![]() | This ![]() It is of interest to the following WikiProjects: | ||||||||||
|
![]() | This article was the subject of an educational assignment in Fall 2013. Further details were available on the "Education Program:University of Michigan/CHEM 540 (Fall 2013)" page, which is now unavailable on the wiki. |
We completed our final edits to this page. We expanded on the original page by describing the mechanism in more detail in addition to comparing the E1cB mechanism to the other elimination reactions. This also included a detailed discussion of the kinetics that characterize this reaction and several applications. We would appreciate any comments or recommendations that would add to this page.
Thanks!
--
Paracelsus22 (
talk)
15:34, 11 November 2013 (UTC)
The start with E1cB elimination reaction is a type of elimination reaction could be improved.-- Stone ( talk) 21:26, 29 October 2013 (UTC)
The introduction section seems appropriate in language and length, much more so than the original page’s. It may be more helpful to place the breakdown of the name (E=elimination) first, and then proceed into the conditions. The mechanisms section could wiki-link to the inductive effect and delocalization pages to clear up the significance of those terms. The “Distinguishing from other Beta-hydride elimination reactions” section seems to be repetitive of several kinetic effects mentioned in the “Identifying E1cB-elimination mechanisms” section. It might be best if those two are merged on the final page. The Kinetic Isotope Effect in the latter section was very thorough and written in accessible language. The representative example with the Aldol reaction was well done. All in all, excellent accessible language, but make sure to link more to other wiki articles that go into some of your concepts: Steady state approximation in chemical kinetics, reversible vs. irreversible reactions, conjugate bases, nucleophiles. The original page also seems to have a good amount of technical information on specific reaction conditions and named reactions. This should be incorporated with the example reactions in the final version of the page.
The images definitely illustrate the concepts well; however there might be a minor way to improve the abbreviations for base and leaving group. It may be helpful to in the first mechanism on the page, refer to the Base as “Base (:B- )” instead of “:B” and then referring to it in the preferred convention for further mechanisms would be helpful. Novices might think you mean boron anions are good bases. Also referring to the Leaving groups as “LG” in their first image would be more acceptable notation for non-chemists. Lastly the image in the “Distinguishing from other Beta-hydride elimination reactions” may need a slight edit: in the product of k2 reaction, after the double bond forms, it should be a planar molecule. However these mechanisim and figures are much more helpful than the original article’s and they appear to be drawn accurately for the most part.
The required numbers of sources are present and well dispersed between journals and textbooks that should be available in most academic libraries.
Overall the article is very accessible to the Wikipedia audience, and is well-illustrated with pertinent and mostly accurate images. It does get repetitive in the 3rd and 4th section, and it would be best to combine these or make a separate section for only kinetics. The fact that approximately half the references are text rather than online journals is commendable as well. I think this article will definitely elucidate the concepts mentioned on the original article, which was written in much more technical language.
Thank you very much for your helpful insights relating to our page! We really appreciate your comments, and here are some changes that we made:
One change that we respectfully disagreed on relates to how we described the naming of E1cB mechanisms. You suggested that it "may be more helpful to place the breakdown of the name (E=elimination) first, and then proceed into the conditions." We felt that describing the conditions served as the first stepping stone to getting to what the name stood for. It followed the logic of "here is the mechanism and what it does, so it makes sense that it is called this."
Thank you again for your suggestions!
-- Paracelsus22 ( talk) 16:34, 8 November 2013 (UTC)
The introductory section is definitely an improvement over the previous page. It is not too detailed, and I think it is accessible to those who are studying sophomore level organic chemistry. However I'm not sure that in this sentence: Elimination refers to the fact that this mechanism is for a Beta-Hydride elimination that "for" is the correct word to use. Other than that I find it clear and think that less experienced chemists could understand. Also, I think the introduction should be above the table of contents. In my opinion it would make the introduction section clearer. I do think that the length of each section is helpful and the ideal length. I think the content here is helpful and necessary, and I don't think there is much duplication. Just a few notes though: saying something "will want to leave" is less scientific and might confuse readers who don't understand stability = happiness of molecules. Using "we" like in the rate law kinetic section, I think is less ideal in the wikipedia world. The kinetics discussion was relatively clear though for people who understand kinetics, but I don't think there is another way to explain it without being technical and assuming knowledge. During the isotope effect a C is missing: The use of 11C can be used. I think some more information could be used in the aldol example as it is "The most well known reaction that undergoes E1cB". I'm not sure exactly what should be added, but perhaps a description of why it is E1cb, because all that is there is a description of the mechanism (which is helpful).
