semester-ii organic chemistry unit-1...
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SEMESTER-II ORGANIC CHEMISTRY
UNIT-1
CONFORMATIONAL ANALYSIS (ACYCLIC SYSTEMS)
SECTION A (Each question carries 5 marks)
1. Describe the Potential energy diagram of n-Butane
2. Write all the possible conformation of ethylene chlorohydrins and
indicate the preferred conformations. Give reasons?
3. Draw the preferred conformation of 1,1,2,2 tetra bromo ethane and
ethylene chlorohydrins?
4. Draw the preferred conformation of amino alcohols.Give reasons?
5. Draw the preferred conformation of 1,2 di bromo ethane and 1,2
difluoro ethane?
6. Illustrate Klyne Prelog terminology with examples?
7. Draw the preferred conformation of a. Acetaldehyde b. Butanone. Give
reasons.
8. Draw the conformation of Ethylene glycol and explain their stability?
9. Draw the preferred conformation of a. Propylene b. Propionaldehyde c.
1-butene.Give reasons.
10. What are conformational enantiomers? Explain with an example?
11. What are conformational enatiomers and conformational diastereomers?
12. Write all the possible conformations of Stilbenedibromide and indicate
the preferred conformations. Give reasons?
13. Write the preferred conformations of ethylene chlorohydrins and
indicate the preferred conformation.
14. Write all the conformations of Butane 2,3diol and indicate the preferred
conformationwith suitable reasons?
15. Write the possible conformations of ethane and indicate the preferred
conformations. Give reasons?
16. Write all the possible conformations of n-Butane and indicate the
preferred conformations. Give reasons?
17. Explain the use of spectral methods in Conformational analysis?
18. State and explain Curtin –Hammett Principle?
19. Explain the Winstein- Holness equation?
SECTION B
Each question carries 10 marks
1. a. What is Klyne- Prelog terminology? Illustrate with examples?
b. Draw the Staggered conformation of 2,3 butane diol and indicate
the preferred one for each. Give reasons?
2. a. State and explain Curtin –Hammett Principle
b. Explain briefly the factors affecting the conformation stability?
3.a. Discuss the importance of IR spectra and dipole moments in
conformational analysis?
b.Explain the Winstein- Holness equation?
4.a. Write all the possible conformations of Stilbenedibromide and
indicate the preferred conformations. Give reasons?
b. Describe the stereo-electronic requirements in E2 eliminations with
examples?
5. a. Write the most preferred conformations with reasons of the following
i) Ethylene glycol ii) Butanone iii) 1- butane iv) Propanaldehyde
v) 1-butane
b. Explain the reactivity of a cyclic diastereomer in undergoing syn
elimination
6. a. Illustrate Klyne- Prelog terminology with examples
b.Draw the staggered conformation of 2,3- dibromo butane and 2,3-
butane diol and explain the preferred conformations of each. Give
reasons?
6. a. Write all the possible conformations of 2,3- dihydroxy butane and 1,2-
dibromoethane and explain their respective stabilities?
b. Describe the role of Curtin –Hammet principle in stereo-selectivity?
8. a. What are Molecular rearrangements? Explain
b. Explain with examples the importance of physical and spectral methods
in conformational analysis?
9. a. State and explain Curtin –Hammet principle.
b. Explain the reactivity of 2S,3S 2,3 dibromobutane and 2R,3S 2,3
dibromo butane towards iodide induced debromonation?
10. a. Explain the use of spectral methods in Conformational analysis?
b. Explain the different factors that effect the stability of conformations?
Unit-2: Organic Reaction Mechanism-II
Section-A: Each question carries 5 marks.
1. Write ArSN2 mechanism. Give evidences.
2. What are SE1& SE
2 reactions? Write mechanism.
3. What is SET mechanism. Illustrate with an example.
4. What are ArSN1 mechanism? Write the mechanism.
5. Explain Ambident Nucleophile by giving examples.
6. Write short notes on non-classical carbocation by giving examples.
7. Predict the product & write its mechanism of formation of the following
reaction.
8. Explain about Von-Richter rearrangement.
9. Write short notes on the following.
a. Ambident nucleophile b. Reactions involving benzyne mechanism
10. Write the differences between classical & non-classical carbocations with
examples.
11. Define Neighbouring group participation. Explain the characteristic
features& also give examples of neighbouring groups.
12.Write about benzyne mechanism with examples & also give evidences for
benzyne mechanism.
13.What is anchimeric assistance? Explain by giving an example of reaction.
