I have recently discovered a paper claiming napthalene can be synthesized like this: "When 4-phenylbut-1-ene is passed over red hot calcium oxide,
naphthalene is formed".
I have a lot of practical questions though:
First off, I have no clue at what temperature calcium oxide gets red hot, but I could probably figure that out myself. I am sure that it is above 218
C though, which is the boiling point of napthalene, and well above the boiling point of the 4-phenyl-1-butene, which is 175-177 C. This makes it a bit
tricky, I geuss.
Second of all, to reach the red hot temperatures, I think the only real option is using a blow torch, in which case the fire possibly will ignite the
hydrogen formed in the reaction, and if I try to contain the apparatus, most likely explode glass everywhere. (At least, if I try it xd)
I suppose I could do something like passing 4-phenyl-1-butene vapour through the red hot calcium oxide, but without fancy specialized metal apparatus,
I probably can't pass it through. Either way, then I would have to assemble a distillation apparatus collecting the napthalene, but I am sure
the water in the condenser will absolutely crack the whole setup, because of the difference in temperature. Also, what would I even use for the
reaction vessel, I can't do glass, since that will likely melt?
Sorry for all the questions - I was really just wondering how you'd go about the synthesis. I tried looking for a procedure for this synthesis, but
couldn't really find any. If any of you can, please send it to me. If not, do you have any ideas?bnull - 10-7-2025 at 06:02
Quote:
I have recently discovered a paper claiming napthalene can be synthesized like this: "When 4-phenylbut-1-ene is passed over red hot calcium oxide,
naphthalene is formed".
Paper, please. I hope it was not one of those Gemini suggestions.
Are you interested in this synthesis for curiosity's sake or for practical purposes? I believe that naphthalene is way cheaper than 4-phenylbut-1-ene.
"Red hot" is above 500 °C, above the safety limits for glass, so metal is the material to use. Electrical heating would be safer; you don't want an
open flame when there's the risk of a "macromolecular rearrangement" of the stuff in your lab, your eyebrows and other bits included.
It looks like an industrial process, when they need naphthalene but have none and have so much 4-phenylbut-1-ene that they don't know what to do with
it.
The paper surely has sources with procedures at the end. It was not a college handout with the "complete the reaction, show the mechanism" sort of
exercise, was it?Maui3 - 10-7-2025 at 09:37
Hi bnull!
Haha, it was not a Gemini suggestion - those are unreliable for normal things, and absolutely dangerous for chemistry.
I was a bit unsure whether to call it a "paper" or not, since it's not really an article. I am actually not quite sure what it is. I found multiple
PDFs and even powerpoint presentations just showing the reaction scheme - no other info included. This was one of them.
I thought I’d give it a go since I haven’t really found a procedure for it, and it seems interesting enough to try. I’m mainly doing it as an
experiment to see if it works - I’m not planning to use the naphthalene for anything else, it’s just for the sake of trying out the synthesis.
Yeah, I was not going to use glass either. Is aluminium's melting point too low for this?
Thank you for the help already jackchem2001 - 10-7-2025 at 15:53
If you're willing to sacrifice some glassware, I would use a combination of electric heating and a blowtorch:
* Boiling flask on a heating mantle containing your starting material. Boiling here gives saturated vapour
* Send through some glass tubing you lightly blowtorch to superheat the vapour (e.g. fractionating column) <-- but heat transfer will be quite poor
because of low surface area and conductive thermal resistance of the glass
* Distillation head with horizontal tubing containing calcium oxide. You blowtorch this a lot and I would throw it out after the experiment (keep temp
around 450-500 deg)
* Air cooled condenser into receiving vessel
Remember that industrial gas phase reactions are often done under pressure to increase kinetics, even when (in principle) the higher pressure
disfavours product formation moreso than lower pressure at equilbrium. Also, there is not 100% conversion per pass through the reactor.
Use an IR thermometer to keep track of temperatures
Quite a hazardous procedure on a lab scale but certainly doableTsjerk - 10-7-2025 at 23:31
Let's put that here.
Attachment: BP301T-4.pdf (1.8MB) This file has been downloaded 96 times
Haha, it was not a Gemini suggestion - those are unreliable for normal things, and absolutely dangerous for chemistry.
That's very comforting to know.
There's a chance you'll find a procedure in Ullmann's.
Aluminum (actually aluminum alloys) may react at that temperature. I'd use copper or stainless steel.
Since you just want to see if the reaction works, there's something you can do. Lets see: 4-phenylbut-1-ene boils at about 180 °C, naphthalene boils
at 218 °C; the former reacts with red hot CaO while the latter doesn't; this means reflux at 200 °C to begin with; inert atmosphere because you
don't want an explosion; blowtorch is out of question; a suspended boat with CaO and electrical heating. Flask is flushed with inert gas (I think
CO2 would do) and heated. Meanwhile, electrical heating is turned on to drive off any moisture and convert any calcium hydroxide to calcium
oxide. Air condenser, heating mantle, no open flame because of hydrogen and the hydrocarbons. I guess you can devise something from this jumble. Small
scale, of course (semimicro?).Maui3 - 11-7-2025 at 08:00
Thank you.
Yes I will be able to devise something from that! Thanks, again.
I will make a post about the synthesis when I get to doing it chempyre235 - 12-7-2025 at 05:39
This procedure sounds eerily similar to that of producing benzene from acetylene. Of course, this sounds much safer than superheating acetylene over a
transition metal...
