[Cacoethes]

Ok I have a quick question.  A question reads: Provide an efficient synthesis for benzaldehyde using toluene as your only organic source.  Note: the last step in your synth. should produce 2 moles of benzaldehyde.

So yeah, im not exactly sure how i'd get 2 moles...if anyone could help me out with the reasoning that'd be awesome.  So far, I have the correct synthesis, just not sure if it makes 2 moles of the benzaldehyde.

Toluene --> benzoic acid using Jones reagent.  Benzoic acid --> primary alcohol using LiAlH4.  Primary alcohol --> Benzaldehyde via PCC.

Just not sure about the 2 moles..?  Can I just double everything?

[azmanam]

There's nothing wrong with your synthesis... except you only get 1 molar equivalent.  that is, for every mole of toluene you start with, you get 1 mole of benzaldehyde.

If the question wants you to make 2 molar equivalents (which I think the question IS asking), you need to dimerize toluene before your last step.

What chapter are you working on.  You'll probably need a concept from that chapter.

[Cacoethes]

We have been doing oxidation-reduction reactions and carbonyl I reactions.  I just skimmed through the chapters and don't recall anything having to do with a yield of 2 moles etc.  Hmm, any basic ideas?  I'm not sure I know what you mean by the dimerization of toluene (I know what a dimer is, but not the reaction).

[Cacoethes]

no one else cares to help?  I'm not asking for the answer, just something to go with would be nice, ty

[gfunk]

Off the top of my head, I can only think of PhCHCHPh --ozonolysis/Me₂S--> as a way to yield two moles of benzaldehyde.  But going through the trouble of coupling them doesn't seem like the most efficient strategy...

[gfunk]

Poking around a bit, I found that you can do an oxidative coupling of methane groups (and with the toluene methyl groups) with Bi₂O₃, but I don't know if you're supposed to know that lol.

2 * Toluene --Bi₂O₃, 580*--> PhCH=CHPh --1) O₃, 2) Me₂S--> 2 * PhCHO

Reference: Seriya Khimicheskaya 1975, 10, 2378

Edit: I don't know if that's 580*C or *F, I don't have access to that journal, just the abstract.  I'm sure a delta symbol should suffice .

[azmanam]

Based on my understanding of the question, you need to go through stilbene with ozonolysis as the final step.  I also don't know an efficient way to get there... which is why I thought your chapter would give me a hint.  It doesn't.  I thought you were going to need an organometallic reaction (Heck, Suzuki... something like that).  Maybe your professor can push you in the right direction.

[ufalynn88]

hmm...what about
1. allylic bromination w/nbs
2. SN2 w/NaOH
3. oxidation w/ PCC to form aldehyde
4. wittig using benzaldehyde type wittig (this is the step im unsure of), whether such a reagent is possible....but if so...
5. ozonolysis to form 2 benzaldehydes