{"id":13676,"date":"2015-03-20T11:12:25","date_gmt":"2015-03-20T11:12:25","guid":{"rendered":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=13676"},"modified":"2015-03-20T11:19:49","modified_gmt":"2015-03-20T11:19:49","slug":"ionizing-yet-more-ultra-strong-acids-with-water-molecules","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=13676","title":{"rendered":"Ionizing yet more ultra-strong acids with water molecules."},"content":{"rendered":"
\n

This might be seen as cranking a handle by producing yet more examples of acids ionised by a small number of water molecules. I justify it (probably only to myself) as an exercise in how a scientist might approach a problem, and how it linearly develops with time, not necessarily in the directions first envisaged. A conventional scientific narrative published in a conventional journal tells the story often with the benefit of hindsight, but rarely how the project actually unfolded chronologically.\u2021<\/sup> So by devoting 7 posts to this, you can judge for yourself how my thoughts might have developed (and I am prepared to acknowledge this may only serve to show my ignorance).<\/p>\n

To pick up the story where it ended in the 6th post, I set off to hunt<\/a> for a strong acid that might require precisely two water molecules to ionise it. So here are some more candidates:<\/p>\n\n\n\n\n\n\n\n\n\n\n
Acid<\/th>\nAcid…H length, \u00c5<\/th>\nOH length\u00a0in 2H2<\/sub>O<\/th>\nData-DOI<\/th>\n<\/tr>\n
bis-triflylamine<\/a><\/td>\nNH=1.056<\/td>\n1.622<\/td>\n[1]<\/a><\/span><\/td>\n<\/tr>\n
bis-triflylamine<\/td>\nOH=1.575<\/td>\n1.007<\/td>\n[2]<\/a><\/span><\/td>\n<\/tr>\n
Perchloric acid<\/td>\n1.024<\/td>\n1.540<\/td>\n[3]<\/a><\/span><\/td>\n<\/tr>\n
Perchloric acid<\/td>\n1.514<\/span> <\/strong>(3H2<\/sub>O)<\/td>\n1.026<\/span><\/strong>\u00a0(3H2<\/sub>O)<\/td>\n[4]<\/a><\/span><\/td>\n<\/tr>\n
Perbromic acid<\/a><\/td>\n1.030<\/td>\n1.518<\/td>\n[5]<\/a><\/span><\/td>\n<\/tr>\n
Fluorosulfonic acid<\/td>\n1.028<\/td>\n1.504<\/td>\n[6]<\/a><\/span><\/td>\n<\/tr>\n
Fluoroselenic acid<\/td>\n1.025<\/td>\n1.522<\/td>\n[7]<\/a><\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Of these, perchloric acid is thought to be stronger than eg HBr, and indeed whereas the latter requires four water<\/a> molecules for ionization, the former seems to require only three (I include this in the table above to show what happens to the bond lengths upon ionisation). But two is not quite enough, although it does appear to be on the edge. Nor does perbromic acid achieve this, or fluorosulfonic or fluoroselenic acids.<\/p>\n

This search also illustrates another proclivity of humans, to set themselves targets, and on occasion fairly pointless targets. But one never knows whether even an apparently pointless target at the outset might not result in the discovery of something much more unexpected (even climbing Mt Everest might have brought some benefits to humanity, although I cannot name one here). I think a fair few discoveries have gone down that route. But, sadly, the hunt for acids ionized by precisely two water molecules in the gas-phase has not (yet?) borne such fruits.<\/p>\n

\n

\u2021<\/sup>We recently tried to write an article in such a chronological fashion. We had a hypothesis, initially thought we might be able to prove it, did more experiments and ultimately proved the hypothesis wrong (in solution!). The referees did not take to this perhaps slightly too honest account of our efforts. Since the hypothesis was wrong, why did we need to publish the story? Well, it did get published in the end, and you can make your own mind up.[8]<\/a><\/span><\/p>\n

\n

References<\/h2>\n
  1. H.S. Rzepa, \"C 2 H 5 F 6 N 1 O 6 S 2\", 2015. https:\/\/doi.org\/10.14469\/ch\/191136<\/a>\n\n<\/li>\n
  2. H.S. Rzepa, \"C 2 H 5 F 6 N 1 O 6 S 2\", 2015. https:\/\/doi.org\/10.14469\/ch\/191137<\/a>\n\n<\/li>\n
  3. H.S. Rzepa, \"H 5 Cl 1 O 6\", 2015. https:\/\/doi.org\/10.14469\/ch\/191139<\/a>\n\n<\/li>\n
  4. H.S. Rzepa, \"H 7 Cl 1 O 7\", 2015. https:\/\/doi.org\/10.14469\/ch\/191138<\/a>\n\n<\/li>\n
  5. H.S. Rzepa, \"H 5 Br 1 O 6\", 2015. https:\/\/doi.org\/10.14469\/ch\/191140<\/a>\n\n<\/li>\n
  6. H.S. Rzepa, \"H 5 F 1 O 5 S 1\", 2015. https:\/\/doi.org\/10.14469\/ch\/191143<\/a>\n\n<\/li>\n
  7. H.S. Rzepa, \"H 5 F 1 O 5 Se 1\", 2015. https:\/\/doi.org\/10.14469\/ch\/191141<\/a>\n\n<\/li>\n
  8. P. Bultinck, F.L. Cherblanc, M.J. Fuchter, W.A. Herrebout, Y. Lo, H.S. Rzepa, G. Siligardi, and M. Weimar, \"Chiroptical Studies on Brevianamide B: Vibrational and Electronic Circular Dichroism Confronted\", The Journal of Organic Chemistry<\/i>, vol. 80, pp. 3359-3367, 2015. https:\/\/doi.org\/10.1021\/jo5022647<\/a>\n\n<\/li>\n<\/ol>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

