{"id":23973,"date":"2021-07-01T12:41:53","date_gmt":"2021-07-01T11:41:53","guid":{"rendered":"https:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=23973"},"modified":"2021-07-21T14:50:28","modified_gmt":"2021-07-21T13:50:28","slug":"two-record-breakers-for-the-anomeric-effect-one-real-the-other-not","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23973","title":{"rendered":"Two record breakers for the anomeric effect; one real, the other not."},"content":{"rendered":"
\n

The classic anomeric effect operates across a carbon atom attached to oxygens. One (of the two) lone pairs on the oxygen can donate into the \u03c3* orbital of the C-O of the other oxygen (e.g.<\/i> the red arrows) tending to weaken that bond whilst strengthening the donor oxygen C-O bond. Vice versa<\/em> means e.g.<\/em> the blue arrows weakening the other C-O bond. This effect tends to increase charge separation and the question then arises: how large can this effect get? To try to find out, we are going to do some crystal structure mining in this post! \"\"<\/a><\/p>\n

I need to list the parameters defining this crystal mining.<\/p>\n

    \n
  1. Firstly, we note that the donating lone pair has to overlap in an anti-periplanar fashion with the C-O bond that is going to weaken. To get a handle on this overlap we are going to define the absolute value of the two torsion angles, T1 and T2 (minimum value 0\u00b0 and maximum value\u00a0180\u00b0). Since a lone pair has no defined position in crystallographic coordinates, we will have to infer the angle of the lone pair from that of the torsion angles RO-CO and R’O-CO, which will then constitute a measure of how the oxygen lone pairs are oriented.<\/li>\n
  2. If T1 or T2 have values of ~60\u00b0 we might infer that one lone pair torsion may have a value of 60+120\u00b0 = 180\u00b0 and therefore that it is indeed antiperiplanar to a C-O bond.<\/li>\n
  3. Next we define the two C-O distances. If BOTH the oxygen lone pairs are oriented at ~180\u00b0 to the C-O bond, then both the red and the blue resonances can occur more or less equally and so each C-O bonds is both strengthened and weakened. The anomeric effect operates in both directions, meaning the two C-O bond lengths are more or less equal in length.<\/li>\n
  4. If however only one of the lone pair torsions is 180\u00b0 and not the other, a bond length inequality will be set up, which can be detected crystallographically.<\/li>\n<\/ol>\n

    Now for a search of the Cambridge crystal structure database. The definition is shown below, and included constraining the central carbon to 4-coordination (R = C or H), no errors and R < 0.05.\u00a0<\/p>\n

    \"\"<\/a>\n<\/p>\n

    Firstly the result for the two C-O distances. The point ringed in red is clearly an error, but the two ringed in green are real (IFJIO and IFEJUA) for which extreme inequality of the two C-O bond lengths appears. But before discussing this, I note that there is a double “hot spot” (red) for which the two C-O distances are more or less equal.\"\"<\/a><\/p>\n

    By constraining one of the R groups to R=H, a single hot spot is obtained showing unequal bond lengths (~1.395, 1.430\u00c5) whilst the double hot spot only appears when both R are C. Something \u00a0interesting \u00a0going \u00a0on \u00a0there?\"\"<\/a><\/p>\n

    Next, a torsion plot is more directly revealing of an operating anomeric effect. The hot spot appears at values of each torsion of 60\u00b0 which suggests that the most common conformation for these molecules is to have both<\/strong> oxygen atoms aligning with one lone pair antiperiplanar to the other C-O bond. This would not result in bond length inequality.<\/p>\n

    \"\"<\/a><\/p>\n

    However, the remaining distribution shows both a vertical and a horizontal distribution in which only one of the oxygen atoms aligns a lone pair antiperiplanar to the C-O bond. According to the argument presented above, these should show bond length inequality. To check that the distribution above is not due to constraints of rings, a search in which both C-O bonds are specified as acyclic (i.e. not part of a ring) reveals the same effect.<\/p>\n

