{"id":2798,"date":"2010-11-17T20:55:11","date_gmt":"2010-11-17T19:55:11","guid":{"rendered":"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=2798"},"modified":"2011-06-12T09:14:39","modified_gmt":"2011-06-12T09:14:39","slug":"a-historical-detective-story-120-year-old-crystals","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=2798","title":{"rendered":"A historical detective story: 120 year old crystals"},"content":{"rendered":"
\n

In 1890, chemists had to work hard to find out what the structures of their molecules were, given they had no access to the plethora of modern techniques we are used to in 2010. For example, how could they be sure what the structure of naphthalene was? Well, two such chemists, William Henry Armstrong (1847-1937) and his student William Palmer Wynne (1861-1950; I might note that despite working with toxic chemicals for years, both made it to the ripe old age of ~90!) set out on an epic 11-year journey to synthesize all possible mono, di, tri and tetra-substituted naphthalenes. Tabulating how many isomers they could make (we will call them AW here)\u00a0would establish beyond doubt the basic connectivity of the naphthalene ring system. This was in fact very important, since many industrial dyes were based on this ring system, and patents depended on getting it correct! Amazingly, their collection of naphthalenes survives to this day. With the passage of 120 years, we can go back and check their assignments. The catalogued collection<\/a> (located at Imperial College) comprises\u00a0263 <\/strong>specimens. Here the focus is on just one, specimen number number 22<\/strong>, which bears an original label of trichloronaphthalene [2:3:1]<\/em> and for which was claimed a melting point of 109.5\u00b0C. What caught our attention is that a search for this compound in modern databases (Reaxys if you are interested, what used to be called Beilstein) reveals the compound to have a melting point of ~84\u00b0C. So, are alarm bells ringing? Did AW make a big error? Were many of the patented dyes not what they seemed?<\/p>\n

\"\"<\/a>

1,2,3-trichloronaphthalene<\/p><\/div>\n

The story starts to get murky when Reaxys reports the earliest literature for this compound as being 1941 (DOI: 10.1039\/JR9410000243<\/a>), the authority being Wynne himself (now a sprightly 80). The collection of 263 specimens was thought to go back to the 1890s, so how could it contain a compound only made about 50 years later? Time to do an X-ray determination. Remarkably, the 120 year old crystals of specimen 22<\/strong> were still in good shape, but the determined structure held an initial surprise. The compound was in fact 1,6,7-trichloronaphthalene, quite a different species from the label.<\/p>\n

\"\"<\/a>

1,6,7-trichloronaphthalene<\/p><\/div>\n

So, did AW get things badly wrong, and were all those patents based on these structures potentially invalid? A little more detective work using Reaxys reveals that the 1,6,7 isomer melts at 109.5\u00b0C, the same as reported by AW in 1890 (Chem. News J. Ind. Sci<\/em>., 1890<\/strong> , 61<\/em>, p. 273). So how did the 1,6,7-compound come to be mistaken for a 1,2,3,-isomer? The culprit turns out to be one prime (‘).<\/p>\n\n\n\n
\"\"

1,6,7 = 2:3:1' Click for 3D<\/p><\/div><\/td>\n

\"\"

Updated (see comment) Click for 3D<\/p><\/div><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

The numbering system in 1890 was different from what it is now. Then, primes were used to distinguish the numbering on each ring. When the collection was catalogued (in the 1990s), the 1′ <\/strong>was mistaken for 1<\/strong> (you can see the prime on the original label). AW were correct all along, and the patent owners for all those naphthalene dyes can rest easy.<\/p>\n

\"\"<\/a>

Sample 22 from AW collection<\/p><\/div>\n

What this teaches us is that crystallography on 120 year old organic compounds is perfectly viable. Indeed, can anyone else claim to have solved the structure of such an old compound? And that those old chemists knew what they were doing, despite not having any instrumentation to help them. Oh, and a final comment. Precious few collections of molecules made by the original scientists exist nowadays. Many a collection has literally been skipped because of health and safety concerns. <\/em>The AW collection itself was rescued from oblivion by the narrowest of margins. <\/em>And we have permanently lost the opportunity for any detective work of the type described above. You can see that I am very upset by this. Heritage conservation should not just be old buildings, paintings etc, but the chemical heritage collections as well.<\/p>\n

Thanks to Andrew White<\/em><\/strong> for the crystal structures (of this and three other samples, but their stories are for another day).<\/p>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

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The factory where he founded the British (nay, the World) fine organic chemicals industry is in\u00a0Greenford,\u00a0just up the road from where we live. The factory used to be close to the Black Horse pub (see below) on the banks of the\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":"Perkin-Factory-plaque","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2013\/03\/Perkin-Factory-plaque.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":5204,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=5204","url_meta":{"origin":2798,"position":1},"title":"Historical detective stories: colourful crystals.","author":"Henry Rzepa","date":"October 21, 2011","format":false,"excerpt":"Organic chemists have been making (more or less pure) molecules for the best part of 180 years. Occasionally, these ancient samples are unearthed in cupboards, and then the hunt for their origin starts. I have previously described tracking down the structure of a 120 year-old sample of a naphthalene derivative.\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\/2011\/10\/DSCF8570.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":3507,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=3507","url_meta":{"origin":2798,"position":2},"title":"The colour of purple","author":"Henry Rzepa","date":"February 24, 2011","format":false,"excerpt":"One of my chemical heroes is William Perkin, who in 1856 famously (and accidentally) made the dye mauveine as an 18 year old whilst a student of August von\u00a0Hofmann, the founder of the Royal College of Chemistry (at what is now\u00a0\u00a0Imperial College London). Perkin went on to found the British\u2026","rel":"","context":"In "General"","block_context":{"text":"General","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=1"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/02\/220px-Rees1.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":12539,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=12539","url_meta":{"origin":2798,"position":3},"title":"An original chemistry lab from the early 19th century.","author":"Henry Rzepa","date":"May 18, 2014","format":false,"excerpt":"Not a computer in sight! I refer to a chemistry lab from the 1800s I was recently taken to, where famous french chemists such as Joseph Gay-Lussac, Michel Chevreul and Edmond Fremy were professors. Although not used for chemistry any more, it is an incredible treasure trove of objects. Here\u2026","rel":"","context":"In "Historical"","block_context":{"text":"Historical","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=565"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":20333,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=20333","url_meta":{"origin":2798,"position":4},"title":"The history of Alizarin (and madder).","author":"Henry Rzepa","date":"October 18, 2018","format":false,"excerpt":"The Royal Society of Chemistry historical group (of which I am a member) organises two or three one day meetings a year. Yesterday the October meeting covered (amongst other themes) the fascinating history of madder and its approximately synthetic equivalent alizarin. Here I add a little to the talk given\u2026","rel":"","context":"In "Historical"","block_context":{"text":"Historical","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=565"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":2423,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=2423","url_meta":{"origin":2798,"position":5},"title":"The oldest reaction mechanism: updated!","author":"Henry Rzepa","date":"September 14, 2010","format":false,"excerpt":"Unravelling reaction mechanisms is thought to be a 20th century phenomenon, coincident more or less with the development of electronic theories of chemistry. Hence electronic\u00a0arrow pushing as a term. But here I argue that the true origin of this immensely powerful technique in chemistry goes back to the 19th century.\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.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2010\/09\/wheland.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\/2798","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=2798"}],"version-history":[{"count":0,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/2798\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2798"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2798"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2798"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fppma_author&post=2798"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}