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CSS Chemistry Paper II Past Paper 2023

CSS Chemistry Paper II 2023 carries 100 marks over 3 hours. It has 7 questions.

Marks
100
Time
3 hours
Questions
7

Years

How to attempt: Attempt ONLY FOUR questions from PART-II. ALL questions carry EQUAL marks.

Questions

Question 1 (Part I) is the paper's MCQs, which are not reproduced here.

  1. Q. 2
    (20)
    • (a)
      Arrange the following alkenes in order of their relative stability. How will you proceed to determine the order practically?
      (5)
      • (i)
        1-hexene
      • (ii)
        cis-3-hexene
      • (iii)
        trans-3-hexene
      • (iv)
        2-methyl-2-pentene
      • (v)
        2,3-dimethyl-2-butene
    • (b)
      Explain why?
      (5)
      • (i)
        Poly substitution is a complicating factor in aromatic alkylation but not in aromatic nitration or halogenation.
      • (ii)
        A undergoes nitration predominantly at the ortho/ para positions but B mainly at meta position
        Two benzene rings: A bears a CH2CH2CN side chain; B bears an HC=CHCN side chain.
    • (c)
      Compare the basicity of:
      (5)
      • (i)
        (CHX3)X3N\ce{(CH3)3N} & (CClX3)X3N\ce{(CCl3)3N}
      • (ii)
        CX6HX5CHX2NHX2\ce{C6H5CH2NH2} & CHX3CX6HX4NHX2\ce{CH3C6H4NH2}
      • (iii)
        Aniline & Cyclohexyl amine
      • (iv)
        Two benzene rings joined by '&': the first has H2N and CN meta to each other (3-aminobenzonitrile); the second has NC and NH2 para to each other (4-aminobenzonitrile).
      • (v)
        Two benzene rings joined by '&': the first bears NHCH2CH3 (N-ethylaniline); the second bears NHCOCH3 (acetanilide).
    • (d)
      Explain why? (2.5 each)
      (5)
      • (i)
        Tertiary carbocation is more stable than primary.
      • (ii)
        Ethanol has higher boiling point than diethyl ether.
  2. Q. 3
    (20)
    • (a)
      Write the structural formula for more stable conformation of each of the following compounds.
      (8)
      • (a)
        trans-1-Fluoro-3-methylcyclohexane,
      • (b)
        cis-1-Iodo-4-methylcyclohexane
      • (c)
        cis-1-tert-Butyl-4-methylcyclohexane,
      • (d)
        cis-1,3,5-Trimethylcyclohexane
    • (b)
      Mention R & S configuration of the following compounds.
      (5)
      Three wedge-dash structures: butan-2-ol (skeletal, with H on a wedge and OH on a dash on C2); 1-chloroethylbenzene (a benzene ring on a carbon bearing Cl on a wedge, H and a methyl); and a carbon bearing H (wedge), OCH3 (dash), HOH2C and COOH.
    • (c)
      Draw and label the E and Z isomers for each of the following compounds.
      (5)
      Four condensed formulas: CH3CH2C(Cl)=CHCH2CH3; HOCH2CH2C(CH=O)=C(C(CH3)3)C≡CH; CH3CH2C(CH2CH2CH2CH3)=C(CH2Cl)CH(CH3)CH3, drawn with the butyl chain above and the CHCH3/CH3 branch below; and CH3CH2CH=CHCH3.
    • (d)
      Draw the structure of (Z)-3-isopropyl-2-heptene.
      (2)
  3. Q. 4
    (4each)
    (20)
    • (a)
      In benzaldehyde, two of the ring protons have resonance at 7.87 ppm, and the other three have resonance in the range from 7.5 to 7.6 ppm. Explain.
    • (b)
      Arrange the following protons in the decreasing order of their δ values in 1H-NMR and account for your order: Methyl, ethylenic, acetylenic, aryl and aldehydic.
    • (c)
      List the solvents most commonly used in IR spectroscopy. Why water and ethanol are not suitable solvents?
    • (d)
      The UV spectrum of acetone shows absorption maxima at 166, 189, and 279 nm. What type of transition is responsible for each of these bands?
    • (e)
      What types of electronic transitions are possible for each of the following compounds?
      • (i)
        Cyclopentene,
      • (ii)
        Acetaldehyde,
      • (iii)
        Dimethyl ether,
      • (iv)
        Methyl vinyl ether.
  4. Q. 5
    (10 each)
    (20)
    • (a)
      Write down the reagents, conditions and mechanisms of the following reactions.
      • (i)
        Kolbe reaction.
      • (ii)
        Williamson synthesis
      • (iii)
        Dow Process
      • (iv)
        Reimer-Tiemann reaction
      • (v)
        Bromination of phenol
    • (b)
      Outline all steps involved in the synthesis of the following compounds from benzene or toluene, assuming that the ortho / para mixtures are separable.
      • (i)
        n-Butylbenzene
      • (ii)
        m-Nitrotoluene
      • (iii)
        p- Bromonitrobenzene
      • (iv)
        p- Bromobenzoic acid.
      • (v)
        1,2-Dibromo-4-nitrobenzene
  5. Q. 6
    (20)
    • (a)
      Describe with equations all possible methods that can be used for the preparation of n-hexane.
      (10)
    • (b)
      Why Corey-House Method is more suitable as compared to Wurtz reaction for the synthesis of alkane. Explain with examples.
      (5)
    • (c)
      Draw the structures of following compounds and label them with IUPAC systematic rules.
      (5)
      • (i)
        3-cyclopentylhexane
      • (ii)
        2-cyclobutyl-3-methylpentane
      • (iii)
        Isopropylcyclodecane
      • (iv)
        2-methylbicyclo [3.2.0] heptanes
      • (v)
        8-methylbicyclo [3.2.1] octane
  6. Q. 7
    (20)
    • (a)
      How can you prepare each of the following substances by a reaction involving Grignard reagent?
      (5)
      • (i)
        A cyclopropane ring (triangle) whose ring carbon is written CHOH (cyclopropanol).
      • (ii)
        A cyclobutane ring (square) whose ring carbon is written CHCH2OH (cyclobutylmethanol).

