(3-Lauramidopropyl)dimethylbetaine
[CAS 4292-10-8]

Identification

• Classification: Surfactant >> Zwitterionic surfactant >> Betaine type
• Name: (3-Lauramidopropyl)dimethylbetaine
• Synonyms: Lauramidopropylbetaine; N,N-Dimethyl-N-dodecanoylaminopropylbetaine; (Carboxymethyl)(3-lauramidopropyl)dimethylammonium hydroxide inner salt
• Molecular Formula: C₁₉H₃₈N₂O₃
• Molecular Weight: 342.52
• CAS Registry Number: 4292-10-8
• EC Number: 224-292-6
• SMILES: CCCCCCCCCCCC(=O)NCCC[N+](C)(C)CC(=O)[O-]

Safety Data

• Hazard Symbols: GHS05;GHS07 Danger
• Risk Statements: H315-H318-H319-H412
• Safety Statements: P264-P264+P265-P273-P280-P302+P352-P305+P351+P338-P305+P354+P338-P317-P321-P332+P317-P337+P317-P362+P364-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin irritation	Skin Irrit.	2	H315
Eye irritation	Eye Irrit.	2	H319
Serious eye damage	Eye Dam.	1	H318
Chronic hazardous to the aquatic environment	Aquatic Chronic	3	H412
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400

Discovery and Applications

(3-Lauramidopropyl)dimethylbetaine is an amphoteric surfactant commonly used in personal care and cleaning formulations, especially shampoos, body washes, and mild detergents. It belongs to the class of betaine surfactants, which contain both a quaternary ammonium group and a carboxylate group within the same molecule, giving it zwitterionic character.

The molecular structure consists of a long hydrophobic lauryl-derived chain (typically C₁₂ fatty acyl group) attached through an amide linkage to a propyl spacer. This spacer is connected to a dimethyl-substituted quaternary ammonium group, which carries a permanent positive charge. At the same time, the molecule contains a carboxylate group, resulting in an internal balance of positive and negative charges depending on pH conditions. This dual ionic nature is responsible for its amphoteric behavior.

The lauryl group originates from lauric acid, a naturally occurring fatty acid commonly found in coconut and palm kernel oils. Through amidation with 3-dimethylaminopropylamine, followed by quaternization and carboxymethylation steps, the final betaine structure is formed. This synthetic route is typical for cocamidopropyl betaine-type surfactants and related compounds.

(3-Lauramidopropyl)dimethylbetaine exhibits excellent surface-active properties due to its amphiphilic structure. The long hydrophobic chain interacts with oils and lipids, while the polar head group interacts with water. In aqueous solution, the molecules form micelles above the critical micelle concentration, enabling emulsification and solubilization of nonpolar substances.

One of the key features of betaine surfactants is their mildness compared with traditional anionic surfactants such as sodium lauryl sulfate. The internal charge balance reduces interaction with skin proteins, resulting in lower irritation potential. This makes (3-lauramidopropyl)dimethylbetaine particularly suitable for use in formulations designed for sensitive skin and daily personal care products.

In formulations, this compound is often used as a secondary surfactant in combination with anionic surfactants. It helps stabilize foam, improve viscosity, and enhance overall mildness. It also contributes to foam quality by producing dense, stable foam structures that are desirable in shampoos and cleansers.

The amphoteric nature of the molecule means its charge state can vary depending on pH. At low pH, the carboxyl group may be protonated, and the molecule behaves more like a cationic surfactant. At higher pH, it exists predominantly in a zwitterionic form. This pH-dependent behavior contributes to its versatility in different formulation environments.

From a physicochemical perspective, (3-lauramidopropyl)dimethylbetaine reduces surface tension effectively, allowing better wetting and spreading of aqueous solutions on surfaces. Its ability to stabilize emulsions and foams makes it useful not only in personal care products but also in household cleaning agents and industrial formulations.

Overall, (3-lauramidopropyl)dimethylbetaine is a zwitterionic surfactant derived from fatty acid chemistry and amine functionalization. Its combination of a long hydrophobic chain and a charged head group gives it strong emulsifying, foaming, and mild cleansing properties, making it an important ingredient in modern personal care and detergent systems.

References

2024. Safety assessment of cocamidopropyl betaine, a cosmetic ingredient. Toxicological Research.
DOI: 10.1007/s43188-024-00243-2