Ormarion
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Hexaphenyl benzene synthesis
Hey everyone, tought i might make a post about a project i have ongoing (hopefully should soon release a video about it) : the synthesis of hexaphenyl
benzene
I must say i went the "easy way" buy ordering directly the dibenzyl ketone as for me it is relatively cheap to get. However it can be made several
ways, the best i found so far involved the reaction of phenylacetic acid with DCC and DMAP
The following procedure were inspired from orgsyn protocoles:
http://www.orgsyn.org/demo.aspx?prep=CV3P0806
http://www.orgsyn.org/demo.aspx?prep=CV5P0604
Tetraphenylcyclopentadienone synthesis:
-21g of benzil and diphenyl ketone were mixed with 150 ml of dry ethanol in a round bottom flask
-the reaction mix was heated for 30min
-3g of KOH was dissolved in 30ml of warm dry ethanol and the mixed was stirred to ensure full dissolution
-after 30min of reflux the solution of KOH in ethanol was added in 2 time trough the condenser end and the mix was refluxed for 15 more minutes ,
vigurous boiling was observed upon addition of KOH with a color change from yellow to dark red/brown (nice irridescence appeared for a few seconds in
the bubble formed)
-the reaction mixed once cooled to 0°c was filtered under vacuum on a sintered funnel and washed with 3x10ml of ethanol
the washing were continued till the filtrated changed from dark brown to a pale brown color
Final product was dried under vacuum over P2O5 to afford the product as a dark purple shiny powder : m= 36g (94% yeild)
Hexaphenyl benzene synthesis:
-In a round bottom flask 10g of benzophenone was added and slowly heated on a open flamme until fully melted
-2g of diphenylacetylen and 2g of the Tetraphenylcyclopentadienone were added rapidly before a air condenser was set up on the round bottom flask
-Heating was continued for 1h with mild boiling of the benzophenone as color slowly shifted from dark red to brown (Reaction produce carbon monoxide
so i recommend to do it outside, even if my meter didnt seem to pick it up when pointing the exit tube at it)
-After 1h heating was stopped and 2ml of diphenyl ether was added
-The mix precipitated and was heated again until it fully dissolved
-Heating was then stopped and reaction mix was let to cool to room temperature forming some small crystals
-Once cooled the reaction mix was filtered under vacuum and washed with cold toluene
-The product was recrystallized in approximately 20ml of diphenyl ether and filtered once cooled, followed by washings with cold toluene
The melting point of hexaphenyl benzene is relatively high (450°c) and could not be reached with my hotplate, however by deduction the obtained
product cannot be any of the reactants as no melting was observed at 300°C
Diphenylacetylen melting point : 59°C
Benzophenone melting point : 48,5°C
Tetraphenylcyclopentadienone : 217 to 222°C
Final product was obtained as white flakes : m =2,4g (84%, same yeild as litterature)
I performed a TLC testing different solvent, the best i found was AcOEt/ toluene 5/5
From left to right : ketone start mat, acetylene start mat, diphenyl ether, crude product + diphenyl ether, pure product + diphenyl ether
(diphenyl ether was used because product was v insoluble into toluene)
I havent been able to perform a NMR but i might try to in the future
Hope you enjoyed ! ill be sure to link the video once i finished derushing it.
Im not certain what i will use for , prob gonna try a Scholl reaction with MeNO2 and FeCl3 to form the hexabenzocorronene or further alkylated
derivatives of it
       
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Niklas
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Nice synthesis!
Using benzophenone as a solvent, never seen that before, great to see the yields being the same as literature (that’s the beautiful thing about
Orgsyn really).
Making hexaphenylbenzene has been on my bucket list as well, just that I was thinking about making it by the trimerization of diphenylacetylene. Seen
a paper using McMurry type of conditions for this process but I can’t recall where I saw it..
Actually got some dibenzylketone a while back though, for a project I don’t know if I will ever continue, so I may give your approach a shot.
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Niklas
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On a different note, this made me remember this thing I was thinking about a long time ago, nanographenes. I did legitimately think about attempting
this synthesis back then, but I don’t think I ever will, like for many ideas from back when I just started doing homechemistry.
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Dr.Bob
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I remember both making this in organic chemistry lab in college, back a few decades ago, as well as teaching this lab when I TA'd organic later in
graduate school. It is a neat bit of chemistry and the colors are quite bright.
Excellent job, Ormarion, and your writing is better than most of my students, and likely much better than I did.
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Ormarion
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Posts: 62
Registered: 19-12-2017
Location: France
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Mood: Alkylating her DNA
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Thanks a lot for your replies, i was thinking to go this way eventually once i got some PIFA, at first i wanted to make the hexaphenyl bpin..but
considering their last step has a yeild of 0.8% im probably gonna try to connect some aryl or something on there. Honestly im curious about the
fluorescence i can achieve by increasing its size and conjugaison
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