IUPAC name
Other names
3D model (JSmol)
ECHA InfoCard100.000.727
RTECS numberMF8260000
Molar mass151.13 g/mol
AppearanceWhite amorphous solid.
Density2.200 g/cm3 (calculated)
Melting point 360 °C (680 °F; 633 K) decomposes
Boiling pointSublimes
Acidity (pKa)3.3 (amide), 9.2 (secondary), 12.3 (primary)[1]
Main hazardsIrritant
NFPA 704
Flash pointNon-flammable
Related compounds
Related compounds
Cytosine; Adenine; Thymine; Uracil
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Guanine (n/; or G, Gua) is one of the four main nucleobases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine (uracil in RNA). In DNA, guanine is paired with cytosine. The guanine nucleoside is called guanosine.

With the formula C5H5N5O, guanine is a derivative of purine, consisting of a fused pyrimidine-imidazole ring system with conjugated double bonds. Being unsaturated, the bicyclic molecule is planar.


Guanine, along with adenine and cytosine, is present in both DNA and RNA, whereas thymine is usually seen only in DNA, and uracil only in RNA. Guanine has two tautomeric forms, the major keto form (see figures) and rare enol form.

It binds to cytosine through three hydrogen bonds. In cytosine, the amino group acts as the hydrogen bond donor and the C-2 carbonyl and the N-3 amine as the hydrogen-bond acceptors. Guanine has the C-6 carbonyl group that acts as the hydrogen bond acceptor, while a group at N-1 and the amino group at C-2 act as the hydrogen bond donors.

Cytonum2.png Guannum2.png

Guanine can be hydrolyzed with strong acid to glycine, ammonia, carbon dioxide, and carbon monoxide. First, guanine gets deaminated to become xanthine.[2] Guanine oxidizes more readily than adenine, the other purine-derivative base in DNA. Its high melting point of 350 °C reflects the intermolecular hydrogen bonding between the oxo and amino groups in the molecules in the crystal. Because of this intermolecular bonding, guanine is relatively insoluble in water, but it is soluble in dilute acids and bases.

Other Languages
العربية: غوانين
تۆرکجه: قوانین
Bân-lâm-gú: Guanin
беларуская: Гуанін
български: Гуанин
bosanski: Guanin
brezhoneg: Guanin
català: Guanina
čeština: Guanin
dansk: Guanin
Deutsch: Guanin
eesti: Guaniin
Ελληνικά: Γουανίνη
español: Guanina
Esperanto: Guanino
euskara: Guanina
فارسی: گوانین
français: Guanine
Gaeilge: Guainín
galego: Guanina
한국어: 구아닌
հայերեն: Գուանին
हिन्दी: गुआनिन
hrvatski: Gvanin
Ido: Guanino
Bahasa Indonesia: Guanina
interlingua: Guanina
italiano: Guanina
עברית: גואנין
Basa Jawa: Guanin
ქართული: გუანინი
қазақша: Гуанин
kurdî: Guanîn
lietuvių: Guaninas
magyar: Guanin
македонски: Гванин
Nederlands: Guanine
日本語: グアニン
norsk: Guanin
norsk nynorsk: Guanin
occitan: Guanina
polski: Guanina
português: Guanina
română: Guanină
русиньскый: Гуанин
русский: Гуанин
Scots: Guanine
Simple English: Guanine
slovenčina: Guanín
slovenščina: Gvanin
српски / srpski: Гуанин
srpskohrvatski / српскохрватски: Guanin
suomi: Guaniini
svenska: Guanin
Tagalog: Guanine
தமிழ்: குவானின்
Türkçe: Guanin
українська: Гуанін
Tiếng Việt: Guanine
中文: 鳥嘌呤