Benzyl chloride

[ADDkid]

Swig would like to know how long it would take to distill benzyl chloride, swig has been using fractional distillation and it stays between 85 and 95C, for at least an hour or so.

[Rhodium]

That question is like asking "How long does it take to run a distance?" without specifying the distance, the fitness of the runner or if the feat is to be performed in dense jungle or on a highway.

It obviously is a function of the amount and the distillation rate, and the latter depends on the applied heat and the nature of the distillation setup. Apply more heat and it will go faster, but the distillate will also be less pure due to lowered separation.

[ADDkid]

the problem is that too much shit is coming out between 85-95, and then it just go suck on 82, what do you think? Also smoke seems to acumlating in the flask.  This is the weirdest distillation.

[Osmium]

Since the boiling point of benzyl chloride is higher than 85-95°C (if I remember correctly) that doesn't really matter, or does it?

[ADDkid]

Look, Swig knows how to distill, the problem involved the smoke, burning.  There was no stabliztion, temp kept going up and down.  I am starting to think that it was due to drafts, and could never get hot enough to make it up to 179.

[Rhodium]

Then your heat source is clearly insufficient.

[ADDkid]

Veg. oil was used, should sand be used instead. I always have a worse bumping problem with sand than oil, I don't have a coffee mug or boiling stones, that is why I usally use oil.

[Novice]

I believe what Rhodium ment was that your heat source is insufficient, which is the hot plate or whatever you're using. Either increase the heat, or get a new hot plate with greater capacity.

[lugh]

If you would have bothered to read

https://www.thevespiary.org/rhodium/Rhodium/chemistry/benzylchloride.html

before proceeding with your efforts, encountering difficulties and then posting this thread; you would know this:


Transfer the reaction mixture to a Claisen flask and distil under atmospheric pressure until the temperature reaches 135-140° (2). Distill the residue under diminished pressure and collect the benzyl chloride at 64-69°C at 12 mmHg. The latter upon redistillation boils largely at 63-65°C at 12 mmHg. The yield of benzyl chloride is about 100 g.

   1. An alternative method of determining the completion of the reaction is to weigh the flask and toluene, and to stop the passage of chlorine when the increase in weight is 37 g.
   2. The benzyl chloride may also be isolated by distillation under atmospheric pressure. The material boiling between 175°C and 185°C is collected and redistilled, the final product is collected at 178-182°C (pure benzyl chloride has bp 179°C). The resulting benzyl chloride is, however, of lower purity unless a fractionating column is used.



Clearly, your heat source is inadequate to reach the temperatures required for atmospheric distillation, and unless you have a fractonating column, the resultant benzyl chloride will be  less pure than if it were vacuum distilled    Clearly you need to study this process much more thoroughly, then obtain equipment up to the job  

[amalgum]

Look, Swig knows how to distill, the problem involved the smoke, burning.  There was no stabliztion, temp kept going up and down.  I am starting to think that it was due to drafts, and could never get hot enough to make it up to 179.

No offense, but obviously not.  SWIM thought he knew how to distill also when he first tried to make benzyl bromide (his first real fractionation), and got similar results.

First you need to make sure your heat source is adjustable.  Never just apply a bunch of heat and expect the distillation to run it's course.  You must first turn on the heat and set it at a low setting, lets say 80C.  Let it sit until everything that's gonna come over comes over.  Then gradually increase the heat.  DO this as you move through the fractions.  Do it very slowly and gradually.  The slower the better.

Also the rate of distillation is a factor.  A big one.  No distillation is gonna be fast.  For purity and good results, you must do it very slowly.  Vogels says around two to three drops a second collecting is fast enough.  As soon as you start to hit a fraction thats coming over, decrease or increase heat until your rate is about two to three drops a sec.  Distill at this rate, and do things as SWIM says, and you should recive more accurate results.  And if it seems more than just benzyl chloride is coming over at it's boiling point (or it comes over in a boiling range like say 172-180 for example), then that fraction that comes over at those temps is going to have to be redistilled, for extra purity.

