Indira Gandhi National Open University (IGNOU) 2005 B.Sc Chemistry Organic reaction Mechanism - - Question Paper
CHE-6
BACHELOR OF SCIENCE (B.Sc ) Term-End Examination June, 2005
CHEMISTRY CHE-6 : ORGANIC REACTION MECHANISM
Maximum Marks 50
Time : 2 hours
Note : Attempt any four questions. All questions carry equal marks.
1. (a) Why does methylbromide undergo substitution
reaction with sodium hydroxide faster than ethyl
2
4
4
bromide ?
(b) What is meant by intramolecular nucleophilic substitution ? Explain it by taking the example of
4-bromobutanol.
{c) Which of the following shows aromatic character and
why ? Draw its resonating structures.
(d) Write the structure of the product formed when aniline reacts with bromine water. Give its IUPAC
name also. oL
2
2* (a) Predict the products of reaction of hydrogen bromide and 3,3-dimethyl buM-ene with the help of a suitable mechanism. 4
(b) Why does chlorofumaric acid undergo elimination 50 times faster than chloromaleic acid ? Write the product of elimination. 2
(c) A, B and C are isomeric heptenes. On ozonolysis, A
gives ethanal and pentanal, B gives propanone and
butanone and C gives ethanal and 3-pentanone. Give
structural formula of A, B and C. 4I
2
(d) Write the reaction involved in the reduction of 2-butyne with sodium metal and liquid ammonia. Specify the isomer formed. 2
3. (a) Discuss any two of the following reactions giving
mechanism : 7
(i) Wittig reaction
(ii) Perkin reaction Cannizzaro reaction
(b) Why is photoinduced (4+2) cycloaddition symmetry forbidden ?
(c) Triphenylmethyl radical is stabilised due to extensive delocalisation. Justify your answer with the help of resonating structures. 2-
4. (a) How will you carry out any one of the following
conversions ? Write its mechanism also, 3
(i) Diphenyl ketone to N-Phenylbenzamide
(ii) Benzamide to Aniline
(b) State the product for any three of the following
reactions : 3
(i) CH3 CH2 CH2 CH CH3 alc~ KQH ->
Br
Heal
(ii) CH3 CH2 CH2 ~ CH N (CH3)3 .
CH,
Fuming HN03
h2so4
Tollens reagent
(iv) CH3CH = CHCHO ->
{v) chci3, koh
(c) Explain the terms, thermodynamic control and kinetic control. Illustrate with the help of an example in each case. 4
(d) What are benzynes ? Write the'mechanism of a reaction involving the formation of benzyne intermediate.
2
5. (a) Iodide ion is a good nucleophile but a weak base.
Explain. 2
(b) Predict the product of the following reactions with a suitable mechanism. Give the name of the reactions also. 6
OH OH
I | j_|+
(i) 02N i(oV- G C oV- NOo ->
C2H5ONa
(ii) ch3cooc2h5 >
(c) What Is the product of photoisomerisation of fumaric
acid ? iL
2
(d) A mixture of 3-chlorobuM-ene and l-chlorobut-2-ene is obtained during the photochemical chlorination of but-2-ene, Explain the reaction with the help of mechanism involved. 3
6* (a) What are azo dyes ? Draw the structure of any one
azo dye. 2
(b) What are analgesics ? Draw the structure of any one analgesic. 2
(c) How is soap manufactured ? Why are soaps not effective as cleansers when used in hard water ? 4
(d) Name the monomer in Nylon 6 and Nylon 6} 6. 2
(e) How will you prepare a dicarboxylic acid from diethylmalonate ? 2-
CHE-6 5
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