Pyrimidine
From Wikipedia, the free encyclopedia
| Pyrimidine | |
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| Chemical name | Pyrimidine |
| Chemical formula | C4H4N2 |
| Molecular mass | 80.08796 g/mol |
| CAS number | [289-95-2] |
| Density | 1.016 g/cm3 |
| Melting point | 20–22 °C |
| Boiling point | 123–124 °C |
| SMILES | C1=NC=NC=C1 |
| Disclaimer and references | |
Pyrimidine is a heterocyclic aromatic organic compound similar to benzene and pyridine, containing two nitrogen atoms at positions 1 and 3 of the six-member ring [1]. It is isomeric with two other forms of diazine.
Contents |
[edit] Nucleotides
Three nucleobases found in nucleic acids, namely cytosine, thymine, and uracil, are pyrimidine derivatives:
In DNA and RNA, these bases form hydrogen bonds with their complementary purines. Thus the purines adenine (A) and guanine (G) pair up with the pyrimidines thymine (T) and cytosine (C) respectively.[citation needed]
In RNA, the complement of A is U instead of T and the pairs that form are adenine:uracil and guanine and cytosine.[citation needed]
These hydrogen bonding modes are for classical Watson-Crick base pairing. Other hydrogen bonding modes ("wobble pairings") are available in both DNA and RNA, although the additional 2'-hydroxyl group of RNA expands the configurations through which RNA can form hydrogen bonds.[citation needed]
[edit] Chemical properties
A pyrimidine has many properties in common with pyridine, as the number of nitrogen atoms in the ring increases the ring pi electrons become less energetic and electrophilic aromatic substitution gets more difficult while nucleophilic aromatic substitution gets easier. An example of the last reaction type is the displacement of the amino group in 2-aminopyrimidine by chlorine [2] and its reverse [3]. Reduction in resonance stabilization of pyrimidines may lead to addition and ring cleavage reactions rather than substitutions. One such manifestation is observed in the Dimroth rearrangement.[citation needed]
Compared to pyridine N-alkylation and N-oxidation is more difficult and pyrimidines are also less basic: the pKa value for protonated pyrimidine is 1.23 compared to 5.30 for pyridine.[citation needed]
[edit] See also
- Pyrimidine biosynthesis
- Pyrazine, an analog with the nitrogen atoms in positions 1 and 4.
- Pyridazine, an analog with the nitrogen atoms in positions 1 and 2.
- Simple aromatic rings
- ANRORC mechanism
- Links to external chemical sources
[edit] References
- ^ Heterocyclic Chemistry (3rd Edition) Thomas. L. Gilchrist ISBN 0-582-27843-0
- ^ Organic Syntheses, Coll. Vol. 4, p.182 (1963); Vol. 35, p.34 (1955) Link
- ^ Organic Syntheses, Coll. Vol. 4, p.336 (1963); Vol. 35, p.58 (1955) Link
| Major Families of Biochemicals | ||
| Peptides | Amino acids | Nucleic acids | Carbohydrates | Lipids | Terpenes | Carotenoids | Tetrapyrroles | Enzyme cofactors | Steroids | Flavonoids | Alkaloids | Polyketides | Glycosides | ||
| Analogues of nucleic acids: | Types of Nucleic Acids | Analogues of nucleic acids: |
| Nucleobases: | Adenine | Thymine | Uracil | Guanine | Cytosine | Purine | Pyrimidine | |
|---|---|---|
| Nucleosides: | Adenosine | Uridine | Guanosine | Cytidine | Deoxyadenosine | Thymidine | Deoxyguanosine | Deoxycytidine | |
| Nucleotides: | AMP | UMP | GMP | CMP | ADP | UDP | GDP | CDP | ATP | UTP | GTP | CTP | cAMP | cADPR | cGMP | |
| Deoxynucleotides: | dAMP | TMP | dGMP | dCMP | dADP | TDP | dGDP | dCDP | dATP | TTP | dGTP | dCTP | |
| Ribonucleic acids: | RNA | mRNA | piRNA | tRNA | rRNA | ncRNA | sgRNA | shRNA | siRNA | snRNA | miRNA | snoRNA | LNA | |
| Deoxyribonucleic acids: | DNA | mtDNA | cDNA | plasmid | Cosmid | BAC | YAC | HAC | |
| Analogues of nucleic acids: | GNA | PNA | TNA| LNA | morpholino | |
