Chem.Sci./6-IUPAC Nomenclature of Simple Organic & Inorganic Compounds

6 – IUPAC Nomenclature of Simple Organic & Inorganic Compounds

Nomenclature of poly-functional organic compounds:

            In polyfunctional organic compounds, one functional group is treated as principle functional group while others are treated as substituents.

            Order of principle functional group,

 

     In writing IUPAC name, principle group written as suffix while other substituents are written as prefixes,

 

pent-3-ene-1-yne and hex-2-ene-4-yne

Following are the different important examples.

    i) Ethylethanoate ( the suffix used as ate represent the ester family of organic compounds)

    ii) Propanoicanhydride  

    iii) 3-carboxy-1,5-pentandioicacid (since long chain of carbon contain five, at position 1 and 5 there is carboxylic group hence 1,5-pentandioic acid used and at position 3rd carboxyl group will consider as substituent).

    iv) Formylmethanoicacid (since carboxylic acid is more reactive than aldehyde hence formyl group will consider as substituent and parent name will be written as oic suffix in last)

v) 1-cyclopropyl-3-methylpent-1-ene ('ene' in suffix represent alkene family of organic compounds)

vi) Methylbenzene

vii) 2-chloro-1-methylbenzene

 vii) 1,2-diethylcyclohexane (When two or more substituents are present in the alicyclic ring, then numbering is done in such a way that the sum of the locants number of the substituents is the lowest is called Lowest sum rule )

Examples from SET exams:
1) SET exam January 2018 booklet A: Paper II: 
    Example No. (25):
    The correct IUPAC nomenclature of the following compound is,

 

A) 5-Bromo-2-chloroheptane     

B) 2-Chloro-5-bromoheptane

C) 3-Bromo-6-chloroheptane     

D) 6-Chloro-3-bromoheptane

Ans: D) 3-Bromo-6-chloroheptane (in poly halogen numbering is based on alphabetical order)

2)  SET exam April 2017 booklet A: Paper II:

      Example  No. (26):

      The correct IUPAC nomenclature of the following compound is;

 

A) 4-Ethyl-2-methyl- 1-propylcyclohexane

B) 1 -Ethyl-3-methyl-4-propylcyclohexane

C) 5-Ethyl- 1-methyl-2-propylcyclohexane

D) 3-Ethyl-1-methyl-6-propylcyclohexane

Ans: A) 4-Ethyl-2-methyl- 1-propylcyclohexane (Lowest sum rule: 1+2+4= 7 is lower than 1+3+4=8)

3)  SET exam May 2016 booklet A: Paper II:

      Example  No. (17):

      The correct IUPAC nomenclature of the following compound is;

A) 3, 4, 9-trimethyl decane

B) 2, 7, 8-trimethyl decane

C) isotetradecane

D) 7-methyl-2-(1-methylpropyl) octane

Ans: B) 2, 7, 8-trimethyl decane

 

4)  SET exam Sep. 2015 booklet A: Paper II:

     Example No.(17)

     The correct IUPAC nomenclature for the following compound is;

A) (E) Pent-2-en-4-yne

B) (E) Pent- 1-yne-3-ene

C) (E) Pent-4-yne-2-ene

D) (E) Pent-3-en-1-yne

Ans:D) (E) Pent-3-en-1-yne (E relates with trans with respect to alkene)