---
title: "Guanine Structure (C5H5N5O): 3D Model, Formula & Molar Mass | MolDraw"
url: https://www.moldraw.com/molecules/guanine.html
description: "Structure of Guanine (C5H5N5O, 151.13 g/mol): rotatable 3D model, 2D skeletal formula, IUPAC name, SMILES, shape, polarity, uses and FAQ."
lang: en
publisher: Scidart Academy
generated: 2026-10-26
---
[MolDraw](https://www.moldraw.com/) › [3D molecule models](https://www.moldraw.com/molecules/) › Guanine structure

# Guanine structure and 3D model (C5H5N5O)

Guanine is a purine base with a C=O at C6 and an NH₂ group at C2. It pairs with cytosine in DNA and RNA.

**Quick answer:** Guanine is **C5H5N5O**, molar mass **151.13 g/mol**. Flat fused-ring system; very polar but almost insoluble in water because the solid is held together by strong hydrogen bonds.

Atom labels Hydrogens Spin

Drag to rotate · pinch or scroll to zoom. 3D coordinates: computed with RDKit (ETKDG conformer, force-field optimised).

## Guanine at a glance

| Formula | C5H5N5O |
| --- | --- |
| Molar mass | 151.13 g/mol |
| IUPAC name | 2-amino-1,7-dihydropurin-6-one |
| Atoms / bonds | 16 / 17 |
| H-bond donors / acceptors | 3 / 4 |
| logP (estimated) | -0.8 |
| SMILES | `C1=NC2=C(N1)C(=O)NC(=N2)N` |
| InChIKey | `UYTPUPDQBNUYGX-UHFFFAOYSA-N` |
| PubChem | [135398634](https://pubchem.ncbi.nlm.nih.gov/compound/135398634) |

![2D structural formula of Guanine (C5H5N5O)](https://www.moldraw.com/molecules/img/guanine.svg)

2D structure (skeletal formula) · [Draw it in MolDraw](https://www.moldraw.com/)

## What the 3D model of Guanine shows

The model contains **16 atoms** (11 heavy atoms and 5 hydrogens) joined by **17 bonds**; in ball-and-stick mode every stick is one bond, and double or aromatic bonds are drawn as multiple sticks. Switch to *space-filling* to see the molecule as its electron cloud, scaled to van der Waals radii: this is the shape other molecules actually "feel". It can donate 3 and accept 4 hydrogen bonds, and its estimated logP of -0.8 means it is very water-loving (hydrophilic). Its topological polar surface area is 100 Ų.

## Shape and bond angles

| Atom(s) | Geometry / hybridisation | Angles & lengths |
| --- | --- | --- |
| ring atoms | Trigonal planar, sp²; fused rings | ≈ 108–128° |
| C6 carbonyl carbon | Trigonal planar, sp² | ≈ 120° |
| exocyclic NH₂ | Near-planar, conjugated | ≈ 120° |

### Is Guanine polar?

Yes. It has several N–H donors and N and O acceptors. Its crystals are packed with hydrogen bonds, so it barely dissolves in water.

## Elemental composition of C5H5N5O

| Element | Atoms | Mass (g/mol) | Mass % |
| --- | --- | --- | --- |
| Carbon (C) | 5 | 60.055 | 39.74% |
| Hydrogen (H) | 5 | 5.040 | 3.33% |
| Nitrogen (N) | 5 | 70.035 | 46.34% |
| Oxygen (O) | 1 | 15.999 | 10.59% |

Calculated from IUPAC standard atomic weights. Check any formula with the [molar mass calculator](https://www.moldraw.com/tools/free-chem-tools/molar-mass-calculator.html).

## Uses of guanine

- One of the four bases in DNA and RNA
- Part of GTP, which powers protein synthesis and cell signalling
- Guanine crystals give the shimmer in fish scales and some cosmetics

## Interesting facts

- Guanine was first isolated from guano (bird droppings), which gave it its name.
- The G–C pair has three hydrogen bonds, one more than A–T.
- Crystalline guanine is used as a pearly pigment called pearl essence.

**Drawing structures for your notes?** MolDraw is a free online chemical structure editor for molecules, reactions and lab diagrams.

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## Frequently asked questions

### What is the structure of Guanine?

Guanine is a purine base with a C=O at C6 and an NH₂ group at C2. It pairs with cytosine in DNA and RNA. Its SMILES is C1=NC2=C(N1)C(=O)NC(=N2)N.

### Why does guanine pair with cytosine?

Their shapes line up three hydrogen bonds: guanine's C=O, ring N–H and NH₂ match cytosine's NH₂, ring N and C=O.

### Is guanine a purine?

Yes. Like adenine it has a six-membered ring fused to a five-membered ring.

### What is the chemical formula and molar mass of Guanine?

Guanine is C5H5N5O with a molar mass of 151.13 g/mol. It contains 16 atoms: 5 carbon, 5 hydrogen, 5 nitrogen, 1 oxygen.

### What is the IUPAC name of Guanine?

The IUPAC name is 2-amino-1,7-dihydropurin-6-one.

### How do I draw Guanine?

Open the MolDraw editor, paste the SMILES C1=NC2=C(N1)C(=O)NC(=N2)N or type "Guanine" in name search, and the structure is drawn for you. You can then export it as PNG, SVG, MOL or CDXML.

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