        (Two ways)

      • (iii)
        (CHX3)X3CD\ce{(CH3)3CD}
      • (iv)
        CHX3CHX2CHOHCHX3\ce{CH3CH2CHOHCH3} (Two ways)
      • (v)
        (CHX3CHX2)X3COH\ce{(CH3CH2)3COH} (Three ways)
    • (b)
      How will you bring about the following conversions?
      (5)
      • (i)
        CHX3CHBrCHX2COOCX2HX5→HOOCCHX2CH(CHX3)CHX2COOH\ce{CH3CHBrCH2COOC2H5 -> HOOCCH2CH(CH3)CH2COOH}
      • (ii)
        CHX3CH(COOCX2HX5)X2→HOOCHX2CH(CHX3)CHX2COOH\ce{CH3CH(COOC2H5)2 -> HOOCH2CH(CH3)CH2COOH}
    • (c)
      How would you synthesize each of the following compounds by the Reformatsky reaction?
      (5)
      • (i)
        Condensed chain H3C—CH2—CH2—C(H2)—C(=O)—CH2—CH3, with the C=O drawn above the fifth carbon (a heptan-3-one).
      • (ii)
        A cyclohexane ring carbon bearing OH and a CH(CH3) group, which is attached to C(=O)O-CH2-CH3 (ethyl 2-(1-hydroxycyclohexyl)propanoate).
    • (d)
      How would you synthesize each of the following compounds by the Wittig reaction?
      (2.5)
      • (i)
        Condensed formula C6H5C=CH2 with a CH3 drawn on a vertical bond below the C (α-methylstyrene).
      • (ii)
        CX6HX5CH=CHCX6HX5\ce{C6H5CH=CHC6H5}
    • (e)
      How will you synthesize each of the following substances by an actoacetic ester synthesis?
      (2.5)
      • (i)
        3,4-dimethyl-2,5-hexanedione
      • (ii)
        3-acetyl-5-hexanoic acid.
  7. Q. 8
    (20)
    • (a)
      Discuss the following topics. (6 each)
      (12)
      • (1)
        Prostaglandins
      • (2)
        Terpenes
    • (b)
      Name the epimers of d -glucose.
      (4)
    • (c)
      Clearly represent the most stable conformation of the -pyranose form of each of the following sugars.

      A Greek letter (likely β) before '-pyranose' is missing in the printed paper.

      (4)
      • (a)
        D-Galactose
      • (b)
        D-Mannose
      • (c)
        L-Mannose
      • (d)
        L-Ribose
  1. Part-II is to be attempted on the separate Answer Book.
  2. Attempt ONLY FOUR questions from PART-II. ALL questions carry EQUAL marks.
  3. All the parts (if any) of each Question must be attempted at one place instead of at different places.
  4. Candidate must write Q. No. in the Answer Book in accordance with Q. No. in the Q.Paper.
  5. No Page/Space be left blank between the answers. All the blank pages of Answer Book must be crossed.
  6. Extra attempt of any question or any part of the attempted question will not be considered.
  7. Use of calculator is allowed.