I have tried this method:

enter image description here

Can anyone suggest me a shorter route?

Criteria: Benzene has to be produced, it is not available.

Edit : I don't understand why the question has been put on hold. They provide the reason that there may be possibly to many good answers or the question is very broad. As far as my knowledge goes, I haven't received any correct answer that addresses what I have asked.

I would request the authority to reconsider on their decision.

  • $\begingroup$ Not really a better method but you can covert it into n-heptane and make it into toluene by Cr2O3-Al2O3 . $\endgroup$ – Black Jack 21 Feb 2 '17 at 15:03
  • $\begingroup$ @AlphaRomeo ethanol to n-heptane? How? $\endgroup$ – Resorcinol Feb 2 '17 at 15:05
  • $\begingroup$ your question is good, although there are many ways and synthesis route, there is one in which ethyne can be directly converted to benzene but it requires very high temperatures (4000-degree celsius) $\endgroup$ – phenolicdeath Feb 2 '17 at 15:05
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    $\begingroup$ LOL - Two steps (1) Sell ethanol to a wino (2) Use the money to buy benzoic acid. $\endgroup$ – MaxW Feb 2 '17 at 16:43
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    $\begingroup$ @Resorcinol Given that I dropped the first close vote here is my rationale: You are asking to synthesise one compound from a completely different compound. There are about a gazillion possible routes none standing out in any way as preferable. There is nothing that would instantly suggest itself. This is basically the same as asking us to come up with a plan for the total synthesis of <insert natural product here>. Too many possible answers → too broad. $\endgroup$ – Jan Feb 3 '17 at 16:29

enter image description here Here is how I would do it.

Part I: Blue

First, ethanol 1 is oxidised to acetaldehyde 2, which undergoes nucleophilic addition with $\ce{KCN}$ and $\ce{HCN}$ to form the hydroxynitrile 3, and finally dehydrated and hydrolysed at the same time with sulfuric acid to give acrylic acid 4.

Part II: Red

First, ethanol 1 is reacted to form the Grignard reagent 5, then combines with the aldehyde 2 to form the alcohol 6. It is dehydrated to form butene 7, dihydroxylated to form the diol 8, and dehydrated again to get the diene 9.

Part III: Black

In the final part, 4 and 9 participate in a Diels-Alder reaction with the Lewis acid $\ce{TiCl4}$ to give 10. Selenium dioxide gives the diol 11 and subsequent dehydration gives us benzoic acid, 12.

Although it may be longer, it does not involve things such as high reaction temperatures and therefore may be more feasible in the context of a laboratory.

EDIT: Here is another attempt:

enter image description here

Ethanol 1 is oxidised to acetaldehyde 2, and subsequently with excess formaldehyde and acidic conditions forms pentaerythritol 3, and is oxidised again to form the quadruple aldehyde 4. Strong heating causes 3 to turn into the diol 5. The Grignard reagent 6 is formed and oxidation and reduction of the alkene forms the reactant 7.

Now, both 4 and 7 react to form the ring product 8, and with strong heating thus produces benzoic acid 9.

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    $\begingroup$ I guess your method is not shorter than mine. Still you provided me with new methods. Thanks! $\endgroup$ – Resorcinol Feb 2 '17 at 15:52
  • $\begingroup$ I agree, however I daresay it is easier to do since a lot of these reagents and conditions are easily found in the lab and many of these reactions involved dehydration. Your reaction in a hot iron tube is more like an industrial reaction which requires extremely high temperatures as pointed out. Besides, you are dealing with gases like ethene and ethyne which are hard to control whereas all my reactants are liquid at tolerable temperatures. $\endgroup$ – Linus Choy Feb 2 '17 at 15:56
  • $\begingroup$ Yes, I agree with you. But I won't be able to accept your answer because I am expecting a shorter route. $\endgroup$ – Resorcinol Feb 2 '17 at 16:50
  • $\begingroup$ Wonder which method has a better yield. $\endgroup$ – MaxW Feb 2 '17 at 16:51
  • $\begingroup$ At 10 can you use Pd directly to get aromatic compound? $\endgroup$ – Black Jack 21 Feb 3 '17 at 11:22

You Provided a few very great routes I really like the convergent approach of Linus Choy. I'd prefer a shorter route. short route

In the first step we are preparing the ethylhalogen. There are different procedures. I'd use $\ce{HCl}$ and $\ce{ZnCl2}$. by heating around 60 mins there should be conversion. My Main Point here is so we can go for a Friedel-Crafts reaction.

Second step is the Friedel-Crafts reaction with $\ce{AlCl3}$ or $\ce{FeCl3}$ onto the Benzene Ring. So we end up with ethylbenzene as product.

For the third reaction I also considered $\ce{KMnO4}$ and $\ce{H2SO4}$ for oxidation, there should be procedures leading to the same product. But I really liked the idea of the oxidation by $\ce{ZnO}$ in DMF here because the reaction only takes a few minutes in the Microwave and has good yields.

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    $\begingroup$ I had this idea. Unfortunately you are unlikely to get a good yield of ethylbenzene because you will get polyalkylation since ethylbenzene is more reactive than benzene. There are ways around it but they will need more steps. $\endgroup$ – bon Feb 2 '17 at 20:15
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    $\begingroup$ I would suggest using Friedel-Crafts acylation instead, then simply oxidising the mixture with a chromium derivative. Kudos for trying though! $\endgroup$ – Linus Choy Feb 2 '17 at 20:30
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    $\begingroup$ I don't think you can use benzene.i know it's easily available but then why would resorcinol ask such a question? $\endgroup$ – Black Jack 21 Feb 3 '17 at 11:24
  • $\begingroup$ Considering what @bon said, you can instead do a $\ce{KMnO4}$ oxidation to acetic acid, eliminate water to form anhydride, perform a Friedel Crafts acylation, then do Clemenssen reduction. But of course, that's alot of steps, so it's not much preferred. $\endgroup$ – Pritt says Reinstate Monica Jun 23 '17 at 4:37

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