{"id":4592,"date":"2011-07-10T10:17:40","date_gmt":"2011-07-10T10:17:40","guid":{"rendered":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=4592"},"modified":"2012-10-09T09:10:16","modified_gmt":"2012-10-09T08:10:16","slug":"the-stereochemistry-of-82-pericyclic-cycloadditions","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4592","title":{"rendered":"The stereochemistry of [8+2] pericyclic cycloadditions."},"content":{"rendered":"
\n

Steve Bachrach has blogged<\/a> on the reaction shown below. If it were a pericyclic cycloaddition, both new bonds would form simultaneously, as shown with the indicated arrow pushing. Ten electrons would be involved, and in theory, the transition state would have 4n+2 aromaticity. In fact\u00a0Fernandez, Sierra and Torres have reported<\/a> that they can trap an intermediate zwitterion 2<\/strong>, and in this sense therefore, the reaction is not pericyclic but nucleophilic addition from the imine lone pair to the carbonyl of the ketene (it finds the half way stage convivial). But this got me thinking. Does this reaction have any pericyclic character at all? And if so, could it be enhanced by design?<\/p>\n

\"\"

A formal 8+2 cycloaddition.<\/p><\/div>\n

Steve as usual provided the coordinates of the transition state, and I had a good look at the 3D structure (in fact, his post brilliantly illustrates the point of providing coordinates, because playing with them may always enable new aspects to be spotted). My annotation of the transition state (labelled TS1<\/strong>in Steve’s post) is shown below.<\/p>\n

\"\"

8+2 transition state. Click for 3D.<\/p><\/div>\n

The 8\u03c0 component has bonds forming on the nitrogen (and if it were pericyclic, on the ring carbon as well). If you load the 3D coordinates by clicking on the above graphic, you will see these two bonds appear to be forming from opposite faces of the\u00a08\u03c0 system. The term for this is antarafacial<\/em>. The 2\u03c0 component of the ketene is also twisted, and one can observe at least a hint that the two bonds to it are also from opposite faces (for more details, see this article<\/a> we published in 1993), again antarafacial<\/em>. It was only in 2005<\/a>\u00a0that it was recognised that a transition state with two antarafacial components would be 4n+2 aromatic (equivalent to a doubly twisted M\u00f6bius system), and it has to be said no good examples of this mode have yet to be observed experimentally. In fact, in the present example, that second bond does not go on to form in a concerted manner with the first, so the reaction is in fact stepwise and not pericyclic. But it does seems to at least initially have some features of a\u00a0doubly twisted M\u00f6bius cycloaddition. The IRC (intrinsic reaction coordinate) for TS1 which reveals the stepwise nature is in fact a classic (the lhs forms the zwitterion, typically with a small reverse barrier).<\/p>\n

\"\"<\/a>

Intrinsic reaction coordinate for TS1.<\/p><\/div>\n

\"\"<\/p>\n

    \n
  1. So on to the design. Attempt one is to remove the nucleophilic nitrogen lone pair, and the electrophilic carbonyl, thus suppressing the desire of the reaction to form a stable ionic intermediate. The cycloaddition between an octatetraene (the 8\u03c0 component) and ethene (the 2\u03c0 component), formally labelled as a\u00a0\u03c0<\/sub>8a<\/sub>+\u03c0<\/sub>2a<\/sub> cycloaddition, looks as below.<\/li>\n<\/ol>\n
    \"\"

    A Di-antarafacial 2+8 cycloaddition. Click for 3D.<\/p><\/div>\n

    In fact, this too is not a proper concerted transition state for a pericyclic reaction, since it has a second (albeit small) imaginary mode of 84 cm-1<\/sup> corresponding to desymmetrisation so that one bond forms before the other. Ethene, it seems, is not fond of cycloadding bonds antarafacially<\/em>. The transition state is however aromatic, with all the ring bonds of the correct length (~1.4\u00c5). In the interests of balance, I do have to note that a competing \u03c0<\/sub>8s<\/sub>+\u03c0<\/sub>2s\u00a0<\/sub>reaction is likely to be lower in energy.<\/p>\n

      \n
    • The design is now to try to convert that second negative force constant to a positive one. Let us try replacing ethene with O=C=C=O, which might object less to an antarafacial<\/em> mode across the central C=C bond. No luck there, the second mode is still imaginary (92i<\/em>). The pericyclic mode is also unusual, involving breaking the central OC-CO bond.
      \n
      \"\"

