kindly , I need the calculations thanks phenol electrophilic aromatic substituti

Question

kindly , I need the calculations thanks

phenol electrophilic aromatic substitution Weigh 1.30 g of phenol and transfer it quantitatively to a 250 ml chronic flask with about 50 ml of demineralized water. Add 10 mL of 2 M sulfuric acid and 0.5 g of solid KBr with stirring. When all is dissolved add with full pipette 15.0 ml of 0.100 KBr03. Stirring for 10 minutes to the reaction is elapsed. 10 ml of 0.5 M KI are added and the resulting iodine amount is titrated with 0.100 M Na2S203, adding 2 ml of 0.2% starch solution. The titration to the iodine / starch color disappears Amout of titrator, Na2S203 used: 2 mL 1) calculate the total amount of BR2 (from 15.0 ml of 0.100 M bromate) 2) Calculate the amount of thiosulfate used 3) and then the surplus of Br2 4) How large a substance Br2 has reacted with phenol 5) Calculate the relationship between the amounts of reacted br2 and phenol used

Explanation / Answer

Electrophilic aromatic bromination of phenol

Reactions,

KBrO3 + 5KBr + 3H2SO4 --> 3K2SO4 + 3Br2 + 3H2O

1) Total amount of Br2 generated from KBrO3 = 3 x 0.1 M x 0.015 L = 0.0045 mol

I2 + 2NaS2O3 ---> Na2S4O6 + 2NaI

2) amount of thiosulfate used = 0.1 M x 0.002 L = 0.0002 mol

Br2 + 2KI ---> 2KBr + I2

3) surplus Br2 = 0.0002 mol/2 = 0.0001 mol

Phenol + Br2 --> bromophenol + HBr

4) amount of Br2 reacted with Phenol = 0.0045 - 0.0001 = 0.0044 mol

5) moles of Phenol = 1.30 g/94.11 g/mol = 0.014 mol

Relationship between amount of Br2 reacted and phenol used = 0.014 (phenol)/0.0044 (Br2) = 3.2

So we have reacted 3.2 mol of phenol with 1 mol of Br2 in the given reaction.

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