Loyola College Organic Chemistry Question Papers

Loyola College M.Sc. Chemistry April 2008 Organic Chemistry Question Paper PDF Download

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LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

GH 50

 

FIRST SEMESTER – APRIL 2008

CH 1801 – ORGANIC CHEMISTRY – I

 

 

 

Date : 16-04-08                  Dept. No.                                        Max. : 100 Marks

Time : 1:00 – 4:00

 

Part-A

                                                     Answer ALL questions.                                       (10 ´ 2 = 20)

 

  1. Explain Prelog’s rule with a suitable example.
  2. What is mutarotation? Give an example.
  3. How would you resolve racemic alcohols?
  4. Dehydrobromintion of threo-1-bromo-1,2-diphenylpropane is faster than erythro. Explain.
  5. ‘Aryldiazonium salt involves both in electrophilic and nucleophilic substitutions’. Justify.
  6. What is first order asymmetric transformation? Give an example.
  7. How do inductive and field effects affect the second substitution in aromatic systems?
  8. In 4-t-butylcyclohexanecarboxylic acid, trans form is more acidic than cis isomer in 66% aquesous DMF. Explain.
  9. How is the existence of NO2+ proved in nitration reaction?
  10. How does trapping method help in determining the mechanism of a chemical reaction?

Part-B

                                                Answer any EIGHT questions.                                  (8 ´ 5 = 40)

  1. The diazotization of aniline in moderately concentrated acid has been found to be

second order in HNO2. Explain.

  1. How will you determine the configuration of
    a) (-) mandelic acid with respect to (+) lactic acid?
    b) (-) lactic acid  with respect to (+) tartaric acid?
  2. How will you correlate the configuration of (+)-a-phenyl-a-methylbutyric acid and     (-)-2-phenyl-2-butanol by Baeyer-Villiger rearrangement?
  3. How do cross over experiments help in determining the mechanism of a chemical

reaction. Explain with an example.

  1. Explain the following:
    a) Asymmetric destruction            b) Biochemical asymmetric transformation
  2. What is Bucherer reaction? Explain the mechanism of the reaction.
  3. Explain the mechanism of sulphonation of benzene in presence of oleum? Why is sulphonation of benzene reversible?
  4. Dehydrobromination of diastereoisomeric a-phenyl-b-bromo-b-benzolypropionic acids with hot pyridine give different products. Explain.
  5. Acetolysis of  diastereoisomeric   3-phenyl-2-pentyltosylate   and 2-phenyl-3-pentyl tosylate give different products.   Account for your answer and explain the formation of the products.
  6. What are consecutive reactions? Give two examples. Apply conditions and derive specific rate expression.
  7. Explain the conformation of n-butne(C2-C3 rotation) with potential energy diagram.
  8. What are the different stereoisomeric aldopentoses? Draw their structures and give their names.

 

PART-C

                                               Answer any FOUR questions.                                  (4 ´ 10 = 40)

  1. a) How do isotopic labeling and stereochemistry help in predicting suitable reaction mechanisms? Give examples.
  2. b) ‘meso form of stilbene dichloride has a dipole moment 1.27D while the dl-pair has 2.75D’.
  3. a) Explain the racemization via cations and anions with suitable examples.
  4. b) Prove that Hammett equation is LFER. How is the orientation and reactivity of

electrophiles normally studied? Briefly explain with examples.

  1. a) Discuss the similarities and differences in Friedel Crafts alkylation and acylation

reactions with suitable examples.

  1. b) Which one among 2,6-Dimethyl-4-nitroaniline and 2,5-dimethyl-4-nitroaniline is a weaker base?  Justify your answer.
  2. a) Explain the octant rule with a suitable example.
  3. b) The cotton effect curves of (+)-3-methylcyclopentanone in methanol shows only a 24% reaction upon addition of acid
  4. a) Compare the ipso-attack in aromatic electrophilic substitution with the SNAr  mechanism.
  5. b) ‘The reaction between ethylene oxide and HBr in water is a third order reaction’. Explain.
  6. Explain the following:
    a) meso-stilbene dichloride on heating with pyridine at 200°C gives no product while dl-isomer gives alkene readily.
    b) erythro-3-bromo-2-butanol with HBr gives meso product
    c) Dehydrochlorination of 1,2-diphenyl-1-chloroethane gives trans product fastly but cis product slowly.
  7. d) Benzyne intermediate can be trapped using anthracene.

