Talk:Aldol reaction

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Featured article star Aldol reaction is a featured article; it (or a previous version of it) has been identified as one of the best articles produced by the Wikipedia community. Even so, if you can update or improve it, please do.
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Archive 1 ( - Feb 2006)

Contents

[edit] Revisions

Hey guys, I have a little time to work on this article again...I'm open for suggestions. I was going to add a bit on the newer organocatalytic and catalytic, asymmetric methods, plus some stuff on thiazolodinethione auxiliaries. Any ideas? It's a pretty big article already. What do we need to do to get it to "featured article" level? Eugene Kwan 16:30, 24 November 2006 (UTC)

  • Hi Eugene, welcome back, I haven't changed my view on this article since the last time (see my notes somewhere in the text above) but the article should be considered for featured article as it is. I am having some problems though with your use of syn and anti with respect to linear aliphatic chains in the text V8rik 17:39, 24 November 2006 (UTC)

OK, sure...thanks. What problems are you referring to? Are they mentioned above? Eugene Kwan 04:33, 25 November 2006 (UTC)

    • they are in this part. There was some unfinished discussion on what the average Wiki reader is and I maintain that you cannot expect the average reader to have any knowledge on the Aldol reaction. On the other hand you can simply direct to other articles when thing are unclear. One example: if the reader is unfamiliar with nucleophilic addition you simple link it in the text as nucleophilic addition, a reader already familiar with nucleophilic addition can skip it and read on. If you go for FA status non-chemists will review the article and I am sure you will get questions on unclear technical terms. I have already taken care of stereoinduction and allylic strain but other unexplained terms remain V8rik 18:25, 25 November 2006 (UTC)
  • This reaction is a standard part of the second-semester syllabus in most US introductory undergraduate organic chem courses, so probably many thousands of students check this page (mostly around April, when it is usually taught). These students should know the basics of organic chemistry, including basic carbonyl chemistry, but many will probably be unfamiliar with terms like regiochemistry, stereoselectivity, asymmetric induction, kinetic vs. thermodynamic products. They should hear in class about use LDA and alkoxide bases (no others!), dehydration, and the problem of control in crossed aldols. In the UK it's probably similar, but may go a little deeper (e.g. kinetic vs thermodynamic enolates). I also cover the reaction in more detail in my advanced organic class - a much smaller number of students take this - and for that course the more advanced coverage in this article (E/Z enolates, Evans, etc.) is excellent. I hope this provides some guidance on what I'd guess the "average" reader of this page could be expected to know. Walkerma 06:22, 26 November 2006 (UTC)

OK, I'll tell you what. I'll let you guys figure out what sort of editing to do, and I'll just add some more material. I am a bit concerned about the length of this article, however. Any thoughts? Eugene Kwan 22:29, 26 November 2006 (UTC)

I've added a lot of new material, and am still in the process of finishing it. Please let me know what you think. Eugene Kwan 23:22, 27 November 2006 (UTC)

1. This article could easily be MUCH longer given what's known about aldols. 2. The carreira Cu enolate aldol under header "Mukaiyama aldol reaction" is an enolate mechanism, and therefore NOT a Mukaiyama aldol, and it should be moved or made into a new category.

[edit] Introduction

I would vote for

The aldol reaction is an important method for forming carbon-carbon bonds

instead of "constructing". One constructs the skeleton of a molecule, or perhaps even the stereochemistry around a particularly difficult center, but a simple carbon-carbon bond is just "formed".

