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'''Common names and geneva system Introduction'''

IUPAC (Geneva System of Nomenclature)

(i) Regular pattern of naming side chain + alk + (-)ane or (=)ene or (=)yne + suffix of main functional group 1C Math 4C But

2C Eth 5C Pent

3C Prop 6C Hex

(ii) Selection of LPCC ( longest possible carbon chain)

The longest possible chain is numbered from one side to the other by Arabic numerals, the direction being so chosen as to given the lowest numbers possible to the side chains. When series of locants containing the same number of terms are compared term by term, that series is “lowest” which contains the lowest number on the occasion of the first difference (Lowest sum rule). This rule is applied irrespective of the nature of the side chains.

Examples :

Univalent branched radicals derived from hydrocarbon are named by prefixing the designation of the side chains to the name of the unbranched alkyl radical containing the LPCC starting from the carbon atom with the free valence, this atom being numbered as 1.

The following names can be followed for the unsubstituted radicals only:

If two or more side chains of different nature are present, they are cited in alphabetical order and decided as follows

If two or more side chains of different nature are present, they are cited in alphabetical order and decided as follows

(i) The names of simple radicals are first alphabetized and the multiplying prefixes are then inserted.

Example :

Ethyl is cited before methyl, thus 4-Ethyl-3, 3-dimethylheptane (ii) The name of a complex radical is considered to start with the first letter of its complete name.

Example :

(iii) In cases where names of complex radicals are composed of identical words, preference for citation is given to that radical which contains the lowest locant at the first cited point of difference in the radical.

Example :

If two or more side chains are in equivalent positions the one to be assigned the lower number is that cited first in the name.

Examples :

If LPCC’S of equal length are competing for selection as main chain in a saturated branched acyclic hydrocarbon, then the choice given in following order to number of side chains with Lowest sumrule.

(a) Choose LPCC which follow lowestsum rule.

Example:

(b) Choose LPCC whose side chains have the lowest-numbered locants.

Example: (c) Choose LPCC having the highest number of carbon atoms in the smaller side chains.

Example:

(d) Choose LPCC which contains the least branched side chains.

Example:

(iii) Numbering in alkenes and alkynes (unsaturated hydrocarbons)

Chemical reactivity of C = C is more than In alkynes there is dense  which is difficult to break. So that if double or triple bonds are present on the same carbon atom than numbering starts from double bond side.

(f) always write 'ene' first than 'yne' due to alphabetical order.

(g) if the number of C = C or is two or more than two in LPCC than we use 'alka' in place of 'alk.'

IUPAC names of compounds containing poly functional groups. (IUPAC preferance order)

Order of nameing for poly functional groups

If carbon containing Functional group works as suffix then its carbon is included in the carbon length otherwise not. Use of formyl or Oxo where – CHO group works as prefix

IUPAC names of amines

IUPAC names of ethers IUPAC names of Cyclic etheres (epoxides)

If the ring contains less carbon atoms than the alkyl group attached to it, the compound is named as a derivative of alkane and the ring is treated as cycloalkyl substituent, otherwise, it is named as a derivative of cycloalkane. This is clear from the following examples.

If however, the side chain contains multiple bond or a functional group, the alicyclic ring is treated as the substituent irrespective of the size of the ring.

If some characteristic functional group alongwith other substituent group are present in the ring, it is indicated by using suitable prefixes and suffixes as in case of acyclic compounds. If the functional group, directly attached to the ring contains carbon atom, then suitable suffixes are used to indicate the presence of such groups. In such cases the carbon atoms of such groups are not counted in the word root. Suffixes for such groups are as follows.

Compounds containing —SH as the principal group directly attached to carbon are named “thiols”. In substitutive nomenclature their names are formed by adding “ -thiol” as a suffix to the name of the parent compound. When —SH is not the principal group, the prefix “ mercapto-” is placed before the name of the parent compound to denote an unsubstituted —SH group.

