorn
Dark xanthous brown crystals
m-aminobenzoic acid
137.1
178-180
–
–
Irritant
Light brown pulverization
Dimethylformamide ( DMF )
73.1
-61
153
0.944
Irritant
Clear, colourless liquid
95 % Ethanol
46.1
-130
78
0.785
Flammable
Clear, colourless liquid
m- ( 2,4-dinitroanilino ) benzoic acid
303.2
& gt ; 240
–
–
–
Yellow-Brownish pulverization
Deionized Water
18.01528
0
99.98A
1000A kg/m3
–
Clear, colourless liquid
Table 2. Datas and Consequences
Experimental Stairss
Measurement
Initial Description
Physical belongingss after reaction
Mixed and heated:
2,4-dinitrochlorbenzene
m-aminobenzoic acid ( MABA )
DMF
Mass of DNCB: 1.010g
Yellowish-Brown crystals
Dark Yellowish Brown Liquid solution
Mass of MABA: 0.680g
Light brown Powder
Volume of DMF:25 milliliter
Clear, colourless liquid
Added Deionized Water
Volume used: 100mL
Dark Yellowish Brown semi-transparent Liquid
Opaque Mustard Yellow liquid solution
Vacuum Filtration
Precipitate obtained: Yellow Brown pulverization
Added 95 % ethyl alcohol
Initially added 25 milliliter
Then added more till precipitate disappeared and solution is clear
Yellow brown clear liquid solution
Added Deionized Water
Volume used: added until solution became cloudy
Mustard cloudy yellow liquid solution
Vacuum filtered
Precipitate: Mustard yellowish Brown pulverization
Weight of Watchglass
29.234g
Concluding mass of merchandise
m- ( 2,4-dinitroanilino ) benzoic acid
1.421g
Discussion:
Nucleophilic aromatic permutation of 2,4-dinitrochlorbenzene ( DNCB ) by m-aminobenzoic acid ( MABA ) was done to bring forth m- ( 2,4-dinitroanilino ) benzoic acid. 2,4-dinitrochlorbenzene ( DNCB ) which appeared to be granulated dark xanthous brown solid is a benzene derived function. It has a Chlorine on place one of substituted halobenzenes that besides carry two nitro groups ( electron retreating substituents ) inA ortho and para place, which in this experiment, was really substituted by a nucleophilic onslaught of a good nucleophile, MABA, which has negatron donating substituents. ( see fig. 1 p.1 ) ( refer to postpone 1 for belongingss of reactants ) .
hypertext transfer protocol: //www.chemgapedia.de
Fig.2 Electrostatic possible surface ofA chloro-2,4-dinitrobenzene
“ Comparison of the electrostatic possible surfaces illustrates the well stronger chlorine-carrying C ‘s positive polarisation by the electron-withdrawing nitro groups, which enables a nucleophilic onslaught on this C ( ruddy means a more negative potency, bluish means a more positive potency ) ” . Dr. Oliver Kamp hypertext transfer protocol: //www.chemgapedia.de
Initially, DNCB which appeared to be granulated dark xanthous brown solid was combined with MABA which can be described as a light brown pulverization in a polar aprotic dimethylformamide ( DMF ) dissolver which is a clear colorless liquid. DMF stabilizes the passage province which enhances the addition-elimination reaction besides, it does non solvate the nucleophile. As the solids dissolves in the dissolver. MABA becomes deprotonated and onslaughts DNCB in DMF solution hence doing it a good nucleophile. The solution turned into a dark xanthous brown opaque solution. To ease reaction, the solution was heated in a H2O bath for an hr. The solution turned into a translucent xanthous brown solution lighter than earlier.
The reaction returns easy harmonizing to the figure of the substituents in the aromatic ring that withdraw negatrons from the pealing itself. However, substituents in orthoA andA paraA place, above all, advance a nucleophilic onslaught, while substituents inA metaA place about ne’er do. A± These observations may be explained by a mechanism.
Figure 3. Mechanism: Nucleophilic aromatic permutation of 2,4-dinitrochlorobenze by m-aminobenzoic acid.
This nucleophilic aromatic permutation is an addition-elimination mechanism. The aromatic system is broken by the onslaught of the nuclephile, MABA- and non the other manner around. An intermediate cabanion is formed and delocalized. It is so distributed among the once aromatic, A sp2-hybridized ring Cs. The intermediate carbanion ‘s negative charge is stabilized by the resonance and ( – ) inductive effects the substituents create. Stabilization of NO2 in a parity positionis the best because it is in the centre which has the largest negative charge denseness. Ortho place has a lesser grade than the para place stabilisation but still lend. Since Chloride atom is a better go forthing group and because it can suit more of the negative charge than the entrance nucleophile, it so splits off.
To precipitate the merchandise and take DMF which is soluble in H2O, deionized H2O was added. The solution turned mustard xanthous opaque solution. The dark xanthous pulverization precipitate was obtained by vacuum filtration of the solution. 95 % of ethyl alcohol was so added and the solution was heated to boil to fade out drosss and merchandise. Once the solution turns yellow- brown and clear, it was so removed from heat and deionized H2O was added to precipitate merchandise. A dark xanthous chocolate-brown pulverization merchandise m- ( 2,4-dinitroanilino ) benzoic acid is non soluble in H2O therefore it precipitates from the solution. The runing point finding was omitted because it is greater than 240 A°C. The concluding merchandise was weighed and a mass of 1.421g was obtained.
Decision:
In this experiment, the nucleophilic aromatic permutation of 2,4-dinitrochlorobenzene by m-aminobenzoic acid was successfully performed. Better understanding on how benzene substituent ‘s contributes to the responsiveness and orientation of the nucleophilic onslaught which hence predicts the construction of the concluding merchandise. The concluding mass of the concluding merchandise m- ( 2,4-dinitroanilino ) benzoic acid was 1.421g. The theoretical output of 1.516g was non to the full obtained. A pecent mistake of 6 % might be due to experimental mistakes such as failure to hold exact or accurate measurings of reactants, loss of merchandise during transferral stairss. Besides, some of the merchandise was loss due to the failure of the vacuity filtration system because of deficient aspirator in the research lab. Having a better vacuity filtration apparatus in a extremely controlled research lab apparatus will likely lend to a higher merchandise output.
Answers to Questions.
Why is dimethylformamide instead than H2O used as the dissolver in this reaction?
DMF is a polar aprotic dissolver which does non hold a proton to donate in the reaction. It besides does non solvate the nucleophile hence non impacting the merchandise of reaction. It besides stabilizes the passage province therefore heightening the add-on riddance reaction in the experiment.
What merchandise may be formed when chlorobenzene is reacted with Na hydrated oxide utilizing H2O as a dissolver.
Since Chloride is a better go forthing group than a hydrated oxide, a benzine with a hydrated oxide in the 2nd C will be produced in this reaction.
From the FT- IR spectrum ( figure. ) assign the major preaks for m- ( 2,4-dinitroanilino ) benzoic acid. Delegate the protons in the NMR spectrum ( Figure ) for 2,4-dinitrochlorobenzene.