Also, I'm not really in favor or "naturally occurring molecules". "Natural products" is what the total synthesis folks synthesize, and using any other word is imprecise language and talking down to the readership. They deserve better. Dr Zak 22:09, 7 December 2006 (UTC)

It should also be pointed out that two stereocenters are set up in one reaction step, it's a salient feature. Dr Zak 22:28, 7 December 2006 (UTC)

I agree, especially with using forming instead of constructing. These are always called bond formation reactions in my experience. Maybe the idea was to avoid the funny-sounding "for forming", but that could be avoided by rephrasing. Maybe "The aldol reaction is an important carbon-carbon bond formation reaction", or "The aldol reaction is an important method for the formation of carbon-carbon bonds". Itub 23:34, 7 December 2006 (UTC)
OK, agreed. I just thought the ordinary person would not have the terms "natural product" or "bond formation" in their vocabulary. It's a tough job. What's the FA status? Will it just sit on the FA nominees list forever? Also, I felt thalidomide was a bad example, since the enantiomers interconvert in the body. Eugene Kwan 03:36, 8 December 2006 (UTC)
Amen, brother, on the thalidomide. Plus it's not an aldol adduct either. By the way, shouldn't it read "multigram-scale quantities of the drug" near the end of the first paragraph? Dr Zak 03:43, 8 December 2006 (UTC)
Yes, that works too. Eugene Kwan 00:06, 9 December 2006 (UTC)

Hey, this is great! Good work, everyone! A note about chemistry images: PNG looks fine, but there's a big problem with getting all the images to look the same size. It looks really weird with all the structures being different sizes. So I don't like PNG for the structures. Anyways, if you guys see any more errors, please, let me know! Eugene Kwan 05:57, 9 December 2006 (UTC)

[edit] Level of contributor

I have a question: what would you estimate is the average contributor's level for this article? My personal estimate is 3rd year undergraduate Chemistry major. Does that sound reasonable? The reason I ask is because the average contributor is W is much lower than that and I would love it if guys are your level could help to reconcile these two things (essays? whatever):

BTW: My own qualifications are B.S. in Chem. Eng., RPI '83. -- 64.9.234.5 02:42, 26 January 2007 (UTC)

Actually, I think most of the contributors are Ph.D. level. I'm a 3rd year Ph.D. student. Eugene Kwan 17:10, 26 January 2007 (UTC)

Thanks. I have noted that in the WP:100K project. I hope that they authors of that article set some realistic goals. IMHO, it seems like 5K FA by the end of 2007 would be something close to miraculous. To be honest, even 2K FA by the end of 2007 seems a tad aggressive to me, but I am for aiming high. Still, 100K seems to be a goal declared by the unrealisitic. I say: aim for 5K (or less if you think failure is discouraging) and pray for a miracle. -- 199.33.32.40 22:37, 26 January 2007 (UTC)
I am thinking of recommending that we maybe need to protect the feelings and the work of a scare resource: hard-science experts (HSE) who are active within the project. The WikiProject efforts are a step in that direction, but active HSE's are a scarce resource that require special protection. There are templates like {{ExpertChemistry}}, but they protect articles, not users. In a psychological way, maybe this article can be used, sort of as an ornate mace, to cow into submission any trolls who would otherwise interfere with and drive away true HSE's who are still willing to contribute to the project. But, I am getting ahead of myself. We need a small, gentle solution first. Maybe we should make a user template to the effect:

HSE This user is a hard-science expert. Please defer to their credentials, accomplishments and experience.

Let's not tie it to whatever Hard science artilce defines unless that article reaches a high level of stability and we can live with that definition. Now, let's think about what hard-science does not include: Humanities (maybe they can get their own user template), fiction writers, even hard-science science fiction writers. Math (again, get their own template), Technology. In other words, in terms of the top-level groups on the Main Page, we are talking about Science and Geography. I would love to include Math and Technology, but I would think that we would need a special requirement of "must be at M.S. or PhD level". I would love to include History and Economy (which is also single out by the Nobel Prize process) and that is about it. Anyway, I just cannot stand to see what it happening with WP:QUIT. I really miss Jnc and KimvdLinde and those guys. There were very nice and they became discouraged because the community did not give them support when they, in an emotional way, needed that support. I think that we can use this kind of article as a threshold without drawing too much attention to it (lest it become a target for disgruntled sub-experts). In other words, if they cannot get themselves through this article, then they probably are not a HSE in anything. I say that because while Math obviously touches every hard science, I tend to think that every true HSE has enough knowledge of chemistry to get through this article also. If we cannot develop the MediaWiki software technology in a timely fashion to give HSE's some clout and comfort, then we must do so within the less formal community process. What do you guys think? -- 70.231.154.13 17:55, 30 January 2007 (UTC)
Let's also recognize that this article has a good clean "threashold tool" because, unlike biology and cosmology, it has no obvious social or religious implications and so it does not tend to attract trolls. See the paragraph about technology in Dehumanization#Other topics for a deeper understanding of the "technology vs. religion" problem, which seems to be writ large here at Wikipedia. But with the advent of biotechology, there is no question that there is a pool of biology experts, again, KimvdLinde being among them, who need defending from determined trolls, under-educated know-it-alls, creationists, and whatnot. -- 70.231.154.13 19:40, 30 January 2007 (UTC)