14. Acetolysis of δ-methoxy butyl brosylate takes place 1000 times faster than
n-butylbrosylate. Explain.
15. Explain Oxygen as Neighbouring group by giving an example of reaction.
16. Expalin halogen as Neighbouring group by giving an example of reaction.
17. Expalin the mechanism for the formation of products.
a) Erythro-2-bromo-3-butanol + HBr -------- Meso-2,3-dibromo butane
b) Threo-2-bromo-3-butanol + HBr ------ dl mixture of 2,3-dibromo butane
18. Acetolysis of trans-2-iodo cyclohexylbrosylate takes place nearly 3 million
times faster than cis isomer. Expalin
19.Expalin NGP of Sulphur& nitrogen by giving example of reactions.
20. Explain NGP of π & ϭ bond by giving example of reactions.
21.ExpalinSEi mechanism with examples.
Section-B: Each question carries 10 marks.
1. a. What is NGP? Explain its manifestation by giving two examples.
b. What is Von-Richter rearrangement? Write its mechanism & give
evidences.
2. a. Write notes on Non classical carbocation with examples.
b. Write about following: i. Ambident Nucleophile ii. Anchimeric assistance.
3. a. Give an account of different types of aliphatic electrophilic substitution
reactions by giving examples.
b. Compare classical & non-classical carbocations with examples.
4. a. Illustrate NGP using ϭ & π bonds with examples.
b. Discuss about benzyne mechanism. Give evidences for its existence.
5. a. Explain NGP of aryl group by giving examples.
b. Explain different types of SE2 mechanism by giving examples of reactions
with mechanisms.
6. a. Discuss about aromatic nucleophilic substitution by benzyne mechanism.
b. What are SE1 reactions? Explain with mechanism.
7. a. Write the product & its mechanism of formation when aryl diazonium salts
are heated in the presence of base.
b. Differentiate between SE1& SE
2 reactions with examples.
8. a. Nucleophilic Substitution reactions are accompanied by retention in the
configuration. Explain.
b. Explain NGP of alkyl group with example
9. a. Explain NGP of Cyclopropyl group with example.
b. Explain aromatic bimolecular nucleophilic substitution reaction with
mechanism by giving suitable reaction.
10. Explain the following reactions with mechanism.
a) L-Erythro-2-phenyl- 3-butyl tosylate + OAc- ------- L-Erythro-2-
phenyl-3-butyl acetate.
b) L-Threo-2-phenyl- 3-butyl tosylate + OAc- -------D & L mixture of –
Threo-2-phenyl-3-butyl acetate.
11. a. Write ArSN1 mechanism with suitable mechanism.
b. Explain SET mechanism.
12. a. Write ArSN2mechnaism with suitable mechanism.
b. Explain NGP of Nitrogen &sulphur atoms by giving examples.
13. a. Explain NGP of oxygen with suitable examples.
b. Explain NGP of halogens with suitable examples.
Unit-3: Reactive Intermediates & Molecular Rearrangements
Section-A: Each question carries 5 marks.
1. Arrange the following free radicals in the order of increasing stability by giving
proper explaination.
i) (CH3)3 C. ii) Ph2CH
. iii) Ph-CH2
. iv) Ph3C
.
2. Explain Bayer-Villiger oxidation with mechanism by giving an example.
3. Write about Pinacol-Pinacolone Rearrangement with example of reaction.
4. Name the rearrangement involved in the conversion of acid azides to
isocyanates. Explain the mechanism with an example.
5. How are carbocations generated?
6. Discuss the geometry & reactions of carbenes.
7. How are nitrenes generated?
8. write the mechanism of favourskii rearrangement.
9.Discuss the geometry & reactions of carbocations.
10. Describe Wolff rearrangement with mechanism.
11. Give the hybridization of the charged carbon in the following species.
a. Ph-CH2+
b. CH3-CH2+
c. CH2=CH-CH2-
d. CH3-CH2-CH2-
12. Explain the migrating aptitude of the groups with respect to Pinacol-Pinacolone
rearrangement & Baeyer –Villiger oxidation.
13. How are free radicals generated? Give their structure.
14. Discuss the stability & detection of carbocations.
15. Explain the mechanism of Beckmann rearrangement.
16. Predict the product & write the mechanism of the following reactions.
17. Explain the mechanism of the following rearrangements.
i. Smiles rearrangement ii. Favourski Rearrangement.
