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Pyrimidine



Pyrimidine
IUPAC name pyrimidine
Identifiers
CAS number 289-95-2
PubChem 9260
MeSH pyrimidine
SMILES C1=CN=CN=C1
Properties
Molecular formula C4H4N2
Molar mass 80.088
Melting point

20–22 °C

Boiling point

123–124 °C

Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox 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.

Additional recommended knowledge

Contents

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.

In RNA, the complement of A is U instead of T and the pairs that form are adenine:uracil and guanine:cytosine.

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]

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]

Organic synthesis

Pyrimidines can also be prepared in the laboratory by organic synthesis. One method is the classic Biginelli reaction. Many other methods rely on condensation of carbonyls with amines for instance the synthesis of 2-Thio-6-methyluracil from thiourea and ethyl acetoacetate [4] or the synthesis of 4-methylpyrimidine with 4,4-dimethoxy-2-butanone and formamide [5].

A novel method is by reaction of certain amides with carbonitriles under electrophilic activation of the amide with 2-chloro-pyridine and trifluoromethanesulfonic anhydride [6]:

See also

References

  1. ^ Heterocyclic Chemistry (3rd Edition) Thomas. L. Gilchrist ISBN 0-582-27843-0
  2. ^ Organic Syntheses, Coll. Vol. 4, p.182 (1963); Vol. 35, p.34 (1955) Link
  3. ^ Organic Syntheses, Coll. Vol. 4, p.336 (1963); Vol. 35, p.58 (1955) Link
  4. ^ Organic Syntheses, Coll. Vol. 4, p.638 (1963); Vol. 35, p.80 (1955) Link
  5. ^ Organic Syntheses, Coll. Vol. 5, p.794 (1973); Vol. 43, p.77 (1963) Link
  6. ^ Single-Step Synthesis of Pyrimidine Derivatives Mohammad Movassaghi and Matthew D. Hill J. Am. Chem. Soc.; 2006; 128(44) pp 14254 - 14255; (Communication) doi:10.1021/ja066405m


Nucleobases: Purine (Adenine, Guanine) | Pyrimidine (Uracil, Thymine, Cytosine)
Nucleosides: Adenosine/Deoxyadenosine | Guanosine/Deoxyguanosine | Uridine | Thymidine | Cytidine/Deoxycytidine
Nucleotides: monophosphates (AMP, GMP, UMP, CMP) | diphosphates (ADP, GDP, UDP, CDP) | triphosphates (ATP, GTP, UTP, CTP) | cyclic (cAMP, cGMP, cADPR)
Deoxynucleotides: monophosphates (dAMP, dGMP, TMP, dCMP) | diphosphates (dADP, dGDP, TDP, dCDP) | triphosphates (dATP, dGTP, TTP, dCTP)
Ribonucleic acids: RNA | mRNA (pre-mRNA/hnRNA) | tRNA | rRNA | gRNA | miRNA | ncRNA | piRNA | shRNA | siRNA | snRNA | snoRNA
Deoxyribonucleic acids: DNA | cDNA | gDNA | msDNA | mtDNA
Nucleic acid analogues: GNA | LNA | PNA | TNA | morpholino
Cloning vectors: phagemid | plasmid | lambda phage | cosmid | P1 phage | fosmid | BAC | YAC | HAC
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Pyrimidine". A list of authors is available in Wikipedia.
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