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CSS Chemistry Paper II Past Paper 2016

CSS Chemistry Paper II 2016 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
    Write briefly on the following terms: (2 each)
    (20)
    • (i)
      Hyper-conjugation
    • (ii)
      Aromaticity
    • (iii)
      Grignard’s reagent
    • (iv)
      SN1\text{S}_{\text{N}}1 reaction
    • (v)
      Molecular chirality
    • (vi)
      Monosaccharides
    • (vii)
      Chemical shift
    • (viii)
      Glycolysis
    • (ix)
      Detergents
    • (x)
      Friedal Craft alkylation
  2. Q. 3
    • (a)
      How would you synthesize each of the following molecule from an alkene of appropriate structure (structure of your choice).
      (8)
      • (i)
        Condensed structure HC(H3C)2-CH-CH3 with an OH group drawn above the CH carbon (3-methylbutan-2-ol).
      • (ii)
        Condensed structure H2CCl-CH(OCH(CH3)2) with an H3C group drawn above the CH carbon (a chloro ether: 1-chloro-2-isopropoxypropane).
      • (iii)
        Condensed structure H3CH2CH2C-CH(Br)-CH(Br)-CH2CH2CH3, with Br on each of the two central carbons (4,5-dibromooctane).
      • (iv)
        A decalin (two fused six-membered rings) with a CH3 on one ring-fusion carbon and an epoxide (O bridge) across the bond at the lower fusion carbon.
    • (b)
      Write the expected major product of the reaction of propyne with each of the following reagents.
      (6)
      • (i)
        CuX2ClX2\ce{Cu2Cl2}, OX2\ce{O2}, pyridine
      • (ii)
        Na, NDX3\ce{ND3}
      • (iii)
        [(CHX3)X2CHCHX2CHX2]X2BD\ce{[(CH3)2CHCH2CH2]2BD} then CHX3COX2H\ce{CH3CO2H}
      • (iv)
        HX2O\ce{H2O}, HgSOX4\ce{HgSO4}, HX2SOX4\ce{H2SO4}
      • (v)
        Di-isoamylborane, then NaOH, HX2OX2\ce{H2O2}
      • (vi)
        Di-isoamylborane, then CHX3COX2D\ce{CH3CO2D}
    • (c)
      Starting with benzene, design reasonable syntheses of each of the following compounds.
      (6)
      • (i)
        Benzene ring bearing a CH2OH group (benzyl alcohol).
      • (ii)
        Benzene ring bearing a CHO group (benzaldehyde).
      • (iii)
        Benzene ring bearing a CH2CH(NH2)CH3 side chain, with CH3 drawn below the CH carbon (amphetamine).
  3. Q. 4
    • (b)
      Draw the structures of the following molecules:
      (10)
      • (i)
        5-(2,2-Dimethylpropyl)nonane
      • (ii)
        2,3-Dimethylhept-3-ene
      • (iii)
        1-Chloro-1-methoxy-2-methylbut-1-ene
      • (iv)
        6-Chloro-2-nitrooct-1-en-3-yne
      • (v)
        8-Chloro-7-methoxy-5-methyl-4-nitroundec-5-ene
      • (vi)
        4-(2-Ethylbutyl)decane
      • (vii)
        5-Ethyl-4,6-dimethylhept-4-en-2-yne
      • (viii)
        5,5-Dichloro-3-methylhepta-3,6-dien-1-yne
      • (ix)
        6-bromo-5-chloro-9-nitropentadecane
      • (x)
        6-chloroocta-1,3-diyne
    • (c)
      • (i)
        The structure(I) given below has significant dipole moment. Which end of the molecule would you expect to owe positive charge, and which tend to be negative.
        (2)
        Structure (I): a seven-membered ring with three C=C double bonds (cycloheptatriene) joined by an exocyclic C=C double bond to a five-membered ring with two C=C double bonds (cyclopentadiene), i.e. sesquifulvalene.
        (I)
      • (ii)
        The structure(II) given below is a component of certain oral contraceptives:
        (3)
        Structure (II): a steroid skeleton (four fused rings, one C=C in the first ring) with atoms numbered 1 to 22; C18 is a CH3 on the ring fusion carbon 10, and C12 of the five-membered ring carries a C19≡C20H ethynyl group and an O21-H22 hydroxyl group.
        (II)