      8+2 cycloaddition involving carbon suboxide.<\/p><\/div>\n<\/li>\n

    • One more go, this time to replace ethene with cyclopropene (the double bond might be expected to be more reactive now). Still no luck (126i<\/em> cm-1<\/sup>).<\/li>\n
    • In fact, a more complete exploration reveals that all these various combinations exhibit the same behaviour; \u03c0<\/sub>6a<\/sub>+\u03c0<\/sub>4a<\/sub>, \u03c0<\/sub>10a<\/sub>+\u03c0<\/sub>4a<\/sub>, \u03c0<\/sub>8a<\/sub>+\u03c0<\/sub>6a<\/sub> and the\u00a0triple-twist M\u00f6bius\u00a0\u03c0<\/sub>4a<\/sub>+\u03c0<\/sub>4a<\/sub>+\u03c0<\/sub>4a<\/sub>.<\/li>\n<\/ul>\n

      This post attempts to show how one can take an experimental observation, couple it with some calculations, and see if anything out of the ordinary might emerge. One might then try to tweak the reaction to amplify any effects one might observe. In this case, it does seem that trying to coerce two antarafacial modes onto simple alkenes may not be possible.<\/p>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

      Steve Bachrach has blogged on the reaction shown below. If it were a pericyclic cycloaddition, both new bonds would form simultaneously, as shown with the indicated arrow pushing. Ten electrons would be involved, and in theory, the transition state would have 4n+2 aromaticity. In fact\u00a0Fernandez, Sierra and Torres have reported that they can trap an […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"activitypub_content_warning":"","activitypub_content_visibility":"","activitypub_max_image_attachments":5,"activitypub_interaction_policy_quote":"anyone","activitypub_status":"","footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[4],"tags":[620,619,24,625,410,2650,623,20,624],"ppma_author":[2661],"class_list":["post-4592","post","type-post","status-publish","format-standard","hentry","category-interesting-chemistry","tag-antarafacial","tag-cycloaddition","tag-energy","tag-fernandez","tag-mobius","tag-pericyclic","tag-sierra","tag-steve-bachrach","tag-torres"],"yoast_head":"\nThe stereochemistry of [8+2] pericyclic cycloadditions. - Henry Rzepa's Blog<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4592\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"The stereochemistry of [8+2] pericyclic cycloadditions. - Henry Rzepa's Blog\" \/>\n<meta property=\"og:description\" content=\"Steve Bachrach has blogged on the reaction shown below. If it were a pericyclic cycloaddition, both new bonds would form simultaneously, as shown with the indicated arrow pushing. Ten electrons would be involved, and in theory, the transition state would have 4n+2 aromaticity. In fact\u00a0Fernandez, Sierra and Torres have reported that they can trap an […]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4592\" \/>\n<meta property=\"og:site_name\" content=\"Henry Rzepa's Blog\" \/>\n<meta property=\"article:published_time\" content=\"2011-07-10T10:17:40+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2012-10-09T08:10:16+00:00\" \/>\n<meta property=\"og:image\" content=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/07\/2+8.jpg\" \/>\n<meta name=\"author\" content=\"Henry Rzepa\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Henry Rzepa\" \/>\n\t<meta name=\"twitter:label2\" content=\"Estimated reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"4 minutes\" \/>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"The stereochemistry of [8+2] pericyclic cycloadditions. - Henry Rzepa's Blog","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4592","og_locale":"en_GB","og_type":"article","og_title":"The stereochemistry of [8+2] pericyclic cycloadditions. - Henry Rzepa's Blog","og_description":"Steve Bachrach has blogged on the reaction shown below. If it were a pericyclic cycloaddition, both new bonds would form simultaneously, as shown with the indicated arrow pushing. Ten electrons would be involved, and in theory, the transition state would have 4n+2 aromaticity. In fact\u00a0Fernandez, Sierra and Torres have reported that they can trap an […]","og_url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4592","og_site_name":"Henry Rzepa's Blog","article_published_time":"2011-07-10T10:17:40+00:00","article_modified_time":"2012-10-09T08:10:16+00:00","og_image":[{"url":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/07\/2+8.jpg","type":"","width":"","height":""}],"author":"Henry Rzepa","twitter_card":"summary_large_image","twitter_misc":{"Written by":"Henry Rzepa","Estimated reading time":"4 minutes"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"Article","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4592#article","isPartOf":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4592"},"author":{"name":"Henry Rzepa","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#\/schema\/person\/2b40f7b9c872a4dc1547e040a11b6281"},"headline":"The stereochemistry of [8+2] pericyclic cycloadditions.","datePublished":"2011-07-10T10:17:40+00:00","dateModified":"2012-10-09T08:10:16+00:00","mainEntityOfPage":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4592"},"wordCount":767,"commentCount":2,"image":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4592#primaryimage"},"thumbnailUrl":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/07\/2+8.jpg","keywords":["antarafacial","cycloaddition","energy","Fernandez","M\u00f6bius","pericyclic","Sierra","Steve Bachrach","Torres"],"articleSection":["Interesting chemistry"],"inLanguage":"en-GB","potentialAction":[{"@type":"CommentAction","name":"Comment","target":["https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4592#respond"]}]},{"@type":"WebPage","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4592","url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4592","name":"The stereochemistry of [8+2] pericyclic cycloadditions. - Henry Rzepa's Blog","isPartOf":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#website"},"primaryImageOfPage":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4592#primaryimage"},"image":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4592#primaryimage"},"thumbnailUrl":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/07\/2+8.jpg","datePublished":"2011-07-10T10:17:40+00:00","dateModified":"2012-10-09T08:10:16+00:00","author":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#\/schema\/person\/2b40f7b9c872a4dc1547e040a11b6281"},"breadcrumb":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4592#breadcrumb"},"inLanguage":"en-GB","potentialAction":[{"@type":"ReadAction","target":["https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4592"]}]},{"@type":"ImageObject","inLanguage":"en-GB","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4592#primaryimage","url":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/07\/2+8.jpg","contentUrl":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/07\/2+8.jpg"},{"@type":"BreadcrumbList","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4592#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog"},{"@type":"ListItem","position":2,"name":"The stereochemistry of [8+2] pericyclic cycloadditions."}]},{"@type":"WebSite","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#website","url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/","name":"Henry Rzepa's Blog","description":"Chemistry with a twist","potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"en-GB"},{"@type":"Person","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#\/schema\/person\/2b40f7b9c872a4dc1547e040a11b6281","name":"Henry Rzepa","image":{"@type":"ImageObject","inLanguage":"en-GB","@id":"https:\/\/secure.gravatar.com\/avatar\/897b6740f7f599bca7942cdf7d7914af5988937ae0e3869ab09aebb87f26a731?s=96&d=blank&r=g370be3a7397865e4fd161aefeb0a5a85","url":"https:\/\/secure.gravatar.com\/avatar\/897b6740f7f599bca7942cdf7d7914af5988937ae0e3869ab09aebb87f26a731?s=96&d=blank&r=g","contentUrl":"https:\/\/secure.gravatar.com\/avatar\/897b6740f7f599bca7942cdf7d7914af5988937ae0e3869ab09aebb87f26a731?s=96&d=blank&r=g","caption":"Henry Rzepa"},"description":"Henry Rzepa is Emeritus Professor of Computational Chemistry at Imperial College London.","sameAs":["https:\/\/orcid.org\/0000-0002-8635-8390"],"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?author=1"}]}},"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/pDef7-1c4","jetpack-related-posts":[{"id":9,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=9","url_meta":{"origin":4592,"position":0},"title":"A Disrotatory 4n+2 electron anti-aromatic M\u00f6bius transition state for a thermal electrocyclic reaction.","author":"Henry Rzepa","date":"April 2, 2009","format":false,"excerpt":"Mauksch and Tsogoeva have recently published an article illustrating how a thermal electrocyclic reaction can proceed with distoratory ring closure, whilst simultaneously also exhibiting 4n electron M\u00f6bius-aromatic character. Why is this remarkable? Because the simple Woodward-Hoffmann rules state that a disrotatory thermal electrocyclic reaction should proceed via a H\u00fcckel-aromatic 4n+2\u2026","rel":"","context":"In "pericyclic"","block_context":{"text":"pericyclic","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=559"},"img":{"alt_text":"Electrocylization of [14] annulene","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2009\/04\/p322.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":11642,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=11642","url_meta":{"origin":4592,"position":1},"title":"Avoided (pericyclic) anti-aromaticity: Reactions of t-butyl-hydroxycarbene.","author":"Henry Rzepa","date":"November 13, 2013","format":false,"excerpt":"Not long ago, I described a cyclic carbene in which elevating the carbene lone pair into a \u03c0-system transformed it from a formally 4n-antiaromatic \u03c0-cycle into a 4n+2 aromatic \u03c0-cycle. From an entirely different area of chemistry, another example of this behaviour emerges; Schreiner's trapping and reactions of t-butyl-hydroxycarbene, as\u2026","rel":"","context":"In "pericyclic"","block_context":{"text":"pericyclic","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=559"},"img":{"alt_text":"H-mig","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2013\/11\/H-mig.gif?