18. Arrange the following carbanions in the increasing order of their stability &
Explain the reason for your answer.
i. Cyclopropyl ii. Phenyl iii. Benzyl iv. Vinyl
19. What is the difference between Lossen& Hoffmann Rearrangements.
Explain with examples & mechanism.
20. Write the products formed in the following reactions.
21. What are the factors affecting the stability of Carbanions?
Section-B: Each question carries 10 marks.
1. Explain the mechanism of the following rearrangements:
a. Smiles Rearrangement
b. Favourski Rearrangement
2. a. Predict the product & write the mechanism of the following reaction:
b. Write the mechanism of Bayer- villiger oxidation.
3. a. Explain the mechanism of the following rearrangements:
i. Sommelet- Hauser Rearrangement
ii. Benzil-benzilic acid Rearrangement
b. Discuss the generation, geometry & reactions of carbanions.
4. a. Write the products formed & the mechanism of the following reactions.
b. Discuss the reactions of carbenes&nitrenes.
5.a. Write the products formed & the mechanism of the following reactions.
6.a.How are carbenes generated? Discuss their structure.
b. Explain the following mechansms:
i. Hoffmann Reaction ii. Lossen Rearrangement
7.a. Discuss the generation of carbanions. Write any two reactions.
b. Describe the mechanism of following rearrangements.
i. Pinacol-Pinacolone Rearrangement ii. Baeyer-Villiger oxidation
8.a. How are carbenes generated? Write any two reactions.
b. Explain the mechanism of the following rearrangements:
i. Beckmann Rearrangement ii. Smiles Rearrangement
9.a. How nitrenes are generated? Describe their two important reactions.
b. Describe the mechanism of following rearrangements.
i. Benzilic acid Rearrangement ii. Baeyer-Villiger oxidation
10.a. Describe the general methods of generation of carbon free radicals & how
they are detected
b. Write the mechanism of the following reaction mechanism.
i. Curtius Rearrangement ii. Schmidt Rearrangement
11.a. Discuss the factors affecting the stability of carbocations.
b. Write the products formed in the following reactions.
12.a. Explain any two methods of detection of free radicals.
b. Predict the product in the following & suggest the mechanism.
13.a. Outline the mechanism of Bayer Villiger& Wolff Rearrangement
b. Discuss the generation, structure & stability of carbocations.
14.a. Discuss the molecular rearrangements involving electron deficient
nitrogen with an example.
b. How are carbanions generated? Write any 2 reactions.
15.a. Define Rearrangement. Discuss the mechanism of Rearrangement
involving electron deficient oxygen.
b. Discuss the structure & generation of carbanions.
16. a. outline the mechanism of the following:
i. Favourski Rearrangement ii. Beckmann Rearrangement
b. Explain Allylic rearrangement with examples.
17.a. Write any 3 methods of generation of free radicals.
b. Explain Transannular Rearrangement with 2 examples & write mechanism
18.a. Write any 3 methods of generation of carbocations.
b. Explain the mechanism of the following reactions.
19.a. Discuss the Favourskii rearrangement with mechanism by giving
examples
b. What is the order of stability of the following carbanions.
i. R3C-CH2- ii. R2CH=CH
- iii. R-C≡C
-
20.a. Arrange the following free radicals in the order of increasing stability by
giving proper explaination.
i. (CH3)3 C.
ii. Ph2-CH. iii. Ph-CH2
. Iv. Ph3-C
.
b. Explain how the following transformation can be effected.
21.a. Predict the product & write the mechanism of the following reaction.
i. β-phenyl ethyl bromide + NaOEt ------------ ?
ii.
b. Arrange the following carbocations in the increasing order of their stability
& explain the reason.
UNIT-4: HETEROCYCLIC COMPOUNDS &NATURAL PRODUCTS
SECTION-A(5Marks)
Heteocyclic Compounds:
1)Write the IUPAC names for the following heterocyclics
NH
CH3
N
CH3
OHO
O
i)
ii)
iii)
2) Describe FischerIndole synthesis
3)Outline the Bischler-Napieralski synthesis of isoquinoline.
4)Explain why quinoline is a stronger base than indole.
5)Discuss the classification of nitrogen heterocycles based on their ring size,with
IUPAC nomenclature.
6)Write the importance of heterocyclics.
7)Why electrophilic substitution takes place on 3rd
position of indole? Explain.
8)Indole+ CHCl3/KOH → ?
9)Write the IUPAC names for the following Heterocyclics.
