Question

State any 3 rules of nomenclature of organic compounds??

Answer 1

1) first select the longest continues chain of carbo atoms that serves as parent name.
2) Number the longest chain from the end closer to substituents
3)Identify the substitutent (branch or side group) , name the branch and indicate its position by the number of carbon atom to which it is attached
4) The whole name is written as one word

Answer 2

Answer:

Explanation:

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Longest chain rule ;

1. Select the longest continuous chain of carbon atoms, which is regarded as parent chain & is given the name of parent hydrocarbon.
2. If two chains of equal number of carbon atoms is identified, choose the one with maximum number of substituents (side chains) as parent chain.

Lowest number rule

• Number the carbon atoms from the end that is nearest to the point of branching. The number which indicates the position of substituent is called locant.
• The sum of all the locants should be the lowest.

Identify the substituents

• Assign number to each substituents according to its position on the parent chain.
• If two substituents are present on same carbon atom, assign them same number.
• There should be as many numbers in the name as there are substituents.

Write the name as single word.

• While writing the name, use hyphens to separate locant & alkyl groups and commas to separate numbers.
• If two or more substituents are present, write them in alphabetical order.
• For identical substituents, use prefixes such as di, tri, tetra etc. However, these prefixes should not be alphabetized.
• If two different substituents are located at equivalent positions from the teo ends of the parent chain, the numbering is done in such a way that the alkyl group which comes first in alphabetical order gets the lowest number.

IUPAC rules for naming organic compounds having functional groups

First give appropriate prefix & suffix to the functional groups

Groups       —prefix                               suffix

>C=C<             -----                                     −ene

−C≡C−          ------                                        -yne

−X                 —halo                                        --

−OH            —hydroxy                                   ol

−CHO            —formyl                                   al

>C=O              —oxo                                     one

−OR                —alkoxy                                   ---

−COOH          —carboxy                                oicacid

−COO−R              -----                                      −oate

−NH2               —amino                                   −amine

−C≡N                 —cyano                                  −nitrile

−NO2                  —nitro                                         ---

• Now, the longest carbon chain is numbered from the end which is nearest to the functional group. Using the appropriate number of functional group, the complete name is written.
• In case of polyfunctional compounds, one of the function group is choosen as the principle functional group & the compound is named on that basis. The remaining functional groups are named as substituents using appropriate prefixes. We use following priority in choosing principle functional group

−COOH,−COOR,−CONH2,−CN,−CHO,>C=O,−OH,−NH2,>C=C<,−C≡C−

• If two or more functional groups are of same type, they are indicated by using terminology di, tri etc. In such case, full name of parent alkane is written

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