[discodermolide]

That's quite a lot of benzaldehyde.
I wonder if you are getting some C=C cleavage, don't ask me how, but with the oxidant you are using who knows?

[curiouscat]

That's quite a lot of benzaldehyde.
I wonder if you are getting some C=C cleavage, don't ask me how, but with the oxidant you are using who knows?

Agreed!

Luckily, or unluckily, I care less about the actual pathway but if you have any tips ( catalyst, conditions, excess reagents, addition order etc.) that'd have a shot at maximizing my selectivity towards the halohydrin do let me know!

[discodermolide]

What's your order of addition?

[curiouscat]

What's your order of addition?

All three at once in almost exact stoichiometric ratios. Starting fluid in reactor is an excess of weak spent acid.

[discodermolide]

Why not add the oxidant to the styrene? Or better add styrene to the oxidant, then you may have more control?

[curiouscat]

Why not add the oxidant to the styrene?

I'll try. Reaction temp. being 60°C plus I was afraid high, hot styrene conc. were invitations for runaway or polymerization byproducts. That was the reason I was diluting down the reaction mix.  But only speculating.

Or better add styrene to the oxidant, then you may have more control?

That's worth a shot too.

[discodermolide]

So add the styrene to the oxidant. This is a two phase reaction mixture? If so then stirring is an important factor.

[curiouscat]

So add the styrene to the oxidant. This is a two phase reaction mixture? If so then stirring is an important factor.

It is indeed.

Can you think of any co-solvents etc. that might ease the two-phase mass transfer issues? A phase transfer catalyst?

[discodermolide]

You could use a tetraalkylammonium salt.
Or *Ignore me, I am impatient* up the temperature, and make sure the process is addition controlled, i.e. never an excess of styrene, almost complete conversion by the time the addition is complete. You've got great heat capacity in the water, so you should be OK thermally.

[discodermolide]

I think that toluene is a by-product in styrene manufacture. This may be the source of the benzaldehyde, if you have any toluene in your styrene?

[curiouscat]

So add the styrene to the oxidant.

Will try. Thanks.

PS. A mix of H2O2 + HCl (both ~30% w/w) at ~70°C is not crazy is it? Just checking. Earlier this went in together  as it reacted but now I'll need a lot of it. (if I'm adding Styrene in slowly to oxidant)

Any obvious incompatibility? Outside of the general nastiness of peroxides and acids, of course. That's for granted.

[discodermolide]

Test it out in the lab first, you will soon see. Or have you access to a DSC?

[curiouscat]

Test it out in the lab first, you will soon see. Or have you access to a DSC?

Oh yes, of course. Wasn't meaning I'd try this on pilot / production scale direct.

DSC would have been great, but no, don't have one.

[discodermolide]

Well just heat the mixture at 70°C for a few times your reaction time and see what happens. You can always check the peroxide of Cl content, if it does not go bang!

[Archer]

Could you make your product by chemical reduction (NaBH₄) of phenacyl chlroide?

I reduced some phenacyl bromide (as I had some in stock) to the alcohol very crudely to see if I could then oxidise it to benzaldehyde with NaOCl in acetic acid. I couldn't!, in fact the major product looks like ring chlorination!)

The reduction was quite effortless though (no benzaldehyde), the only side reaction was some epoxide which may be because I didn't neutralise during the work up I just removed the methanol with a stream of nitrogen as it was only very small scale (10 mg in 1 ml).