[edit] Organocatalysis

User:Zghajos From Wikipedia, the free encyclopedia Jump to: navigation, search Remarks to the Wikipedia Organocatalytic aldol reactions

Zoltan G. Hajos zghajos(AT)t-online.hu

The reaction scheme (a) as shown in the Wikipedia Organocatalytic aldol reactions page has only been described in the Hajos, Parrish Patent (b) and the Hajos, Parrish paper (c).

Since Hajos and Parrish worked at ambient temperature using a catalytic amount (3% molar equiv.) of (S)-(-)-proline they could isolate the optically active intermediate bicyclic ketols a prerequisite of elucidating the reaction mechanism. This was most likely the reason for Professor Claude Agami to call the reaction the Hajos-Parrish reaction in his paper in J.Chem.Soc., Chemical Commun., 1985, 441-442 (d).

The Hajos, Parrish Patent (b) also described the Asymmetric synthesis utilizing (S)-(-)-proline even in the absence of added solvent.

The last few lines of the Hajos, Parrish 1974 paper read: "We believe our results may be considered an example of a simplified model of a biological system in which (S)-(-)-proline plays the role of an enzyme." This has been referred in a publication by Mohammad Movassaghi and Eric N. Jacobsen of the Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA: The Simplest "Enzyme" Science, 6 December 2002, Vol. 298, 1904-1905 (e).

The above is also described in the Benjamin List Tetrahedron report number 613 in 2002 (f). This Tetrahedron report shows that the Schering group executed the reaction under non biological conditions using (S)-Proline (47 mol%), 1N perchloric acid, in acetonitrile at 80 degrees C. Hence, they could not isolate the Hajos, Parrish intermediate bicyclic ketols. The original 1985 naming of the reaction by Claude Agami (d) has been expanded in this 2002 paper (f) by adding three more names of the Schering group.


References to the Zoltan G. Hajos Remarks. a.http://upload.wikimedia.org/wikipedia/commons/d/de/Organocatalytic1.gif]

b. Hajos, Z, G.; Parrish, D. R. Asymmetric Synthesis of Optically Active Polycyclic Organic Compunds. German Patent DE 2102623, July 29, 1971.

c. Hajos, Z. G.; Parrish, D. R. J. Org. Chem. 1974,39,1615.

d. Agami, C.; Levisalles, J.; Puchot, C. J. Chem. Soc., Chem. Commun. 1985, 8, 441-442. doi:10.1039/C39850000441

e. Movassaghi, M.; Jacobsen, E. N., Science, 2002, 298, 1904-1905. doi:10.1126/science.1076547

f. List, B, Tetrahedron 2002, 58, 5573-5590 doi:10.1016/S0040-4020(02)00516-1 references 12 doi:10.1021/jo00925a003 and 13 doi:10.1002/anie.197104961

The above was posted by User:Zghajos (15:55 UTC, 5 February 2007) and moved here later that day by User:Walkerma, for discussion. Walkerma 16:49, 5 February 2007 (UTC)

I'm not sure I understand what's being said here...what is the proposed modification? When people talk about the "Hajos-Parrish reaction", they refer to the example I provided. I haven't investigated the history behind the reaction closely. Eugene Kwan 16:56, 5 February 2007 (UTC)