Most of the figures are helpful. As a person who understands a little bit of chemistry, some of them seem a bit repetitive, but I think they could be helpful. The figure for Ethiofencarb should say that it is the molecule, otherwise it appeared to be just a seemingly overly-complicated amide/ester molecule. The figure of the beta elimination section of the E1cb is great, but the last structure should have better bond angles. I'm not sure if there are figures you could make for KIE, but if you could that would only help the section. Also, (extremely trivial) in my opinion, for consistency's sake, the font in the chemdraw figures should all be the same. Some are helvetica, and some are times new roman.
The references are good sources, mostly books and reviews, which makes them accessible. The only problem is that the in-text citations are not always consistent. Sometimes the in text citation (numbers) follow or precede the period, and they should follow the period.
I think it's a great page, especially considering where it came from, with the exception of a few small details that could be changed/expanded or clarified. A lot of aspects of the mechanism were clarified, which I think is the ultimate goal of the page. The only comments I have for improvement are the little things stated above.
Mechem13 ( talk) — Preceding unsigned comment added by Mechem13 ( talk • contribs) 00:00, 4 November 2013 (UTC)
Thank you for your review. Here are some of the edits we made based on your comments.
-- Physchem 13 ( talk) 16:28, 8 November 2013 (UTC)
UMChemProfessor ( talk) 02:45, 5 November 2013 (UTC)There needs to be some consistency between each figure in terms of size, format, style, etc. For example, whether hashed/wedged bonds are used, or not. The peer reviewers also made some great suggestions.
-- Physchem 13 ( talk) 16:36, 8 November 2013 (UTC)
This page should be merged with elimination reactions
I agree IlyaV 20:08, 9 March 2008 (UTC) —Preceding unsigned comment added by IlyaV ( talk • contribs)
I rated this page as mid, but I suspect it could be high importance if viewed in light of the Elimination reaction article. To my mind, E1cB is less fundamental than E1 and E2, but I'm flexible as to which of mid/high it falls into. Brammers ( talk/ c) 17:08, 8 January 2012 (UTC)
In my opinion, this article contains mistakes.
1. It states: "This reaction mechanism explains the formation of alkenes from (mostly) alkyl halides through a carbanion intermediate". However, alkyl halides are absolutely not typical substrates for E1cB.
2. It states: "The reaction takes place around a sp3 - sp3 carbon to carbon covalent bond with an α-acidic hydrogen atom substituent and a β-leaving group". alpha and beta to what??? Seems someone forgot to mention the presence of a mysteriously acidifying functional group?
3. It states: "This leaving group can be a halide or a sulfonic acid ester such as a tosyl group." However, E1cB is only possible if the leaving group is not overly good. For halides and sulfonates, I expect E2 mechanisms. Why should such potent leaving groups wait before they eliminate. Fluoride may be the most typical of all halides for E1cB, because it is such a bad leaving group.
4. It states: "A named reaction displaying E1cB elimination mechanism is the Boord olefin synthesis." However, the Boord olefin synthesis does not start from an acidic CH substrate, but from a halo-hetero-substrate, where the halo is reductively converted to a carbanion, which must be an irreversible step. So, the carbanion in that reaction is generated irreversibly, and in the absence of a base. That is certainly not a typical E1cB mechanism, since the acid to the conjugated base is not the starting material.
