MHT CET202520 Apr 2025Evening ShiftChemistryBiomoleculesActual
What are the positions of ' N ' atoms present in pyrimidine ring of nucleic acids?
Options
- A1 and 5
- B1 and 3
- C1, 3 and 5
- D3 and 5
Correct answer
B. 1 and 3
Step-by-step solution
The pyrimidine ring is a six-membered heterocyclic aromatic compound where the nitrogen atoms occupy positions 1 and 3 according to standard IUPAC numbering. This structural pattern is maintained in all pyrimidine bases found in nucleic acids: cytosine, thymine, and uracil. The nitrogen atoms are therefore located at positions 1 and 3 .