Proportion of Acid to Alcohol in Esters (Natural or Synthetic)

I am wondering about some of the Wax Esters that are being synthetically produced, specifically about the amount of acid to alcohol combined.  In nature, I don't know if esters form in predominantly equal amounts, or if they are more random.  When humans synthetically formulate esters, they combine a specific chosen type of acid, and likewise an alcohol, but not sure if they are joining them in equal proportions or not.

For example, with "Cetyl Palmitate", is that 50 percent Cetyl Alcohol, and 50 percent Palmitic Acid?  Or is it closer to 80/20?  It matters when formulating, but not sure why that information is not readily available.  I know that "Cetyl Esters NF" (which is predominantly Cetyl Palmitate) is a synthetic version of man-made was esters that were developed to replace/mimic the natural spermaceti wax that used to be harvested from the sperm whale.

Another example of natural wax esters would be from Jojoba Oil (which is longer chain, like mostly C20-C22), but still would leave me wondering what proportion contains fatty acids, and what proportion of it is long chain alcohols.

The last example I'm wondering about it C12-15 Alkyl Benzoate, which may be a more complicated ester to form.

Anyone have knowledge about this?


Comments

  • I will start this off and sure you willl get many comments. Esterification is based on Stochiometry using equimolar amounts of each component so  cetyl pamitate(CP) which you mention is formed using one mole of palmitic acid (256 parts by weight) which  reacts with one mole of cetyl alcohol (242 parts by wt,) to provide 480 parts of CP. During the reaction (which is acid catalized usually H2SO4) one mole of water (18 parts by weight is lost) to yield 480 parts by weight of he CP ester.During the process the acid portion loses one H and the alcohol loses OH to account for the water; so the acid portion of the CA provides 255 parts by weight or 53,1% and the alcohol or cetyl portion contributes 46.9%.This will vary depending upon the molecular weights of each of the components employed which are combined via the law of Mass action in fixed stochiometric ratio.I think I will stop here and let others weigh in.
  • BelassiBelassi Member, PCF student
    ^^^^ That.
    It's all about stoichiometry.
    Cosmetic Brand Creation. Concept to name to IMPI search to logo and brand registration. In-house graphic design inc. Pantone specs. Cosmetic label and box design & graphics.
  • Okay, thanks for that information, that's very helpful to have that understood.  So then, what I am curious about is the "Stearyl Palmitate" product I've been buying that indicates it's an ester of Stearyl Alcohol and "Methyl Palmitate".... why would the Palmitic Acid need to be methylated first?  I'm assuming that methyl alcohol was combined with palmitic acid, and then esterified with stearyl alcohol, right?  But why wouldn't it just follow the same process that was used to produce Cetyl Palmitate?  I don't believe cetyl palmitate is "Cetyl Alcohol" esterified with "Methyl Palmitate"... so I don't see why there would be a difference in the processing aspect of Cetyl Palmitate vs. Stearyl Palmitate.  Make sense?


  • PerryPerry Administrator, Professional Chemist
    edited June 2017
    @doctorbrenda - I'm not sure about the answer to the methyl palmitate vs palmitic acid. It could be that by methylating the palmitic acid first they get a better esterification reaction yield.  That is suggested in this patent. 

    https://www.google.com/patents/US20050240040
  • @doctorbrenda The manufacturer uses transesterification of the methyl esters with stearyl alcohol because it a cost effective process.The former are likely derived from vegetable oil as an inexpensive feedstock and easily transesterified and or reacted  with other compounds to use for other industrial applications We used to make alkanolamides from the methyl esters to get higher yields.See scheme 15 in article below:(rest is good reading also)
    http://jbcs.sbq.org.br/imageBank/PDF/v9n3a02.pdf
  • Very fascinating.  Makes sense that they'd want to do transesterification of vegetable oils for many other uses, not just cosmetic stuff, if it's low cost and higher yield (for medical/pharmaceutical, industrial, etc.).  Thanks everyone, for sharing input.
Sign In or Register to comment.