Talk:Birch reduction

My contributions

I just included a bit more detail regarding kinetic vs. thermodynamic protonation of the anion intermediate. Gly 23:55, 3 February 2007 (UTC)

Opening statement is midleading?

"This reaction provides an alternative to catalytic hydrogenation, which is extremely difficult to perform on aromatics, due to the stability of the extended conjugated system." Here are the problems with this statement: (i) catalytic hydrogenation of arenes is not really extremely difficult and (ii) catalytic hydrogenation of arenes tends to go all the way, one rarely obtains cyclohexadienes. Thus I propose to revise this statement to the effect that Birch is a method for making cyclohexadienes. Comments or suggestions are welcome.--Smokefoot 13:47, 1 August 2007 (UTC)

I agree and I made the change. Is this acceptable?Silverchemist 05:58, 20 August 2007 (UTC)

Mechanism cleanup

The mechanism of the birch reduction seems to be spot on as proposed by Dr. Zimmerman and is consistent with the accepted mechanism of this reaction. Dr. Zimmerman has done some excellent chemistry and remains an expert in this field. Dr. Zimmerman would be considered an expert, and I for one would believe anything that Dr. Zimmerman has to say about a Birch reduction.--theslave (talk) 21:31, 21 June 2010 (UTC)

I will volunteer to take a look at the regioselectivity of this reaction. I think that Dr. Zimmerman has made some valid points. I will pull the literature and look at it on Scifinder. As stated below. Cheers--theslave (talk) 19:12, 21 June 2010 (UTC)

"....and alcohol such as ethanol and tert-butanol can be used instead of ammonia."

This is incorrect - alcohols cannot act as a substitute to ammonia. In fact, an alcohol is necessary to facilitate a Birch reduction (the alcohol acts as a proton source). The text under "reaction mechanism" is also incorrect - ammonia is NOT (and cannot be) deprotonated under Birch conditions (it is far easier to protonate ammonia than it is to deprotonate it!). —Preceding unsigned comment added by 220.233.115.217 (talk) 08:36, 17 January 2008 (UTC)

Well you can whine about the problematic section or you can do something about it (with a reference). --Smokefoot (talk) 14:33, 17 January 2008 (UTC)

• My esteemed colleague of course means he is inviting you to assist in the wikipedia effort: My March tells me you are only half right, so we are looking forward to your edits. V8rik (talk) 17:27, 17 January 2008 (UTC)

From March (6th ed.), p1068: "Thus the function of the alcohol is to supply protons, since with most substrates ammonia is not acidic enough for this purpose. In the absence of the alcohol, products arising from the dimerization of 110 are frequently obtained."

OK, I'll concede a slight error on my part, but I was not that far off, no? Upon re-readiing the article I also feel there is scope for expansion; specifically a section discussing the effect of substituent groups upon regioselectivity. —Preceding unsigned comment added by 150.203.34.37 (talk) 02:56, 18 January 2008 (UTC)

• I would agree the article needs an update on the purpose of the alcohols and expanding the article is more than welcome. V8rik (talk) 21:17, 18 January 2008 (UTC)

• Updated the article accordingly V8rik (talk) 18:02, 25 January 2008 (UTC)

I'm not certain that this is the place to put this as suggested input for the Birch Reduction which is now incomplete not really correct. Also I have a ChemDraw equation which I can't paste into this spot.

The Birch Reduction and Regioselectivity:

The mechanism of the Birch Reduction accounting for its regioselectivity. The original Birch mechanism suggested that the initial radical anion protonation was meta to ring methoxy and alkyl groups and the last step was ortho. Using simple Hückel computations in 1961 it was shown that this is incorrect and reversed. After decades of controversy, an esoteric experimental test was devised. This demonstrated that the ortho protonation mechanism was correct. Additionally, in the 1990 and 193 publications computational support for the initial ortho protonation was reported. This now accepted in textbooks. The basic mechanism is given in the following equation where the electron comes from sodium or lithium in liquid ammonia and the proton donor HA is an alcohol as ethanol or t-butyl alcohol. The rate limiting and product determining step is the first protonation of the radical anion formed by addition of the first electron to the pi system.