 

 

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Loyola College B.Sc. Chemistry April 2003 Organic Chemistry I Question Paper PDF Download

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LOYOLA  COLLEGE (AUTONOMOUS), CHENNAI-600 034.

B.Sc. DEGREE  EXAMINATION  – chemistry

second SEMESTER  – APRIL 2003

CH  2500/ che 502 organic chemistry – I

23.04.2002

9.00 – 12.00                                                                                        Max: 100 Marks

 

 

PART – A                      (10 ´ 2 = 20 Marks)

                                                 Answer ALL the questions.

 

  1. Which alcohol of the following pair would you expect to be more

easily dehydrated? Why?

(CH3) C(OH) CH2 CH3 (or)  (CH3)2 CH CH (OH)  CH3.

  1. State and explain Markonikov’s rule.
  2. How would you distinguish 1-butyne from 2-butyne?
  3. Identify the product in the following.

R-CH = CH2  +  CCl4             ?

  1. Anti-Markonikov’s rule is possible only for the addition of HBr in presence of

peroxides to an unsymmetrical alkene  and not for HCl or HI.  Why?

  1. ‘The presence of a small amount of O2 slows down the chlorination of methane’.
  2. In a study of Chlorination of  propane, four products of formula C3 H6 Cl2

were isolated.  What are their structures?

  1. Acidity of the following Carboxylic acids is in the following order.

Cl2 CH COOH   >  F CH2 COOH  >  Cl CH2 COOH.  Explain.

  1. Many -but not all molecules – that contain a cheral centre are chiral.
  2. How do the properties of diasteromers compare?

 

PART – B                          (8 ´ 5 = 40 Marks)

Answer any eight questions

  1. Identify the products of obtained in the dehydration of 3 -methy1-2 butanol.

Which one is major?  Justify your answer.

  1. Arrange the following compounds in order of reactivity toward dehydrohalogenation  by strong base.   Account for your answer.

1-bromobutone, 1-brome-2,2 – dimethyl propane,

1-bromo-2 methylbutane, 1-bromo-3-methylbutane.

  1. Account for the following

(i)         trans -alkene is more stable than cis -alkene.

(ii)        NBS is preferred for allylic halogenation.

  1. 98% H2 SO4 is required to hydrate ethylene while 63% H2 SO4 is enough for

isobutylene.  Explain

  1. Explain with mechanism the addition of HBr to 1,3-butadiene as 1,2-  Vs 1,4 addition.
  2. How would you prepare cis and trans alkenes from alkynes?

Explain with an example.

  1. Give the mechanism of chlorination of methane is the presence of uv light.

Explain the relative reactivities of F2, Cl2, Br2 & I2 towards methane.

 

 

 

 

 

 

  1. How do you prepare the following?

(i)         n-nonane starting with CH3 Br.

(ii)        3- methyl octane starting with sec-butyl chloride.

  1.    In the halogenation of alkanes, bromine atom is much more selective than

chlorine atom.  Explain [ relative rate factors of  1600: 82:1 for Br2 Vs 5.0: 3.8:1 for Cl2 for the reaction at tertiary: secondary: primary hydrogen]

  1.    Account for the following.

(a)        Chlorination of ethane is  400 times  faster than that of methane when         equimolar   amounts of  both are reacted with  a small amount of C12 .

(b)        chlorination of propane gives 45% of CH3 CH2 CH2 Cl and
55%  of CH3CH(Cl) CH3.

  1.    Draw and specify as  R or S, the enantiomers of

(i)  CH3 CH (OH) COOH  (ii) Sec-butyl chloride
(iii)   Bromo chloro iodomethane

  1.    What is a racemic modification?  Discuss any two methods of resolving a

recemic modification.

 

 

PART – C                           (4 ´ 10 = 40 Marks)

Answer any FOUR questions.

  1. a) Explain the stability of conjugated dienes based  on hydrogenation data.
  2. b) Explain the acidity of acetylene compared with water, ammonia and
  3. Account for the following
  4. Hydration of acetylene gives CH3
  5. Industrially acetylene is prepared from coal.
  6. Propene reacts with HOCl gives propylene chloro hydrin.
  7. 2-methyl-l-butanol on dehydration mainly gives 2-methyl 2-
  8. Sec-butyl trimethyl ammonium ion on treatment with strong base              undergoes elimination.
  9. a) Explain the mechanism of addition of halogens to alkene.
  10. b) Explain the mechanism of anti-Markonikov’s rule.
  11. Explain homogenous and heterogeneous hydrogenation of alkenes with an     Discuss the mechanism for both in detail.
  12. Draw the different conformation of ethane and n-butane, considering the

rotations about the bonds shown.  CH3-CH3 and CH3CH2-CH2CH3.  Draw the

potential energy Vs rotation curve for both and explain the strain and rotational  barrier involved.

