Solved Assignment 2018-2019
CHE-05: Organic Chemistry
Course Code: CHE-05
Assignment Code: CHE-05/TMA/2018
Maximum Marks: 100
1. (a) Give the IUPAC names of the following compounds:
(i)
(ii)
(iii)
(b) Write the structures of the following compounds:
(i) Methyl 3-methyl butanoate
(ii) 4-Hydroxy-4-methyl-2-pentanone
2. Draw cis and trans- isomers of 1,3-cyclobutane carboxylic acid. Comment on the (5)
dipole moment of these isomers.
3. What are racemic mixtures? How are they obtained? Discuss one method of their (5)
resolution.
4. Give reason for the following:
(i) -carotene is a red coloured compound. (1)
(ii) Carbonyl compounds absorb radiation in
4
7. (a) Explain the following in one to two lines. (3)
(i) Alkenes are more soluble in water than corresponding alkanes.
(ii) Addition reactions of alkenes are exothermic processes.
(iii) Hydroboration appear as anti-Markownikoff’s addition.
(b) Fill in the following blanks: (2)
(i) In the UV spectrum, the ethylenic chromophore shows an absorption band
below __________nm.
(ii) In the IR spectrum, the cis isomer of internal alkenes gives band at _____ cm1
.
8. (a) Arrange the following in the decreasing order of their basic strength: (2)
alkaline anion; alkene anion; alkynide anion
Justify your answer.
(b) How will you prepare the following ? (3)
(i) 10 -Hexyne from ethyne
(ii) Ethanol from ethyne
(iii) 3-Hexanone from 3-hexyne.
9. (a) What is resonance energy? Explain taking the example of benzene. (2½)
(b) What are the limitations of Friedel-Crafts alkylation? (2½)
10. (a) 2-Position of pyrrole is more reactive towards electrophilic substitution than
3-position. Explain giving all possible resonance structures of carbocations formed.
Explain. (2)
(b) Predict the product(s) of the following reactions: (3)
(i) Nitration of azole
(ii) Friedel-Crafts acylation of pyridine
(iii) Reduction of pyrrole with zinc and ethanoic acid.
11. Among alkyl halides, order of reactivity of SN2 reaction is
CH3X > p-RX > Sec-RX > tert-RX
Discuss the factors which are mainly responsible for this order.
(5)
12. Write the chemical equation for following named reactions: (5)
(a) Reimer-Tiemann reaction
(b) Kolbe reaction
(c) Claisen reaction
(d) Knoevenagel reaction
(e) Willgerodt reaction
13. Suggest the reaction that can best be used to prepare following ethers by Williamson
ether synthesis
(5)
(a)
CH3CH2 O CH CH2
(b)
CH3CH2CH OCH3
CH3
5
14. Write the mechanism for the Haloform reaction. (5)
15. Explain Hell-Vollhard-Zelinski reaction. Also illustrate its synthetic importance. (5)
16. Write chemical reactions for the following: (5)
(i) Kolbe Schmidt reaction
(ii) Strecker synthesis
(iii) Dieckmann condensation
(iv) Knoevenagel reaction
(v) Perkin condensation
17. Discuss various methods of reduction of esters giving the products formed. (5)
18. (a) Why do nitro compounds dissolve in sodium hydroxide? (2)
(b) What is a form of nitroethane? Discuss. (3)
19. Match the following ions with their correct pKa values and give reasons for your answer: (5)
Column I, Ion Column II, pKa
(a)
NH3
+
(i) 5.07
(b)
NH3
O2N
+
(ii) 4.62
(c)
NH3
H3C
+
(iii) 4.85
(d)
NH2CH3
+
(iv) 1.11
20. What are nucleotides? Draw the structures of nucleotides present in DNA and give their (5)
names.
