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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
AbstractSodium 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. -
12 Replies
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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 dissolvedCompare 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.pdfParabens
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®ion=USPropylparaben 180.20 mol wt
https://www.sigmaaldrich.com/catalog/product/usp/1577008?lang=en®ion=USAnd Sodium hydroxide 40.00 m.w.
https://www.sigmaaldrich.com/catalog/product/mm/30620m?lang=en®ion=USSo, 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
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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=ENI’ll try to react:
400 mg methylparaben
190 mg propylparaben400 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 NaOHAs 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 propylparabenI 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 neededOnly 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.
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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.
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@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!!
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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.
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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 mgAccording 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 mlSo
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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