    \"\"<\/a><\/p>\n

    Next, we combine both the distance and the torsion values as below. The mean of both torsion angles at 60\u00b0 is again a hot-spot and this is associated with no difference in the two bond lengths. Conversely, the maximum difference in the bond lengths occurs at a mean torsion of ~ 90\u00b0, which can occur when the individual torsions are 60 and 120\u00b0, the former of which implies a lone pair is antiperiplanar to the \u00a0C-O bond. The rings again correspond to those identified above.\u00a0<\/p>\n

    \"\"<\/a><\/p>\n

    Now to investigate those ringed molecules. The red one is SUCROS35[1]<\/a><\/span> which was reported in 2012 as a high pressure polymorph of sucrose in which the hydrogen bonding pattern of regular sucrose has been substantially modified. Could application of pressure really induce an enormous anomeric effect?<\/p>\n

    \"\"<\/a>

    SUCROS35<\/p><\/div>\n

    One way of applying a “reality check” is to calculate the geometry at a high level DFT level (\u03c9B97XF\/Def2-TZVPPD) which reveals that the three C-O bond lengths annotated above are predicted as 1.400, 1.416 and 1.392\u00c5 (FAIR Data DOI: 10.14469\/hpc\/8374<\/a>). These are regular C-O lengths and exhibit nothing unusual. We might conclude that the crystal data for this specific set of coordinates is in error and should certainly be re-investigated.\u00a0<\/p>\n

    The two real examples of large bond length difference are both related[2]<\/a><\/span> and the larger of which is the version with R=H,C rather than R=C,C. The example with \u00a0R=H is certainly augmented because of the hydrogen bond set up to the triflate group, which tends to forming an oxyanion, which is a stronger electron donor than e.g. methoxy.<\/p>\n

    \"\"<\/a>

    IFEJIO<\/p><\/div>

    \"\"<\/a>

    IFEJUA<\/p><\/div><\/p>\n

    The reason for these record breakers is that the anomeric effect in this case induces not so much charge separation as charge relocation<\/strong>. One way of quantifying the effect is to calculate the NBO E(2) interaction term between the donating oxygen lone pair and the accepting\u00a0C-O\u00a0\u03c3* orbital. Click on the image below to view this interaction (blue = magenta; red = orange). <\/p>\n

    \"\"<\/p>\n

    The values are 60.8 (IFEJIO, structure at DOI: 10.5517\/cc111jxj<\/a>), 46.5 (IFEJUA, structure at DOI:\u00a010.5517\/cc111jyk<\/a>) and 20.8 (SUCROS35, structure at DOI: 10.5517\/ccx16sx<\/a>) kcal\/mol. The latter in fact corresponds to a “normal” anomeric effect, which shows that our two record breakers are more than twice as large!<\/p>\n

    I conclude by noting that in the above distribution plots, there are five or so other “outliers” which need verifying and which may also prove interesting. \u00a0We have yet to find the largest anomeric effect exhibiting charge separation rather than relocation.<\/p>\n

    References<\/h2>\n
    1. E. Patyk, J. Skumiel, M. Podsiad\u0142o, and A. Katrusiak, \"High\u2010Pressure (+)\u2010Sucrose Polymorph\", Angewandte Chemie International Edition<\/i>, vol. 51, pp. 2146-2150, 2012. https:\/\/doi.org\/10.1002\/anie.201107283<\/a>\n\n<\/li>\n
    2. G. Gunbas, W.L. Sheppard, J.C. Fettinger, M.M. Olmstead, and M. Mascal, \"Extreme Oxatriquinanes: Structural Characterization of \u03b1-Oxyoxonium Species with Extraordinarily Long Carbon\u2013Oxygen Bonds\", Journal of the American Chemical Society<\/i>, vol. 135, pp. 8173-8176, 2013. https:\/\/doi.org\/10.1021\/ja4032715<\/a>\n\n<\/li>\n<\/ol>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