  1. Draw the stereocherical formulas of the dichlorobutanes obtained by the

free-radical chlorination of (i) (S) -Sec-batyl chloride,  (ii) (R) -Sec-butyl chloride and  (iii)  racemic-Sec-butyl chloride.  Give  the ratios of the different 2,3-dichlorobutanes obtained in the case of  (i),(ii) & (iii) and Explain.  Also comment on the optical activity of the mixtures of 2,3-dichlorobutanes  obtained in (i)  ,(ii), & (iii).

 

               

 

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Loyola College B.Sc. Chemistry April 2006 Organic Chemistry – II Question Paper PDF Download

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             LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

B.Sc. DEGREE EXAMINATION – CHEMISTRY

LM 9

FOURTH SEMESTER – APRIL 2006

                                                     CH 4500 – ORGANIC CHEMISTRY – II

(Also equivalent to CHE 507)

 

 

Date & Time : 25-04-2006/9.00-12.00         Dept. No.                                                       Max. : 100 Marks

 

 

Part A

Answer all the questions.                                                                          10´2=20

  1. Give an evidence for the resonance structure of benzene.
  2. What is aldol condensation?
  3. Cyclopropane readily undergoes ring-opening reactions. Explain
  4. Why is tropylium cation aromatic?
  5. What will be the major product formed on dehydrohalogenation of 2-bromo-2,3-dimethylbutane.
  6. Name the following alcohols by carbinol and IUPAC system:
    • CH3-CHOH-CH=CH2
    • CH3-CH2-C(CH3)(OH)-CH2-CH2-CH3
  1. C-O-C bond angle in diethyl ether is greater than H-O-H bond angle in water. Explain.
  2. Arrange the following in the order of increasing acidity.

p-toluic acid, phenyl acetic acid, m-nitrobenzoic acid, benzoic acid.

  1. Accont for the lower boiling point and decreasing water solubility of o-nitrophenol as compared with their m- and p- isomers.
  2. What is coupling reaction? Give an example.

Part B

Answer any eight questions.                                                                      8´5=40

  1. Aromatic electrophilic substitution in phenol takes place at ortho and para positions. Explain.
  2. Design a synthesis that would convert phenol primarily to a) o-bromophenol
    b)p-bromophenol.
  3. Give the major products of the following reactions with reason.
  1. bromination of p-fluorotoluene
  2. nitration of p-nitrotoluene
  3. Explain the stability of cyclohexane on the basis of Sache Mohr theory and the potential energy diagram.
  4. Give reasons for the following:
    1. p-chloronitrobenzene has less dipole moment than p-nitrotoluene.
    2. Nitrobenzene and not benzene is used as a solvent for Friedel-Craft’s    alkylation of bromobenzene.
    3. c) Halogens are o-p directors but are deactivating.
    4. Explain the mechanism of Cannizaro reaction.
    5. Explain the mechanism of hydroboration-oxidation of alkenes.
    6. Write the mechanism of nitration of methyl phenyl ether.
    7. Convert the following:
  5. Phenol into salicylic acid
  6. Salicylic acid into a-chloro benzoyl chloride.
  7. Explain Gabriel phthalimide synthesis.  How would you use this method in the preparation of glycine and n-propyl amine?
  8. What is diazodisation? How is benzene diazonium chloride prepared? Give its

mechanism.

  1. Discuss the mechanism of pinacol-pinacolone rearrangement.

Part C

Answer any four questions.                                                                     4´10=40

  1. a) Explain the mechanism of formation of 2,4-dinitrophenylhydrazone derivative from acetone.
  2. b) Compound A with the molecular formula C5H8O2 on reduction forms n-pentane and forms dioxime with hydroxylamine. It gives positive test with Tollen’s reagent and also forms iodoform. Suggest a suitable structure of the compound.
  3. a) Two isomeric hydrocarbons A and B have molecular formula C8H10. A on oxidation gives benzoic acid while a dicarboxylic acid is formed by the oxidation of B which later on heating forms anhydride. Suggest the structures of A and B.
  4. b) CH3-CH (X) – CH2– CH2– CH3 on dehydrohalogenation forms 2-pentene and 1-

pentene. The major and minor product varies with respect to the substituents.