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":25633,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=25633","url_meta":{"origin":4592,"position":2},"title":"A new type of bispericyclic reaction: Cyclopropanone + butadiene.","author":"Henry Rzepa","date":"September 30, 2022","format":false,"excerpt":"The term bispericyclic reaction was famously coined by Caramella et al in 2002 to describe the unusual features of the apparently innocuous dimerisation of cyclopentadiene. It shows features of two paths for different pericyclic reactions, comprising a 2+4 cycloaddition in the early stages, but evolving into a (degenerate) pair of\u2026","rel":"","context":"In "reaction mechanism"","block_context":{"text":"reaction mechanism","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=1086"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2022\/09\/anomalous.gif?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":22774,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=22774","url_meta":{"origin":4592,"position":3},"title":"Trimerous pericyclic reactions.","author":"Henry Rzepa","date":"October 8, 2020","format":false,"excerpt":"I occasionally spot an old blog that emerges, if only briefly, as \"trending\". In this instance, only the second blog I ever wrote here, way back in 2009 as a follow up to this article. With something of that age, its always worth revisiting to see if any aspect needs\u2026","rel":"","context":"In "Curly arrows"","block_context":{"text":"Curly arrows","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=2327"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2020\/10\/10-1024x671.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":5655,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=5655","url_meta":{"origin":4592,"position":4},"title":"A modern take on pericyclic cycloaddition. Dimerisation of cis-butene","author":"Henry Rzepa","date":"November 28, 2011","format":false,"excerpt":"The \u03c02 + \u03c02 cyclodimerisation of cis-butene is the simplest cycloaddition reaction with stereochemical implications. I here give it the same treatment as I did previously for electrocyclic pericyclic reactions. The photochemical reaction is known to give a mixture of two tetramethylcyclobutanes in the ratio of 1.3:1.0, with the all-cis\u2026","rel":"","context":"In \"energy\"","block_context":{"text":"energy","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?tag=energy"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/11\/2%2B2-exo.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":10611,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=10611","url_meta":{"origin":4592,"position":5},"title":"Another Woodward pericyclic example dissected: all is not what it seems.","author":"Henry Rzepa","date":"May 22, 2013","format":false,"excerpt":"Here is another example gleaned from that Woodward essay of 1967 (Chem. Soc. Special Publications (Aromaticity), 1967, 21, 217-249), where all might not be what it seems. Woodward notes that the reaction between the (highly reactive) 1 does not occur. This is attributed to it being a disallowed \u03c06 +\u2026","rel":"","context":"In \"free energy barrier\"","block_context":{"text":"free energy barrier","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?tag=free-energy-barrier"},"img":{"alt_text":"w2+2+2","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2013\/05\/w2%2B2%2B2.gif?resize=350%2C200","width":350,"height":200},"classes":[]}],"jetpack_likes_enabled":false,"authors":[{"term_id":2661,"user_id":1,"is_guest":0,"slug":"admin","display_name":"Henry Rzepa","avatar_url":"https:\/\/secure.gravatar.com\/avatar\/897b6740f7f599bca7942cdf7d7914af5988937ae0e3869ab09aebb87f26a731?s=96&d=blank&r=g","0":null,"1":"","2":"","3":"","4":"","5":"","6":"","7":"","8":""}],"_links":{"self":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/4592","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=4592"}],"version-history":[{"count":6,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/4592\/revisions"}],"predecessor-version":[{"id":7915,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/4592\/revisions\/7915"}],"wp:attachment":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=4592"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=4592"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=4592"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fppma_author&post=4592"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}