(Edit conflict) OK, I'm at work so can't comment more, but how should we incorporate this information into the article? Dr. Hajos has graciously given us some helpful refs on the reaction that bears his name, I suggest we try to review this to decide how best to incorporate the key parts of it in an "encyclopedic" way. Eugene, K, and others, what do you think? (I see Eugene has already commented!) Walkerma 16:59, 5 February 2007 (UTC)

Dr. Hajos has privately proposed to me that we simply call it the "Hajos-Parrish" reaction. Knowing nothing about the history behind the reaction, I have no opinion. If it turns out he reported the reaction first, then I don't object. If both groups reported the reactions at the same time, then both should be given credit, even if the conditions were harsher for one group. Eugene Kwan 14:47, 8 February 2007 (UTC)

This article may shed some light on the history - which is obviously important for the naming. I plan to order the Angewandte article so I can look at it; U. Eder, G. Sauer, R. Wiechert, Angew. Chem. Int. Ed. 1971, 10, 496. DOI. Since both works (the other being the Hajos patent) came out in 1971, we need to look more closely at this, I think. Walkerma 16:13, 8 February 2007 (UTC)
I don't know the history, but I believe that the current version of the article is correct in saying "This is commonly referred to as the Hajos-Parrish-Eder-Sauer-Wiechert reaction", because that is the only way I've seen people refer to this reaction. Itub 16:24, 8 February 2007 (UTC)

Please comment on my more neutral statement. Eugene Kwan 22:48, 9 February 2007 (UTC)

Hello Dr.Kwan: Thank you for making the changes in the text below the reaction equation leading to the bicyclic ketol or aldol, if you wish. The fact remains that, one cannot synthesize this compound under the "harsher" Schering reaction conditions which bypass this compound and lead to the optically active bicyclic dione. The reaction scheme as it is shown in the article has only been reported by us (ZGH and DRP); the Schering group has not reported it. Thanks again and greetings, Zoltan (March 2, 2008) 84.2.146.123 (talk) 08:19, 2 March 2008 (UTC)

[edit] Comment from OTRS

"In the section of "the Stereoselectivity: Alpha stereocenter on the enolate," there are figures for Z and E enolates right underneath the description "In the case of an E enolate, the dominant control element is allylic 1,3-strain whereas in the case of a Z enolate, the dominant control element is the avoidance of 1,3-diaxial interactions. The general model is presented below:" I believe the structure for Z enolate is correct, but I think your E enolate structure is false, as you notice both of your E and Z are the same. Please let me know, because it doesn't really make sense otherwise."

Well above my head, please review and fix if necessary. Thanks, Guy (Help!) 17:56, 5 May 2007 (UTC)

My apologies. You see the enolate structures are correct above, but not below. I have made the appropriate correction. Eugene Kwan 01:03, 6 May 2007 (UTC)

[edit] Complex articles and introduction articles - input requested

As the editors of this article have produced an example of what I would say can fairly be called a complex article, could I ask for input on the issues of complex articles and "introduction to" articles at Wikipedia talk:Featured article candidates/Introduction to general relativity? I mention this article down near the bottom of that talk page, and list a series of "introduction to" articles. Thanks. Carcharoth 00:23, 15 July 2007 (UTC)

  • The editors of this page have made sure that the introduction is easy to understand. If the introduction is still too technical changes should be made to the introduction. A introduction to page will not help. The general relativity page is a disaster, it should be trimmed down to 15% of its current size and the details should be left to the satellite pages (there are 13 Main article links!). There should be no need for a intro page there also. V8rik 19:41, 15 July 2007 (UTC)

[edit] Footnote lecture

How to add a footnote:

NOTE: Footnotes in this article use names, not numbers. Please see Wikipedia:Footnotes for details.
  1. Assign your footnote a unique name, for example TheSun_Dec9.
  2. Add the macro[1] to the body of the article, where you want the new footnote.
  3. Take note of the name of the footnote that immediately precedes yours in the article body.
  4. Add #^  to the footnote numbered-list, immediately below the footnote you noted in step 3. No need to re-number anything!
  5. Multiple footnotes to the same reference: see Wikipedia:Footnotes for a how-to, if you do not succeed by simply following the pattern.

