When benzyl bromide is made from benzyl ...

[ADDkid]

When benzyl bromide is made from benzyl alcohol and HBr, and the product is cleaned as mention in the "purification of Lab. chemicals", around what precent of impurties might be presence?, before distillation? ADDkid

[Rhodium]

I don't think that has been determined. It is however easy to find out by checking the yield of material distilling at the proper temperature. If you find out that distilling 100 grams of crude benzyl bromide returns 85g pure material, then you can conclude that the amount of impurities is <15%.

[ADDkid]

Why do most references use benzyl chloride, swig reads very little of benzyl bromide.  Is benzyl chloride less of a lachamayor (I think that is how you spell it),  When swig try to distill benzyl bromide, it started to turn brown, Then swig left it over night to cool, and check again, and some liquid still remained, swig wonders if the brown was benzyl alcohol by product from oxidation, or benzyl bromide from to much light.  What do you  suggest for working with this compound, it is very irrating

P.S.  Is there a way to use this for a grignard without distilling.  It seems swigs only problem is un-reacted benzyl alcohol, which has active hydrogen’s.  What are the best methods to remove benzyl alcohol.  Swig tried to freeze but could not get pass -3C

[Rhodium]

Why do most references use benzyl chloride, swig reads very little of benzyl bromide. 

Because benzyl chloride is a lot cheaper gram for gram than benzyl bromide. Also, as the molecular weight of benzyl bromide is significantly higher, this makes the $/mole difference so much larger.

When swig try to distill benzyl bromide, it started to turn brown, Then swig left it over night to cool, and check again, and some liquid still remained, swig wonders if the brown was benzyl alcohol by product from oxidation, or benzyl bromide from to much light.

Are you saying you distilled the benzyl bromide, and that the initially clear distillate turned brown overnight? Between which temperature interval did you collect the benzyl bromide? According to Analytical Chemistry, 32(4), 551-554 (1960) pure benzyl bromide has a bp of 198°C at atmospheric pressure.

From a Benzyl bromide MSDS:

Stability Condition To Avoid: DECOMPOSES ON EXPOSURE TO LIGHT.

Is there a way to use this for a grignard without distilling.  It seems swigs only problem is un-reacted benzyl alcohol, which has active hydrogen’s.

That's very simplistic. You know bromine is an oxidizer, right? It's very likely that benzaldehyde has formed, and maybe benzoic acid, and hence also benzyl benzoate by simple esterification. Not to mention benzal bromide (which is likely to polymerize upon addition of Mg...

[ADDkid]

Swig added a few drops (prob. 1.5-3mL) in a 50ml flask, preheated oil bath, and heated.  As the temp. got to about 70c, Swig notice whiteness swirling around, as clear liquid ran down the flask. Swig turned the heat off and rest until the next day, where he found brown gak, however clear liquid still remained floating on top, and round the brown gak.  Swig used a flash light, and was attempted without reduce pressure.

Wouldn't benzyl bromide be the best choice, since it makes a better organometallic compound.  Also it seems that benzyl chloride is harder to purify then benzyl bromide.

Swig was thinking test run, do you think he would get some product if it was not distilled?  What would you do if you did not have a source for reduce pressure, besides finding a source for reduce pressure. Thanks ADDkid

P.S. Swig was thinking about taking some CaCl2 and placing it in a cup of water, and then drying to form CaCl2*H2O, which could be use to get colder temperture, and seprating. What do you think?

[Rhodium]

Swig added a few drops (prob. 1.5-3mL) in a 50ml flask, preheated oil bath, and heated.  As the temp. got to about 70c, Swig notice whiteness swirling around, as clear liquid ran down the flask. Swig turned the heat off and rest until the next day, where he found brown gak, however clear liquid still remained floating on top, and round the brown gak.  Swig used a flash light, and was attempted without reduce pressure.

What did you intend to accomplish by heating the benzyl bromide to 70°C and then letting it cool overnight?

Wouldn't benzyl bromide be the best choice, since it makes a better organometallic compound. 

