{"id":24045,"date":"2021-07-22T08:30:51","date_gmt":"2021-07-22T07:30:51","guid":{"rendered":"https:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=24045"},"modified":"2021-07-22T08:37:00","modified_gmt":"2021-07-22T07:37:00","slug":"another-very-large-anomeric-effect-with-a-twist","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=24045","title":{"rendered":"Another very large anomeric effect – with a twist."},"content":{"rendered":"
\n

In the earlier post on the topic of anomeric effects, I identified <\/a>a number of outliers associated with large differences in the lengths of two carbon-oxygen bonds sharing a common carbon atom.<\/p>\n

\"\"<\/p>\n

Here is another of these outliers (MUZZIS[1]<\/a><\/span>) which shows equally unusual properties. This is an oxyanion (counterion is trimethylbenzylammonium) which is part of a very strong O-H-O hydrogen bond in which the\u00a0O…O distance is\u00a02.44\u00c5 and the O-H distances are each indicated as 1.23\u00c5, suggesting the hydrogen is symmetrically disposed about the two oxygens. The anomerically lengthened C-O bonds (shown in red below) are\u00a01.513\/1.516\u00c5, which is indeed long for a\u00a0C-O bond.<\/p>\n

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

A \u03c9B97XD\/Def2-SVPP\/SCRF=chloroform calculation reveals a less symmetrical hydrogen bonding system, with calculated\u00a0O-H distances of 1.046\/1.434 (mean 1.24\u00c5) and an O-O distance of 2.48\u00c5. The anomerically lengthened C-O distances are 1.479\/1.582\u00c5. There are several reasons for these differences:<\/p>\n

    \n
  1. The temperature at which the X-ray data were recorded was 173K and it remains possible that the data represent an averaged position for the atoms at this temperature rather than a truly symmetrical hydrogen bond.<\/li>\n
  2. The basis set\/DFT method for the calculation may itself favour unsymmetrical hydrogen bonds.<\/li>\n<\/ol>\n

    The two\u00a0NBO energy perturbation terms<\/a> for one lone pair on the oxygens interacting with the empty C-O\u00a0\u03c3* orbital are 31.6 and 57.5 kcal\/mol. If the hydrogen bond is in reality entirely symmetric, then the NBO term would be expected to be approximately the average of these two values.<\/p>\n

    \"\"

    Click image to obtain 3D model<\/p><\/div>\n

    The earlier record anomeric holder<\/a> achieved this by virtue of charge relocation involving an oxenium cation rather than the normal effect of charge separation. Here we have a similar effect, this time involving oxy-anionic charge relocation. Both are therefore special cases.<\/p>\n

    References<\/h2>\n
    1. R. Bengiat, M. Gil, A. Klein, B. Bogoslavsky, S. Cohen, and J. Almog, \"Bis(benzyltrimethylammonium) bis[(4<i>SR<\/i>,12<i>SR<\/i>,18<i>RS<\/i>,26<i>RS<\/i>)-4,18,26-trihydroxy-12-oxido-13,17-dioxaheptacyclo[14.10.0.0<sup>3,14<\/sup>.0<sup>4,12<\/sup>.0<sup>6,11<\/sup>.0<sup>18,26<\/sup>.0<sup>19,24<\/sup>]hexacosa-1,3(14),6,8,10,15,19,21,23-nonaene-5,25-dione] sesquihydrate: dimeric structure formation<i>via<\/i>[O\u2014H\u2014O]<sup>\u2212<\/sup><i>negative charge-assisted hydrogen bonds (\u2013CAHB)<\/i>with benzyltrimethylammonium counter-ions\", Acta Crystallographica Section E Crystallographic Communications<\/i>, vol. 72, pp. 399-402, 2016. https:\/\/doi.org\/10.1107\/s2056989016002899<\/a>\n\n<\/li>\n<\/ol>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

