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:
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
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
https://www.sigmaaldrich.com/catalog/product/usp/1432005?lang=en®ion=US
Propylparaben 180.20 mol wt
https://www.sigmaaldrich.com/catalog/product/usp/1577008?lang=en®ion=US
And Sodium hydroxide 40.00 m.w.
https://www.sigmaaldrich.com/catalog/product/mm/30620m?lang=en®ion=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.
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).
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
@Belassi
Agreed!
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.
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.
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.