Disulfides, trisulfides, etc., and polysulfides are named analogously to sulfides, except that “di-”, “tri-”, or “poly-sulfide” replaces “sulfide”, and that “di-”, “tri-”, or “poly-thio-” replaces “thio-”. Nomenclature of bicyclic compounds

We name compounds containing 2 fused or bridged rings as bicyclo alkanes and we use the name of the alkane corresponding to the total number of carbon atoms as the base name. The carbon atoms common to both the rings are called bridgeheads, and each bond, or chain of atoms connecting the bridgehead atoms, is called a bridge.

In between the words bicyclo and alkane we interpose in the name an expression in the square brackets that denotes the number of carbon atoms in each bridge (in descending order). For example,

If substitutions are present, we number the bridged ring system beginning at one bridgehead, proceeding first along the longest bridge to the other bridgehead, then along the next longest bridge back to the first bridgehead. The shortest bridge in numbered last.

Polycyclic Systems

(a) The main ring shall inculcate as many aspossible carbon atoms, two of which must work as bridgeheads for the main bridge system.

(b)The main ring shall be divided as symmetrically as possible by the main bridge.

(c) The main bridge system shall be as largest as possible in the complete system of IUPAC Examples of Bicyclo, polycyclic and others

Note: The superscripts locating the other bridges shall be as small as possible

Spiro Compounds

A “spiro structure” is one formed by a single atom which is the only common member (quternary carbon) of two cyclic rings where name of these compound starts with the prefix spiro and preceding with shortest path and go through to longer path. Numbering always in increasing order just opposite to bicyclo compounds where decreasing order is followed.

IUPAC names of Aromatic Compounds

Compounds containing one or more of benzene rings are known as aromatic family.

Out of these three, the last one is preferred because it represents the resonance hybrid of the first two structures. An aromatic compound may contain one or more side chains of carbon atoms. Substitution can take place either in the ring or in the side chain or both can be substituted.

If only one hydrogen atom of the benzene ring is replaced by another atom or group of atoms, a monovalent substituted derivative is formed. It can exist only in one form as all the six hydrogen atoms in benzene are equivalent. For example.

However, if two or more hydrogen atoms of the benzene ring are replaced by other atoms or group of atoms, these are indicated by Arabic numerals i.e., 1, 2, 3....... etc. In case of disubstituted compounds, it is also indicated by the following method.

(a) Ortho. The compound is termed as ortho if the two substituents are on the adjacent carbon atoms. In IUPAC system to indicate these positions are 1, 2.

(b) Meta. The compound is termed as meta if the two substituents are on alternate carbon atom. In IUPAC system to indicate these position are 1, 3.

(c) Para. The compound is termed as para if the two substituents are present on diagonally opposite carbon atoms. In IUPAC system to indicate these positions are 1, 4.

If the ring contains three or more substituents only Arabic numerals are used with alphabetical order. For example;

1. Nomenclature of aromatic compound.

The IUPAC and common names (given in brackets) of some important members are given below. However, if only one name is given, this indicates that the common name has been adopted by IUPAC system.

2. Nomenclature of aryl groups.

Note :	(a) In case of tolyl group, no substitution is allowed. (b) In case of phenyl group, unlimited substitution is allowed 3. Nomenclature of halogen derivatives.

4. Nomenclature of hydroxy derivative.

5. Nomenclature of aromatic ethers.

6. Nomenclature of aldehydes and ketones.

Note: Aromatic ketones in which > CO group is directly attached to the benzene ring as termed as phenones.

In above carbon chain is numbered from the end which gives lowest position to the > C = O group.

IUPAC nomenclature of two or more similar cyclic hydrocarbon units joined by a single bond

These systems are named by placing a suitable numerical prefix before the name of the repetitive hydrocarbon unit. The numerical prefixes used in this nomenclature are given below: Number of cyclic hydrocarbon units	Two 	Three 	Four	Five Prefix	bi	ter	quater	quinque

Starting from either end, the carbon atoms of each repetitive hydrocarbon unit are numbered with unprimed and primed Arabic numerals such as 1, 2, 3,................. 1', 2', 3',............ : 1", 2", 3",.............etc. The point of joining of the repetitive hydrocarbon units are indicated by placing the appropriate locants before the name. For example,

As an exception, unbranched assemblies consisting of benzene rings are named by using appropriate prefix under the name phenyl instead of benzene. For example,