It would likely be more reactive, but benzyl chloride is one of the most reactive grignards as it is, and with increased reactivity you sometimes risk getting more side reactions.

Also it seems that benzyl chloride is harder to purify then benzyl bromide.

How do you know, when you haven't bothered to even try?

Swig was thinking test run, do you think he would get some product if it was not distilled?

Maybe, but why risk getting nothing or an impure mess?

What would you do if you did not have a source for reduce pressure, besides finding a source for reduce pressure.

Distill the benzyl bromide, collecting the fraction boiling at ~198°C, discarding any forerun and high-boiling residue.

P.S. Swig was thinking about taking some CaCl2 and placing it in a cup of water, and then drying to form CaCl2*H2O, which could be use to get colder temperture, and seprating. What do you think?

Evaporating a calcium chloride solution at room temp forms the hexahydrate, CaCl₂·6H₂O (mp 27°C), which you can use in a cooling bath mixture together with crushed ice.

[ADDkid]

What did you intend to accomplish by heating the benzyl bromide to 70°C and then letting it cool overnight?

Swig turned the heat off once oxidation seemed to be
occuring.

Distill the benzyl bromide, collecting the fraction boiling at ~198°C, discarding any forerun and high-boiling residue.

So are you saying that Swig should be ok with ~198°C?

Also it seems that benzyl chloride is harder to purify then benzyl bromide

Just by first looks in "Purification of Lab. Chemicals", plus chlorination is slower then bromination, which seems that more benzyl alcohol would be present. Your comments have been helpful to swig. ADDkid

[Rhodium]

Swig turned the heat off once oxidation seemed to be occuring.

Thermal decomposition is something which occurs in almost all distillations, it's only the extent which varies. If I would stop any distillation in which the liquid in the boiling flask changed color, I wouldn't get much done.

So are you saying that Swig should be ok with ~198°C?

Yes - just avoid strong illumination. Distill very slowly if you don't have a fractionation column.

Just by first looks in "Purification of Lab. Chemicals"

The procedures look rather identical to me, it's just the details which differs. Note that they are presenting several alternative purifications, not that you should perform all the different methods.

chlorination is slower then bromination, which seems that more benzyl alcohol would be present

No, it means that you should allow the reaction to run for a longer time, or use a larger excess of HCl.

[amalgum]

When SWIM did the bromide thing, the still flask contents turned brown as well during distilling.  Also the still flask had that "brownish gakk" residue collecting at the bottom of the flask that was very hard to remove. However, just like Rhodium had said, thermal decomposition happens anyway during distillation.  Also the distillate SWIM had collected even though the still contents were turning brown was clear (crude fraction coming over around 195-202C or something likle that if SWIM can remember, it had a wide boiling range in SWIMS opinion).  SWIM did another distillation with a column as slow as he could bear (that shit is really killer on the mucous membranes, SWIM suggests to have better ventilation than him, or pipe the fumes somewhere safe).

So are you saying that Swig should be ok with ~198°C?

Yes - just avoid strong illumination.

Hmmm, SWIM didn't know that then.  SWIM distilled right in front of a window during the day dammnit!  Maybe weird gak formations and color changes in the still flask will be way less if done in a darker setting, probably giving higher yeilds.

SWIM still sticks with his original opinion in the original thread you started.  If your gonna fuck with benzyl halides at all, just use the chloride.  Like Rhodium had said it's cheaper, easier, and way less messy.  SWIM can also "back that up" from personal experience.

Hey Rhodium:
A halide swap will work for a benzyl halide right?

[Rhodium]

A halide swap will work for a benzyl halide right?

Smoothly.

[ADDkid]

Amalgam, did you use Al foil to contain the heat, what oil was used, did you do a reaction with the benzyl bromide?

Rhodium, From everything that swig has read, benzyl bromide is better, and benzyl iodine is even better.  Would you go the chloride route or bromide, if you had HBr around.

