Why Do Compounds Smell?

Discussion in 'Chemistry' started by OilIsMastery, Jul 8, 2008.

  1. OilIsMastery Banned Banned

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    How come elements like Hydrogen, Nitrogen, and Carbon don't smell individually but when you put them together they smell?

    Hydrogen is odorless. Nitrogen in the air we breathe is odorless. Carbon in the form of diamonds and graphite is odorless.

    But CH4 (Methane) and NH3 (Ammonia) have unique and unmistakable smells.

    Why?
     
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  3. Enmos Staff Member

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    Because our olfactory sensors have evolved to detect them, or similar compounds.
     
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  5. synthesizer-patel Sweep the leg Johnny! Valued Senior Member

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    seems to make sense - elements on their own are generally either very rare in nature, or in the case of air ( ok it a mixture of mostly 2 elements) very abundant and everywhere - either way there would be little or no selective pressure on the ability to detect them.

    as an aside - I could be mistaken but I thought methane had no smell at all - it's other compounds in chuffs and rotting vegetable matter then imbue it with its charming aroma - likewise I read somewhere that we add something to the natural gas we use for heating etc for safety reasons - so we can smell if we have gas leak.
     
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  7. Enmos Staff Member

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    Hmm yea.. I don't really know whether or not methane has an odor.
    But my argument holds for any compound.
    If we can smell it it's because we evolved to smell it, similar compounds, or compounds that have a similar group.
    If a compound can bind to olfactory cell receptors we can detect it. The receptors are not there by accident.

    On natural gas.
    The gas we use to cook is not methane, but propane or butane, or a mixture of the two

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    Edit:
    By the way, how are you doing buddy ?

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  8. synthesizer-patel Sweep the leg Johnny! Valued Senior Member

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    Pretty good - been away for a few weeks - just got back from Scotland where I was working on a field course for the undergrads - its the same field course I did a couple of years ago, it was great fun to experience it from the other side of the fence so to speak and I amazed myself with how much I remembered, but a bit wierd to be seen as a teacher and a responsible adult tho.

    I stuck around for an extra 2 weeks when I also got a chance to help one of the researchers there with some work she's doing on basking sharks -something I've been trying to get involved in with another researcher for a few years - but he's a protective sonofabitch (probably becuase he hogs all the grant money) and won't speak to me about it - I've got an invite to spend next summer working on an energetics project I devised as an undegrad - all I need is the funding and permission from my boss - peice of piss ( I don't think)

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  9. Enmos Staff Member

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    Great ! Good luck

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    To stay on topic..

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    If a compound can be detected by smell, the ability evolved because detecting it posed some evolutionary advantage.
    For instance, a smell can be an indicator of something toxic or an otherwise harmful substance (rotting cadavers, feces, rotting food).
    But it can also be an indicator of food (fruits) or familiarity (home).
    So smell provides us with a range of information ranging from alarm bells to the presence of food.
    Bare elements such as hydrogen or nitrogen are either insignificant (provide no useful information) or are so commonplace that smelling them would be a disadvantage (pointless investment).
    Carbon, such as in diamonds, are strongly bound to each other. They don't get airborne in the first place.
    Carbon in burned wood for example doesn't need to be smelled because of the tell-tale smells of other compounds burned wood releases into the air.
    There is also trade-off between advantage and investment of course.
     
  10. OilIsMastery Banned Banned

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    Any intelligent people care to respond? :shrug:
     
  11. Enmos Staff Member

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    LOL What don't you agree with ?
     
  12. OilIsMastery Banned Banned

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    PAHs are not biological.

    http://www.sciforums.com/showthread.php?t=82778

     
  13. Enmos Staff Member

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  14. OilIsMastery Banned Banned

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    I'm not trolling my own thread; I'm looking for responses from intelligent people who don't subscribe to the biogenic religious cult and medieval fringe theories like Vital Force. Carbon is an abiotic element not a living organism.
     
  15. Enmos Staff Member

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    Yes you are.

    Like NASA ? And what the hell is Vital Force ?

    I agree.
     
  16. OilIsMastery Banned Banned

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    Vitalism is your religion. Carbon is an abiotic element not a living organism.
     
  17. Enmos Staff Member

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    No it isn't, you moron.

    I agree.
     
  18. OilIsMastery Banned Banned

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    You don't agree. You believe hydrocarbons are biological.
     
  19. Enmos Staff Member

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    Let me ask you this. Which of the following elements is biological ?

    Oxygen, Carbon, Hydrogen, Nitrogen, Calcium, Phosphorus, Potassium, Sulfur, Chlorine, Sodium, Magnesium, Iron, Cobalt, Copper, Zinc, Iodine, Selenium, Fluorine.
     
  20. Enmos Staff Member

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    What ? Can't catch your tongue ?

    Those are the elements that make up the human body you idiot. Are you saying that the human body is not biological.

    I suggest you buy a dictionary and look up the word "hydrocarbons".


    Now consider the answers I gave you to the question posed in the OP.
     
  21. spidergoat Valued Senior Member

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    Compounds smell because you forgot to wash them. Elements don't because they are pure.
     
  22. Enmos Staff Member

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    Spider, can you please get rid of this moron ?
     
  23. synthesizer-patel Sweep the leg Johnny! Valued Senior Member

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    what about those stinky old halides?
     

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