Has anyone reacted parabens with Sodium hydroxide to make paraben Sodium salts?

It looks like using parabens Sodium salts is a must
even if they get initially dissolved by heating water, some then precipitates out of solution in the finished formulation, once it has cooled down.

Is making paraben Sodium salts as simple as weighn parabens and NaOH stochiometrically proportional to each other, heat water and stir?

I see that paraben has a -OH (hydroxy) group, so it ain't as simple as neutralizing a carboxylic acid.


I was unable to find the compete study:

Study on Synthesis of Sodium Methylparaben

Abstract
Sodium methylparaben,a derivant of methylparaben,is a new type of multifunctional and high performance food or cometic additive。The preparation of sodium methylparaben by methylparaben and sodium hydroxide as raw materials was studied。The main factors affecting the quality of product were determined by experiments。The optimal reaction conditions for the synthesis of sodium methylparaben were obtained by studying the influence of reagent ration,reaction temperature and methods of feeding materials。The final purity of products reached 99.5% which meeted the pharmacopoeia standards.

Comments

  • To gauge if it's properly reacting
    maybe we can use a limited amount of water
    so mostly paraben Sodium salts and not much bare parabens will get dissolved

    Compare paraben Sodium salts solubility:

    Solubility of Paraben Salts within various solvents.
    All results in GR/100 ML at 25ºC Solvent
    Water: Sodium Methylparaben 80
    Water: Sodium Propylparaben 100
    http://www.nardev.com/UploadSection/ProdCat-184-1444197298.pdf

    Parabens
    Solubility (gR/100gR) 25º C
    Water: Methylparaben 0.25
    Water: Propylparaben 0.04
    http://www.nardev.com/UploadSection/ProdCat-183-1444197164.pdf
  • Methylparaben has a 152.15 molecular weight
    https://www.sigmaaldrich.com/catalog/product/usp/1432005?lang=en&region=US

    Propylparaben 180.20 mol wt
    https://www.sigmaaldrich.com/catalog/product/usp/1577008?lang=en&region=US

    And Sodium hydroxide 40.00 m.w.
    https://www.sigmaaldrich.com/catalog/product/mm/30620m?lang=en&region=US

    So, if a stoichiometric ratio concentration is desired, use the above mentioned proportions.
    I hope to get test results posted by the next week.
  • Sodium Methyl Paraben available easily
  • Unfortunately Sodium salts ain't available here, so I would need to import them by plane.
    So maybe I can avoid that.


    As to follow EU regulations
    0.4% methylparaben
    0.19% propylparaben
    https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32014R1004&from=EN

    I'll try to react:
    400 mg methylparaben 
    190 mg propylparaben

    400 mg methylparaben = 400 mg / 152.15 = 2.63 mmol = by 40.00 = requires 105.16 mg NaOH
    190 mg propylparaben = 190 mg / 180.20 = 1.05 mmol = by 40.00 = requires 42.18 mg NaOH
    Total 147.34 mg NaOH

    As for water, 10 ml would be fine, I believe
    All Sodium salts will get dissolved
    but not much unreacted parabens.

    0.14734 g in 10 ml
    equals 14.734g in 1 L
    14.734g / 40.00 = 0.37 M NaOH
    So the solution is safe to handle (with gloves).

  • Most of it dissolved within 15 minutes! = success  :) 

    I poured
    5 ml demineralized water
    150 mg Sodium hydroxide flake (solid)
    400 mg methylparaben
    190 mg propylparaben

    I didn't wait for the Sodium hydroxide flake to dissolve
    I just poured everything the above ingredients in that order
    as expected, parabens didn't dissolve at first
    but within 15 minutes (I wasn't checking it, I went to prepare myself a cup of coffee), most dissolved with little stirring, no heating needed

    Only a few, tiny granules remain undissolved on the bottom of the test tube.
    I wonder if they're impurities. Will leave them over the weekend with occasional stirring to see if they dissolve.
    If not, will just filter them out.

    I will repeat the test by the next week, and check its pH.
    But so far, a working aliquot of predissolved paraben preservatives seems perfectly workable,
    ... and it's truly self preserving lol 
  • Very interesting, I wish more of us would experiment and do synthesis.
    Design of anti-aging creams, gels, and serums; shampoos; and therapeutic cosmetics. In-house label and box design capability.
  • Great! Keep us updated!

    @Belassi
    Agreed!
  • @Belassi I understand your point regarding synthesis and as a Chemist it does appeal to me. However (and I am sure you can appreciate the aspects) since I have these products readilly available and my primary goal is to create products that reach the market, the actual synthesis is really not feasible. I do envy you the fact of having some time to return to the synthesis basics.
    markfuller@microformulation.com Microformulation.com Microformulation Cosmetic Consulting provides Custom Formulations for both large Commercial accounts as well as smaller entrepreneurs. We can provide Naturally compliant Formulations under the NSF, NPA, Whole Foods and USDA Organic Certifications.
  • edited July 16
    @Gunther I'm curious about a few things;

    1) When attempting the in-situ synthesis for (I presume) why not just synthesize them separately and add the required amount of solution/salt?

    2) How are you going to keep track of the potential ester hydrolysis? (We might be the only ones but I don't have a TLC plates or appropriate solvents lying around most of the time).

    3) Keep us updated!!


    Dabbling Formulator — Qualified Cosmetic Safety Assessor — experienced in claim substantiation & EU regulatory affairs.
  • A surprising (and somewhat disappointing) aspect of being a cosmetic chemist is that you don't actually do much chemical reacting.

    As an organic chemist, you mix things together and hope something happens.

    As a cosmetic chemist, you mix things together and usually hope nothing happens.

    But as has been said, if your focus is on making the best end product you can make, becoming an expert in organic synthesis is not terribly helpful.
  • Thanks guys I feel flattered for the synthesis comments,
    even though it's technically synthesis, it's a really simple one.

    @Microformulation thanks
    even tough Sodium salts of parabens are available worldwide, just not here (Central America, Latin America), so I tried to see if I can avoid int'l shipping costs.
    Same for dishwashing sulfonates, they are available, but linear sulfonic acid + NaOH is cheaper.


    @Sibech
    1) I reacted them together as I wanted a ready-made paraben mix with the proportions allowed in EU for methyl and propylparaben.
    They can be reacted separately
    You can allow water to evaporate for dry Salts.
    2) You're right. They may hydrolyze over time, so it makes sense to make small batches, to be used quickly.
    3) I surely will.
  • It held fine in 5ml
    but wow I'll see if I can make a more concentrated solution.

    For 100 ml
    0.4% methylparaben Sodium salt = 400 mg
    0.19% propylparaben Sodium salt = 190 mg

    According to this
    http://www.nardev.com/UploadSection/ProdCat-184-1444197298.pdf
    their solubilities in water @ 25 C are:
    methylparaben Sodium salt  80g /100 ml
    propylparaben Sodium salt  100g / 100 ml

    So 
    400 mg methylparaben Sodium salt needs 0.5 ml water to dissolve
    190 mg propylparaben Sodium salt needs 0.19 ml water to dissolve
    total 0.69 ml
    (and the afore mentioned 147.34 mg NaOH)

    So it's possible to make a EU-regulations complying paraben Sodium salt concentrate where you just need to pour 1 ml of parabens concentrate, to preserve 100 ml of formulation.
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