Explain the reactions with reason.

Substituents 2-pentene 1-pentene
Br 80% 20%
Cl 75% 25%
F 65% 35%
S+R2 30% 70%
N+R3 30% 70%

 

  1. a) When nitrobenzene is nitrated m-dinitrobenzene is formed as the major product whereas anisole on nitration forms a mixture of o- and p-nitro compounds. Explain.
  2. How are the following conversions done?
    1. phenol to cyclohexane
    2. cyclopropane to butanoic acid.       (6+2+2)
    3. i) Explain the mechanism of Reimer-Tiemann’s reaction. (4+6)

ii)Identify the products ( A, B, C and D) in the following sequence of reactions.

Isopropyl alcohol   A

B   C  D

  1. a)Write any two methods of preparation of each primary, secondary and tertiary

amines.                                                                                                               (6)

b)Phenol is less acidic than trinitrophenol and carboxylic acids.  Explain.       (4)

  1. a) Explain the mechanism of Hofmann rearrangement. (6)
  2. b) How will you convert phenol into salicylaldehyde? Give the mechanism.   (4)

 

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Loyola College B.Sc. Chemistry April 2006 Organic Chemistry – I Question Paper PDF Download

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             LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

B.Sc. DEGREE EXAMINATION – CHEMISTRY

LM 4

SECOND SEMESTER – APRIL 2006

                                                     CH 2500 – ORGANIC CHEMISTRY – I

(Also equivalent to CHE 502)

 

 

Date & Time : 24-04-2006/1.00-4.00 P.M.   Dept. No.                                                       Max. : 100 Marks

PART – A

                                                Answer all questions                         (10 ×2 = 20 marks)

  1. Draw the sawhorse and Newman projection structures of propane.
  2. Arrange the following in the increasing order of stability.
    1, 3-butadiene, 1, 2-butadiene, 1, 4-butadiene.
  3. Draw the structure of
    (a) (Z)-3-isopropyl-2-heptene (b) (E)-1-bromo-2-chloropropene.
  4. Define the following (a) racemic mixture (b) resolution.
  5. Arrange the following in the increasing order of reactivity towards Diel’s-Alder reaction.
  6. What are the factors that affect the free radical halogenation of alkanes?
  7. What is Baeyer’s test?
  8. What happens when calcium carbide is treated with water?
  9. What is Wurtz reaction?
  10. Draw the structure of the following compounds
  11. a) 2,6-dimethyl-4-ethyl-2,4-heptadiene
  12. b) 3,5-diethyl-1,7-octadiyne.

PART – B

                                                Answer any eight questions             (8 × 5 = 40 marks)

  1. What are conformers? How are they different from configuraitonal isomers? Give an example.
  2. Predict the product with mechanism for the reaction of 2, 4-hexadiene with HCl.
  3. The specific rotation of R-(+)-glyceraldehyde is + 8.7°. If the observed rotation of a mixture of R-glyceraldehyde and s-glyceraldehyde is +1.4°, what percent of glyceraldehydes is present as the R enantiomer?
  4. Draw the various stereoisomers of 3-chloro-2-butne and indicate which of them are entantiomers and diastereomers.
  5. Predict the product with mechanism
  6. Define the following
    a) asymmetric synthesis b) chemoselectivity c) regioselectivity.
  7. Compare the free radical chlorination and bromination of methane for reactivity and quantum yield.
  8. Why the alternative mechanism of chlorination of methane is not possible? Explain with proof.
  9. What is Kolbe’s synthesis? How is butane synthesized by above method?
  10. How is ozonolysis used to differentiate 1-butene and isobutene. Write the mechanism of the above reaction.
  11. What are the products formed when 1-butyne is subjected to hydroboration and oxidation. Explain the mechanism of the reaction.
  12. Give the mechanism of addition of bromine to ethylene.

