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SECTION IV Subjective Questions
LEVEL I
1. An organic compound (A) C6H10on reduction, first give (B) 6 12C H and finally (c) 6 14C H
. (A) on reaction with ozone followed by hydrolysis in presence of Zn gives two
aldehydes 2 2 2C H O (E). Oxidation of (B) with acidified 4KMnO gives acid (F) 3 6 2C H O .
Determine structures of (A) to (F) with proper reasoning.
2. Identify (a) the chiral compound C, 10 14C H , that is oxidized with alk. 4KMnO to
PhCOOH, and (b) the achiral compound D, 10 14C H , inert to oxidation under the same
condition.
3. An alkyl halide, (X), of formula 6 13C H Cl on treatment with potassium tertiary butoxide
gives two isomeric alkenes Y and Z 6 12(C H ) . Both alkenes on hydrogenation gives 2, 3-
dimethylbutane. Predict the structures of X, Y and Z.
4. a)2
Br (A)
CH3
HPh
H
HBr/peroxide
(B)
Identify A and Bb) Write the product(s) of the following reactions:
Peroxide
3 2 3CH CH CH BrCCl ?
5. Write the major products of the hydroboration and oxidation of:
a) 1-Ethyl cyclopentene
b) Methylene cyclopentene.
6. Give the missing compounds in the following:
a)3 3BH .THF CH COOH? ?
b) 3 3BH .THF CH COOH? ? c) 3 3BH .THF CH COOH? ?
d)
3
3
( i)BH .THF
(ii)CH COOH?
7. Complete the following equation:
a) 2 2H H
3 3 3 2 2 3Pt PtCH C CCH (A) CH CH CH CH
b) 2 5Na C H OH
3 3 2 5CH C CCH (B) NaOC H
8. a) Starting with any alkyne, prepare ethyl cyclohexyl ethyne.b) Starting with cyclohexyl ethyne, prepare acetyl cyclohexane.
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is reductively ozonized to 2Me C O . Give the structures of (l) and (J) and explain the
formation of the latter.
5. a) Identify X, Y and Z in the following sequence of reactions giving stereo chemical
structures wherever possible.
3 32
4 2
( i) CH CO H(i )H(i) Na(ii) Br Pd BaSO (ii) H / H OC CH (X) (Y) (Z)
b) Complete the following sequences
i)3AlCl
3 2 2C H C H C H C l
ii) 2 2
3
Br i) NaNH (3 equi.)
6 5 2 ii )CH IC H CH CH A B
6. Hydrocarbon (A) C6H10 on treatment with H2/Ni, H2/Pd BaSO4 and Na/liquid NH3
forms three different reaction products (B), (C) and (D) respectively. (A) does not form
any salt with ammoniacal AgNO3 solution but forms a salt (E) on heating with NaNH2in
an inert solvent. Compound E reacts with CH3I to give (F). Compound (D) on oxidativeoznolysis gives n-butanoic acid along with another product. Give structures of (A) to (F)
with proper reasoning.
7. A hydrocarbon (A) containing 90% carbon reacts with dil. H2SO4in presence of HgSO4
to give (B). Compound (B) is reduced by LiAlH4 to (C) which on heating with H2SO4
gives (D) directly by hydrogenation in presence of deactivated Pd-CaCO3 catalyst.
Outline the reactions.
8. Identify the missing compound in the following sequence of reaction:i) 2 2 2 2H O H Br NaNHKOH( alc.)
2 Lindlar's catalystHCaC (A) (B) (C) (D) (E)
ii)
22 4 2 4 2
2
2
4H O LiAlH Conc. H SO Br H / Hg
2 3 H O
NaNH
Mg C (A) (B) (C) (D)
(E) (F)
iii) 2 2 4 4Br / h Br / CCl KMnOalcoholic KOH alcoholic KOH
3 2 2 3 1 mol HCH CH CH CH A B C D E
9. An hydrocarbon (A), C8H14, decolourises Br2/CCl4and cold dil. neutral KMnO4solution,
but does not react with ammonical AgNO3 and Cu2Cl2 solutions. It on ozonolysis
produced two molecules of the same acid (B), C4H8O2, which on heating with sodalimegave propane. What are (A) and (B) ?
