nomenclature of hetero cyclic (secound year)

8/2/2019 Nomenclature of Hetero Cyclic (Secound Year)

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Chemistry of HeterocyclicCompounds


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Whats Heterocyclic Compound?

A heterocyclic compound is one that

contain rings made up, in addition tocarbon, one or more heteroatoms like0,N,S,P. etc.


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Heterocyclic compounds can be

classified into

1)aliphatic heterocycles::

Examples


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Heterocyclic compounds can be

classified into

2)Aromatic heterocycles:

Examples


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NOMENCULATURE OFHETEROCYCLES


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NOMENCULATURE OF HETEROCYCLES

a-Trivial names:

b- Generic names, and Trade names:

C-

IUPAC (or systemic or chemical name):


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B-Nomenclature of non Fused

Heterocycles

Prefix + Stem + Suffix


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1- The Prefix It indicates the type of the heteroatom, their

numbers and their positions. (Table I):

When two or more heteroatom of same type arepresent, the prefix di, tri,...etc. is used.

If the heteroatoms are different, their order ofcitation start with the heteroatomof as high a

group in the periodic table and as low an atomicnumber in thatgroup. Thus the order of namingwill be: O > S > Se >N >P > Si > B > Hg etc (see table I):


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A Reference book of such IUPAC nomenclature .outlined here is:

CRC Handbookof Chemistry and Physics by Robert. C.W and Melvin.J. A. 60th edition. 1979-1980 p. (C33-C44


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2-The stem It determines the ring-size from 3

membered ring to 10 membered ring.


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3- The Suffix

It determines the state of

saturation or unsaturation whichdepends upon

(i) the presence or absence of N

and

(ii) the ring size.


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saturation or unsaturation state


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Table III (cont): a: The complete saturation isindicated by prefixing "perhydro " added before

the total name of the unsaturated state.

b: no suffix

c: no stem

N.B: If the ring size is more than 10, use thecarbocyclic monocyclic name and theheteroatom is indicated by prefixes: Oxa, thic,aza


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Example


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Manner of numbering of themonocyeles


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Rule 1

Monocyles containing one heteroatom,

are numbered beginning at theheteroatom and the substituents takesthe least possible number:


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Rule 2

Cycles containing more than one different

heteroatoms the numbering begins at theatoms of the higher order of priority(shown in table I) and proceeds round thering in order to give other heteroatoms

the least possible numbers withoutregards to the substituents;


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Rule 2


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Nomenclature of PartiallySaturated Ring


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Rule 1

If the number of double bonds is less

than the maximum, prefix dihydrotetrahydro,. etc are added to thesame name of unsaturated state. Thesaturated positions are given the least

numbers after the hetero atom:


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Rule 1


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Rule 2

- Obligatory saturation of a single

position is indicated by a symbol 1H, 2H,3H... etc. according to the position of thesaturated atom


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Rule 2


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Rule 3

In case of 4 & 5 membered rings with

partial saturation (i.e) contain only onedouble bond. The suffix will be (ine) whenN is present and (ene) when N is absent,and indicate the position of the double

bond over A symbol.


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Rule 3


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The following are the IUPAC and trivial

names of most monocycles


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B-Nomenclature of FusedHeterocycles


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B-Nomenclature of Fused Heterocycles

(B I) Carbocycle fused with heterocyclicsystem.

(B II) Heterocycle fused with anotherheterocyclic system


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I-Nomenclature of Carbocycle fused

with Heterocycles IUPAC name:

1. The Parent name(written at the end) isthe name of the heterocyclic ring.

2. The fused name(written at first) is thename of the fused benzene called

(Benzo).


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3. The Side of fusionof the parent ringwith the fused benzene ring is indicated

by alphabetical numbering and put suchletter (a, b, c, ... etc) between squarebrackets in between the prefix and parentname. In this case the parent ring is

numbered as usual (p 5 ) and the sides1,2, take letter (a), side 2,3 takesletter (b), side 3, 4 takes letter (c), ... etc


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4- The total numbering ofthe completefused system in done to determine thepositions of saturations or substitutionsaccording to the following rules:

a- The fused system is oriented so that:

The greatest number of ring is in ahorizontal row, and the remaining ringsabove the right of this horizontal row.