PART – C

                                                Answer any four questions   (4 × 10 = 40 marks)

  1. Indicate whether the following pairs of compounds are identical or enantiomers or constitutional isomers.
  2. Perform a conformational analysis of rotation of C2-C3 bonds in n-butane and explain using a potential energy diagram.
  3. a) Dienes undergo free radical reactions faster than alkenes. Why?
    b) What are atropisomers? Give suitable example.
    c) Which of the following conjugated dienes would not react with a dienophile in
    Diel’s-Alder reaction? Why?
  4. Explain in detail the chlorination reaction of methane. How many products are formed? Discuss the rate of the reaction and the reaction mechanism of the reaction.
  5. a) A hydrocarbon reacts with conc. H2SO4 to form an alkyl hydrogen sulphates which on hydrolysis yields tert-butyl alcohol. What is the structural formula of the hydrocarbon? Write the equations.
  6. b) Write the structure of the alkene, which on ozonolysis gives 2-butananone and 2-mehtylpropanaldehyde. Write the mechanism of the reactions.
  7. a) compound A, C4H6 gave the following tests
  8. i) A + Br2 / CCl4 ® B (C4H6Br4)
  9. ii) A + H2 / Pt® C (C4H10)

Identify A, B and C

  1. b) What are the uses of the following compounds?
  2. i) ethylene ii) acetylene iii) propene

 

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Loyola College B.Sc. Chemistry April 2007 Organic Chemistry – I Question Paper PDF Download

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LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

B.Sc. DEGREE EXAMINATION – CHEMISTRY

LM 05

SECOND SEMESTER – APRIL 2007

CH 2500 – ORGANIC CHEMISTRY – I

 

 

Date & Time: 20/04/2007 / 1:00 – 4:00        Dept. No.                                                Max. : 100 Marks

 

 

PART – A

 

Answer ALL the questions                                   (10 x 2 = 20)

 

  1. Classify the following groups into +I and –I groups: i) CH3 ii) NH2 iii) NO2 iv) Cl
  2. Give the differences between mesomeric effect and inductive effect.
  3. Define torsional strain and torsional energy.
  4. Give the eclipsed and staggered conformations of n-butane.
  5. Give the IUPAC names and the structures of the products formed by the reaction of 1-pentyne with one mole of HBr and a peroxide.
  6. What is Markownikoff rule? Explain with an example.
  7. Why is acetylene acidic?
  8. What is Diels-Alder addition reaction?
  9. Differentiate between enantiomers and diastereomers.
  10. Assign R & S notation to the following compounds:

 

PART – B

Answer any Eight questions                                                        (8 x 5 = 20)

 

  1. Distinguish between a) absolute and relative configuration b) meso and racemic forms
  2. Draw the Fischer-projection formulae for all the possible stereoisomers of 2,3-dichlorobutane and specify as R or S configurations to the asymmetric carbon.
  3. How is 1,3-butadien prepared? Give the reactions of 1,3-butadiene with a) maleic anhydride     b) HBr.
  4. Explain the mechanism of halogenation of alkane.
  5. How will you prepare the following compounds from acetylene:
  6. a) acetaldehyde              b) ethyne         c) vinyl chloride
  7. Write short notes on i)Wurtz synthesis ii) Corey House synthesis.
  8. How will you prepare the following:
  9.             i)  n-propanol from propene    (ii) Glycol from ethylene.

 

  1. Explain the mechanism of markownikoff and antimarkownikoff addition of propene.
  2. Write short notes on a)hydroboration reaction b) addition polymerization reaction
  3. Explain the mode of hybridization of carbon in methane, ethylene and acetylene.
  4. Explain cis and trans addition with an example.
  5. Write down the structural formulae of the olefin from which the following products are obtained on ozonolysis:
  6.                     a) cyclopentanone and acetone   b) ethylmethyl ketone and propanaldehyde

 

PART – C

 

Answer any FOUR questions                                                (4 X 10 = 40)

 

  1. a) Explain why aliphatic amines are more basic than aromatic amines.

b)Explain the various factors affecting the stability of primary, secondary,                                                     tertiary and methyl carbonium ions

  1. Explain the rate of halogenation of alkanes and the factors affecting the rate of the reaction.
  2. Explain the 1,4- and 1,2- addition reactions of butadiene in detail.
  3. Give the mechanism of the following reactions: a) dehydration of alcohols b) dehydrohalogenation c) peroxide effect d) alkylation of alkene.
  4. Bromination of an organic compound(A) of formula C6H12 yields C6H12Br2. On reduction of the compound gives 2-methylpentane. On oxidation it yields a mixture of acetic acid and isobutyric acids. Assign the structural formula to the organic compound. Express the above reaction by chemical equation and give the IUPAC names of A and other products.
  5. a) Discuss the conformational analysis of 1,2-dichloroethane with potential energy diagram. b) Give the E or Z notation to the following compounds:

 

 

 

 

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Loyola College B.Sc. Chemistry April 2007 Organic Chemistry – II Question Paper PDF Download

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LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

B.Sc.

