Product Overview
1,2-propadiene (Allene), commonly known as allene, is a unique and highly reactive hydrocarbon characterized by two cumulative double bonds (C=C=C). This colorless, flammable gas is the simplest member of the allene family. Its unusual linear structure with adjacent sp²-hybridized carbon atoms results in distinctive chemical properties, making allene a valuable and specialized building block in organic synthesis and materials science research. Unlike its more common isomer propyne (methylacetylene), allene offers a divergent reactivity profile that enables the construction of complex molecular architectures, particularly in pharmaceutical and advanced material applications.
Basic Information
| CAS No. | 463-49-0 |
| UN No. | UN2200 (Propadiene, inhibited) |
| Molecular Formula | C₃H₄ |
| Hazard Classification | 2.1 (Flammable gas) |
Key Attributes & Parameters
| Purity | Available in research and high-purity grades, typically ≥98.0%. Higher purity grades (≥99.5%) are offered for sensitive synthetic applications. |
| Physical State | Colorless, flammable gas at standard conditions; often supplied as a liquefied gas under pressure. |
| Boiling Point | -34.5 °C (-30.1 °F) |
| Critical Properties | Critical temperature |
| Key Property | Possesses a non-linear, perpendicular orientation of the two CH₂ groups, giving it chiral axial geometry in substituted derivatives. |
Features & Advantages
Unique Cumulative Double Bond System
The defining feature of allene is its C=C=C framework, which provides a versatile and highly reactive platform for cycloadditions, oligomerizations, and transition-metal-catalyzed transformations unavailable with simple alkenes or alkynes.
Versatile Building Block for Complexity
Enables efficient synthesis of complex cyclic and polycyclic structures through controlled reactions, making it invaluable for creating novel pharmacophores and organic materials.
Axial Chirality Precursor
Substituted allenes can exhibit axial chirality, making them crucial intermediates in asymmetric synthesis for producing enantiomerically enriched compounds, especially in pharmaceutical research.
Research & Development Enabler
Its distinctive chemistry supports innovation in developing new catalytic methodologies, organic semiconductors, and ligand systems.
Functional Characteristics
Allene is a reactive gas whose primary function is to serve as a diene or a unique two-carbon synthon in organic synthesis. Its cumulative diene system allows it to participate in [2+2] and [4+2] cycloadditions, though often with different regioselectivity than conjugated dienes. It readily undergoes polymerization, metal complexation, and insertion reactions. Due to its high reactivity and tendency to polymerize, it is typically handled in solution at low temperatures or used immediately upon generation in situ for many applications. Commercial allene is stabilized with inhibitors (e.g., p-methoxyphenol) for safe storage and transport.
Primary Application Fields
Pharmaceutical & Fine Chemical Synthesis
Serves as a key intermediate in the synthesis of complex natural products, drug candidates, and chiral auxiliaries. Used to build cyclobutanes, cyclopentenones, and other strained or functionalized ring systems.
Advanced Materials Research
Used as a monomer or precursor in developing specialty polymers, carbon-rich materials, and molecular scaffolds for organic electronics.
Organometallic & Catalysis Research
Acts as a ligand or precursor to ligands in transition metal catalysis. Its ability to coordinate to metals in various modes is exploited to develop new catalytic processes.
Fundamental Organic Chemistry Studies
Employed to study pericyclic reaction mechanisms, develop new synthetic methodologies, and explore the properties of cumulenes.
Customer Collaboration Case
A biotechnology company focused on developing novel kinase inhibitors encountered a roadblock in synthesizing a core tricyclic scaffold with a specific three-dimensional geometry. Traditional alkene-based approaches failed to deliver the required stereochemical control and ring strain. Our team of synthetic chemists proposed using a chiral allene-based strategy. We supplied them with high-purity, stabilized allene and collaborated on developing a tailored palladium-catalyzed cyclization sequence. The unique reactivity of the allene moiety allowed for a concise, three-step construction of the desired core with excellent enantioselectivity (>95% ee). This allene-enabled route not only solved their synthetic challenge but also reduced the step count from their previous route by 40%. The successful delivery of multi-gram quantities of the key intermediate using our allene feedstock accelerated their preclinical development timeline by nearly six months, showcasing the transformative potential of specialized gas intermediates in complex molecule synthesis.
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