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FPSC · CSS 2020

Chemistry, Paper II

80 marks · 3 hours · 7 questions
This paper Chemistry · all yearsQ. 2 · Inductive and Field effectsQ. 3 · “The resonance effect has an…Q. 4 · How would you carry out…Q. 5 · The following reactions can be…Q. 6 · How would you convert cyclohexanone…Q. 7 · How can a racemic mixture…Q. 8 · Starch, glycogen and cellulose are…With this paper← 20202021 →
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Part II

Q. 2
  1. (i)Inductive and Field effects [5]
  2. (ii)Inductive and Resonance effects [5]
  3. (iii)Localized and Delocalized bonding [5]
  4. (iv)Conjugation and Hyperconjugation [5]
(20)
Q. 3
  1. (a)“The resonance effect has an appreciable influence on physical characteristics and the chemical reactivity of organic molecules”. Elaborate the statement with the help of examples. [10]
  2. (b)Outline the EAS mechanism (Electrophilic Aromatic Substitution) through which aromatic compounds react with electrophiles. [5]
  3. (c)Discuss factors which favour an elimination reaction occurring over a substitution reaction. [5]
(20)
Q. 4

How would you carry out the following conversions? Account for your answer with mechanism in each case.

  1. (i)(CH3)3CCH=CH2 → (CH3)2C(OH)CH(CH3)2 [4]
  2. (ii)(CH3)3CCH=CH2 → (CH3)3CCH(OH)CH3 [4]
  3. (iii)(CH3)3CCH=CH2 → (CH3)3CCH2CH2OH [4]
  4. (iv)(CH3)3CC≡CH → (CH3)3CCOCH3 [4]
  5. (v)(CH3)3CC≡CH → (CH3)3CCH2CHO [4]
(20)
Q. 5

The following reactions can be used for the preparation of alkanes or cycloalkanes. Elaborate them with the help of reaction mechanisms.

  1. (i)Corey House reaction [5]
  2. (ii)Wurtz reaction [5]
  3. (iii)Kolbe reaction [5]
  4. (iv)Simmons - Smith Reaction [5]
(20)
Q. 6

How would you convert cyclohexanone into the following compounds? Write down the mechanisms of the reactions.

  1. (a)Caprolactone [4]
  2. (b)Caprolactam [4]
  3. (c)Cycloheptanone [4]
  4. (d)Cyclohexa-1,2-dione [4]
(20)
Q. 7
  1. (a)How can a racemic mixture be separated into its components? Describe different methods. [16]
  2. (b)(-)-Lactic acid has a specific rotation of -3.8°. What will be the specific rotation of a solution containing 7.5g of (-)-lactic acid and 2.5 g of (+)-lactic acid? [4]
(20)
Q. 8
  1. (a)Starch, glycogen and cellulose are polymers of glucose. How will you differentiate among these three both structurally and functionally. [12]
  2. (b)Explain precisely the following terms. [8]
(20)

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About this paper

The 2020 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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