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A partially completed reaction pathway for the synthesis of the painkiller ibuprofen is given below - VCE - SSCE Chemistry - Question 8 - 2009 - Paper 1
Question 8
A partially completed reaction pathway for the synthesis of the painkiller ibuprofen is given below.  i. In the appr... show full transcript
Worked Solution & Example Answer:A partially completed reaction pathway for the synthesis of the painkiller ibuprofen is given below - VCE - SSCE Chemistry - Question 8 - 2009 - Paper 1
Step 1
i. In the appropriate box, write the formula for reagent A.
Answer
The reagent A is typically a strong base used in nucleophilic substitution reactions. In this case, the likely candidates could be sodium hydroxide (NaOH) or potassium hydroxide (KOH), which would facilitate the displacement reaction. Thus, the formula for reagent A is:
Reagent A: NaOH or KOH
Step 2
ii. In the appropriate box, complete the structure for compound 1.
Answer
The compound 1 formed after the reaction involving reagent A would include a hydroxyl group (-OH) replacing the chloride. The structure of compound 1 can be completed as follows:
CH3
|
CH3-C-CH2-CH-
|
(OH)-C6H4
This shows the hydroxyl group attached to the aromatic ring.
Step 3
iii. Write a balanced half-equation for the reduction of dichromate ions to Cr^3+ ions in an aqueous acid solution.
Answer
The balanced half-equation for the reduction of dichromate ions (Cr_2O_7^{2-}) in an acidic medium can be written as:
Cr_2O_7^{2-} (aq) + 14 H^+ (aq) + 6 e^- → 2 Cr^{3+} (aq) + 7 H_2O (l)
This equation indicates that dichromate ions are reduced to chromium (III) ions, consuming electrons in the process.