EQUATION WITH FIVE STUCTURES - Anisole, the Radial Anion, the Protonated Radical Anion, Addition of the Second Electron, The Central Protonated cyclohexadienyl anion and FINAL PRODUCT (A ChemDraw structure is available).

"Orientation in Metal Ammonia Reductions," Zimmerman, H. E, Tetrahedron, 1961, 16, 169-176.

"The Regioselectivity of the Birch Reduction", Zimmerman, H. E.; Wang, P. A., J. Am. Chem. Soc., 1990, 112, 1280-1281.

"Regioselectivity of the Birch Reduction", Zimmerman, H. E.; Wang, P. A., J. Am. Chem. Soc., 1993, 115, 2205-2216.

“Advanced Organic Chemistry: Reactions and synthesis”, Francis A. Carey, Richard J. Sundberg, pg 437.

Howard E. Zimmerman 20:12, 31 January 2010 (UTC) —Preceding unsigned comment added by Hezimmerman (talk • contribs) Howard E. Zimmerman (Why is this listed as "Unsigned"

75.100.82.175 (talk) 20:34, 31 January 2010 (UTC)

Regioselectivity

• I will volunteer to take a look at the regioselectivity of this reaction. I think that Dr. Zimmerman has made some valid points. I will pull the literature and look at it on Scifinder. Cheers--theslave (talk) 19:12, 21 June 2010 (UTC)

• has a discussion of the regioselectivity of the second protonation been omitted intentionally? Whilst the explanations can be quite wooly I think it would merit discussion... Seansheep (talk) 17:45, 19 March 2008 (UTC)

• Regioselectivity issues still have to be dealt with , volunteers? V8rik (talk) 18:33, 19 March 2008 (UTC)

• Apropos of that, I just added in that the regioselectivity of Birch reduction on benzoic acid is to begin the addition of e- on the ipso carbon. That's based on a problem set my organic chemistry gave in class. I don't know what her source is, but it can probably be found in the literature. Crystal whacker (talk) 22:15, 17 November 2008 (UTC)

Correction - I was putting in the correction on Regioselectivity when it disappeared.

The missing references are: "Orientation in Metal Ammonia Reductions," Zimmerman, H. E, Tetrahedron, 1961, 16, 169-176.

"The Regioselectivity of the Birch Reduction", Zimmerman, H. E.; Wang, P. A., J. Am. Chem. Soc., 1990, 112, 1280-1281.

"Regioselectivity of the Birch Reduction", Zimmerman, H. E.; Wang, P. A., J. Am. Chem. Soc., 1993, 115, 2205-2216.

The 1961 correction was based on Hueckel calculations which were the best available at the time The 1990 and 1993 publications described both Experimental and Computations evidence which showed Birch to be in error. The correct mechanism is now found in most textbooks.

Howard E. Zimmerman 17:18, 10 January 2010 (UTC) —Preceding unsigned comment added by Hezimmerman (talk • contribs)

moved Zimmerman content from article to Talk

Section below was added to article itself. V8rik (talk) 17:32, 18 March 2010 (UTC)

An Alternative, Expanded Birch Article

with Treatment of the Regioselectivity of Methoxy and Methyl Aromatics and a Complete Mechanistic Presentation (e.g. Regioselectivity of the Protonation of the Initial Radical Anion and Central Protonation of the Penultimate Cyclohexdienyl Carbanion - With Explanation of Why the Regiochemistry Goes as it Does).

Including a historical survey of Arthur Birch's changing views on the Protonation as well as the Modern Understanding). References are given in detail. I have this in my User:HEZimmerman page. And I have some very pretty drawings (in .gif and ChemDraw .cdx formats) but have not been able to paste these in where drawings are indicated. I need help on that.

Howard E. Zimmerman 21:17, 17 March 2010 (UTC)

Merge discussion

Talk about "Merging the article "Birch Reduction detailed" with the "Birch Reduction" one.

This suggestion does not make sense. There is very little in the old article, other than mistakes, which is not in the current New article. I've indicated some of the errors earlier. But also the old article covers about 10% of the material in the New One. Thus combining the two would be problematical.

It is probably correct that the old article was written from looking at textbooks rather than original literature (references) while the New one was written with knowledge about the subject matter.

