8 ms·

Benzene’s bond lengths corrected

61 points by respinal 4y ago

wjnc 4y ago
1 Ångström = 1e-10 m 11.5 mÅ = 1.15e-12 m That’s a mind boggling measurement.
jchanimal 4y ago
My chemistry professor told me 10 Ångström is about how long your fingernails grow in the time it takes to say "10 Ångström"
- jsharf 4y ago
  I just did the math, and it looks like this is correct! Assuming 2.5mm per month (quick google search), that's 2.5e+7 angstrom/month Divide by the number of seconds in a month (30 * 24 * 3600) and you get about 10 angstroms per second. It takes about 1 second to say 10 angstroms. Very cool!
  - hilbert42 4y ago
    Now that's just the type of knowledge my brain loves to collect and store in its useless information department (and it's pretty full already). Useless? Well perhaps not. But one thing's certain I'll never forget the fact. Incidentally, it's worth remembering we owe the beginnings of this story to August Kekulé's remarkable insight-benzene's structure and the snake swallowing its tail. That too is also unforgettable information (but likely more useful, methinks).
    - alliao 4y ago
      there's a Japanese phrase for it.. まめちしき literally translates to bean knowledge. It quite a nice image though, little beans which may end up sprouting and connecting with others to form a web of knowledge somehow, someday
      - hilbert42 4y ago
        Sorry for not acknowledging your post earlier but I simply forgot. Anyway, thank you for that little gem of wisdom; I've already 'noted' it in my mind's useless info dept. :-) It's an excellent metaphor because that's what happens. Over the years I've noted many times that some facts (even seemingly irrelevant ones) in one field can play an important role in me understanding a concept in a totally different (and often unrelated) one. The trouble is that I've never had a photographic memory so all too frequently when I encounter something new then I can be left thinking 'now I recognize that from something I've come across previously but where?'. It's a nuisance but I put it down to my brain's 'garbage collection mechanism' being overly efficient. Sometimes it's also a burden especially when you can't mentally discard or turn off an old 'connection' as it can become annoying. Here's an example you might appreciate. It's well known fact there's a propensity for English language speakers to steal words from other languages then incorporate them effortlessly into English as if they'd always been there—simply because the foreign imports sound fashionable or posh—and that this practice happens even when well-known and perfectly adequate English words or phrases exist. The trouble is that inevitably they never take the time or effort to pronounce these imports correctly. (Right, it's no wonder English is such a bastard language). When in Japan years ago I learned to pronounce tsu - つ, ツ - perhaps not perfectly but likely better than many Westerners/English speakers do who have never been there. Nowadays, the transliteration of the Japanese word ツナミ is more commonly used in English than its original native counterpart! Unfortunately, the trouble is that almost no native English speaker takes the time or effort to pronounce tsu correctly even though the Latin characters provide a reasonable facsimile of/guide to its correct pronunciation (even those who've much better diction than me—BBC announcers for instance—usually make a mess of it). Thus, whenever I hear a slurred-out overly-long tsu it inevitably grates with me. If I'd never learned the correct Japanese pronunciation, which, given that I'm a native English speaker (thus it's essentially useless information), then I could be blissfully ignorant of the fact just like everyone else. ;-) No doubt, having provided the phrase 'まめちしき', you are also aware of the difficulty we native English