[curiouscat]

I would love the oportunity to test these theories experimentally. I think we all agree that this warrants further investigation.

I do have a experimental rig going on. So will be glad to try anything that comes up.

If there are any ideas for an experiment, do post and I'll try to run them. So far we've only been trying to optimize our product distribution in a pretty brute-force approach.

[Archer]

I would look at careful acidification of hypochlorite solution, and visa verse, see how that works out.

 I would chlorinate styrene n DCM with Cl₂ and try to form your product in conc. HCl 

Third I would heat your product in conc HCl to see if the epoxide forms.

The only thing I hate more than being wrong is being wrong twice! I do a lot of this chemistry and all I care about is the product. How I got there is academic so It's nice  have a different theory to consider, thanks guys!

My interest for my research in this would be the  β methyl styrene and the effect on relative configuration. Using your method (i.e cis vs trans).

[curiouscat]

Thanks for your tips.

I would look at careful acidification of hypochlorite solution, and visa verse, see how that works out.

What did you mean by this one? I dose acid / H2O2 and the substrate together; do you mean changing the ratios? The hypochlorite solution gets generated in situ, if at all.

[Archer]

Expt 1 I would add the substrate to sodium hypochlorite solution and slowly add HCl (no H₂O[₂.) This would make hypochlorous acid and maybe your product.

Expt 2 add substrate to HCl and add sodium hypochlorite slowly, the equilibrium should favour Cl₂ see what the outcome of this reaction is.


In addition to the other recommendations I made previously (treating phenyl-1,2-dichloroethane and your product with HCl) you could also see what happens when you treat styrene oxide with HCl and/or with HCl & H₂O₂

Others may consider these a complete waste of time, this is just what I would (rightly or wrongly) try to develop a better understanding the potential processes which are going on. These can all be done on a relatively small scale but really you have to question whether all this is an effective use of your time.

[magician4]

I apologise for maybe raining on someone's parade, but ... :

having done some mechanistic studies in the past whilst doing my PhD, I strongly would recommend to define the very scientific question you are about to research before going into experimental details

we see from the literature and the side products that at least 3 pathways might occur which are worthy of further investigation

furthermore , we know form the byproduct "benzaldehyde" that at least one complete set of interactions between them educts / intermediates is beyond even our professional imagination for the time being

  I would be highly astonished to learn that from a handfull of well chosen experiments the whole situation comes apart in a way, that will reveal the truth of the matter like the sun rising in the morning
there's more to it , much more, my guts tell me...

so, what is the goal of the endeavour?
for-real improving of a technical process?

... and if not, i.e. if we're talking a scientific analysis of the different pathways etc., this will require a lot of time and money to shine a substantial light on the fines of the action

remember: even those seemingly simple systems like "oxygene / hydrogene - reaction leading to water" know dozends of pathways and species, and to the best of my knowledge still is not fully completed in mechanistic studies yet


regards

Ingo

[Archer]

Benzaldehyde is a common side reaction (sometimes the main product) of oxidation of certain benzyl alcohols with hypochlorous acid and could also happen with Cl₂, although I have never tried.

Unfortunately I can't describe how I know this in too much detail as this would violate the forum rules but put simply the bonding electrons between the benzylic carbon and the next carbon in the chain are transferred to the oxidant.

[magician4]

Benzaldehyde is a common side reaction (sometimes the main product) of oxidation of certain benzyl alcohols with hypochlorous acid and could also happen with Cl2, although I have never tried.

to the best of my knowledge, you would need a Ar-CH(OH)-R structure to achieve this, with R being either H or -COOH

any pathway including an explanation to the benzaldehyde findings hence would have to explain the intermediate formation of mandelic acid first (or any alternative path to get rid of the terminal =CH₂ fragment, exchanging it for hydrogens)


regards

Ingo

[Archer]

to the best of my knowledge, you would need a Ar-CH(OH)-R structure to achieve this, with R being either H or -COOH

any pathway including an explanation to the benzaldehyde findings hence would have to explain the intermediate formation of mandelic acid first (or any alternative path to get rid of the terminal =CH₂ fragment, exchanging it for hydrogens)

Indeed Ar-CH(OH)-R is what you need but this could be the result of hydrolysis of any epoxide formed or even just the product of the reaction.

