Aromatic Ring Polymers

Discussion in 'Chemistry' started by Captain Kremmen, Nov 22, 2008.

  1. Captain Kremmen All aboard, me Hearties! Valued Senior Member

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    Are there any?
    If not why not?
    They would have some interesting properties I think.


    This is a Phtylate, which starts off well, but then gives up on the job.
    The chemical smells as satisfying as its appearance.
    It is what gives cars their new car smell.
    Beautiful, isn't it.

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    Last edited: Nov 22, 2008
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  3. Forceman May the force be with you Registered Senior Member

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    If there is a benzene ring in the middle of the resonance formula, why does it not produce a revolting odor?
     
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  5. Roman Banned Banned

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    There are structures of linked rings. Naphthalene, Anthracene, Phenanthrene, Pyrene, Benzo[a]pyrene, and Coronene, to name a few. Benzo[a]pyrene is a major carcinogen in cigarette smoke. It gets converted into a diol epoxide, which binds to DNA's amino groups, causing mutations.

    Because the side groups are what gives things odor. You'll find benzene rings in all sorts of aromatic compounds. Thyme and vanilla, for instance, both have phenols (benzene with an -OH) in them. Curry also contains two phenols, and has been shown to have anti-cancer properties due to angiogenesis inhibition.
     
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  7. Captain Kremmen All aboard, me Hearties! Valued Senior Member

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    That's not quite what I meant.
    I meant polymers, where the chain goes on for hundreds, perhaps thousands of units.
    I've found this natural one, lignin in wood.
    Are there any man made ones?

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  8. leopold Valued Senior Member

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    if i'm not mistaken "aromatic" is the standard name for any compound that contains a benzine ring.
     
  9. Roman Banned Banned

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    Ohhh, polymers.
    Right.

    Chitin is scleretized with quinones. I can't find any images of it though. I'm unsure if it's what you're thinking of, where the aromatic rings are attached to each other. I think the quinones are added as side groups.

    Here's polyether ether ketone. According to encylopedia britannica, they're pretty bomber.

    Makes sense, as most of the bonds aren't very reactive.

    Wikipedia also has an article on them. Looks like they're relatively simple to put together.
     
  10. Roman Banned Banned

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    Yup.
    I was being a little tongue in cheek, since aromatic comes from a certain physical property that compounds that demonstrate aromaticity share.
     
  11. Captain Kremmen All aboard, me Hearties! Valued Senior Member

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    Yes, you've got what I mean now.
    Poly ether ether ketone (PEEK) would be one.
    This is a molecular diagram I found for PEK.

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    There's another one in the family too.
    SPEEK, sulphonated........

    They make very strong plastics, and are heat resistant.
     
    Last edited: Nov 22, 2008
  12. Roman Banned Banned

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    So how do plastics work? Is it simply one VERY long string of molecules, or is that stuff held together with dipole moments?
     
  13. Captain Kremmen All aboard, me Hearties! Valued Senior Member

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    Dipolar molecules do form chains.
    Water does.
     
  14. Roman Banned Banned

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    1. Water isn't structurally strong.
    2. Water hydrogen bonds, which is the strongest of intermolecular forces.

    PEEK is very sturdy, and doesn't look like it can form any hydrogen bonds. I am wondering what intermolecular forces hold it together.
     
  15. Captain Kremmen All aboard, me Hearties! Valued Senior Member

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    Polystyrene has rings, but they do not form part of the chain.
    It must be difficult to get rings to string together.
    PEEK was only made in 1962.

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    Thanks for your efforts in keeping this thread alive, Roman, but keeping a thread going on this section is like threading a needle wearing boxing gloves.
     
    Last edited: Nov 23, 2008
  16. Trippy ALEA IACTA EST Staff Member

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    That was the origin of the term, the most odiferous substances in nature tend to be terpenes.

    The term Aromatic in its current usage in chemistry actually refers to having a set of conjugated double bonds that are capable of undergoing resonance.

    Specifically, we have Hückel's Rule, which essentially states that in order for a molecule to be aromatic, it must be planar, and it must have 4n+2 π electrons.

    For example:

    [14]Annulene:

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    and [18]Annulene:

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    Are Aromatic, however...
     
  17. Trippy ALEA IACTA EST Staff Member

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    [16]Annulene:

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    [10]Annulene:

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    And Cyclooctatetraene (or [8]Annulene):

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    Are not aromatic.

    The interesting thing about Hückel's Rule is that it brings into play some interesting aromatic compounds.

    So for example, while Cyclopentadiene is not aromatic, the cyclopentadienyl anion is.

    Cycloheptatriene is not aromatic, but the cyclopentatrienyl cation (tropylium ion) is aromatic, as is the cyclopropenyl cation.

    There's also a class of compounds that are classed as being Anti aromatic.

    Aromatic hydrocarbons have a lower total energy then their straight chain counterparts.

    Antiaromatic hydrocarbons have a higher total energy then their straight chain counterparts.
     
  18. Trippy ALEA IACTA EST Staff Member

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    Then there's compounds that are classed as non-benzenoid aromatics, such as Azulene:

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    Which, unlike most of the Annulenes, doesn't have anything that resembles the benzene structure, or benzene structural components.

    I should also point out that Hückel's Rule is only applicable to monocyclic structures. For example, Pyrene is aromatic, even though it has a non-Hückel number of electrons (14).

    However, if you pay attention to the peripheral structure, it resembles [14]Annulene, and 14 is a Hückel number. Based on this you can predict that the periphery of Pyrene might be aromatic by itself, and this has been confirmed by experiments involving trans-15,16-Dimethyldihydropyrene (Pyrene with two methyl groups added trans across the central double bond) which still behaves in an aromatic fashion.

    I hope that this is at least somewhat useful.
     
  19. Roman Banned Banned

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    If you bridge [10]Annulene at the 1,6 positions with a methyl, it becomes aromatic. This is because it becomes planar, with the cloud of pi electrons above and below.

    I just has a test on aromatic compounds

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  20. Idle Mind What the hell, man? Valued Senior Member

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    Unless they messed up the image, that would be a cyclohexane in the middle there.
     
  21. Captain Kremmen All aboard, me Hearties! Valued Senior Member

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    Looking again at that phtylate, why wouldn't it form polymers?
    Surely, in place of one of those OH groups it could bond to another phtylate molecule.
     
  22. Idle Mind What the hell, man? Valued Senior Member

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    Yes, but you would end up with a messy polymer, since you likely wouldn't have control over which phosphate bound to which.
     
  23. Captain Kremmen All aboard, me Hearties! Valued Senior Member

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    Messy polymers. I get your meaning.
    Ones that bond all over the place.

    Do they exist, and are they used for anything?
     

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