2
$\begingroup$

I was told that "Sodium Tallowate, sodium cocoate and sodium palm kernelate are the 'natural' forms of SLS". Is this true? I thought "natural" SLS would be SLS derived from a natural product such as coconut oil.

$\endgroup$
  • $\begingroup$ Hi jrennie, welcome to Chemistry StackExchange! Could you describe a bit what you mean by “the natural form of SLS”? Wikipedia has a nice page on SLS, which you linked to. It includes details on its production, which appears to be from coconut or palm kernel oil. $\endgroup$ – F'x May 16 '12 at 14:07
6
$\begingroup$

Conventional soaps are the sodium salts of long chain carboxylic acids (aka fatty acids). These are formed by the hydrolysis of triglycerides, a process known as saponification. This process breaks the triglyceride at its ester linkages and yields three fatty acid molecules and glycerol molecule.

As the aforementioned wikipedia article indicates, sodium lauryl sulfate is formed by refunctionalising the fatty acid lauric acid. In this case, the $\ce{R-OOH}$ (carboxylic acid) head group has been replaced with an $\ce{R-OH}$ (alcohol) group, which is in turn replaced by $\ce{R-OSO3^{-}}$ (sulfate). Here I am using $\ce{R}$ to refer to the long alkyl chain of the molecule.

I'm not sure whether sodium lauryl sufate occurs naturally, however the other molecules you mention are different in the sense that they have carboxylate ($\ce{R-COO^{-}}$) head groups whereas sodium lauryl sulfate has the sulfate head group ($\ce{R-OSO3^{-}}$). Both classes of molecule will act as surfactants as they have polar head groups which are hydrophilic, and nonpolar alkyl tails which have an affinity for fats and oils.

Lauric acid derivatives spotter's guide

(These were drawn using the nifty ChemFig package for (La)TeX.)

Some molecules

The last two (sodium laurate and sodium lauryl sulfate) are sodium salts. Both carboxylic acids ($\ce{R-COOH}$) and hydrogen alkyl sulfates ($\ce{R-OSO3H}$) are fairly willing to ionise to give the corresponding carboxylate ($\ce{R-COO^{-}}$) or sulfate ($\ce{R-OSO3^{-}}$). Sodium ions happily associate with these anions, balancing the negative charge.

$\endgroup$
  • $\begingroup$ The original discussion re: SLS and the compounds used to derive it can be found here: parenting.stackexchange.com/questions/5047/… Sodium Tallowate, sodium cocoate and sodium palm kernelate are derived from coconut oil, palm kernel oil and tallow. Sodium cocoate is the sodium salt of fatty acids from coconut oil; lauric acid is the primary component of this oil. Sodium tallowate and palm kernelate likewise contain the fatty acids used for SLS formulation. $\endgroup$ – Darwy May 16 '12 at 19:39

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.