Does this apply to old-style footnotes?--SallyForth123 20:31, 30 July 2007 (UTC)

Sorry changed your eddit to make it better readable--Stone (talk) 12:06, 2 March 2008 (UTC)

[edit] RACEMIC (+/-) mixture

hi,

how about adding a comment stating that the SYN or ANTI diastereoselectivity involve RACEMIC product mixtures?

see: http://www.chem.usyd.edu.au/~mcerlean/CHEM3115Lecture4.pdf

I think this keyword is key for making this article more "complete", or helpful.

--Koala Paw (talk) 17:52, 11 March 2008 (UTC)

e.g.: draw two Zimmerman-Traxler 6-membered-chair transition states as mirror images: get two enantiomeric transition-states which are equal in energy...

can also point out that one enolate adds to the "Si"-face, the other to the "Re"-face, according to CIP rules / nomenclature, etc.

--Koala Paw (talk) 18:10, 11 March 2008 (UTC)

  • Sounds interesting, by all means make the edits you think will expand / improve this article V8rik (talk)

and last, maybe not, but anyway not least: IF you have an "alpha"-chiral aldehyde, one can PREDICT (by making use of the Felkin-Ahn model, for instance) whether the enolate attacks the "Si"- or "Re"-face of the "alpha"-chiral aldehyde...

note though that NOW the two 'enantiomers' are no longer equal in energy... (if they were, we'd get a RACEMIC mixture, once again!)

--Koala Paw (talk) 22:15, 11 March 2008 (UTC)

By all means reword it if you think it will make it more clear, but I think the term diastereoselectivity speaks for itself. You do get a racemic mixture if you start with an achiral enolate and achiral aldehyde, but you might well not if either is optically active. I think doubling each Z-T transition state would just confuse things. Eugene Kwan (talk) 01:29, 12 March 2008 (UTC)

doubling (mirroring) it _once_ would do, to make the ORIGIN of my argument clearer. and I don't intend to change the main page... I'll leave that up to the wiki formatting experts...

on a different note, as long as what is written is written lucidly and intelligibly and most importantly coherently (!) that's fine. but this ALDOL page is getting quite long (many 15" screens to scroll down...) - a well placed "tautology" (which I would argue racemic & diastereomeric, as it were, is not) IMHO would help, rather than confuse any old reader...

--Koala Paw (talk) 11:04, 12 March 2008 (UTC)

[edit] boron enolate

hi.

What is good:

  • The two key examples / reactions for cis & trans boron enolates are given.
  • The antiperiplanarity drawing.

I would add:

  • Deprotonation is _NOT_ through a chair transition-state.
  • elucidate the transition-state further, eg with two supplemental drawings for two said reactions:
    • free rotation about (CO)-CH2Me bond, and the orientation of the methyl DEPENDS on whether the base OR the boron ligand is the BULKY candidate...

--Koala Paw (talk) 23:06, 16 March 2008 (UTC)

Hi Koala, I appreciate the comments, but I'm really not sure what you're getting at. It's certainly probable that deprotonation does not conform to the Ireland model; I merely mentioned it for historical reasons. That's why I mention that its validity is questionable. Which reactions are you referring to? Eugene Kwan (talk) 03:08, 19 March 2008 (UTC)

Oh, the Ireland model is fine for LDA, but I wasn't referring to that "type of" enolisation:

The above was explicitly and only referring to BORON ENOLATES and their formation.

That they are formed differently (than, say, Li+ enolates), viz _not_ via an Ireland chair and that we have tools / other models / rationalizations to predict E vs Z / trans vs cis enolate outcomes is important to note and know, I think.

Bene?

--Koala Paw (talk) 20:05, 19 March 2008 (UTC)