Cocamidopropyl betaine (CAPB) is a mixture of closely related
organic compounds derived from
coconut oil and
dimethylaminopropylamine.[2] CAPB is available as a viscous pale yellow solution and it is used as a
surfactant in personal care products and
animal husbandry. 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.
Production
Despite the name cocamidopropyl betaine, the molecule 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 a quaternary ammonium center (a quaternization reaction).[3]
The impurities AA and DMAPA are most critical, as they have been shown to be responsible for skin sensitization 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.
Niche Uses
CAPB is also used as a co-surfactant with
Sodium dodecyl sulfate for promoting the formation of
gas hydrates.[8] CAPB, as an additive, helps to scale-up the gas hydrates' formation process.[9]
Safety
CAPB has been claimed to cause allergic reactions in some users,[5][6][7] but a controlled pilot study has found that these cases may represent irritant reactions rather than true allergic reactions.[10] 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.[11][12] Other studies have concluded that most apparent allergic reactions to CAPB are more likely due to amidoamine.[13][14] Cocamidopropyl betaine was voted 2004
Allergen of the Year by the American Contact Dermatitis Society.[15]
^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. Vol. 68 (2nd ed.). New York: Marcel Dekker, Inc. p. 359.
ISBN978-0-8247-9805-5. Retrieved 9 December 2012.
^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.
PMID16956456.
^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.
PMID15573641.
^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.
PMID1479082.
^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.
PMID12786723.
S2CID9944011.
^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.
PMID9455630.
S2CID7933812.