5. The most common examples for E1cB (aldol elimination) are not even mentioned, when some fancy special cases from recent research literature is treated in all detail. 116.14.37.220 ( talk) 12:33, 22 March 2013 (UTC)
My comments:
![]() | This ![]() It is of interest to the following WikiProjects: | ||||||||||
|
![]() | This article was the subject of an educational assignment in Fall 2013. Further details were available on the "Education Program:University of Michigan/CHEM 540 (Fall 2013)" page, which is now unavailable on the wiki. |
We completed our final edits to this page. We expanded on the original page by describing the mechanism in more detail in addition to comparing the E1cB mechanism to the other elimination reactions. This also included a detailed discussion of the kinetics that characterize this reaction and several applications. We would appreciate any comments or recommendations that would add to this page.
Thanks!
--
Paracelsus22 (
talk)
15:34, 11 November 2013 (UTC)
The start with E1cB elimination reaction is a type of elimination reaction could be improved.-- Stone ( talk) 21:26, 29 October 2013 (UTC)
The introduction section seems appropriate in language and length, much more so than the original page’s. It may be more helpful to place the breakdown of the name (E=elimination) first, and then proceed into the conditions. The mechanisms section could wiki-link to the inductive effect and delocalization pages to clear up the significance of those terms. The “Distinguishing from other Beta-hydride elimination reactions” section seems to be repetitive of several kinetic effects mentioned in the “Identifying E1cB-elimination mechanisms” section. It might be best if those two are merged on the final page. The Kinetic Isotope Effect in the latter section was very thorough and written in accessible language. The representative example with the Aldol reaction was well done. All in all, excellent accessible language, but make sure to link more to other wiki articles that go into some of your concepts: Steady state approximation in chemical kinetics, reversible vs. irreversible reactions, conjugate bases, nucleophiles. The original page also seems to have a good amount of technical information on specific reaction conditions and named reactions. This should be incorporated with the example reactions in the final version of the page.
The images definitely illustrate the concepts well; however there might be a minor way to improve the abbreviations for base and leaving group. It may be helpful to in the first mechanism on the page, refer to the Base as “Base (:B- )” instead of “:B” and then referring to it in the preferred convention for further mechanisms would be helpful. Novices might think you mean boron anions are good bases. Also referring to the Leaving groups as “LG” in their first image would be more acceptable notation for non-chemists. Lastly the image in the “Distinguishing from other Beta-hydride elimination reactions” may need a slight edit: in the product of k2 reaction, after the double bond forms, it should be a planar molecule. However these mechanisim and figures are much more helpful than the original article’s and they appear to be drawn accurately for the most part.
The required numbers of sources are present and well dispersed between journals and textbooks that should be available in most academic libraries.
Overall the article is very accessible to the Wikipedia audience, and is well-illustrated with pertinent and mostly accurate images. It does get repetitive in the 3rd and 4th section, and it would be best to combine these or make a separate section for only kinetics. The fact that approximately half the references are text rather than online journals is commendable as well. I think this article will definitely elucidate the concepts mentioned on the original article, which was written in much more technical language.
Thank you very much for your helpful insights relating to our page! We really appreciate your comments, and here are some changes that we made:
One change that we respectfully disagreed on relates to how we described the naming of E1cB mechanisms. You suggested that it "may be more helpful to place the breakdown of the name (E=elimination) first, and then proceed into the conditions." We felt that describing the conditions served as the first stepping stone to getting to what the name stood for. It followed the logic of "here is the mechanism and what it does, so it makes sense that it is called this."
Thank you again for your suggestions!
-- Paracelsus22 ( talk) 16:34, 8 November 2013 (UTC)
The introductory section is definitely an improvement over the previous page. It is not too detailed, and I think it is accessible to those who are studying sophomore level organic chemistry. However I'm not sure that in this sentence: Elimination refers to the fact that this mechanism is for a Beta-Hydride elimination that "for" is the correct word to use. Other than that I find it clear and think that less experienced chemists could understand. Also, I think the introduction should be above the table of contents. In my opinion it would make the introduction section clearer. I do think that the length of each section is helpful and the ideal length. I think the content here is helpful and necessary, and I don't think there is much duplication. Just a few notes though: saying something "will want to leave" is less scientific and might confuse readers who don't understand stability = happiness of molecules. Using "we" like in the rate law kinetic section, I think is less ideal in the wikipedia world. The kinetics discussion was relatively clear though for people who understand kinetics, but I don't think there is another way to explain it without being technical and assuming knowledge. During the isotope effect a C is missing: The use of 11C can be used. I think some more information could be used in the aldol example as it is "The most well known reaction that undergoes E1cB". I'm not sure exactly what should be added, but perhaps a description of why it is E1cb, because all that is there is a description of the mechanism (which is helpful).