LM 11

DEGREE EXAMINATION –CHEMISTRY

FOURTH SEMESTER – APRIL 2007

CH 4500 – ORGANIC CHEMISTRY – II

 

 

Date & Time: 21/04/2007 / 9:00 – 12:00          Dept. No.                                                     Max. : 100 Marks

 

 

 

PART-A                                      

Answer ALL questions.                                                                                  (10 ´ 2 = 20)

  1. ‘cyclopropane is more reactive than cyclohexane’.  Explain.
  2. How will you prepare a vicinal dihalide from an alkene?
  3. Why are lower member of alcohols soluble in water but not the higher members?
  4. Ka of CH3COOH, ClCH2COOH, Cl2CHCOOH and CCl3COOH are 1.75 ´10-5,
    136 ´10-5, 5530 ´10-5 and 23,200 ´10-5 respectively. Provide a suitable explanation.
  5. What is the stereochemistry of the products obtained on the addition of bromine on

maleic acid?

  1. How will you synthesise ethylbenzene from acetophenone?
  2. How will you distinguish between benzaldehyde and acetophenone?
  3. Arrange the following series of compounds in order of increasing acid strength. Give reasons for the order you select.

Benzoic acid, p-ethylbenzoic acid, p-nitrobenzoic acid, o-,p-dinitrobenzoic acid.

  1. What is Kolbe reaction?
  2. Write any one example for diazo coupling reaction.

 

PART-B                                      

Answer any eight questions.                                                                           (8 ´ 5 = 40)

  1. Write the mechanism for the following reaction

CH3-CH2-CH=CH2   ­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­

  1. How will you prepare 4-methyl pentanoic acid using diethyl malonate?
  2. Explain Baeyer’s strain theory of cycloalkanes.
  3. a) Write the mechanism for the action hydroiodic acid on ethyl methyl ether? (3)
  4. b) What is the action of ethyl iodide on sodium phenoxide? (2)
  5. Complete the following reactions.
  6. a) Acrylic acid     +     HBr        ¾¾®
  7. b) Neopentane     +      Cl2
  8. c)   Bromoethane   +      C6H6
  9. d) Propanol
  10. e) 2 – bromobutane
  11. How would you distinguish between primary, secondary and tertiary alcohols by Victor-Meyer’s method?
  12. Give the mechanism of Friedal-Craft’s acylation of benzene.
  13. Write a note on: (a) Cannizaro reaction (b) Perkin reaction
  14. Write any three synthetic applications of acetoacetic ester.
  15. What happens when benzamide is treated with bromine in KOH solution? Explain the mechanism.
  16. Write a note on: Reimer-Tiemann reaction.
  17. Give the product and write the mechanism.

C6H5COCH2CH3 ??

 

 

PART-C

Answer any FOUR questions.                                                                       (4 ´ 10 = 40)

 

  1. a) Explain the mechanism of the following reaction and discuss the

stereochemistry of the product formed.                                                           (6)

CH3Br    +    KOH      ¾®     CH3OH   +   KBr

  1. b) Discuss the effect of polarity of the solvent on the rate of SN1 and SN2 reactions.           (4)
  2. a) Explain the stability of various conformations of cyclohexane with a potential

energy diagram.                                                                                                  (6)

  1. b) Explain the factors affecting the stability of conformations.                           (4)
  2. a) How will you prepare the following alcohols using a Grignard reagent? (6)

(i) n-butyl alcohol    (ii) tert-butyl alcohol      (iii) sec-butylalcohol

  1. b) How will you distinguish CH3OH and C2H5OH using a simple chemical test.(4)
  2. a) Discuss the molecular orbital structure of Benzene. (5)
  3. b) Write a note  on: Benzoin condensation                                                           (5)
  4. a) How will you synthesise sulphanilamide from aniline? Give its importance.  (5)
  5. b)  How will you synthesise m-nitrophenol from nitrobenzene?                          (5)
  6. a). How will you convert phenol into:

(i)  benzene  (ii) anisole   (iii) 2,4,6-tribromophenol.                                 (2+2+2)

  1. b) What is Claisen rearrangement? Explain the p-migration mechanism of
    2,6-dimethyl allyl phenyl ether.                                                                    (4)

 

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“Loyola College B.Sc. Chemistry April 2008 Organic Chemistry – II Question Paper PDF Download”

by

LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

B.Sc. DEGREE EXAMINATION – CHEMISTRY

GH 54

 

FOURTH SEMESTER – APRIL 2008

CH 4500 – ORGANIC CHEMISTRY – II

 

 

 

Date : 26/04/2008                Dept. No.                                        Max. : 100 Marks

Time : 9:00 – 12:00

 

 
Part-A

                                                     Answer ALL questions.                              (10 ´ 2 = 20)

 

  1. ‘cyclopropane is more reactive than cyclohexane’. Why?
  2. What are the conformers possible for cyclohexane? Which one is more stable? Why?
  3. How would you distinguish methanol from ethanol by means of chemical tests?
  4. ‘Williamson’s synthesis is useful for the preparation of both simple and mixed ethers’. Justify this statement with suitable examples.
  5. Arrange the following in the increasing order of their acidity. Justify your answer.

Monochloroacetic acid, Dichloroacetic acid, Acetic acid, Formic acid and Trichloro acetic acid.

  1. What happens when maleic acid is treated with bromine? Identify the stereochemistry of the product obtained?
  2. Name the electrophile in nitration of benzene. What are the evidences for its existence?
  3. ‘Aniline does not undergo Friedel-Craft’s reaction’. Why?
  4. How would you prepare the following from benzene diazonium chloride?
    (i) Benzene   and  (ii) Benzoic acid
  5. Give the mechanism of Reimer-Tiemann reaction.

 

Part-B

                                                 Answer any EIGHT questions.                      (8 ´ 5 = 40)

 

  1. Explain Baeyer’s strain theory in the stability of cycloalkanes.
  2. How are alcohols prepared from hydroboration-oxidation method? Explain with mechanism.
  3. An amide(A) having molecular formula C3H7ON on hydrolysis gives an acid C3H6O2(B). (B) on chlorination in the presence of red phosphorus produces a chloroacid(C).The latter on boiling with aqueous NaOH and subsequent acidification forms lactic acid(D).Write the reactions and identify the structure of A, B, C and D.
  4. What happens when benzaldehyde is heated with alcoholic KCN solution? Explain the mechanism.
  5. How would you prepare 4-methylpentanoic and 3-methylbutanoic acid using diethyl malonate?
  6. Explain the mechanism of Hofmann-bromamide reaction. Name the intermediate in this reaction.
  7. ‘Nitration of benzene is irreversible while sulphonation of benzene is a reversible reaction.’ Explain.
  8. What are sulpha drugs? Explain the mechanism of action of  sulpha durgs.
  9. What happens when 3-bromo-2, 3-dimethyl pentane is treated with alcoholic KOH? Identify the different products obtained and explain with mechanism.
  10. Explain the mechanism of Baeyer-Villiger rearrangement.
  11. Explain the synthetic utility of acetoacetic ester with examples.
  12. Explain aromaticity, antiaromaticity and nonaromaticity with suitable examples.

 

 
 
Part-C

                                                 Answer any FOUR questions.                       (4 ´ 10 = 40)

 

  1. a) Explain the mechanism of reduction of CH3COOC2H5 by LiAlH4.
  2. b) Compare the stereochemistry of products obtained in Sn1 and Sn2 reactions.
  3. a) How are grignard reagents used in the preparation of primary, secondary and     tertiary alcohols? Explain with suitable examples.
  4. b) Explain the mechanism of preparation of ethers by oxymercuration-    demercuration method.
  5. a) How are the following compounds prepared?
    (i) acrylic acid             (ii) cinnamic acid      (iii) maleic acid
  6. b) Explain the action of heat on a-, b- and g-hydroxy acids and identify the     products obtained.
  7. a) Explain the mechanism of sulphonation of benzene
  8. b) ‘Halogens are deactivating groups but o-, p- directing’.
  9. a) How will you synthesise the following compounds from benzaldehyde?

(i) Mandelic acid         (ii) m-Benzaldehydesulphonic acid

  1. b) Write a note on: (a) Cannizaro reaction (b) Perkin reaction
  2. a) Explain Claisen and abnormal Claisen rearrangements with mechanism.
  3. b) How would you convert m-nitrophenol from nitrobenzene? Explain all the steps involved in this process.

 

 

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