      In the earlier post on the topic of anomeric effects, I identified a number of outliers associated with large differences in the lengths of two carbon-oxygen bonds sharing a common carbon atom. Here is another of these outliers (MUZZIS) which shows equally unusual properties. This is an oxyanion (counterion is trimethylbenzylammonium) which is part of […]<\/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":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[1745],"tags":[],"ppma_author":[2661],"class_list":["post-24045","post","type-post","status-publish","format-standard","hentry","category-crystal_structure_mining"],"yoast_head":"\nAnother very large anomeric effect - with a twist. - 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=24045\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Another very large anomeric effect - with a twist. - Henry Rzepa's Blog\" \/>\n<meta property=\"og:description\" content=\"In the earlier post on the topic of anomeric effects, I identified a number of outliers associated with large differences in the lengths of two carbon-oxygen bonds sharing a common carbon atom. Here is another of these outliers (MUZZIS) which shows equally unusual properties. This is an oxyanion (counterion is trimethylbenzylammonium) which is part of […]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=24045\" \/>\n<meta property=\"og:site_name\" content=\"Henry Rzepa's Blog\" \/>\n<meta property=\"article:published_time\" content=\"2021-07-22T07:30:51+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2021-07-22T07:37:00+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2021\/07\/dist-vs-dist-1024x747.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=\"1 minute\" \/>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"Another very large anomeric effect - with a twist. - 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=24045","og_locale":"en_GB","og_type":"article","og_title":"Another very large anomeric effect - with a twist. - Henry Rzepa's Blog","og_description":"In the earlier post on the topic of anomeric effects, I identified a number of outliers associated with large differences in the lengths of two carbon-oxygen bonds sharing a common carbon atom. Here is another of these outliers (MUZZIS) which shows equally unusual properties. 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Each oxygen itself bears two bonds and has two lone pairs, and either of these can align with one of three other C-O bonds to generate an anomeric\u2026","rel":"","context":"Similar post","block_context":{"text":"Similar post","link":""},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2024\/04\/Screenshot-304.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\/04\/Screenshot-304.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2024\/04\/Screenshot-304.jpg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2024\/04\/Screenshot-304.jpg?resize=700%2C400&ssl=1 2x"},"classes":[]},{"id":23973,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23973","url_meta":{"origin":24045,"position":1},"title":"Two record breakers for the anomeric effect; one real, the other not.","author":"Henry Rzepa","date":"July 1, 2021","format":false,"excerpt":"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.\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\/dist-vs-dist-1024x747.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":16696,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=16696","url_meta":{"origin":24045,"position":2},"title":"A periodic table for anomeric centres, this time with quantified interactions.","author":"Henry Rzepa","date":"August 8, 2016","format":false,"excerpt":"The previous post contained an exploration of the anomeric effect as it occurs at an atom centre X for which the effect is manifest in crystal structures. Here I\u00a0quantify the effect, by selecting the test molecule MeO-X-OMe, where X is of two types:A two-coordinate atom across the series B-O and\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":"","width":0,"height":0},"classes":[]},{"id":26009,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=26009","url_meta":{"origin":24045,"position":3},"title":"Tunable aromaticity? An unrecognized new aromatic molecule?","author":"Henry Rzepa","date":"May 21, 2023","format":false,"excerpt":"Some time ago in 2010, I showed a chemical problem I used to set during university entrance interviews. It was all about pattern recognition and how one can develop a hypothesis based on this. In that instance, it involved recognising that a cyclic molecule which appeared to have the cyclohexatriene\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":[]},{"id":24019,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=24019","url_meta":{"origin":24045,"position":4},"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":16601,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=16601","url_meta":{"origin":24045,"position":5},"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":[]}],"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\/24045","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=24045"}],"version-history":[{"count":22,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/24045\/revisions"}],"predecessor-version":[{"id":24109,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/24045\/revisions\/24109"}],"wp:attachment":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=24045"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=24045"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=24045"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fppma_author&post=24045"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}