        Locate in this structure an example of each of the following bonds or atoms

        ➢ A highly polarized covalent bond

        ➢ Sp-hybrid carbon atoms

        ➢ A nearly unpolarized covalent bond

  4. Q. 5
    • (a)
      Consider the reaction of bromocyclohexane with each of the four reagents below, and answer the questions below. Also write down the reaction mechanism in each case.
      (7)
      HX2O\ce{H2O}OHX−\ce{OH^-}CHX3COOH\ce{CH3COOH}CHX3COOX−\ce{CH3COO^-}
      (i)(ii)(iii)(vi)
      • (i)
        What is the most important type of reaction mechanism in each case?
      • (ii)
        Which reagent gives the most elimination product?
      • (iii)
        Which reagent is most useful in synthesizing the alcohol?
    • (b)
      Evaluate each of the possible alcohol syntheses below as being good (the desired alcohol is major or only product), not so good (the desired alcohol is a minor product, or worthless).
      (5)
      • (i)
        CHX3CHX2Cl→CHX3CHX2OH\ce{CH3CH2Cl -> CH3CH2OH}
      • (ii)
        H3C-CH(CN)-CH3 (NC drawn above the central carbon) with OH⁻, H2O, Δ over the arrow, giving H3C-CH(OH)-CH3 (HO drawn above the central carbon).
      • (iii)
        HX3COCHX3→OHX−,HX2O,ΔCHX3OH\ce{H3COCH3 ->[OH^-, H2O, $\Delta$] CH3OH}
      • (iv)
        O2SOH3C- attached to a benzene ring that bears CH3 at the para position (methyl tosylate drawn as O2SOH3C-C6H4-CH3), with OH⁻, H2O, Δ over the arrow, giving CH3OH.
      • (v)
        Iodocyclohexane (cyclohexane ring with I) with OH⁻, H2O, Δ over the arrow, giving cyclohexanol (cyclohexane ring with OH).
    • (c)
      Write the major product(s) of each of the following reactions. It is implied that aqueous work-up has taken place in all those cases that require it to obtain the organic product.
      (8)
      • (i)
        HX3CCHO→2 ⋅ HX+,HX2O1 ⋅ LiAlDX4\ce{H3CCHO ->[1. LiAlD4][2. H^+, H2O]}
      • (ii)
        A cyclopentane ring bearing Br at the top carbon and an epoxide (O bridge) across the two lower carbons, with LiAlH4, (CH3CH2)O over the arrow.
      • (iii)
        H3C-CH(MgBr)-CH3 (BrMg drawn above the central carbon) + cyclohexanone drawn as a plain six-membered ring, with (CH3CH2)O over the arrow.
      • (iv)
        Skeletal hexane-2,5-dione (H3C-C(=O)-CH2-CH2-C(=O)-CH3) with H2, Pt over the arrow.
  5. Q. 6
    • (a)
      The two isomers of carvone are given below. Which is R and which is S?
      (2)
      Two carvone structures: (+)-Carvone, a cyclohexenone ring with CH3 on the alkene carbon next to C=O and, at the ring carbon opposite, a hashed H and a wedged isopropenyl group (H2C=C-CH3); (−)-Carvone, the mirror-image drawing with the C=O on the left.
    • (b)
      The structure of compound given below is a sugar called (−)-arabinose. Its specific rotation is −105˚.
      (3)
      Fischer projection of (−)-arabinose: CHO (H-C=O) at the top, then HO left and H right, H left and OH right, H left and OH right, and CH2OH at the bottom.
      • (i)
        Draw enantiomer(s) of (−)-arabinose
      • (ii)
        Draw diastereomer(s) of (−)-arabinose
      • (iii)
        Does (−)-arabinose have any optically inactive diastereomers? If it does, draw one.
    • (c)
      Assign E,Z designation to the following structures.
      (7)
      • (i)
        Cyclopentane with CH3 groups on two adjacent carbons, both drawn with wedge bonds (cis-1,2-dimethylcyclopentane).
      • (ii)
        H3C-N=N-H with a lone-pair orbital drawn on each nitrogen (methyldiazene).
      • (iii)
        Decalin (two fused six-membered rings) with a wedged CH3 on the upper ring-fusion carbon and a hashed CH3 on the lower ring-fusion carbon.
      • (iv)
        Cyclohexane with a wedged OH on one carbon and a hashed CH3 on the adjacent carbon.
      • (v)
