See
Post 96788 (missing)
(Professor: "real question anyone please /trans-beta-methylstyrene", Chemicals & Equipment) and the yield is advertised as 93%.
H2O2 which is 7 month old should be checked (how to: Search), it is also important to know how much light has gotten to the bottle in that lifespan, a lot of light will decompose it quicker. There is a nice simple method to check the real percentage of H2O2 and its purity somewhere on the Hive.
Technical grade 85-88% Formic acid should be good enough, eventually check the real percentage also by titration with a base or compare its weight per ml to a table in literature.
You can repeat the procedure with fresh H2O2, and take samples at intervals to use TLC on, so you can see when the conversion peaks. Then you stop stirring and proceed to the next step.
Different starting materials could need shorter or longer stirring times, the data for a certain compound are only sure after someone did a series of real testruns, like you are doing now.
Stirr your propenylbenzene, DCM and sodiumbicarbonate a bit longer perhaps, or use sodiumcarbonate.
You could also try the Rhodium/Semtexium peracetic acid procedure instead of the buffered performic, less harsh, just a little longer.
Now put the word " propenylbenzene " in the FSE, you'll get 508 hits , the first 100 will already give you a days work to study, f.e.
Post 436456
(Aurelius: "Primary Carbon", Chemistry Discourse),
Post 322503
(hypo: "bps and mps of various propenyl and allylbenzenes", Methods Discourse), bps and mps of various propenyl and allylbenzenes
Post 431689
(FriendlyFinger: "Allylbenzene to propenylbenzene", Methods Discourse) your post on isomerization of allylbenzene.
Post 434529
(FriendlyFinger: "Thanks for the references, I understand it...", Methods Discourse):
this is your own post on how you made your trans-beta-methylstyrene. You stated there:
""eventually got about 40% visually of something ---Don't get me wrong I'm not unhappy with what I did. I just don't know what I'm doing here and there.""
I hope you understand that your statement in this, your last post:
""Got B-Methylstyrene from Propiophenone and It came over at the right temp. Right on the nose and I'm impressed with the yield. ""
got me a bit worried about your obtained supposed trans-beta-methylstyrene. Or there must be a post from you about the same topic slipped through my event horizon since 21 May.
Now this answer costed me quite some time to establish, but I hope you don't see it as negative critics, just thinking in the blind, I'm not looking at a lot of chems as you do, so keep trying, this whole route should be feasible in quite good yield.
And setbacks are much more occuring than a straight one time result, so keep trying and asking. LT/