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FPSC · CSS 2021

Chemistry, Paper II

100 marks · 3 hours · 7 questions
This paper Chemistry · all yearsQ. 2 · Describe factors that influence keto-enol…Q. 3 · Give the products expected (if…Q. 4 · Write down reagents, reaction conditions…Q. 5 · Draw detailed mechanisms for:Q. 6 · In DNA, a guanine residue…Q. 7 · How can IR be used…Q. 8 · Comment if glycogenesis is anabolic…With this paper← 20202022 →
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Part II

Q. 2
  1. (a)Describe factors that influence keto-enol tautomerization. Elaborate the statement with the help of examples. [10]
  2. (b)Assign “R” or “S” configuration on each of the chiral centers of the given compounds. [10]
(10)
Q. 3
  1. (a)Give the products expected (if any) when ethylbenzene reacts under following conditions: [10]
  2. (b)Account for the following: [10]
(20)
Q. 4
  1. (a)Write down reagents, reaction conditions and important steps for the following conversions: [10]
  2. (b)Write a note that substituents on aromatic rings dictate reactivity and orientation of the incoming electrophile in electrophilic aromatic substitution reactions. [10]
(20)
Q. 5
  1. (i)Draw detailed mechanisms for: [4]
  2. (ii)Draw detailed mechanisms for: [4]
  3. (iii)Draw detailed mechanisms for: [4]
  4. (iv)Draw detailed mechanisms for: [4]
  5. (v)Draw detailed mechanisms for: [4]
(20)
Q. 6
  1. (i)In DNA, a guanine residue reacts with electrophiles predominantly at the 7 and 3 positions of the ring system (see below). Suggest an explanation for this. [5]
  2. (ii)Outline the synthesis of following compound: [5]
  3. (iii)A Grignard reagent that is a key intermediate in an industrial synthesis of vitamin A can be synthesized in the following way: [5]
  4. (iv)What are compounds A and B in the reaction given below? Compound B has a strong IR absorption band in the 1650–1730 cm⁻¹ region and a broad strong band in the 3200-3550 cm⁻¹ region. [5]
(20)
Q. 7
  1. (i)How can IR be used to help interpret NMR spectra? [4]
  2. (ii)What are diastereotopic protons? Explain with examples. [4]
  3. (iii)Determine the structure for a compound with formula C₆H₄N₂O₄ with following ¹H-NMR data: δ 8.76 t (1H), 8.38 dd (2H), 7.97 t (1H) [4]
  4. (iv)Assign chemical shifts of each proton in the above structure. [4]
  5. (v)Why ¹³C-NMR is less sensitive than ¹H-NMR? [4]
(20)
Q. 8
  1. (i)Comment if glycogenesis is anabolic or catabolic. Write down all steps involve in glycogenesis. [4]
  2. (ii)Describe endergonic and exergonic reactions [4]
  3. (iii)Write a note on anionic and cationic surfactants. [4]
  4. (iv)Comment if waste glass can be used for cement production. [4]
  5. (v)What is the chemical composition of nucleic acids and their biological significance? [4]
(20)

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About this paper

The 2021 CSS Chemistry paper set by the FPSC. Question wording only; questions marked “Not yet checked” have not been compared with the official paper yet.

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