Talk:Captodative effect

Peer review and responses during the educational assignment in Fall 2013

Review from Chemumich:

Content: The introductory gives a general overview of definition of the captodative effect and a quick example of that in a case where there are EWG and EDG that are able to stabilize the radical intermediate. There are a few typos and grammar errors that should be easy to fix. In the introductory it might be helpful to just list out a few radical reactions where the captodative effect comes into play (at the end of the section). It would be interesting to also talk about the effects of the HOMO and LUMO energies relative to the SOMO in the introduction. The origin of the name captodative would be worthwhile including, since it is also very easy to understand. In the second section, a shorter title can be used – perhaps something along the lines of “Substituent Effect on Reaction Rates”. The example that they use is very well chosen and easy to understand. The resonance structures also give a clear picture of the captodative effect. Having all the chemdraw figures together rather than separated by text might actually be easier to follow and read. It would also be helpful to link certain terms like activation energy and transition state to the other Wikipedia pages. The polymer science section is a little difficult to follow and it is difficult to understand how the effect is directly related to polymers—it is difficult to tell whether it is the synthesis, mechanism elucidation or the properties, which the author wants to emphasize. In general, organizing this section will help make the content clearer. Providing a specific example of one of the three points would also be helpful. The last section would be greatly enhanced by an example or at least a deeper explanation of the last figure (is it mentioned in the text?).

Figures: The figures explain the concepts, except there seems to be a little bit of a lack of uniformity between the different sections (size and chemdraw style). The chemdraw figures seem vertically elongated. The reaction coordinate graph is a great visual, but the curves might need to be redrawn (I am not sure how easy this is to do). And as stated earlier, maybe just putting all the reaction schemes together in the substituent effect section rather than separately will help the flow of the article. It is difficult to see the direct connection between the first figure under polymer science and text. I think having concrete examples will probably help create a figure that is easier to understand and

References: There references are complete. Most of the references for this article were mostly from journal sources. I think this is probably due to the fact that it is a very specific topic that might not be discussed in many textbooks. After a quick search, I found this book: Substituent Effects in Radical Chemistry (Heinz G. Viehe, Zdenek Janousek, Robert Merényi, 1986). This might be an interesting source to look into for more information to add to the various sections.

Overall: Overall, I think the article has a lot of good information, and some sections just need to be reorganized or reworded to improve clarity. It is certainly a great improvement compared to the present Wikipedia page! --Chemumich (talk) 00:47, 4 November 2013 (UTC)

Review From Tiraxxis

Content The introduction provides some sort of context and has some minimal background about the subject. The image in the intro section has the molecule shifted in some parts differently from others and the dot representing the radical is larger in some parts than others. There are a lot of terms that are listed here in the article that should be outlinked to their respective wikipedia pages. The layout of the last section is strange and should probably be changed so that they are all in line with each other instead of being offset. Two of the sections are long and have a decent amount of material that they cover, but the intro and the use in Synthesis section should be extended.

Figures All images should be the same size ie. they should be done in the same chemdraw file and scaled to be the same format and have the same percentage scale to each other. And the images in the section How substituents can Influence the Rate of a Reaction are all squashed as if they've been scaled after being in chemdraw and should be fixed.

References References are a nice mix of literature references from somewhat reputable journals and textbooks.

Overall The page seems to be coming along nicely and just has some minor things to improve upon, such as content and some aesthetics. ---Tiraxxis (talk) 04:05, 4 November 2013 (UTC)

Additional Comments

UMChemProfessor (talk) 01:56, 5 November 2013 (UTC) I agree that consistency in the figures is needed. Moreover, you have some strange sp angles in the first figure (fix those!). The reaction coordinate diagram should be removed. It doesn't add anything to the site. The reviewers made some great comments and I have nothing further to add.

Suggestions from ChemLibrarian (talk) 15:20, 5 November 2013 (UTC)

1. As suggested by other reviewers, the consistency, location and size of the figures need work. See this page Wikipedia:Picture tutorial for how to place the image at different places and adjust the size. And try to add captions in each figure so that you can refer to them in the text.
2. Remember you don't need the Introduction heading for the introductory paragraph. You may remove that heading when publishing the article.