speakers have in pronouncing tsu. I often wonder what the Japanese think of us given that we're so efficient at mashing up their language and that we don't give a damn about doing so. It annoys me is that we've the hide and arrogance to adopt the word ツナミ then just mangle its pronunciation. In my opinion adopting and incorporating a word from another language and being insensitive or oblivious to its cultural significance is both rude and indicates ignorance. (Here, I make a distinction between incorporating a word into another language and say those who are learning another language and who are having difficulty in pronouncing words in that newly-acquired language). BTW, I don't want to give you the impression that I'm fluent in Japanese as I'm not. Some decades ago, I worked in Japan for a short while but I was never there long enough to acquire an adequate understanding of the language let alone gain fluency. Also, I'm aware that I've a mixture of hiragana and katakana here (kanji is too complicated for me to deal with here). One curiosity I've never quite figured out (except perhaps that it's traditional), which is to ask why a certain formalism seems to have been adopted in the naming of Japanese cities. Why do cities and towns [seemingly] nearly always use kanji for their names (and not hiragana or katakana although there are exceptions); and why do most major cities use two kanji characters whereas smaller cities often use three or even four characters—or sometimes only one (as in the city of Tsu)? I can't remember Tsu's kanji name (character) but I do recall it was a sort of exception in that the hiragana character tsu, つ, is also sometimes used, which seems a little strange to me (but it makes excellent sense [to me] if for no other reason than it seems like a good shortcut).
    - notRobot 4y ago
      Share some of your useless knowledge with us!
      - hilbert42 4y ago
        Ha! And where to start and or what topic with which to begin? You've no idea how potentially dangerous tempting me like that really is (I'd be immediately banned from HN for server overloading)! Take a look at my reply to alliao. Can you imagine thousands of pages like that? Not likely. I'm far from being the brightest spark on the block but I'm smart enough to know I'd be chased off in a greased lightning sprint. ...But you've seeded an idea, some of it could be used as a substitute for Vogon poetry (shame on you). Honi soit qui mal y pense. ;-)
gus_massa 4y ago
Note that the length of the C-C bound is ~1.3Å and the length of the C-H is ~1.0Å, so te corrections is like .5%.
- ta988 4y ago
  The paper is really about the difference between C-H and C-D. Also it uses a physical method (Raman) and statistical approaches that will need to be reproduced to make sure it was not just an artifact of the method.
curiousllama 4y ago
Knowing very little about chemistry and physics, I always enjoy learning the names of new measurements. Milliangstroms? Lmao great name.
- nayuki 4y ago
  Yes, it's a great name like millimetres of mercury (mmHg), kilotons of TNT, light-years, etc. /s But seriously, SI already has appropriate units for these quantities. Milliangstroms should be converted to picometres, millimetres of mercury should be converted to kilopascals, kilotons of TNT should be converted to terajoules, and light-years should be converted to petametres.
  - idiotsecant 4y ago
    'everyone should use the units I want them to use and not the commonly used ones'
    - hypertele-Xii 4y ago
      That's how we get standards.
    - nayuki 4y ago