      The classic anomeric effect operates across a carbon atom attached to oxygens. One (of the two) lone pairs on the oxygen can donate into the \u03c3* orbital of the C-O of the other oxygen (e.g. the red arrows) tending to weaken that bond whilst strengthening the donor oxygen C-O bond. Vice versa means e.g. the […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_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":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[1745],"tags":[],"ppma_author":[2661],"class_list":["post-23973","post","type-post","status-publish","format-standard","hentry","category-crystal_structure_mining"],"yoast_head":"\nTwo record breakers for the anomeric effect; one real, the other not. - 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=23973\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Two record breakers for the anomeric effect; one real, the other not. - Henry Rzepa's Blog\" \/>\n<meta property=\"og:description\" content=\"The classic anomeric effect operates across a carbon atom attached to oxygens. One (of the two) lone pairs on the oxygen can donate into the \u03c3* orbital of the C-O of the other oxygen (e.g. the red arrows) tending to weaken that bond whilst strengthening the donor oxygen C-O bond. Vice versa means e.g. the […]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23973\" \/>\n<meta property=\"og:site_name\" content=\"Henry Rzepa's Blog\" \/>\n<meta property=\"article:published_time\" content=\"2021-07-01T11:41:53+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2021-07-21T13:50:28+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2021\/07\/anomeric.svg\" \/>\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=\"5 minutes\" \/>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"Two record breakers for the anomeric effect; one real, the other not. - 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=23973","og_locale":"en_GB","og_type":"article","og_title":"Two record breakers for the anomeric effect; one real, the other not. - Henry Rzepa's Blog","og_description":"The classic anomeric effect operates across a carbon atom attached to oxygens. One (of the two) lone pairs on the oxygen can donate into the \u03c3* orbital of the C-O of the other oxygen (e.g. the red arrows) tending to weaken that bond whilst strengthening the donor oxygen C-O bond. Vice versa means e.g. the […]","og_url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23973","og_site_name":"Henry Rzepa's Blog","article_published_time":"2021-07-01T11:41:53+00:00","article_modified_time":"2021-07-21T13:50:28+00:00","og_image":[{"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2021\/07\/anomeric.svg","type":"","width":"","height":""}],"author":"Henry Rzepa","twitter_card":"summary_large_image","twitter_misc":{"Written by":"Henry Rzepa","Estimated reading time":"5 minutes"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"Article","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23973#article","isPartOf":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23973"},"author":{"name":"Henry Rzepa","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#\/schema\/person\/2b40f7b9c872a4dc1547e040a11b6281"},"headline":"Two record breakers for the anomeric effect; one real, the other not.","datePublished":"2021-07-01T11:41:53+00:00","dateModified":"2021-07-21T13:50:28+00:00","mainEntityOfPage":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23973"},"wordCount":1045,"commentCount":0,"image":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23973#primaryimage"},"thumbnailUrl":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2021\/07\/anomeric.svg","articleSection":["crystal_structure_mining"],"inLanguage":"en-GB","potentialAction":[{"@type":"CommentAction","name":"Comment","target":["https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23973#respond"]}]},{"@type":"WebPage","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23973","url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23973","name":"Two record breakers for the anomeric effect; one real, the other not. - 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=23973#primaryimage"},"image":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23973#primaryimage"},"thumbnailUrl":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2021\/07\/anomeric.svg","datePublished":"2021-07-01T11:41:53+00:00","dateModified":"2021-07-21T13:50:28+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=23973#breadcrumb"},"inLanguage":"en-GB","potentialAction":[{"@type":"ReadAction","target":["https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23973"]}]},{"@type":"ImageObject","inLanguage":"en-GB","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23973#primaryimage","url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2021\/07\/anomeric.svg","contentUrl":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2021\/07\/anomeric.svg"},{"@type":"BreadcrumbList","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23973#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog"},{"@type":"ListItem","position":2,"name":"Two record breakers for the anomeric effect; one real, the other not."}]},{"@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\/pDef7-6eF","jetpack-related-posts":[{"id":24019,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=24019","url_meta":{"origin":23973,"position":0},"title":"More record breakers for the anomeric effect involving C-N bonds.","author":"Henry Rzepa","date":"September 4, 2021","format":false,"excerpt":"An earlier post investigated large anomeric effects involving two oxygen atoms attached to a common carbon atom. A variation is to replace one oxygen by a nitrogen atom, as in N-C-O. Shown below is a scatter plot of the two distances to the common carbon atom derived from crystal structures.