As you will no doubt be aware the general method for the oxidation of the vicinal diol to benzladehyde is to use periodate, I have never tried to use hypochlorite but this may work to a lesser extent yielding benzaldehyde.

There is an R group of Ar-CH(OH)-R which is known to oxidise to benzaldehyde with hypochlorite, unfortunately I cannot describe this owing to forum rules. I have contacted a moderator to validate this but it is documented in the literature.

As you have already stated the benzylic cation is very stable so benzylic alcohols will  lose electrons to an oxidising agent (such as hypohalite / hypohalous acid) leaving benzaldehyde as the product to a greater or lesser extent.

[curiouscat]

There is an R group of Ar-CH(OH)-R which is known to oxidise to benzaldehyde with hypochlorite, unfortunately I cannot describe this owing to forum rules. I have contacted a moderator to validate this but it is documented in the literature.

Thanks for all your help @Archer! I wouldn't want to tax you to write anything more down  but just in case, I doubt it would violate any Forum Rules if you did.

IMHO, those caveats are for people seeking easy homework solutions whereas here you and @magician seem to have a very interesting discussion going on (and at least I'm finding it very educational) and I doubt the Mods would mind your elaborating any more.

Just my 2 cents. Of course, the Mods can correct me if I am wrong.

[magician4]

I really find this discussion refreshing, and would be astonished to learn that a scientific approach to this problem should be violating forum's rules

besides: I would be eager to learn which groups other than -H , -COOH are sensible to HOCl in the way we're discussing here, coming from styrene in a plausible pathway, as the literature I did look up regarding this didn't mention it.
but then again: who knows all the literature? so pls. be so kind

regarding the discussion in a broader way: periodate will split vic. diols, yes
on the other hand: IMHO no chlorine-based species will do so  (else this much cheaper substance would have been used for this purpose in the SOP's of the old days)
... and even if we had traces of iodine in the HCl , i would believe in the formation of periodate even less than i believe in the formation of high concentrations of HOCl under the conditions described.
epoxides are ok with me, but then we would need findings of the diol, the mandelic aldehyde and the mandelic acid in the trace section , too , aside from just benzaldehyde (which, I would expect, is even more sensible to oxidation than mandelic aldehyde)

as I said: looking into this system seriously, I would expect a whole bunch of interesting things to happen and a lot of work to be done

and by the end of the day, that's all I wanted to mention: this question is none answered in a New York minute


regards

Ingo

[curiouscat]

so, what is the goal of the endeavour?
for-real improving of a technical process?

Goal: To make as much halohydrin as I can from given quantity of styrene (as fast as I can).

This boils down to (IMHO):

1. Minimising pathways leading to (a) benzaldehyde (b) dichloride (c) styrene polymerization

2. Increasing rate constants for primary reaction by optimising temperature / finding  a catalyst

3. Finding conditions that promote hydrolysis of the dichloride to the halohydrin.

[discodermolide]

What is the purity of your styrene?

[curiouscat]

What is the purity of your styrene?

Thanks @disco.

It's commodity Styrene Monomer, not extra pure or anything.  (Lyyondell Basel I think.)

I believe 96%+ is the spec. but I will double check. It comes with inhibitor added at ppm levels.

Can I ask, if you had a particular problem in mind? If I guess, thinking that the Benzaldehyde is an oxidised impurity from the RM?

[discodermolide]

I just wondered if benzyl alcohol was an impurity. How much benzaldehyde do you see?

[curiouscat]

I just wondered if benzyl alcohol was an impurity. How much benzaldehyde do you see?

~5%. In some rare cases a little more.