Introduction and Background
Allyl halides, as well as their precursor allyl alcohol, are very useful but also hazardous chemicals. Because of the hazards, their sale to private
individuals is often restricted. Fortunately, the synthesis of the precursor to allyl halides, allyl alcohol, has been documented on here numerous
times [1, 2]. From then on, you can, according to one source, reflux just allyl alcohol and concentrated hydrochloric acid to get allyl chloride [3] -
though I have not been able to get this to work. Another method, giving higher yields, involves reacting allyl alcohol [3], hydrochloric acid,
sulfuric acid, and copper(I) chloride. Copper(I) chloride is fairly expensive and largely unavailable to the amateur chemist. The sale of sulfuric
acid is also restricted in some places.
Luckily, I did find a patent that substitutes copper(I) chloride for copper(II) chloride and does not use sulfuric acid [4]. The reagents for this
method are much cheaper, though unfortunately the patent reported the composition of the main mixture in percentages that did not even add up to 100%.
I therefore estimated how much to use of each reagent.
Procedure
To a mixture of 120 g 30% hydrochloric acid and 35 g water, 6.25 g of copper(II)chloride was dissolved. Then, 15 g of approximately 40% allyl alcohol
was added (see note 1).
The mixture was added to a round bottom flask equipped with a short path distillation apparatus. The receiver flask was placed in an ice bath, and the
flask was heated (see note 2). When the short path distillation apparatus became too hot to touch, the heating was turned off.
A saturated solution of sodium bicarbonate in water was slowly added to the distillate until no more bubbling occurred. The mixture separated nicely
into two layers and was poured into a separatory funnel, where the upper allyl chloride layer was collected.
The allyl chloride was slightly cloudy, and some calcium chloride could probably have dried it. However, since allyl chloride evaporates so readily, I
wanted to avoid any losses.
The allyl chloride weighed ~7 g. It was stored in a freezer until the next use (see note 3).
Photo of the obtained allyl chloride in a vial.
Notes
Note 1: I used 15 g of allyl alcohol due to a previous miscalculation of its concentration. In a later run I used around 25 g, which seemed to also
work.
Note 2: It is important to use a receiver flask rather than a simple beaker, as allyl chloride readily evaporates - using a flask helps minimize loss
and improves yield.
Note 3: I found that storing the allyl chloride in a freezer is necessary, since it evaporates so readily at room temperature.
Final thoughts
Since I did this synthesis with allyl alcohol of around 40% concentration, I would love to hear the yield and overall results from anyone else trying
this out, possibly using a more standard concentration of allyl alcohol. Please remember, it is very important to minimize the evaporation of allyl
chloride, as it evaporates so readily.
[Edited on 17-10-2025 by Maui3]bnull - 17-10-2025 at 09:56
Nice work.
Quote:
Copper(I) chloride is fairly expensive and largely unavailable to the amateur chemist.
Copper(I) chloride is one of the simplest substances an amateur chemist can make at home, so it is not "largely unavailable" as it may seem. I have at
least 4 methods to make it, depending on how much work and time one can spare.Maui3 - 17-10-2025 at 10:40
Thank you bnull!
When I first looked into making allyl chloride, I also considered preparing copper(I) chloride. If I remember correctly, it can be made fairly easily
from copper(II) chloride and sodium metabisulfite, although metabisulfite isn’t available to everyone. I realize now that “largely unavailable”
might not have been the best wording. What I meant was that it’s probably more efficient to start with copper(II) chloride rather than copper(I)
chloride, since the latter is quite difficult to purchase, and its synthesis would involve more steps.Fery - 20-10-2025 at 01:59
Maui3 - well done!
Do you plane to use allyl chloride for other reaction(s)?Maui3 - 20-10-2025 at 07:48
Thank you Fery!
Yes - I actually do have a plan for some of the reactions I am going to perform with it (and thank you for asking). The reason I needed allyl chloride
in the first place was for a current project I am working on, where I am making a few new derivatives of an older (and quite interesting)
antiseizure/sedative medication. All of my new derivatives are different in that the oxygen atom is replaced by a sulfur atom - but for the ethyl
group in the original molecule, I am finding a unique one for each derivative, one of which is allyl. These sulfur derivatives I am making appear to
never have been studied or even synthesized before - which makes it all quite interesting (and exciting)!
If this seems interesting to anyone, I might post my project on here Fery - 20-10-2025 at 09:27
Great experiments! Will you only synthesize sulfur analogues or also test (on lab. animals of course) ?
Keep us informed. Organosulfur chemistry is very interesting. Of course we would like to know about your experiments, post everything here Maui3 - 21-10-2025 at 04:19
Yes, I will also test then on laboratory animals. I do not have access to labrats, but I do have access to drosophila (fruit flies), which should work
for testing them.
I will keep you all informed kmno4 - 21-10-2025 at 12:42
CuCl in solution ....? Pffff, nothing is simpler :
Quote:
To a mixture of 120 g 30% hydrochloric acid and 35 g water, 6.25 g of copper(II)chloride was dissolved....
Just add to this solution Cu in form of tiny pieces/wire/powder/dust.
Under these conditions, Cu will dissolve, color of solution changes from green to slightly brownish one (colorless in theory).
Protect from the air - it absorbs oxygen.
However, addition of any Cu salt in allyl chloride formation makes no sense for me. Just another "wonderful" modification.
It is known, that allyl group forms complexes with Cu(I), but if it is important in this paricular reaction - I doubt. Maui3 - 21-10-2025 at 13:57
Thanks for the comment! Yeah, bnull also pointed that out. Either way, it is one reagent less - and it still works! :-)
