M.Sc. (Semester (CBCS) Examination Nov/Dec-2018
Chemistry
ORGANIC CHEMISTRY I
Time: 2½ Hours
Max. Marks: 70
Instructions: Attempt in all five questions. Draw neat diagram and give equations wherever necessary. Figures to the right indicate full marks.
Q.1
Multiple choice questions:
14
The correct decreasing order of carbanion stability is
III I II
III II I
I II III
II I II
Which one of the following is electrophilic radical?
CH2-OCH3
CH2-NH2
CH2-CHO
CH2-Br
In an SN2 reaction, there is
Partial racemisation
Complete racemisation
Complete inversion
Complete retension
In the following substitution reaction if the concentration of hydroxide ion is doubled, the rate of the reaction
become double
become one half
become four fold
remain unchanged
Which molecule amongst the following will not undergo Friedel-Craft Acetylation?
Nitrobenzene
Chlorobenzene
Anisole
Toluene
Predict the product:
HBr?BrPh
a)BrPhBr
b)BrBrPh
c)PhBrBr
All
In the given reaction
CCH2-BrCH3CH3CH3Alc. KOH[Z] will be
3-methyl-1-butene
2-methyl-2-butene
2-butene
1-butene

Which one of the following is correctly matched?
Saytzeff rule least substituted alkene
Hofmann rule most substituted alkene
E2 reaction stereospecific reaction
E1 reaction one step reaction
Reaction intermediate of E1cb reaction
carbocation
carbanion
carbene
nitrene
10) Suggest the correct name of following rearrangement.
OOCH3+NH2OHBaseNH2
Lossen
Curtius
Schmidt
Hofmann
11) Predict the product:
OCOC2H5AlCl3600 C0?
o-hydroxyphenylethylketone
p-hydroxyphenylethylketone
m-hydroxyphenylethylketone
phenylethylketone
12) For the two pairs of compounds given below, choose the correct statement.
Pair is enantiomeric while pair is diastereomeric
Pair is diastereomeric while pair is enantiomeric
Both pairs are diastereomeric
Both pairs are enantiomeric
13) The geometry of the two double bonds in the given molecule is
BrH3CClOHCCOOHCH3
2Z, 5Z
2Z, 5E
2E, 5E
2E, 5Z
14) If the optically active compound given below is hydrolysed with aq. acid, then it would
COCOCH3CH3(CH2)3CH2CH3CH3
alcohol
alcohol
alcohol
n-octanol
Q.2
a)Answer the following (any four)
08
Arrange the following compounds in order of increasing acid strength and give reason.
COOHOHOHCOOHOHCOOHOHIIIIII
Define ambient nucleophile with suitable example.
Complete the following reaction:
OHAl2O3?HBrPeroxide?
Give the evidence in favour of the fact the Hofmann rearrangement is intramolecular
Assign E and Z nomenclature of the following compounds:
Bromo-1-chloropropane
1-Bromo-1,2-dichloroethance
b)Write notes on (Any two)
06
Effect of a ring substituent on the acid strength of phenols
Halogens are ring deactivators but p-directors
Hofmann elimination
Q.3
a)Answer the following(Any two)
08
Explain stereospecific and stereoselective addition reaction with suitable example.
What is prochirality? Explain it with suitable prochiral molecules.
Discuss the conformations of 1,2-dimethyl cyclohexane with stability.

b)Answer the following (Any one)
06
What is SN2 reaction? Give an account of following factors affecting on reactivity of SN2 reaction:
Substrate
ii) Solvent
iii) Leaving group
iv) Attacking nucleophile
What is resolution? Discuss their different methods with suitable examples.
Q.4
a)Answer the following (Any two)
10
What are carbocations? Explain their structure, generation, stability and reactivity.
Predict the product(s) and outline the mechanism of following reactions
CCH2-ClCH3CH3CH3AlCl3?+
Explain the addition of HBr to 2-methyl propene under different conditions giving the mechanisms.
b)Answer the following (Any one)
04
What is neighbouring group participation? Explain it with suitable example.
Explain Gatterman-Koch reaction with mechanism.
Q.5 Answer the following (Any two)
14
Predict the product(s) and outline the mechanism for the following reactions:
MeOCCOOOH H2Oi)?
OH3CCHCHCHCH3CH3ii)?
Predict the product(s) and outline the mechanism for the following reactions:
OHCH3CH3CH3H+?i)ii)OHH+?
What is conformational isomerism? Discuss the stability of various conformers of 1,3-dimethyl and 1,4-dimethyl cyclohexane