      This is a disingenuous argument. Do you not see the problems with using application-specific units? They are jargon and don't form a coherent system. When you have a jumble of units, it is hard to relate them. If an acre of land gets an inch of rain, how many gallons of water is that? If you did this in millimetres, metres, and cubic metres, it is easy. If your car's motor is rated in horsepower but electricity is measured in kilowatts, how do you compare those? What about fitting copies of a product measured in ounces in a shipping container measured in short tons? Typesetting measured in points, but paper measured in inches? Fitting metalwork done in mils but woodwork done in binary-fraction inches in a house measured in feet? The list goes on and on. It's easy to say "but my domain is special and deserves its own units". It's much harder to resist and say no, there is a perfectly suitable unit with power-of-1000 prefixes to use in your application.
ta988 4y ago
This is the paper behind that story: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9347355/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9347355/
suifbwish 4y ago
I’m curious will this new knowledge will lead to new discoveries which might not have been possible due to working with the incorrect lengths in calculations?
- quantum_magpie 4y ago
  As a quantum chemist, no.
- whatshisface 4y ago
  It is an example of a new technique being used on a common chemical with an eye towards using it on other chemicals once the technique is proven. ‘And as this technique can be applied to highly symmetric molecules, it opens the door to the characterisation of many chemically important species like polycyclic aromatic hydrocarbons.’ - a researcher quoted in the article
SilasX 4y ago
So ... I'm guessing chemistry wasn't really sensitive to the difference, except in whatever few "edge cases" prompted this re-examination?
nayuki 4y ago
> milliangstroms There is a perfectly sensible nearby SI unit called the picometre (pm). 10 mÅ = 1 pm. https://en.wikipedia.org/wiki/Picometre https://en.wikipedia.org/wiki/Picometre
- gilleain 4y ago
  Yes, while the ångström is often used for bond lengths, I've only heard of picometers used for smaller lengths.
- fritzo 4y ago
  ok but 'milliangstroms' immediately conveys a sense of relative error
- swamp40 4y ago
  Same as "mils" for thousands of an inch. It's actually wildly popular in the US.
  - nayuki 4y ago
    Mils are a terrible compromise. On the one hand, they acknowledge that dividing by 1000 is useful and that it's easier to work on a linear scale instead of mixed units and fractions. On the other hand, it stubbornly clings onto the inch instead of embracing the millimetre or micrometre. As a side note, I heard of carpenters who work in decimal feet. Yeah, that's great, adding yet another option to the mix. Everyone else talks in feet and inches.
- marcosdumay 4y ago
  When every measure around is on the same unity, you use that as your base unity. If you are designing a large steel piece for milling, you will write a length of 1000mm, not 1m.
  - kennywinker 4y ago
    1m and 1000mm are not the same length. 1000mm and 1.000m are the same length.
jl6 4y ago
Makes me wonder if this will result in any computational chemistry projects needing to be reworked.
- mch17 4y ago
  I don’t think it’s likely. A well implemented ab initio calculation will include geometry optimization. It’s possible that some forcefield constants will need to be tweaked in MD jobs, but this is a really small change in the bond length.
deleted 4y ago
[deleted]
fatuna 4y ago
Fun fact, even though most of the world pronounces it "angstrum", "Ångström" should actually be pronounced "ongstrum" (as the Swedish still do).
- iso8859-1 4y ago
  No, it should be /²ɔŋstrœm/ [0]: https://en.wiktionary.org/wiki/%C3%85ngstr%C3%B6m#Pronunciation_2 https://en.wiktionary.org/wiki/%C3%85ngstr%C3%B6m#Pronunciat...
tantalor 4y ago
Title is cringe: > Benzene’s bond lengths corrected First, passive voice should not be used when avoidable. Second, the bond lengths are fine. It's the measurement that was wrong.

