Guanidine Hydroiodide
[CAS# 19227-70-4]

Identification

• Classification: Chemical reagent >> Organic reagent >> Guanidine salt
• Name: Guanidine Hydroiodide
• Molecular Formula: CH₆IN₃
• Molecular Weight: 186.98
• CAS Registry Number: 19227-70-4
• EC Number: 606-268-0
• SMILES: C(=N)(N)N.I

Properties

• Melting point: 194-199 ºC (Expl.)
• Boiling point: 189.7 ºC 760 mmHg (Calc.)^*
• Flash point: 68.6 ºC (Calc.)^*

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS07 Warning
• Hazard Statements: H302-H315-H319-H332-H335
• Precautionary Statements: P261-P264-P264+P265-P270-P271-P280-P301+P317-P302+P352-P304+P340-P305+P351+P338-P317-P319-P321-P330-P332+P317-P337+P317-P362+P364-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315
Acute toxicity	Acute Tox.	4	H302
Specific target organ toxicity - single exposure	STOT SE	3	H335
Acute toxicity	Acute Tox.	4	H332

Discovory and Applicatios

Guanidine hydroiodide is the hydroiodide salt of guanidine, a strongly basic organic compound consisting of a central carbon atom bound to three amino groups. Guanidine itself was first identified in the 19th century as a product of protein and amino acid metabolism, and later became well recognized for its role as a strong base and nitrogen donor in organic and biological systems. The hydroiodide salt form was developed to improve handling and to provide a stable, crystalline derivative suitable for laboratory and industrial use.

The preparation of guanidine hydroiodide typically involves the neutralization of guanidine with hydroiodic acid, yielding a hygroscopic but stable crystalline material. Compared to guanidine in its free base form, which is highly reactive and prone to decomposition, the hydroiodide salt offers improved storage stability and controlled reactivity. This makes it easier to use in synthetic chemistry, where precise control of reaction conditions is required.

In chemical applications, guanidine hydroiodide serves as a versatile reagent and precursor. Its strong basicity and nucleophilicity make it useful for promoting condensation and substitution reactions, particularly in the synthesis of heterocycles and nitrogen-containing scaffolds. Guanidine salts are widely used in pharmaceutical chemistry, and the hydroiodide variant provides access to iodide ion chemistry while maintaining the guanidinium cation as a reactive intermediate.

Guanidine derivatives, including guanidine hydroiodide, have also been employed in the preparation of functional materials. Guanidinium salts can act as ionic components in the formation of hybrid organic–inorganic materials, especially in contexts where hydrogen bonding and ionic interactions are exploited to tune structure and stability. In these systems, the presence of the iodide counterion may further influence crystallization behavior and electronic properties.

Beyond synthetic chemistry, guanidine and its salts are of biochemical significance due to their structural similarity to naturally occurring metabolites. Guanidine groups appear in the side chain of arginine and are central to protein biochemistry. While guanidine hydroiodide itself is not a naturally occurring compound, its chemical reactivity provides a useful model for studying guanidinium interactions and ion pairing in aqueous and solid-state systems.

Overall, guanidine hydroiodide is a stable salt form of guanidine that provides practical advantages in storage, handling, and reactivity. Its discovery followed from efforts to produce manageable crystalline salts of guanidine, and its applications range from synthetic chemistry and heterocycle formation to potential roles in advanced materials. By stabilizing guanidine in an accessible form, guanidine hydroiodide has facilitated both fundamental research and applied developments across several areas of chemistry.

References

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DOI: 10.1038/s41528-024-00376-2

2024. Switchable interfacial reaction enables bright and stable deep-red perovskite light-emitting diodes. Nature Photonics.
DOI: 10.1038/s41566-023-01369-9

2013. A solution-phase parallel synthesis of alkylated guanidines from thioisocyanates and amines. Molecular Diversity.
DOI: 10.1007/s11030-013-9444-z