P.S.  I read that benzyl bromide is a mutagenic and does reproductive harm, what do you think Rhodium. ADDkid

[Rhodium]

If the intended use was to make a grignard reagent, I would not bother to make the bromide - only if I had to perform some reaction which would run sluggishly with the chloride.

I think all benzyl halides are toxic - as they are excellent alkylating agents, they are able to alkylate a lot of biomolecules, including your DNA.

[ADDkid]

It is almost impossible to mess with benzyl bromide and not be expose to it, and since such a small amount causes one to cry, I would hope that it's ability to make one cry is higher then to do damage to ones DNA.  How much should Swig worry? ADDkid

P.S. Rhodium have you ever messed with benzyl chloride, is it much less of a lachamayor then benzyl bromide?

[Rhodium]

I would hope that it's ability to make one cry is higher then to do damage to ones DNA.

That's correct though - the exposure is rather self-limiting... If you avoid skin contact, I don't think you need to worry.

P.S. Rhodium have you ever messed with benzyl chloride, is it much less of a lachamayor then benzyl bromide?

Dunno, I cannot compare, as I have only worked with the chloride (and that is rather vile as well).

[amalgum]

Amalgam, did you use Al foil to contain the heat, what oil was used, did you do a reaction with the benzyl bromide?

When SWIM gently refluxed the crudely distilled Br2 with the toluene, or during workup distillation?  Either way...no.
What oil did I use?  If you mean for a heating bath, none.  SWIM used a controlled mantle.  It's an old ass Glass-Col.

Rhodium, From everything that swig has read, benzyl bromide is better, and benzyl iodine is even better.  Would you go the chloride route or bromide, if you had HBr around.

That all depends.  SWIM cannot get benzyl alcohol in heaping quantities without ordering it from a supplier, which is something SWIM won't do seeing as the end product that'll be made is very illegal and any attention from any supplier is unwanted to SWIM.  SWIM always works 100%otc.  So toluene is something SWIM will start from.
But even if SWIM had HBr (wich SWIM can make very easily anyway) and benzyl alcohol, SWIM would save that HBr for something else.  Muriatic is very cheap to get, just heat the muriatic and the alcohol with lewis acid catalyst to get the chloride.  Separate and distill organics obtaining the chloride.

If benzyl bromide or even the iodide is what you wanted, you could do the halide swap.  The chloride is just as easy to make and is cheaper in the long run.  KI is cheaply available from those local photoshop chemistry stores by the pound (also very cheap).  Dilute the chloride in acetone and add the KI and reflux.  Filter precipitated KCl and distill off the acetone (recycling it for another run perhaps).  Viola, benzyl iodide that after some extra drying will probably run perfectly in a grignard. One thing SWIM has noticed is that when trying to distill the bromide (and probably more so with the iodide) the polymerization gak thing happens in the still flask, but has never seen it with the chloride, as it's bp is lower anyway.  Once one has pure chloride the halide swap will give the iodide (or the bromide) without the need to distill it, probably with higher yeilds to.  There's probably a high loss involved when distilling the bromide (as indicated somewhat by SWIMS past experiments to).

Also, to answer your question about using the bromide SWIM had made in a reaction.....no, not the bromide.  SWIM never made enough and was just tinkering around with the idea anyway, never intended to even get this serious with the bromide.  When SWIM did it, it seemed like too much trouble to go through, cause you have to remember SWIM made his own bromine from KBr, H2SO4 and H2O2 (a rather sucky way I might add), distilled it then added to toluene and refluxed.  The shit brought me to my knees in tears from even just trying to clean my glassware, and the gak shit in the still flask seemed troublesome and was hard to clean, so SWIM left it alone and made the chloride.
SWIM has made the chloride and used it however, to react with alcoholic cyanide solution to make the nitrile, which reacted with 70%H2SO4 to give PAA without a hitch.  SWIM used the PAA to make you know what.

P.S. Rhodium have you ever messed with benzyl chloride, is it much less of a lachamayor then benzyl bromide?

YES!

[amalgum]

Also the only other obvious solution to getting higher yeilds of the bromide from distillation to make it more cost effective is to use a vacuum of course.