Speed and impatience is the enemy here.  In the mean time SWIM strongly suggests going to a book store and buying Zubricks Organic Chem Survival manual.  SWIM thought he knew how to distill and crystallize and everything, but he used to do it with the wrong technique and always wondered why nothing ever worked the way it was supposed to for him.  It's like lifting weights, you can lift all day long and still get results, but to get proper results, you must lift with proper form.
Also SWIM STRONGLY suggests to go here:

https://www.thevespiary.org/rhodium/Rhodium/chemistry/vogel3.html

and download Vogels Guide to Practical Organic chemistry.  You'll learn a whole lot from this book, as well as proper technique in the labrotory.

[ning]

Benzyl chloride is notoriously reactive, and likes to polymerize.

The substance will polymerize under the influence of all common metals except nickel and lead, with evolution of corrosive fumes (hydrogen chloride - see ICSC # 0163), with fire or explosion hazard. On combustion, forms toxic and corrosive fumes (hydrogen chloride). Reacts vigorously with strong oxidants. Reacts with water, producing corrosive fumes (hydrogen chloride - see ICSC # 0163). Attacks many metals in presence of water.

Sure your rig hasn't got any metal in it? And no water in the mixture? CaCl2 would probably dry it enough if there was.

Try using mineral oil or paraffin wax for your bath, it doesn't smoke easily. Wax could go up to 300 C. It also may help to insulate the bath and/or the flask up to the condensor. Hardware stores sell cuffs for wrapping water heater pipes.

[amalgum]

Yup, SWIM thinks this is why it has that lachyrmal properties.  It gets in your eyes and membranes reacts with water there and bam, you got sinus/eye sockets full of shit like HCl and phosgene.  It took me five minutes to type in google's address, then do a search using "benzyl chloride msds" as key words.  The second link I clicked on was this:

http://www.jtbaker.com/msds/englishhtml/b1957.htm

If you scroll down to the section called Stability and Reactivity, you'll see that it says polymerization can occur, esp. in presence of trace amounts of things like aluminum and iron and rust and shit.  Also, right above that it talks about how things like propylene oxide, lime, or even sodium carbonate solutions (hint hint, chalk, or certain pH increaser sold otc somewhere, aww fuck it, go in your cabinet and bake some of that baking soda in the oven at a high enough temp) can be added to help STOP POLYMERIZATION.  Yee-haw.

[quantum]

anyone getting stuff over at 85 C after making benzyl choride is either using a vacum , fucking lying, or realy fucking stupid. toluene + calcium hypocholrite. nothing comes over before 110.
maby you might be asking about a sommelet reaction next go read
a book

[Nitroxamide]

The polymerization is catalyzed by traces of iron compounds...

[ning]

The polymerization is a Friedel-crafts alkylation, catalyzed by Lewis acids.

Any metal which can react with HCl (generated by reaction of benzyl chloride with trace water) to form a lewis acid (Al --> AlCl3, Fe --> FeCl2/FeCl3, etc.), will catalyzed the polymerization.

If this is, in fact, the mechanism, then to preserve your benzyl chloride:

1. keep it dry.
2. No metals, or maybe only noblish metals, like nickel, etc.

[Nitroxamide]

Traces of iron compounds are found in HCl, so that's one place they come from to tar your BzCl.

[ning]

I guess an aqueous solution of EDTA could be used to stabilize benzyl chloride by chelating any ions that happened to come by. Or whatever.

[Rhodium]

Mineral acids can also catalyze the Friedel-Crafts alkylation.

[WizardX]

http://www.orgsyn.org/orgsyn/prep.asp?prep=cv1p0107

The quality of the benzyl chloride markedly affects the yield of pure benzyl cyanide. If a poor technical grade is used, the yields will not be more than 60-75 per cent of the theoretical, whereas consistent results of about 85 per cent or more may always be obtained when a product is used that boils over 10°. The technical benzyl chloride at hand yielded on distillation about 8 per cent of high-boiling material; a technical grade from another source was of unusual purity and boiled over a 2° range for the most part.

[UncleFester]

I did that benzyl chloride to cyanide prep back in the 70's. The crude product after washing and extracting to a fair degree of purity is the most pungent onion-like artificial smell I have seen...or was it garlic??? It just lasts and lasts and won't go away from anything it gets on. A good fractional distillation makes it less offensive.