        A C=C double bond whose left carbon bears an ethynyl group (HC≡C-) above and a vinyl group (H2C=CH-) below, and whose right carbon bears an acetyl group (C(=O)CH3) above and a carboxylic acid (C(=O)OH) below.
      • (vi)
        H3C(H)C=N-H with a lone-pair orbital drawn on the nitrogen (an imine of acetaldehyde).
      • (vii)
        A C=C double bond whose left carbon bears HOH2C above and a butyl group (H3CH2CH2CH2C) below, and whose right carbon bears a methyl ester (C(=O)OCH3) above and a carboxylic acid (C(=O)OH) below.
    • (d)
      Draw the structures of the product(s) described for each reaction. Specify all aspects of the stereochemistry.
      (8)
      • (i)
        Stereospecific anti addition of bromine to cis- and trans-cinnamic acid.
      • (ii)
        Methanolysis of S-3-bromooctane with 6% racemization.
      • (iii)
        Stereospecific syn thermal elimination of acetic acid from 1R,2S-diphenylpropyl acetate
      • (iv)
        Stereoselective epoxidation of bicyclo[2.2.1]hept-2-ene proceeding 94% fromtheexo face.
  6. Q. 7
    Write a brief account on the following: (5 each)
    (20)
    • (a)
      Biological importance of starch
    • (b)
      Classification of Amino acids
    • (c)
      Primary structure of Proteins
    • (d)
      Glycogenesis
  7. Q. 8
    • (a)
      Differentiate following using IR Spectroscopy?
      (4)
      • (i)
        Three skeletal amines: ethylamine (H3C-CH2-NH2), N-methylethylamine (H3C-CH2-NH-CH3) and N,N-dimethylethylamine (H3C-CH2-N(CH3)2).
      • (ii)
        Three carbonyl compounds: acetic acid (H3C-C(=O)-OH), acetone (H3C-C(=O)-CH3) and methyl acetate (H3C-C(=O)-O-CH3).
      • (iii)
        Propane (H3C-CH2-CH3), propene (H2C=CH-CH3) and propyne (HC≡C-CH3).
      • (iv)
        Hexane drawn as a zigzag chain H3C-CH2-CH2-CH2-CH2-CH3, and cyclohexane drawn as a hexagon.
    • (b)
      What type of electronic transition are possible in the following compounds?
      (2)
      • (i)
        Butadiene
      • (ii)
        Diethyl ether
      • (iii)
        Acetaldehyde
      • (iv)
        Trimethylamine
    • (c)
      How will you distinguish the following compounds using UV/Visible spectrophotometer?
      (4)
      • (i)
        Two dihydronaphthalenes (fused pairs of six-membered rings) joined by 'and': on the left the two C=C bonds are in conjugation across the ring fusion; on the right the two C=C bonds are each in a separate ring and not conjugated.
      • (ii)
        Nitrobenzene (benzene ring with NO2) and benzene, joined by 'and'.
      • (iii)
        4-Methylenecyclohex-2-enone (a cyclohexenone with an exocyclic =CH2 opposite the C=O, conjugated) and 4-methylcyclohexanone (saturated ring with C=O and a CH3), joined by 'and'.
      • (iv)
        But-3-en-2-one, H3C-C(=O)-CH=CH2, followed by 'and'.
        Butan-2-one, H3C-C(=O)-CH2-CH3.
    • (d)
      Give the chemical shift of the following compounds for each proton
      (5)
      • (i)
        Tetramethylethylene: a C=C double bond with two H3C groups on the left carbon and two CH3 groups on the right carbon.
      • (ii)
        2-Methylpropene: a C=C double bond with two H on the left carbon and two CH3 groups on the right carbon.
      • (iii)
        2-Chloropropene: a C=C double bond with two H on the left carbon and Cl and CH3 on the right carbon.
      • (iv)
        Neopentyl bromide: a central carbon bearing three methyl groups (H3C above, H3C left, CH3 below) and a CH2-Br group.
      • (v)
        A cyclohexadiene ring bearing Cl (1-chlorocyclohexa-1,3-diene drawn as a hexagon with two C=C bonds and Cl at the top right).
    • (e)
      The mass spectrum of compound shows following peaks: m/e= 120, relative intensity=20% (M+\text{M}^{+} peak), m/e= 105, relative intensity=80%, m/e= 77, relative intensity=96%, m/e= 43, relative intensity=35%. Assign the structure which would be expected.
      (5)
  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.