Lauramidopropyl betaine, the major component of cocamidopropyl betaine
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|Molar mass||342.52 g mol−1|
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Cocamidopropyl betaine (CAPB) is an organic compound derived from coconut oil and dimethylaminopropylamine. It is a zwitterion, consisting of both a quaternary ammonium cation and a carboxylate. CAPB is available as viscous pale yellow solution that 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.
Cocamidopropyl betaine can be viewed as the combination of cocamide and glycine betaine. It is however prepared by combining chloroacetic acid with the amide derived from dimethylaminopropylamine and lauric acid:
- CH3(CH2)10C(O)N(H)CH2CH2CH2N(CH3)2 + ClCH2CO2H + NaOH → CH3(CH2)10C(O)N(H)CH2CH2CH2N+(CH3)2CH2CO2- + NaCl + H2O
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 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. That said, some studies indicate it is an allergen. It also has antiseptic properties, making it suitable for personal sanitary products. It is compatible with other cationic, anionic, and nonionic surfactants.
CAPB is obtained as an aqueous solution in concentrations of about 30%.
- Active *NaCl 4.6 – 5.6%
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.
See also 
- 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.
- Reich, Charles (1997). "Hair Cleansers". In Martin M. Rieger; Linda D. Rhein. 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 : official journal of the American Contact Dermatitis Society, North American Contact Dermatitis Group 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. et al. (2004). "Allergy to cocamidopropyl betaine and amidoamine in North America". Dermatitis : contact, atopic, occupational, drug : official journal of the American Contact Dermatitis Society, North American Contact Dermatitis Group 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.
- 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. contactderm.org