Response to reviews

Thank you reviewers! Based on the reviewers’ comments regarding the introduction, it was decided to introduce the explanation of the name captodative as a combining of captive and dative (donor) substituent effects. However we did not feel a list of common EWD or EDG that give the desired effect would add to the reader’s understanding, but we did wiki-link to the different groups which have examples if the reader required further clarification. Also a clearer example of a captodatively influenced Diels Alder reaction, at the end of the synthesis section was added to demonstrate a reaction proceeding in higher yields when the olefin contains these groups. More information was added to clarify the polymer science aspects as the first reviewer requested. Most figures were redone for consistency and the ambiguous reaction in the synthesis section and rate coordinate diagram removed. Additionally formatting concerns in terms of the removal of the introductory heading, and addition of captions to figures were followed as suggested. We feel we did a comprehensive job of linking within Wikipedia to other pages, but there may have been significant ones we missed. Lastly there were issues with the reference section, originally there were several duplicates, and those were clarified, they were a result of the poor combining of two sandboxes’ content. dgsinUM —Preceding undated comment added 04:16, 11 November 2013 (UTC)

Sources for the figures

I'm helping out with a copyright check for the figures in Template:Did you know nominations/Captodative effect.

The first diagram is based on an unnumbered diagram at top right of page 149 of Viehe, Janousek and Merenyi (1985). Clearly it’s at least redrawn from that picture; there is no copyright violation.

In the section 'Polymer science application' there is an image called File:Solvent Affinity effects of substituents.jpg. The concepts in this figure are taken from Figure 19 of Hidoshi Tanaka (2003), “Captodative modification in polymer science”, which is given as ref. 6 of the WP article. Clearly this figure is redrawn (or at least it is different).

The figure now known as File:General Reaction Scheme.png which is presenting a concept from Osamu Ito et al (1987) does not correspond to any figure in Ito’s paper. It appears to be newly-drawn to restate the point given in the ’Scheme’ figure of Osamu Ito, from their page 187. The structures are not 100% the same. There is a ‘Z’ substituent on the phenyl group which is present in the original and not in the derived version in WP. If Z were hydrogen then the equivalence would work. The name File:General Reaction Scheme.png is not a desirable name (too general) and I suggest that the Commons file be renamed. It looks like you don't need to be a Commons admin to do this since they provide a 'Move' button.

The diagram File:New Transition State.png ought to be renamed to something more specific. That diagram is also based on Ito’s paper but not from a specific figure.

In the section 'Uses in synthesis' there is a citation to reference 8, Stella and Boucher 1982. This must be the source of information for File:Diels Alder.png and File:Friedel Craft Reaction.png. The Stella and Boucher paper is from Tetrahedron Letters in 1982 which I can't get hold of. Consider changing those file names as well. EdJohnston (talk) 20:35, 23 December 2013 (UTC)

The image in File:Friedel Craft Reaction.png misspells 'Craft' as 'Cfraft'. To fix this someone would need to redraw the image. EdJohnston (talk) 22:43, 23 December 2013 (UTC)

Last two sections don't mention radicals

@DMacks: One of the people who commented at Wikipedia talk:WikiProject Chemistry#Image issues in captodative effect notes that "many of the reactions discussed in the "Uses in synthesis" section (Friedel–Crafts and Diels–Alder) are not generally considered to be radical mechanisms and the given reactants are full-octet and in the ground state". However, the opening of the article says that the captodative effect is a "phenomenon associated with the stabilization of radicals by their substituents". I.e. it's a phenomenon involving radicals. The last two sections (on polymers and on uses in synthesis) should make clear how radicals are involved. Also, how does a term such as 'captodative ethylenes' come into use, since a stable molecule is presumably not a radical. Since reference 10 has 'captodative' in its title perhaps the material in that article will have the answer. If so then maybe the opening definition of 'captodative' could need to be broadened. EdJohnston (talk) 16:33, 24 December 2013 (UTC)

I have made changes to the synthesis section, it was badly written and I hope now is clearer. If someone wants to redraw the images )particularly my new one) that would be excellent. Thanks. EdChem (talk) 13:20, 8 January 2014 (UTC)

Also, not worried about the polymer section as it is not wrong, just unclear... olefin polymerization is often a radical process so it probably needs some redrafting to make this point clear. It was the D-A and F-C stuff that was really worrying as the [4+2] D-A reaction is just not a radical process. EdChem (talk) 13:24, 8 January 2014 (UTC)