And, I guess that Wikipedia encourages writing without expertise. The critical references and knowledge overlooked in that old article had a real impact on the writing.

the question is whether you want a an article with insignt or one without.

Ideology should not impact on science.

Of course I have a biased view but every scientist is biased towards reality.

It is late here and I'm probably not doing a complete or good job of explaining. But let me note that originally it was suggested that I could "fix up" the old article. My conclusion was that when fixed up, it would bear no resemblance to the original. Thus, I got to work to write a complete one. I did want Wikipedia to be known for good stuff.

I can write more details later.

Howard E. Zimmerman 02:30, 16 April 2010 (UTC) —Preceding unsigned comment added by Hezimmerman (talk • contribs)

It would probably make sense just to replace the text of the original article with the new one. It does not make sense to have two separate articles on the same material, especially if one of those articles is largely incorrect. (Yes, replacing on text with the other would be a merge. We should do a history merge.) LadyofShalott 03:00, 16 April 2010 (UTC)

Howard, sorry I have not had time to work on this. LadyofShalott is absolutely correct . We can not have two articles. A history merge should be done, which effectively replaces Birch reduction by the new article. The old article will then still be in the history and some material can be moved back in. The introduction does want something from textbooks that explains simply what the reaction actually is. That might be in the old version. Just let the history merge be done. Doing that is one thing I should know how to do as an admin, but I do not and I am still too busy to figure it out and do it. --Bduke (Discussion) 03:45, 16 April 2010 (UTC)

Once it is clear we have consensus to do it, I can. (Until recently history merges scared me, but I made myself play in the sandbox and found that they are not hard to do! I've since done a couple real ones.) LadyofShalott 03:56, 16 April 2010 (UTC)

I must follow your example when I have time. Looking at Birch reduction I think the lede should largely be retained as it give as broad introduction, while the new article wades straight in. --Bduke (Discussion) 04:07, 16 April 2010 (UTC)

A Brief Comment

It is moring and I need to get ready to get to the lab and office, but I have looked further at the Old Birch article (i.e. the original one).

In hasty checking I find about ten errors and misleading statements in that Old Birch article I won't specify the problems since earlier my corrections have just been used by someone to fix the bad article.

But the important point which needs to be made is that Merging an Error-Laden Article with a Good one would result in an Error-Laden Merged Article. That is like putting a patient infected with a serious disease in the same hospital room with one free of diseases.

I wonder if the author of that old article has ever run a Birch Reduction.

13:10, 16 April 2010 (UTC) —Preceding unsigned comment added by Hezimmerman (talk • contribs)

"I won't specify the problems since earlier my corrections have just been used by someone

to fix the bad article." You say that as if it were a bad thing. LadyofShalott 13:12, 16 April 2010 (UTC)

With the consequence of missing a brief breakfast, I do want to note that The LadyofShalott had point which is generally correct. Putting in corrections to that old article would be proper and reasonable if there were not talk of Merging articles. I don't want to minimize how bad the old article is at this point.

I agree with most of what BDuke and LadyofShalott have said about replacing the old article with the new one and having the old one in History.

75.100.81.217 (talk) 13:28, 16 April 2010 (UTC)

Before we do a history merge, the "detailed" article will need to be extensively cleaned up with regard to tone and style (inc. formatting). I'm not sure we are too interested in the blow-by-blow accounts... those paragraphs can be condensed as well to give a little context, but not much more than that. Since Howard wrote the better part of the "detailed" article, he will be in the best place to do that. Of course, that does not preclude others participating in our WP manner. But Howard, perhaps you can take a look at the various style guides such as WP:CHEMMOS and WP:MOS. --Rifleman 82 (talk) 13:51, 16 April 2010 (UTC)

Hello all.

Firstly, I would like to say thanks to all that are helping with this - and, of course, a huge thank-you to Hezimmerman (talk · contribs) for contributing to Wikipedia.

My own involvement thus far has been to offer assistance to Hezimmerman, regarding formatting of the userspace draft.

Hezimmerman, I have indicated all along that a 'merge' may be the way forward, but please do not misunderstand the term. A merge does not have to be in any way 'equal' - it could be total replacement of one article with another, or anything in-between. The main reasons for merging are a) to keep things in one place, and b) to maintain the history of the article - ie to keep the information on who-did-what-when, which is a condition of the GFDL licencing.

Having said that, I do believe that something may be salvaged from the current Birch reduction article. I notice, for example, that Birch reduction detailed does not mention Arthur John Birch or Dyson Perrins Laboratory; also, whilst I appreciate your considerable efforts in writing a lede, Birch reduction detailed does begin with a rather detailed part, which may be beyond understanding for the average reader.

Whilst it is true that some articles do have a 'detailed' review - for example, Introduction to quantum mechanics - but this is quite rare.

I disagree with Rifleman 82 that it is excessively detailed; it is only about 48kB, so I don't think we have to worry about the size issue (the rule of thumb being 100kB articles may need splitting).

In the spirit of WP:BOLD, I'm quite tempted to just do a histmerge right now, leaving the 'new' article on top - but I'll wait for a little more input here before going ahead (if nobody else does in the meantime). Cheers,  Chzz  ►  18:52, 16 April 2010 (UTC)

• According to Zimmerman the current article (already called the old) contains very little other than mistakes is an Error-Laden Article and written without expertise containing about ten errors and misleading statements and merging would imply putting a patient infected with a serious disease in the same hospital room with one free of diseases. adding the statement that he wonders if the author of that old article has ever run a Birch Reduction Welcome to Wikipedia Mr. Zimmerman! Mr Zimmerman should know that there is no single author in a wikipedia article and the Birch reduction article has had about 50 editors contributing to it. And you have managed to offend them all! Unfortunately Wikipedia does not have rules in place banning offensive people from editing but let me address the issue. Problem is, I find nothing at fault with the current article , I have rechecked the content with Jerry March and I am unable to find any factual errors. I am looking forward to the Zimmerman list of 10 errors. The contribution made by Zimmerman would make a nice extension to the current article with respect to regioselectivity, a topic thus far not really touched upon. problem is always to find people to volunteer their time in contributing. A major factual error in the Zimmerman article is that it is stated that where the radical-anion is protonated initially determines the structure of the product which is not true. Mechanism O and M both lead to the same product and the whole Birch-Zimmerman debate strikes me as trivial , it can only be addressed by computational methods or by Zimmermans own admission with highly esoteric experimental methods. I still find this part of the new article a welcome addition but let us realise the topic is highly specialised. V8rik (talk) 19:30, 16 April 2010 (UTC)

• I promised to help Howard with this, but I have been very busy. I am not an organic chemist, so I can not comment on possible detailed errors. Howard's material is very welcome and should be part of the merged article, but is most definitely should not be all of it. For example, the lede, right down to the table of contents, is a much better introduction. We have to tell people what the reaction actually is, who discovered it and where. Some of the other material will also likely be needed, but that needs a better organic chemist than I. I think the merge should be done and then we can start work on the new combined article. --Bduke (Discussion) 22:24, 16 April 2010 (UTC)

 Done I've gone ahead and merged the histories. Now you all who are familiar with the subject matter can hash out how much of each version should be in the resultant article. LadyofShalott 02:17, 17 April 2010 (UTC)

Thanks. I restored the lede from the original article, corrected the headers, and added back the other wiki links, "See also" and categories. I think it up to the organikers now. --Bduke (Discussion) 02:41, 17 April 2010 (UTC)

• Have have restored three more sections, the present configuration should make everybody happy with basic information on top and adding more detail moving towards the bottom of the page V8rik (talk) 12:53, 17 April 2010 (UTC)

Basic reaction mechanism

User:Hezimmerman has raised some concerns with me that he can not fix. It concern the line "In line with the reaction mechanism the reaction can be suppressed by the addition of an radical scavenger." and the reference "Ilich, P. P.; McCormick, K. R.; Atkins, A. D.; Mell, G. J.; Flaherty, T. J.; Bruck, M. J.; Goodrich, H. A.; Hefel, A. L.; Juranić, N.; Seleem, S. (2010). "Solvated Electrons in Organic Chemistry Laboratory". Journal of Chemical Education. 87 (4): 419. doi:10.1021/ed800093n.". He says "The sentence is one I noted earlier to be very odd since most radical scavengers will just consume electrons in the liquid ammonia and don't really provide a specific test of a radical-anion. Without knowing what radical-scavenger is meant, it doesn't make sense." Can any one help by making that sentence make sense and fixing that reference? --Bduke (Discussion) 21:42, 18 April 2010 (UTC)