10. A hydrocarbon (A) is treated with excess of HCl to give a dihalogen
compound (B), Subjective
Problem 1: 2-Butyne undergoes following reactions in steps as indicated. Identify A to H.
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2 2
2
H D / Pt
3 3 Ni B(P2)CH C CCH A B
2D / PtNa/ EtOH C D
2 2
2
H Br
Ni B(P 2)E F
2 2Br H
NiG H
Solution:A is obtained by syn addition A =
CH3
H H
CH3
cis
B is also obtained by syn addition B =
meso
CH3
H
D D
H
CH3
C is obtained by anti addition C =
H
CH3 H
CH3
D is mix of d- and l- (reacemic mixture) D =
d- and l-(racemic)
CH3
H
D H
D
CH3
E is obtained by syn addition E = as A
Addition of 2Br is anti F =
racemic
CH3
H
Br H
Br
CH3
G =
CH3
Br CH3
Br
H = as F
Problem 2: 3(l)Li, NHn BuC CMe A 4 2dil .KMnO /H O
3 2HCO H / H O2H
Lindlar's catalystB
C
Identify A, B and C with proper explanation.
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Solution:
n - BuC C H
H CH3
n - BuC C H
CH3 HA-trans
B-cis
3HCO H
Li,
3NH
2H
Lindlar's catalyst
(by anti addition) (by syn addition)
OH
CH3
H
H OH
n-Bu(C) - and its enantiomer (racemic)
n BuC CMe
4KMnO
Problem 3: One mole of a hydrocarbon (A) reacts with one mole of bromine giving a dibromo
compound 5 10 2C H Br . Substance (A) on treatment with cold, dilute alkaline
4KMnO solution forms a compound 5 12 2C H O . On ozonolysis (A) gives
equimolar quantities of propanone and ethanal. Deduce the structural formulaof (A).
Solution: 32
i) O
ii) HA Propanone + ethanal
So, A is
CH3
CH3
CH32-methylbut-2-ene
CH3
CH3
CH32-methylbut-2-ene
2Br CH3
CH3
Br
Br
CH3
2,3-dibromo-2-methylbutane
CH3
CH3
CH32-methylbut-2-ene
4alk. KMnO CH3
CH3
OH
CH3
OH
2-methylbutane-2,3-diol
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Problem 4: An unsaturated hydrocarbon A 6 10(C H ) readily gives B on treatment with
2NaNH in liquid 3NH . When B is allowed to react with 1-chloropropane a
compound C is obtained. On partial hydrogenation in the presence of Lindlar
catalyst, compound C gives D 9 10(C H ) . On ozonolysis D gives 2, 2-dimethyl
propanal and 1-butanal. With proper reasoning give the structures ofA, B, C and D.
Solution:
A = CH3
CH3
CH3
H
B = CH3
CH3
CH3
C Na
C = CH3CH3
CH3
CH3
D = CH3
CH3
CH3
CH3
Problem 5: A compound (X) when passed through dil 2 4H SO containing 4HgSO gives a
compound (Y) which on reaction HI and red phosphorous gives 2 6C H . The
compound (X) is?
Solution: The compound (X) is likely to be alkyne which reacts with water in presence of
2 4H SO and 4HgSO as catalyst to form a carbonyl compound. HI and red
phosphorous can reduce a carboxyl compound to alkane having same number of
carbon atoms.
Therefore (Y) is likely to be acetaldehyde which is the hydration product of
ethyne2 4
4
H SO
2 2 3HgSOX (Y)
HC CH H O [CH CH OH] CH CHO
red P
3 3 3 2 2CH CHO 4HI CH CH 2I H O
Problem 6: What is the major product by the addition of HCl to 2, 2, 2-trichloropropene?
Solution: 3CCl is a strongly electron withdrawing group. The addition of HCl to >C=C