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b- The numbering starts from the atomnext to the fusion giving the hetero atomthe least possible numbering andcontinue numbering in clockwisedirection (whenever possible) and thefused carbons are given the same

previous number adding to it letters (a, b,c, etc).c- In case of poly cycles, the parent name is

given to the largest heterocyclescontaining many rings (provided it has a

famous trivial name).


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The following are the agreed trivial andIUPAC names of the some of the famous

carbocycles fused with hetero cycl :


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(II) Nomenclature of Heterocycle fused

with another Heterocycles

The IUPAC rules for naming such systemsare also composed of 4 points:

The Parent name given to the more priorheterocycle(s), is used as suffix.

The fussed ring (s) name is the less priorrings and is used as prefix.

The side of fusion for both rings.

The numbering of the total system.


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1. The selection of the parent ring(s) (assuffix) should be according to the following

order of preferences

i- The Nitrogen containingring must be takenas a parent ring:


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ii- If no Nitrogen, the ring contain the moreprior heteratom(according to table l), is

considered as a parent ring:


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iii) The largest ringsize is taken as a parentring if the two rings contain N or does not

contain N.


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iv) The largest number of rings with famoustrivial nameis always used as parent name:


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v) The ring containing the greatestnumber of hetero atoms or greatestvarieties of heteroatoms is the parentring:

5

6

N1

2 4

3 5

4

N3

2

N1

6

d a

bc

HN

1

5

4

2

N3

S

1

2

N3

a

bcd

pyrido(2,3-d)pyrimidine imidazo(4,5-d)thiazole


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vi) A component ring having the moreprior heteroatom(according table I) is theparent ring:

HN

3

4

5

2

Se1

S

1

2

N3

a

bc

d

selenazolo(5,4-d)thiazole


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vii) The parent ring is the ring containinga more number of carbon atoms adjacentto the fusion:

5

6

N

1

2 4

3 5

N4

N

3

2

N 1

6

da

bc

pyrazino(2,3-d)pyrimidine

5

6

N

1

2 4

3 5

N4

3

N2

N 1

6

da

bc

pyrazino(2,3-d)pyridazine


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2- The naming of the prefix of fused (less

prior) heterocycles is given as such:

Furan = furo

Thiophene = thienoPyridine = pyrido

Pyrrole = pyrroloImidazole = imidazo

Quinoline = quino


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3- Determination of the sides of fusionfor both sides of the two fused

heterocycles as such:

a- The side of fusion with the parent ring isnumbered alphabetically and the letter of fusion

is placed between square brackets at its end.

b- The side of fusion of the prefix ring isindicated by two numbers denoting the twopositions of fusion with the parent ring, thesetwonumbers are also placed at first in the squarebrackets. The order of writing these two numbersconforms the direction of lettering of the parentring.


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3- Determination of the sides of fusionfor both sides of the two fused

heterocycles as such:

5

4N

1

S1

2

N

3

a

b

4

5N

7

NH

3

2

S

1

a

b

thiazolo(4,5-b)pyridine thiazolo(5,4-b)pyridine


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4-The peripheral numbering of the totalheterocyclic fused molecule is by the same

discussed rule (page 5), and considering thefollowing other rules

A)Give the lowest number to the more priorheteroatom (according to table I)especially when present just after fusion.But, if the more prior hetero atom is notthe nearest to the fusion side the other

nearest heteroatoms after fusion musttake the least possible numberingregardless of priority of table I.


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O6

5

4

3a

4

7

3

2

N

1

2

3

7-bromo pyrano93,4-b)pyrrole

7

6

N5

4

5

8

S4

3

2

O

1

O2N11

7- nitro-[1,4]oxathiino[3,2-b]pyridine

Br

7

a

b


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b)The hetero atoms in the fusion side arenumbered according to the sequence ofnumbering, but when carbon atoms inthe fusion take the previous number plusletter a, b, c,...etc. and also such carbon

atom follow the least possiblenumbering:


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N8

4a

N4

3

2

N

1

7

6

5 NH2

a

b

1

2

3-amino pyrolo91,2-b)[1,2,4]triazine

e.g.


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c) The saturated atoms take the leastpossible numbering before other

substitutents.


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Radicals Derived from Heterocyclic

Compounds

nomenclature of hetero cyclic (secound year)

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