\u2026","rel":"","context":"In "crystal_structure_mining"","block_context":{"text":"crystal_structure_mining","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=1745"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2021\/07\/N-C-O-distances-1024x758.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":6361,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=6361","url_meta":{"origin":23973,"position":1},"title":"Spotting the unexpected. The trifluoromeric effect in the hydration of the carbonyl group.","author":"Henry Rzepa","date":"March 9, 2012","format":false,"excerpt":"The equilibrium for the hydration of a ketone to form a gem-diol hydrate is known to be highly sensitive to substituents. Consider the two equilibria: For propanone, it lies almost entirely on the left, whereas for the hexafluoro derivative it is almost entirely on the right. The standard answer to\u2026","rel":"","context":"In "Interesting chemistry"","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2012\/03\/diol.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":14508,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=14508","url_meta":{"origin":23973,"position":2},"title":"A visualization of the anomeric effect from crystal structures.","author":"Henry Rzepa","date":"August 27, 2015","format":false,"excerpt":"The anomeric effect is best known in sugars, occuring in sub-structures such as RO-C-OR. Its origins relate to how the lone pairs on each oxygen atom align with the adjacent C-O bonds. When the alignment is 180\u00b0, one oxygen lone pair can donate into the C-O \u03c3* empty orbital and\u2026","rel":"","context":"In "Chemical IT"","block_context":{"text":"Chemical IT","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=2"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":16601,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=16601","url_meta":{"origin":23973,"position":3},"title":"Anomeric effects at boron, silicon and phosphorus.","author":"Henry Rzepa","date":"July 1, 2016","format":false,"excerpt":"The anomeric effect occurs at 4-coordinate (sp3) carbon centres carrying two oxygen substituents and involves an alignment of a lone electron pair\u00a0on one oxygen with the adjacent C-O \u03c3*-bond of the other oxygen. Here I explore whether other centres can exhibit the phenomenon. I start with 4-coordinate boron, using the\u2026","rel":"","context":"In "crystal_structure_mining"","block_context":{"text":"crystal_structure_mining","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=1745"},"img":{"alt_text":"anomeric-bo-sq","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2016\/06\/anomeric-bo-sq-1024x644.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":26896,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=26896","url_meta":{"origin":23973,"position":4},"title":"Detecting anomeric effects in tetrahedral carbon bearing four oxygen substituents.","author":"Henry Rzepa","date":"March 18, 2024","format":false,"excerpt":"I have written a few times about the so-called \"anomeric effect\", which relates to stereoelectronic interactions in molecules such as sugars bearing a tetrahedral carbon atom with at least two oxygen substituents. The effect can be detected when the two C-O bond lengths in such molecules are inspected, most obviously\u2026","rel":"","context":"In \"Interesting chemistry\"","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?tag=interesting-chemistry"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2024\/03\/SILDOH.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2024\/03\/SILDOH.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2024\/03\/SILDOH.jpg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2024\/03\/SILDOH.jpg?resize=700%2C400&ssl=1 2x, https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2024\/03\/SILDOH.jpg?resize=1050%2C600&ssl=1 3x, https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2024\/03\/SILDOH.jpg?resize=1400%2C800&ssl=1 4x"},"classes":[]},{"id":22471,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=22471","url_meta":{"origin":23973,"position":5},"title":"Fascinating stereoelectronic control in Metaldehyde and Chloral.","author":"Henry Rzepa","date":"June 9, 2020","format":false,"excerpt":"Metaldehyde is an insecticide used to control slugs. When we unsuccessfully tried to get some recently, I discovered it is now deprecated in the UK. So my immediate reaction was to look up its structure to see if that cast any light (below, R=CH3, shown as one stereoisomer). A X-ray\u2026","rel":"","context":"In "crystal_structure_mining"","block_context":{"text":"crystal_structure_mining","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=1745"},"img":{"alt_text":"","src":"","width":0,"height":0},"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\/23973","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=23973"}],"version-history":[{"count":32,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/23973\/revisions"}],"predecessor-version":[{"id":24074,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/23973\/revisions\/24074"}],"wp:attachment":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=23973"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=23973"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=23973"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fppma_author&post=23973"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}