Lauramidopropyl betaine, the major component of cocamidopropyl betaine
3D model (JSmol)
|Molar mass||342.524 g·mol−1|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
Cocamidopropyl betaine (CAPB) is a mixture of closely related organic compounds derived from coconut oil and dimethylaminopropylamine. CAPB is available as a viscous pale yellow solution and it is used as a surfactant in personal care products. The name reflects that the major part of the molecule, the lauric acid group, is derived from coconut oil. Cocamidopropyl betaine to a significant degree has replaced cocamide DEA.
Despite the name cocamidopropyl betaine is not synthesized from betaine. Instead it is produced in a two step manner, beginning with the reaction of dimethylaminopropylamine (DMAPA) with fatty acids from coconut or palm kernel oil (lauric acid, or its methyl ester, is the main constituent). The primary amine in DMAPA is more reactive than the tertiary amine, leading to its selective addition to form an amide. In the second step chloroacetic acid reacts with the remaining tertiary amine to form quaternary a ammonium center (a quaternization reaction).
- CH3(CH2)10COOH + H2NCH2CH2CH2N(CH3)2 → CH3(CH2)10CONHCH2CH2CH2N(CH3)2
- CH3(CH2)10CONHCH2CH2CH2N(CH3)2 + ClCH2CO2H + NaOH → CH3(CH2)10CONHCH2CH2CH2N+(CH3)2CH2CO2− + NaCl + H2O
CAPB is a fatty acid amide containing a long hydrocarbon chain at one end and a polar group at the other. This allows CAPB to act as a surfactant and as a detergent. It is a zwitterion, consisting of both a quaternary ammonium cation and a carboxylate.
Specifications and properties
Cocamidopropyl betaine is used as a foam booster in shampoos. It is a medium strength surfactant also used in bath products like hand soaps. It is also used in cosmetics as an emulsifying agent and thickener, and to reduce irritation purely ionic surfactants would cause. It also serves as an antistatic agent in hair conditioners, which most often does not irritate skin or mucous membranes. However, some studies indicate it is an allergen.
CAPB is obtained as an aqueous solution in concentrations of about 30%.
Typical impurities of leading manufacturers today:
- Sodium monochloroacetate < 5 ppm
- Amidoamine (AA) < 0.3%
- dimethylaminopropylamine (DMAPA) < 15 ppm
- Glycerol < 3%
The impurities AA and DMAPA are most critical, as they have been shown to be responsible for skin sensitation reactions. These by-products can be avoided by a moderate excess chloroacetate and the exact adjustment of pH value during betainization reaction accompanied by regular analytical control.
CAPB has been claimed to cause allergic reactions in some users, but a controlled pilot study has found that these cases may represent irritant reactions rather than true allergic reactions. Furthermore, results of human studies have shown that CAPB has a low sensitizing potential if impurities with amidoamine (AA) and dimethylaminopropylamine (DMAPA) are low and tightly controlled. Other studies have concluded that most apparent allergic reactions to CAPB are more likely due to amidoamine. Cocamidopropyl betaine was voted 2004 Allergen of the Year by the American Contact Dermatitis Society.
- Christian Nitsch, Hans-Joachim Heitland, Horst Marsen, Hans-Joachim Schlüussler, "Cleansing Agents" in Ullmann’s Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. doi:10.1002/14356007.a07_137
- Stephen A. Lawrence (2004). Amines: Synthesis, Properties and Applications. Cambridge University Press. p. 281.
- Reich, Charles (1997). "Hair Cleansers". In Martin M. Rieger; Linda D. Rhein (eds.). Surfactants in Cosmetics. Surfactant Science Series. 68 (2nd ed.). New York: Marcel Dekker, Inc. p. 359. ISBN 978-0-8247-9805-5. Retrieved 9 December 2012.
- De Groot, A. C.; Van Der Walle, H. B.; Weyland, J. W. (1995). "Contact allergy to cocamidopropyl betaine". Contact dermatitis. 33 (6): 419–422. doi:10.1111/j.1600-0536.1995.tb02078.x. PMID 8706401.
- Brand, R.; Delaney, T. A. (1998). "Allergic contact dermatitis to cocamidopropylbetaine in hair shampoo". The Australasian Journal of Dermatology. 39 (2): 121–122. doi:10.1111/j.1440-0960.1998.tb01264.x. PMID 9611386.
- Mowad, C. (2001). "Cocamidopropyl betaine allergy". American Journal of Contact Dermatitis. 12 (4): 223–224. doi:10.1053/ajcd.2001.29549. PMID 11753899.
- Shaffer, K. K.; Jaimes, J. P.; Hordinsky, M. K.; Zielke, G. R.; Warshaw, E. M. (2006). "Allergenicity and cross-reactivity of coconut oil derivatives: A double-blind randomized controlled pilot study". Dermatitis : contact, atopic, occupational, drug. 17 (2): 71–76. PMID 16956456.
- Fowler Jr, J. F.; Zug, K. M.; Taylor, J. S.; Storrs, F. J.; Sherertz, E. A.; Sasseville, D. A.; Rietschel, R. L.; Pratt, M. D.; Mathias, C. G.; Marks, J. G.; Maibach, H. I.; Fransway, A. F.; Deleo, V. A.; Belsito, D. V. (2004). "Allergy to cocamidopropyl betaine and amidoamine in North America". Dermatitis : contact, atopic, occupational, drug. 15 (1): 5–6. PMID 15573641.
- Korting, H. C.; Parsch, E. M.; Enders, F.; Przybilla, B. (1992). "Allergic contact dermatitis to cocamidopropyl betaine in shampoo". Journal of the American Academy of Dermatology. 27 (6 Pt 1): 1013–1015. doi:10.1016/S0190-9622(08)80270-8. PMID 1479082.
- Foti, C.; Bonamonte, D.; Mascolo, G.; Corcelli, A.; Lobasso, S.; Rigano, L.; Angelini, G. (2003). "The role of 3-dimethylaminopropylamine and amidoamine in contact allergy to cocamidopropylbetaine". Contact dermatitis. 48 (4): 194–198. doi:10.1034/j.1600-0536.2003.00078.x. PMID 12786723.
- Fowler, J. F.; Fowler, L. M.; Hunter, J. E. (1997). "Allergy to cocamidopropyl betaine may be due to amidoamine: A patch test and product use test study". Contact dermatitis. 37 (6): 276–281. doi:10.1111/j.1600-0536.1997.tb02464.x. PMID 9455630.
- History of Allergen of the Year Archived 2014-04-25 at the Wayback Machine. contactderm.org