That ref is to J. Chem. Educ., 2010, 87 (4), pp 419–422 and the abstract is "A novel experiment is described in which solvated electrons in liquid ammonia reduce a benzyl alcohol carbon without affecting the aromatic ring. The reductive activity of solvated electrons can be partially or completely quenched through the addition of electron scavengers to the reaction mixture. The effectiveness of these scavengers was found to qualitatively correlate with their electron affinities obtained from first-principles electronic-structure calculations. The reaction completion is monitored using 13C NMR spectroscopic analysis of the whole reaction mixture, without separation and purification. This interesting, dynamic, and diverse experiment combines a classical synthetic procedure, NMR spectroscopy, and molecular modeling and is suitable for second-year through fourth-year chemistry and biochemistry majors." Could a better organic chemist than I take a look? --Bduke (Discussion) 21:49, 18 April 2010 (UTC)

I've manually expanded and formatted the ref, but I have to say I share Dr Zimmerman's confusion. If you look, for example, at File:(3) Birch Basic-Mech.gif, I'm not at all sure which radical (the radical anions at B and C or the radical at C) is intended to be "mopped-up" by a scavenger. I would certainly have expected an electron scavenger to simply react with the solvated electrons from the lithium. The reference, for what it's worth, seems to discuss the single-stage reduction of a benzyl alcohol - I'd have hoped for a cite that specifically addressed the Birch reduction to avoid original research. I agree we could do with more editors able to give a view on this. I'll ask for help at Wikipedia talk:WikiProject Chemistry, but if the sentence can't be clarified or cited more specifically, I'd be in favour of removing it. --RexxS (talk) 02:57, 19 April 2010 (UTC)

Hmm... "electron scavangers"? Aren't they what us mere mortals call "oxidizing agents"? Obviously very weak oxidizing agents, as we're talking about solvated electrons in liquid ammonia here, the strongest reducing agent regularly used in chemistry, but an "electron scavanger" is still technically an oxidizing agent...

I'm hesitant to criticize the authors of this paper as I only have access to the abstract, but I would have thought that the controlling factor in this reaction is the stability of the toluide anion or, to put it another way, the relative acidity of the benzylic hydrogen. Deprotonation of the methyl group must be a competing reaction to reduction of the aromatic ring, although it is presumably quite slow as you can do Birch reductions of toluene.

Anyway, that's speculation. I don't think the J. Chem. Ed. paper supports the claim in the article that suppression by "radical scavengers" is support for the proposed mechanism: the proposed mechanism is supported by the kinetic data of Krapcho and Bothner-By, and by the simple first-principles argument that electrons are only available one-at-a-time in this medium so they can only go on one-at-a-time. Physchim62 (talk) 07:13, 19 April 2010 (UTC)

• The citation did look odd (just a DOI nothing else) because for some reason the cite DOI bot has broken down. Simply by clicking on the link (a hyperlink) will still give you the information you need. Publications in J. Chem. Ed. should be considered for implementation in wikipedia because this publication is widely available in schools and universities. The publication addresses the effect of a radical scavenger on the metal / ammonia solution. It supports the mechanism that electrons are involved , it is really that simple. This talk-page discussion raises a lot of questions that should be directed to the authors of the JChemEd article but for now it is not a problem to remove the line. We still need to expand on basic reaction mechanism on other ways for example esr studies and selected substrates such as biphenyl V8rik (talk) 17:46, 19 April 2010 (UTC)

• However, the abstract uses the term "electron scavanger" not "radical scavanger", and that is what Howard Zimmermann is complaining about. He is an expert on the Birch reaction. Does the JChemEd article reverence a research paper? What actually is the scavanger? Adding its name might clarify. I really do not have time to check this as I am winding down for a wikibreak while away. --Bduke (Discussion) 22:19, 19 April 2010 (UTC)

Applications

As a layman, I cannot really understand much of what is written on the article. I don't really mind, but it would be nice to have a list of the applications, an explanation of why the reaction is important. For practical and maybe theoretical reasons. Thanks. Melquiades Babilonia (talk) 09:06, 20 March 2015 (UTC)