61 points by respinal 4y ago

wjnc 4y ago

1 Ångström = 1e-10 m 11.5 mÅ = 1.15e-12 m That’s a mind boggling measurement.

My chemistry professor told me 10 Ångström is about how long your fingernails grow in the time it takes to say "10 Ångström"

jsharf 4y ago
I just did the math, and it looks like this is correct! Assuming 2.5mm per month (quick google search), that's 2.5e+7 angstrom/month Divide by the number of seconds in a month (30 * 24 * 3600) and you get about 10 angstroms per second. It takes about 1 second to say 10 angstroms. Very cool!
- hilbert42 4y ago
  Now that's just the type of knowledge my brain loves to collect and store in its useless information department (and it's pretty full already). Useless? Well perhaps not. But one thing's certain I'll never forget the fact. Incidentally, it's worth remembering we owe the beginnings of this story to August Kekulé's remarkable insight-benzene's structure and the snake swallowing its tail. That too is also unforgettable information (but likely more useful, methinks).
  - alliao 4y ago
    there's a Japanese phrase for it.. まめちしき literally translates to bean knowledge. It quite a nice image though, little beans which may end up sprouting and connecting with others to form a web of knowledge somehow, someday
    - hilbert42 4y ago
      Sorry for not acknowledging your post earlier but I simply forgot. Anyway, thank you for that little gem of wisdom; I've already 'noted' it in my mind's useless info dept. :-) It's an excellent metaphor because that's what happens. Over the years I've noted many times that some facts (even seemingly irrelevant ones) in one field can play an important role in me understanding a concept in a totally different (and often unrelated) one. The trouble is that I've never had a photographic memory so all too frequently when I encounter something new then I can be left thinking 'now I recognize that from something I've come across previously but where?'. It's a nuisance but I put it down to my brain's 'garbage collection mechanism' being overly efficient. Sometimes it's also a burden especially when you can't mentally discard or turn off an old 'connection' as it can become annoying. Here's an example you might appreciate. It's well known fact there's a propensity for English language speakers to steal words from other languages then incorporate them effortlessly into English as if they'd always been there—simply because the foreign imports sound fashionable or posh—and that this practice happens even when well-known and perfectly adequate English words or phrases exist. The trouble is that inevitably they never take the time or effort to pronounce these imports correctly. (Right, it's no wonder English is such a bastard language). When in Japan years ago I learned to pronounce tsu - つ, ツ - perhaps not perfectly but likely better than many Westerners/English speakers do who have never been there. Nowadays, the transliteration of the Japanese word ツナミ is more commonly used in English than its original native counterpart! Unfortunately, the trouble is that almost no native English speaker takes the time or effort to pronounce tsu correctly even though the Latin characters provide a reasonable facsimile of/guide to its correct pronunciation (even those who've much better diction than me—BBC announcers for instance—usually make a mess of it). Thus, whenever I hear a slurred-out overly-long tsu it inevitably grates with me. If I'd never learned the correct Japanese pronunciation, which, given that I'm a native English speaker (thus it's essentially useless information), then I could be blissfully ignorant of the fact just like everyone else. ;-) No doubt, having provided the phrase 'まめちしき', you are also aware of the difficulty we native English speakers have in pronouncing tsu. I often wonder what the Japanese think of us given that we're so efficient at mashing up their language and that we don't give a damn about doing so. It annoys me is that we've the hide and arrogance to adopt the word ツナミ then just mangle its pronunciation. In my opinion adopting and incorporating a word from another language and being insensitive or oblivious to its cultural significance is both rude and indicates ignorance. (Here, I make a distinction between incorporating a word into another language and say those who are learning another language and who are having difficulty in pronouncing words in that newly-acquired language). BTW, I don't want to give you the impression that I'm fluent in Japanese as I'm not. Some decades ago, I worked in Japan for a short while but I was never there long enough to acquire an adequate understanding of the language let alone gain fluency. Also, I'm aware that I've a mixture of hiragana and katakana here (kanji is too complicated for me to deal with here). One curiosity I've never quite figured out (except perhaps that it's traditional), which is to ask why a certain formalism seems to have been adopted in the naming of Japanese cities. Why do cities and towns [seemingly] nearly always use kanji for their names (and not hiragana or katakana although there are exceptions); and why do most major cities use two kanji characters whereas smaller cities often use three or even four characters—or sometimes only one (as in the city of Tsu)? I can't remember Tsu's kanji name (character) but I do recall it was a sort of exception in that the hiragana character tsu, つ, is also sometimes used, which seems a little strange to me (but it makes excellent sense [to me] if for no other reason than it seems like a good shortcut).
  - notRobot 4y ago
    Share some of your useless knowledge with us!
    - hilbert42 4y ago
      Ha! And where to start and or what topic with which to begin? You've no idea how potentially dangerous tempting me like that really is (I'd be immediately banned from HN for server overloading)! Take a look at my reply to alliao. Can you imagine thousands of pages like that? Not likely. I'm far from being the brightest spark on the block but I'm smart enough to know I'd be chased off in a greased lightning sprint. ...But you've seeded an idea, some of it could be used as a substitute for Vogon poetry (shame on you). Honi soit qui mal y pense. ;-)

gus_massa 4y ago

Note that the length of the C-C bound is ~1.3Å and the length of the C-H is ~1.0Å, so te corrections is like .5%.

ta988 4y ago
The paper is really about the difference between C-H and C-D. Also it uses a physical method (Raman) and statistical approaches that will need to be reproduced to make sure it was not just an artifact of the method.

curiousllama 4y ago

Knowing very little about chemistry and physics, I always enjoy learning the names of new measurements. Milliangstroms? Lmao great name.

