Answers for questions : Type One
1) Imidazo[2,1-b]thiazole
2) 1H-pyrazolo[4,3-d]pyrimidine OR 1H-pyrazolo[4,5-d]pyrimidine
3) 1H-pyrazolo[3,4-d]pyrimidine
4) Ethyl pyrimido[5,4-c]pyridazine-3-carboxylate
5) 3-amino-5-methyl oxazolo[5,4-d]isoxazole
6) 6-aminopyrazolo[1,5-a]pyrimidine-5-carbonitrile
7) 5-chloro-2-oxa-1-aza bicyclo[2.2.2]octa-5-ene
8) Isothiazolo[5,4-d]isothiazole
9) 4H-1,3-oxathiolo[5,4-b]pyrrole
10) 2-methylbenzo[d]1,3-oxazine
11) Ethyl 1,4,3-oxathiazine-5-carboxylate
12) Imidazo[1,2-b][1,2,4]-triazine
13) 3-amino isothiazolo[4,5-e][1,2,4]-triazine
14) 5-acetyl-1H-1,2,4-triazole-3-carbonitrile
15) Furo[3,2-b]indole-2-sulphonic acid
16) Thiazolo[4,5-c]quinoline
17) Ethyl 4-amino-1,3-oxathiole-5-carboxylate
18) 2H-furo[3,2-b]pyran
19) 2-acetyl-5H-pyrano[3,2-d]oxazole
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20) 1H-pyrido[2,3-d]1,2-oxazine
21)1H-pyrazolo[4,3-d]oxazole
22) Imidazo[2,1-b]thiazole
23) 3-aminofuro[3,4-c]quinoline
24) 4H-pyrido[2,3-c]carbazole
25) 4H-1,3-oxathiolo[5,4-b]pyrrole
26) 4H-1,3-dioxolo[4,5-d]imidazole
27) Repeated no 12
28) Oxazolo[5,4-d]isoxazole
29) 4H-pyrimido[1,2-b]pyridazine
30) 6-amino pyrazolo[1,5-a]pyrimidine-5-carbonitrile
31) 5-amino thieno[3,4-d]pyridazine
32) Thiazolo[5,4-d]isothiazole
33) 6-amino-4H-pyrano[2,3-c]pyrazole-5-carbonitrile
34) Ethyl 5-amino-7H-thiazolo[3,2-a]pyridine-8-carbonitrile-6-carboxylate
35) Imidazo[4,5-b]quinxaline
36) Ethyl 5-aminoisothiazolo[5,4-d]oxazole-3-carboxylate
37) 4-amino-7-(2-thiazolyl)pyrazolo[5,1-c][1,2,4]-triazine-3-carbonitrile
38) 5-amino pyrazole-4-carbonitrile
39) 4H-1,3-oxathiolo[5,4-b]pyrrole
40) 3-acetyl-1H-1,2,4-triazole-5-carbonitrile
41) 7-amino imidazo[1,2-b][1,2,4]-triazine-3-carbonitrile
42) 3-amino isothiazolo[4,5-e][1,2,4]-triazine
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43) Ethyl 1,4,3-oxathiazine-5-carboxylate
44) Furo[3,2-b]indole
45) 4H-2-methyl benzo[d]1,3-oxazine
46) Ethyl 4-amino-5-methyl furan-3-carbonitrile-2-carboxylate
47) 1,3,4-thiadiazole-2-isothiocyanate
48) 5-methyl-4-phenyl pyrano[2,3-c]pyrrole
49) Thiazolo[4,5-c]isoquinoline
50) 4-amino-4H-1,2,5-thiadiazine
51) 3,5-dimethyl-2-phenyl-1,4,2-dioxazolidine
52) 2H-1,5,2-dithiazine
53) 1,7-dioxa-2,8-diaza cyclododeca-2,8-diene
54) 3-methyl- Δ4-1,3-oxazoline
55) 3H-1,2-diazepine
56) 6-amino-7-chloro-7H-thiazolo[3,2-a]pyridine-8-carbonitrile
57) 4H-1,3-dioxolo[4,5-d]imidazole
Answers for questions : Type Two
19
20
21
22
Answers for questions : Type Three
Answers for questions : Type Three
1) 1,2-dihydro pyridine
1,2-dihydro azine
azacyclohexa-2,4-diene
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2) Piperazine
1,4-diazane ( Perhydropyrazine )
Questions On :
Heterocyclic Chemistry II ( Aromaticity and Reactivity )
Type One : Which of the following compounds is Aromatic , Anti-aromatic
or non-aromatic ? Give reasons.
24
25
26
Type Two : Arrange the following compounds in order of decreasing
the aromatic character
1)
I
IV
V
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II
III
VI
VII
VIII
Answer :
2)
I
II
V
III
VI
Answer :
3)
28
IV
VII
I
II
V
III
VI
IV
VII
VIII
Answer :
4)
I
II
III
IV
V
Answer :
Type Three : State whether the following statements true or false and
Correct the false one
1) According to valence bond theory , NaNH2 reacts with benzene much faster
than pyridine .
( )
2) The e—density on carbon corners of pyrrole is less than that of benzene , so
called π – deficient heterocycle
( )
3) According to valence bond theory , furan is nitrated with slower rate than
that of benzene
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( )
4) The carbon-carbon bond length in pyrrole is about 1.34 Ao while in 2Hpyrrole is about 1.39 Ao
( )
5) Pyridine undergoes addition to carbon-carbon double bonds as well as
substitution of hydrogen atoms
(
6) Thiophene is less aromatic than furan since sulphur is less electronegative
than oxygen
( )
7) The increasing order of aromaticity in the following compounds , is given
by the order :
(
I
<
II
<
III
<
IV
<
)
V
8) In the following compounds : I , III are anti-arromatic , II , V are aromatic
and IV , VI are non-aromatic
( )
I
II
III
IV
V
VI
9)
and
, are aromatic compounds
( )
10) In the following compound , the parent is the ring in which the hetero atoms
are less separated
( )
30
)
11) The compound 2,6-thiaza bicyclo[3.2.0]hepta-6-ene is drawn as :
(
)
12) The name of the following compound is :
4,8,8-trimethyl-2,5-thiaza bicyclo[3.2.1]octa-5-ene
(
)
Type Four : Give reasons for the following
1) Five-membered heterocycles are termed “π –excessive heterocycles “ OR ,
Five-membered heterocycles are more reactive than benzene towards electrophilic
substitution reactions .
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2) Six-membered heterocycles are termed “π –deficient heterocycles “ OR ,
Six-membered heterocycles are more reactive than benzene towards nucleophilic
substitution reactions .
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3) N-methyl pyrrole is more aromatic than 1H-pyrrole
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4) 1H-pyrrole is aromatic while 2H-pyrrole is non-aromatic
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5) 1H-azepine is anti-aromatic
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33
34