Sodium Benzoate conversion to...

[YT2095]

... Benzoic acid and Benzoyl Peroxide.

 

anyone know a clean and simple way of this?

[woelen]

The first is simple. Dissolve some Na-benzoate in water and add some acid (e.g. dilute H2SO4). The benzoic acid precipitates as a coarse flaky precipitate.

 

The second one I do not know.

[budullewraagh]

you could create radicals of hydrogen and benzoate, but that would be tricky to say the least.

[akcapr]

why woould benzoic acid precip out, how do the acidity do it

[woelen]

why woould benzoic acid precip out, how do the acidity do it

Many organic acids, especially, when the organic group is large, compared to the acidic group, have only slight solubility in water, because of the fact that they are bulky mostly apolar compounds.

 

The sodium salts, ammonium salts or potassium salts usually are soluble (as almost all salts of these three cations), but when a strong acid like HCl or H2SO4 is added, then the cation is protonated and the free organic is produced, which in turn precipitates

 

So, in the case of benzoic acid:

 

C6H5COO(-) + H(+) ---> C6H5COOH(s)

 

Here the C6H5- group is bulky compared to the COO(-) group.

[YT2095]

Thanks Woelen

 

I figured it would be some sort of acid, but was unaware that it would precipitate out, that makes life a whole bunch easier! since the sodium benzoate I have is only 97% pure, so converting to benzoic acid should UP this purity further, not only that, but it`s a better starting point for synths requiring a benzene group.

 

Edit: Hmm... Interesting, the reaction occurs instantly, and the yeild seems to be equal in volume to the original sodium benzoate, if not even a little greater.

this Could be an optical illusion however as the sodium benzoate was in tablet form and so compressed, whereas this if a fine white powder, appaerently there`s suposed to be a slight but pleasant odour to it, I can`t smell anything from it at all?

Now I`ve got to look up some interesting things to do with it, maybe try and synth some Aspirin perhaps or maybe Phenol

[woelen]

The fact that the volume seems a little larger indeed is quite possible, because now you have a free powder, while first you had a compressed tablet form.

 

Another reason may be difference in density, but for that I would suggest to look up a table.

 

As far as I know, benzoic acid is odorless and (more or less) tasteless. It is used in small quantities in foods as a preservative and of course for that purpose you don't want added smell or taste.

[budullewraagh]

you could possibly extract the benzoyl peroxide from acne medication- it can be found as 10% OTC in the US.

 

i found a benzoyl peroxide synth in vogel's book. see practical organic chemistry, 3rd edition by vogel.

 

2benzoyl chloride+H2O2---(alkali)--->benzoyl peroxide+2NaCl

so benzoyl chloride+Na2O2 would work well.

the reaction supposedly works best cold.

[YT2095]

Thnx Bud

 

that`s great, and I might have a go at that but only a very tiny amount as I read after that it`s quite dangerous, so probably best not to make more than a few miligrams. but I`ll least I`ll be able to say I`ve done it