    This might be seen as cranking a handle by producing yet more examples of acids ionised by a small number of water molecules. I justify it (probably only to myself) as an exercise in how a scientist might approach a problem, and how it linearly develops with time, not necessarily in the directions first envisaged. […]<\/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":[4],"tags":[53,437],"ppma_author":[2661],"class_list":["post-13676","post","type-post","status-publish","format-standard","hentry","category-interesting-chemistry","tag-mt-everest","tag-scientist"],"yoast_head":"\nIonizing yet more ultra-strong acids with water molecules. - 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=13676\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Ionizing yet more ultra-strong acids with water molecules. - Henry Rzepa's Blog\" \/>\n<meta property=\"og:description\" content=\"This might be seen as cranking a handle by producing yet more examples of acids ionised by a small number of water molecules. 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Here I try out some even stronger acids to see\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":17279,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17279","url_meta":{"origin":13676,"position":1},"title":"The dipole moments of highly polar molecules: glycine zwitterion.","author":"Henry Rzepa","date":"December 24, 2016","format":false,"excerpt":"The previous posts produced discussion about the dipole moments of highly polar molecules. Here to produce some reference points for further discussion I look at the dipole moment of glycine, the classic\u00a0zwitterion (an internal ion-pair). Dielectric relaxation studies of glycine-water mixtures yield values that range from\u00a015.7D to 11.9D although these\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\/2016\/12\/051.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":13645,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=13645","url_meta":{"origin":13676,"position":2},"title":"A 5-high straight flush of water-ionised acids?","author":"Henry Rzepa","date":"March 17, 2015","format":false,"excerpt":"I do not play poker,\u2021 and so I had to look up a 5-4-3-2-1(A), which Wikipedia informs me is a 5-high straight flush, also apparently known as a steel wheel. In previous posts \u00a0I have suggested acids which can be ionised by (probably)\u00a05, 4, 3 or \u00a01 discrete water molecules\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":25391,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=25391","url_meta":{"origin":13676,"position":3},"title":"Unexpected Isomerization of Oxetane-Carboxylic Acids \u2013 catalyst design.","author":"Henry Rzepa","date":"August 13, 2022","format":false,"excerpt":"Previously, a mechanism with a reasonable predicted energy was modelled for the isomerisation of an oxetane carboxylic acid to a lactone by using two further molecules of acid to transfer the proton and in the process encouraging an Sn2 reaction with inversion to open the oxetane ring. We are now\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":"","width":0,"height":0},"classes":[]},{"id":13899,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=13899","url_meta":{"origin":13676,"position":4},"title":"The mechanism of borohydride reductions. Part 1: ethanal.","author":"Henry Rzepa","date":"April 12, 2015","format":false,"excerpt":"Sodium borohydride is the tamer cousin of lithium aluminium hydride (LAH). It is used in aqueous solution to e.g. reduce aldehydes and ketones, but it leaves acids, amides and esters alone. Here I start an exploration of why it is such a different reducing agent. Initially, I am using Li,\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":"","width":0,"height":0},"classes":[]},{"id":13506,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=13506","url_meta":{"origin":13676,"position":5},"title":"How many water molecules does it take to ionise HCN\/HNC? An NCI exploration.","author":"Henry Rzepa","date":"March 2, 2015","format":false,"excerpt":"HCN is a weak acid (pKa +9.2, weaker than e.g. HF), although it does have an isomer, isocyanic\u00a0acid or HNC (pka < +9.2 ?) which is simultaneously stronger and less stable. I conclude my halide acid series\u00a0by investigating how many water molecules (in gas phase clusters) are required for ionisation\u2026","rel":"","context":"In "General"","block_context":{"text":"General","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=1"},"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\/13676","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=13676"}],"version-history":[{"count":10,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/13676\/revisions"}],"predecessor-version":[{"id":13686,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/13676\/revisions\/13686"}],"wp:attachment":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=13676"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=13676"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=13676"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fppma_author&post=13676"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}