NNH
S
CH3
CH3
CHO
i)ii) iii)
10)Write the structures of
i) 2-Methyl benzofuran ii) Indole-3 carboxylic acid iii) 3-Nitro benzofuran.
11)Formulate the synthetic method for benzofuran from O-OH benzaldehyde.
12)
NH
MeMgI
H2O RT
?
13)Explain the importance of heterocyclic compounds in living organisms.
14)Discuss the importance of heterocyclic compounds as drugs.
15)Discuss the classification of oxygen heterocyclics based on ring size and give
their IUPAC names.
16) Write the structure of the following
i) 3-n-propyl-5,6 –dimethyl indole
17) Outline the synthesis of isoquinoline derivatives of Bischler-Napieralski
procedure.
18) Write any two important reactions of Isoquinoline.
19) Write the IUPAC names of the following
O
O
C2H5
O
SECTION-B( 10M)
1) Complete the following reactions and give the products.
N
Li in Liq NH3
?
O OAq NaOH
?
O OLiAlH4 / H2O
?
NH
NaH
DMF r.temp?
2) Write the synthesis of Quilnoline by Skraup synthesis
3) a) What is Skraup synthesis? Discuss its mechanism.
b)Write briefly on the nomenclature of heterocyclic systems based on ring size
and nature of hetero atoms.
4) Predict the products in the following.
N
Li in Liq NH3
?
O O
?
?
NH
HNO3
?
KOH
H2SO4
O
HNO3 / H2SO4
5) Give one synthesis each of the following.
i)Coumarin iv) Quinoline
6) i)Describe with examples, the importance of heterocyclic compounds.
ii) Outline the synthesis of indole derivatives by Fischer synthesis and write the
mechanism.
7)Write the nomenclature rules of heterocyclic compounds.
8) Write notes on Reactivity of indole
9)Discuss the nomenclature of heterocyclic compounds based on the number and
nature of heteroatoms.
10)Describe the synthesis & reactivity of indole.
11)
NH
?CHCl3/ alc KOH
with mech
+ ?
12)Outline the synthesis of i) carbazole iii) isoquinoline
13)Discuss with brief mechanistic outlines of the following
i) Bischler-Napieralski synthesis of isoquinoline
ii)SN2 reactions of quinoline.
14) Explain the reactivity Quinoline
15)Outline two reactions of i) Isoquinoline
16)Give the products and rationalize their formation in the following synthetic
reactions.
NH
+ HCHO + Me2NH
AcOH
heat
?
NH2
H3C
+
O
ZnCl2,FeCl3
EtOH, reflux
?
O2N
P(OEt)3
reflux
?
17) Discuss the reactions of quinoline
18)Outline one method for the synthesis of iii)coumarin iv) carbazole
19) Explain the pi-excessive and pi-deficient systems with one suitable example
for each.
Natural Products:
Section-A (5 M)
1. What are natural products? Draw the structures of any four natural product
drugs.
2. How are terpenoids classified? Give one example for each class.
3. What is the significance of i) isoprene rule ii) special isoprene rule ?
4. Describe the techniques for isolation of monoterpenoids.
5. Define the term alkaloid and list out some important uses of alkaloids.
6. How are alkaloids detected? Describe the general procedures for the extraction
of alkaloids.
7.Write synthesis of camporic and camphoronic acid.
8. What is Hoffmann exhaustive methylation?
9. Formulate the products of the following reaction and explain the mechanism
involved in each case.
Quinotoxine +NaoBr +NaOH →
10. Discuss any two chemical methods employed in the isolation of natural
products.
11. How are alkaloids classified?
12. Define and classify natural products
13. Write the structure of ii)Camphor
14. Write a brief account of the importance of the natural products as drugs.
15. Write the synthesis of camphor.
16. Complete the following
NMe
MeI / AgOH
BrCN/HBr
?
?
17. What is Herzigmayer method?
18. Write the structure of i) camphor iii) Quinine
SECTION-B(10Marks)
1. How the structure of camphor established from degradation reactions?
2. What information one gets from the Hofmann exhaustive methylation and Emde
degradation of an alkaloid? Discuss any two examples.
3. Discuss the structure determination of quininic acid part of quinine.
4. Discuss the structure determination of meroquinine part of quinine.
5. Describe the reactions that give information regarding the linkage of quininic
acid part to meroquinene.
6. Discuss Woodward’s synthesis of quinine.
7.a)Formulate the structure elucidation of camphor
b)Explain the isoprene rule.
8)Discuss the structural elucidation of Camphor.