nayuki 4y ago
Yes, it's a great name like millimetres of mercury (mmHg), kilotons of TNT, light-years, etc. /s But seriously, SI already has appropriate units for these quantities. Milliangstroms should be converted to picometres, millimetres of mercury should be converted to kilopascals, kilotons of TNT should be converted to terajoules, and light-years should be converted to petametres.
- idiotsecant 4y ago
  'everyone should use the units I want them to use and not the commonly used ones'
  - hypertele-Xii 4y ago
    That's how we get standards.
  - nayuki 4y ago
    This is a disingenuous argument. Do you not see the problems with using application-specific units? They are jargon and don't form a coherent system. When you have a jumble of units, it is hard to relate them. If an acre of land gets an inch of rain, how many gallons of water is that? If you did this in millimetres, metres, and cubic metres, it is easy. If your car's motor is rated in horsepower but electricity is measured in kilowatts, how do you compare those? What about fitting copies of a product measured in ounces in a shipping container measured in short tons? Typesetting measured in points, but paper measured in inches? Fitting metalwork done in mils but woodwork done in binary-fraction inches in a house measured in feet? The list goes on and on. It's easy to say "but my domain is special and deserves its own units". It's much harder to resist and say no, there is a perfectly suitable unit with power-of-1000 prefixes to use in your application.

ta988 4y ago

This is the paper behind that story: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9347355/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9347355/

suifbwish 4y ago

I’m curious will this new knowledge will lead to new discoveries which might not have been possible due to working with the incorrect lengths in calculations?

quantum_magpie 4y ago
As a quantum chemist, no.
whatshisface 4y ago
It is an example of a new technique being used on a common chemical with an eye towards using it on other chemicals once the technique is proven. ‘And as this technique can be applied to highly symmetric molecules, it opens the door to the characterisation of many chemically important species like polycyclic aromatic hydrocarbons.’ - a researcher quoted in the article

SilasX 4y ago

So ... I'm guessing chemistry wasn't really sensitive to the difference, except in whatever few "edge cases" prompted this re-examination?

nayuki 4y ago

> milliangstroms There is a perfectly sensible nearby SI unit called the picometre (pm). 10 mÅ = 1 pm. https://en.wikipedia.org/wiki/Picometre https://en.wikipedia.org/wiki/Picometre

gilleain 4y ago
Yes, while the ångström is often used for bond lengths, I've only heard of picometers used for smaller lengths.
fritzo 4y ago
ok but 'milliangstroms' immediately conveys a sense of relative error
swamp40 4y ago
Same as "mils" for thousands of an inch. It's actually wildly popular in the US.
- nayuki 4y ago
  Mils are a terrible compromise. On the one hand, they acknowledge that dividing by 1000 is useful and that it's easier to work on a linear scale instead of mixed units and fractions. On the other hand, it stubbornly clings onto the inch instead of embracing the millimetre or micrometre. As a side note, I heard of carpenters who work in decimal feet. Yeah, that's great, adding yet another option to the mix. Everyone else talks in feet and inches.
marcosdumay 4y ago
When every measure around is on the same unity, you use that as your base unity. If you are designing a large steel piece for milling, you will write a length of 1000mm, not 1m.
- kennywinker 4y ago
  1m and 1000mm are not the same length. 1000mm and 1.000m are the same length.

jl6 4y ago

Makes me wonder if this will result in any computational chemistry projects needing to be reworked.

mch17 4y ago
I don’t think it’s likely. A well implemented ab initio calculation will include geometry optimization. It’s possible that some forcefield constants will need to be tweaked in MD jobs, but this is a really small change in the bond length.

deleted 4y ago

[deleted]

fatuna 4y ago

Fun fact, even though most of the world pronounces it "angstrum", "Ångström" should actually be pronounced "ongstrum" (as the Swedish still do).

iso8859-1 4y ago
No, it should be /²ɔŋstrœm/ [0]: https://en.wiktionary.org/wiki/%C3%85ngstr%C3%B6m#Pronunciation_2 https://en.wiktionary.org/wiki/%C3%85ngstr%C3%B6m#Pronunciat...

tantalor 4y ago

Title is cringe: > Benzene’s bond lengths corrected First, passive voice should not be used when avoidable. Second, the bond lengths are fine. It's the measurement that was wrong.