Didecylamine
[CAS 1120-49-6]

Identification

• Classification: Pharmaceutical intermediate >> Heterocyclic compound intermediate >> Pyrimidine compound >> Amine
• Name: Didecylamine
• Synonyms: N,N-Didecylamine; N-Decyldecanamine
• Molecular Formula: C₂₀H₄₃N
• Molecular Weight: 297.56
• CAS Registry Number: 1120-49-6
• EC Number: 214-312-1
• SMILES: CCCCCCCCCCNCCCCCCCCCC

Properties

• Solubility: Insoluble (1.1E^-3 g/L) (25 °C), Calc.^*
• Density: 0.809±0.06 g/cm³ (20 °C 760 Torr), Calc.^*
• Melting point: 38 - 40 °C (Expl.)
• Boiling point: 372.5 °C 760 mmHg (Calc.)^*, 424.3 - 425.8 °C (Expl.)
• Flash point: 163.5±10.7 °C (Calc.)^*, 113 °C (Expl.)
• Index of refraction: 1.448 (Calc.)^*

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

Safety Data

• Hazard Symbols: GHS05;GHS07;GHS09 Danger
• Risk Statements: H302-H314-H315-H318-H319-H335-H400-H410
• Safety Statements: P260-P261-P264-P264+P265-P270-P271-P273-P280-P301+P317-P301+P330+P331-P302+P352-P302+P361+P354-P304+P340-P305+P351+P338-P305+P354+P338-P316-P317-P319-P321-P330-P332+P317-P337+P317-P362+P364-P363-P391-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Specific target organ toxicity - single exposure	STOT SE	3	H335
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400
Chronic hazardous to the aquatic environment	Aquatic Chronic	1	H410
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315
Acute toxicity	Acute Tox.	4	H302
Skin corrosion	Skin Corr.	1B	H314
Skin corrosion	Skin Corr.	1A	H314
Serious eye damage	Eye Dam.	1	H318

chemBlink Chemical Story

Didecylamine is a secondary aliphatic amine consisting of two linear decyl (C10) alkyl chains attached to a single nitrogen atom. It belongs to the class of dialkylamines and is characterized by a strongly hydrophobic hydrocarbon framework combined with a basic amine functional group. The compound serves as an important intermediate in the synthesis of surfactants, quaternary ammonium compounds, corrosion inhibitors, and other specialty chemicals.

Structurally, the molecule contains a nitrogen atom bonded to two decyl groups and one hydrogen atom. Each decyl substituent is a straight-chain saturated hydrocarbon containing ten carbon atoms connected exclusively through carbon–carbon single bonds. All carbon atoms are predominantly sp³-hybridized, giving the alkyl chains considerable conformational flexibility through free rotation about the carbon–carbon bonds.

The nitrogen atom is also sp³-hybridized and adopts a trigonal pyramidal geometry. It possesses one lone pair of electrons and one N–H bond, making didecylamine a secondary amine. The lone pair is readily available for protonation, allowing the molecule to function as a Lewis base. Under acidic conditions, the nitrogen accepts a proton to form the corresponding dialkyldecylammonium ion.

Unlike tertiary amines, didecylamine contains an N–H bond. Consequently, the molecule can function as both a hydrogen bond donor and a hydrogen bond acceptor in its neutral form. The nitrogen lone pair serves as the hydrogen bond acceptor, while the N–H hydrogen can participate in hydrogen bond donation. These interactions influence its physical properties and intermolecular association.

The two long decyl chains dominate the molecular structure and impart pronounced hydrophobic character. Their flexible nature allows the molecule to adopt numerous conformations in solution. Extensive van der Waals interactions between these hydrocarbon chains contribute significantly to intermolecular attraction and influence properties such as viscosity and melting behavior.

From an electronic perspective, the alkyl substituents donate electron density to the nitrogen through inductive effects, increasing the basicity of the amine relative to aromatic amines. The electron-rich nitrogen readily participates in acid–base reactions and can coordinate to suitable Lewis acids or metal centers through its lone pair.

Physicochemically, didecylamine is amphiphilic but predominantly lipophilic. The single secondary amine contributes localized polarity, while the two C10 hydrocarbon chains constitute the majority of the molecular surface. As a result, the free base exhibits limited water solubility but dissolves readily in many nonpolar and moderately polar organic solvents. Formation of ammonium salts by protonation substantially increases aqueous solubility.

Chemically, the secondary amine group is the principal reactive site. Didecylamine readily undergoes protonation to form ammonium salts with mineral or organic acids. It also participates in alkylation reactions to yield tertiary amines and subsequently quaternary ammonium compounds upon further alkylation. The N–H bond also allows reactions such as acylation to produce amides and condensation with suitable electrophiles, reactions that are not available to tertiary amines.

The saturated hydrocarbon chains are chemically stable under ordinary conditions and generally undergo only reactions characteristic of alkanes, such as combustion or free-radical halogenation under appropriate conditions. Their principal role is to provide hydrophobic character rather than chemical reactivity.

The overall molecular shape is highly flexible because of unrestricted rotation about the carbon–carbon and carbon–nitrogen single bonds. The trigonal pyramidal nitrogen serves as the central junction from which the two long alkyl chains extend, allowing the molecule to adopt numerous low-energy conformations in solution.

Overall, didecylamine is a secondary dialkylamine composed of a trigonal pyramidal nitrogen atom bonded to two linear decyl groups and one hydrogen atom. Its combination of a basic, hydrogen-bonding amine functionality with two long hydrophobic alkyl chains gives the molecule its characteristic amphiphilic nature and defines its chemical behavior, which is dominated by acid–base chemistry and reactions at the secondary amine nitrogen.

References

2022. Multi-Component Sequential Synthesis of Dihydroorotic Acid-Based Amphiphilic Molecules. Synthesis.
DOI: 10.1055/a-1913-3105

2022. Study on the ozonation-modified multi-walled carbon nanotubes in polymer composites. Polymer Bulletin.
DOI: 10.1007/s00289-022-04367-z

2022. Synthesis of CsPbBr3/CsPb2Br5@silica yolk-shell composite microspheres: precisely controllable structure and improved catalytic activity for dye degradation. Advanced Composites and Hybrid Materials.
DOI: 10.1007/s42114-022-00520-4