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Question 1

Two isomeric benzopyridines are

Answer 1

quinoline and isoquinoline

Question 2

Quinoline is the

Answer 2

benzo[b]pyridine

Question 3

isoquinoline is the

Answer 3

benzo[c]pyridine isomer

Question 4

Quinoline and isoquinoline are very important heterocyclic units because

Answer 4

their derivatives widely occur in nature as alkaloids.

Question 5

But unlike benzene the bond lengths of Quinoline and isoquinoline

Answer 5

are irregular

Question 6

nitration of quinoline with fuming nitric acid in concentrated (conc.) sulfuric acid containing SO3 at room temperature gives

Answer 6

a mixture of 5-nitro-and 8-nitroquinolines,
whereas isoquinoline reacts with same reagent at 0°C to give a mixture of 5- and 8- nitroisoquinolines.

Question 7

Sulfonation of quinoline with oleum at 92°C gives

Answer 7

quinoline-8-sulfonic acid

Question 8

Sulfonation of isoquinoline with oleum at 92°C gives

Answer 8

isoquinoline-5- sulfonic acid.

Question 9

Alkyl and acyl halides react directly with the basic nitrogen atom with quinoline and isoquinoline to give

Answer 9

quaternary salts.

Question 10

The C=N bond of the pyridine ring in both of these compounds undergoes nucleophilic addition at low temperature with KNH2, and the adduct on oxidation with KMnO4 at low temperature gives

Answer 10

2- aminoquinoline and 1-aminoisoquinoline in a Chichibabin-type reaction.

Question 11

Indole ring occurs widely in nature as

Answer 11

alkaloids

Question 12

indole undergoes electrophilic substitution at C-2 in the pyrrole ring and regioselectively at C-3 due to

Answer 12

higher resonance stabilization of the intermediate formed by C-3 attack

Question 13

Because of the aromatic stability of the benzene ring, the most important contributing structure of indole to its

Answer 13

reso- nance hybrid is its enamine form.

Question 14

indole easily undergoes protonation to give

Answer 14

indolenium cation

Question 15

indole is sulfonated at C-3 with

Answer 15

pyridinium–N-sulfonate

Question 16

brominated at C-3 with

Answer 16

bromine in pyridine at 0°C

Question 17

acetylated at C-1 and C-3 to give

Answer 17

diacetyl derivative with acetic anhydride in acetic acid,

Question 18

indole methylated at C-3 with

Answer 18

methyl iodide in DMF at 80°C

Question 19

indole formylated at C-3 with

Answer 19

POCl3 and DMF at 5°C

Question 20

indole amino methylated at C-3 with

Answer 20

HCHO and amines (Mannich reaction).

Question 21

benzene ring is fused with a pyrrole ring and hence behaves as

Answer 21

an aromatic heterocyclic compound

Question 22

Small heterocyclic rings

Answer 22

epoxides

Question 23

Epoxides are compounds containing

Answer 23

a three-membered ring with oxygen as a heteroatom

Question 24

The IUPAC name of such rings is

Answer 24

oxiran. They are cyclic ethers

Question 25

epoxides synthesized by

Answer 25

the oxidation of a CPC bond of alkenes with peracids like m-chloroperbenzoic acid (MCPBA).

Question 26

pyridine. Pyridine is classified as

Answer 26

aromatic

Question 27

pyridine bond angles of

Answer 27

120°

Question 28

pyridine heat of combustion indicates a resonance energy of

Answer 28

23 kcal/mol.

Question 29

pyridine is bonded to other members of the ring by

Answer 29

the use of sp2

Question 30

the nitrogen atom makes pyridine a much stronger base than

Answer 30

pyrrole

Question 31

Pyridine is found in

Answer 31

coal tar

Question 32

Oxidation of the picolines yields the

Answer 32

pyridinecarboxylic acids.

Question 33

Reactions of pyridine

Answer 33

undergoes the substitution, both electrophilic and nucleophilic

Question 34

electrophilic substitution pyridine It undergoes

Answer 34

nitration, sulfonation, and halogenation

Question 35

pyridine does not undergo the

Answer 35

Friedel–Crafts reaction

Question 36

Nucleophilic substitution takes place readily, particularly at

Answer 36

the 2- and 4-positions

Question 37

Pyridine is a base with

Answer 37

Kb = 2.3 * 10-9.

Question 38

Pyridine is a base with Kb = 2.3 * 10-9. It is thus much stronger than

Answer 38

pyrrole (Kb ' 2.5 * 10-14) but much weaker than aliphatic amines (Kb ' 10-4)

Question 39

Pyridine has a pair of electrons (in an sp2 orbital)

Answer 39

pyrrole has not

Question 40

Benzene is a stronger acid than

Answer 40

an alkane

Question 41

phenyl anion, C H -, is a weaker 65 base than

Answer 41

an alkyl anion, R-.

Question 42

acetylene is a stronger acid than

Answer 42

benzene

Question 43

acetylide ion is a weaker base than

Answer 43

the phenyl anion.

Question 44

p orbital is at some distance from

Answer 44

the nucleus and is held relatively loosely

Question 45

an s orbital, on the other hand, is close

Answer 45

to the nucleus and is held more tightly

Question 46

Catalytic hydrogenation of pyridine yields

Answer 46

the aliphatic heterocyclic compound piperidine, C5H11N.

Question 47

The simplest of the five-membered heterocyclic compounds are

Answer 47

pyrrole, furan, and thiophene,

Question 48

pyrrole, furan, and thiophene have the properties of

Answer 48

conjugated diene and of an amine,

Question 49

pyrrole, furan, and thiophene have the properties of

Answer 49

conjugated diene and of an amine,

Question 50

thiophene does not undergo

Answer 50

the oxidation

Question 51

pyrrole does not possess the

Answer 51

basic properties typical of amines

Question 52

pyrrole, furan, and thiophene derivatives most commonly undergo

Answer 52

elec- trophilic substitution: nitration, sulfonation, halogenation, Friedel–Crafts acylation, even the Reimer–Tiemann reaction and coupling with diazonium salts

Question 53

Pyrrole and thiophene are found in

Answer 53

small amounts in coal tar.

Question 54

During the frac- tional distillation of coal tar, thiophene

Answer 54

b.p. 84°C

Question 55

During the frac- tional distillation of coal tar, thiophene (b.p. 84°C) is collected along with the benzene

Answer 55

(b.p. 80°C)