Most of the figures are helpful. As a person who understands a little bit of chemistry, some of them seem a bit repetitive, but I think they could be helpful. The figure for Ethiofencarb should say that it is the molecule, otherwise it appeared to be just a seemingly overly-complicated amide/ester molecule. The figure of the beta elimination section of the E1cb is great, but the last structure should have better bond angles. I'm not sure if there are figures you could make for KIE, but if you could that would only help the section. Also, (extremely trivial) in my opinion, for consistency's sake, the font in the chemdraw figures should all be the same. Some are helvetica, and some are times new roman.
The references are good sources, mostly books and reviews, which makes them accessible. The only problem is that the in-text citations are not always consistent. Sometimes the in text citation (numbers) follow or precede the period, and they should follow the period.
I think it's a great page, especially considering where it came from, with the exception of a few small details that could be changed/expanded or clarified. A lot of aspects of the mechanism were clarified, which I think is the ultimate goal of the page. The only comments I have for improvement are the little things stated above.
Mechem13 ( talk) — Preceding unsigned comment added by Mechem13 ( talk • contribs) 00:00, 4 November 2013 (UTC)
Thank you for your review. Here are some of the edits we made based on your comments.
-- Physchem 13 ( talk) 16:28, 8 November 2013 (UTC)
UMChemProfessor ( talk) 02:45, 5 November 2013 (UTC)There needs to be some consistency between each figure in terms of size, format, style, etc. For example, whether hashed/wedged bonds are used, or not. The peer reviewers also made some great suggestions.
-- Physchem 13 ( talk) 16:36, 8 November 2013 (UTC)
This page should be merged with elimination reactions
I agree IlyaV 20:08, 9 March 2008 (UTC) —Preceding unsigned comment added by IlyaV ( talk • contribs)
I rated this page as mid, but I suspect it could be high importance if viewed in light of the Elimination reaction article. To my mind, E1cB is less fundamental than E1 and E2, but I'm flexible as to which of mid/high it falls into. Brammers ( talk/ c) 17:08, 8 January 2012 (UTC)
In my opinion, this article contains mistakes.
1. It states: "This reaction mechanism explains the formation of alkenes from (mostly) alkyl halides through a carbanion intermediate". However, alkyl halides are absolutely not typical substrates for E1cB.
2. It states: "The reaction takes place around a sp3 - sp3 carbon to carbon covalent bond with an α-acidic hydrogen atom substituent and a β-leaving group". alpha and beta to what??? Seems someone forgot to mention the presence of a mysteriously acidifying functional group?
3. It states: "This leaving group can be a halide or a sulfonic acid ester such as a tosyl group." However, E1cB is only possible if the leaving group is not overly good. For halides and sulfonates, I expect E2 mechanisms. Why should such potent leaving groups wait before they eliminate. Fluoride may be the most typical of all halides for E1cB, because it is such a bad leaving group.
4. It states: "A named reaction displaying E1cB elimination mechanism is the Boord olefin synthesis." However, the Boord olefin synthesis does not start from an acidic CH substrate, but from a halo-hetero-substrate, where the halo is reductively converted to a carbanion, which must be an irreversible step. So, the carbanion in that reaction is generated irreversibly, and in the absence of a base. That is certainly not a typical E1cB mechanism, since the acid to the conjugated base is not the starting material.
5. The most common examples for E1cB (aldol elimination) are not even mentioned, when some fancy special cases from recent research literature is treated in all detail. 116.14.37.220 ( talk) 12:33, 22 March 2013 (UTC)
My comments: