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Molecular structure and analysis method

  1. Apr 16, 2009 #1

    ~christina~

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    1. The problem statement, all variables and given/known data
    [tex]\Delta[/tex]9-Tetrahydrocannabinol (THC) is the primary psychoactive constituent of marijuana. Its metabolites include 11-hydroxy- [tex]\Delta[/tex]9-THC (11-OH-THC) and 11-nor-9-carboxy- [tex]\Delta[/tex]9-THC (THC-COOH).

    1)Write down the molecular structure of these three compounds.
    2)Develop an analytical method to determine ng/mL levels of THC, 11-OH-THC and THC-COOH in urine samples, which include:
    a)step-by-step sample preparation
    b)instrumentation
    c)calibration method
    Please provide your reasoning for choosing a specific method or instrument.

    2. Relevant equations

    3. The attempt at a solution
    Well, I looked up the structure of THC, but as for the notation used for the description of the structure, I'm not sure what they all mean. It's been awhile since I took organic...
    Anyway, for the structures, Is it correct to say that it's the ones I found in the links?

    1) THC structure: http://en.wikipedia.org/wiki/Tetrahydrocannabinol" [Broken]
    11-hydroxy- [tex]\Delta[/tex]9-THC (11-OH-THC) : http://en.wikipedia.org/wiki/11-Hydroxy-THC
    11-nor-9-carboxy- [tex]\Delta[/tex]9-THC (THC-COOH) : http://en.wikipedia.org/wiki/11-nor-9-Carboxy-THC" [Broken]

    What does the, "nor" and the [tex]\Delta[/tex] stand for in the notations?

    2) I guess I can look up the steps and such, but with calibration, how would that work?
    Would there be an external standard for the instrument (LC-MS or other instrument)

    In addition I hear about derivatization of samples prior to analysis for this in some papers. What is derivatization and why is it needed here?


    Thank you and the last question I bolded is something I need help on.
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Apr 16, 2009 #2

    chemisttree

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    The 'nor' means that something has been removed and replaced with something. The root structure of these compounds is 'cannibinol'. You will notice that cannibinol has a methyl group at the 9 position. In this case the '11-nor-9-carboxy tetrahydrocannibinol' means that which has been replaced at the 9 position (methyl in this case or 'nor-9') is now a 'carboxy' (nor-9-carboxy').

    Tetrahydrocannibinol has 4 hydrogens added to cannibinol leaving one double bond at the 'delta 9' position. The 'delta' nomenclature indicates which C-C bond has the unsaturation. I have seen this used in unsaturated fatty acids. For example, oleic acid is referred to as the http://en.wikipedia.org/wiki/Fatty_acid" [Broken]

    Derivatization is used to aid in the identification of a compound. In some cases, detection by UV is not possible because the compound doesn't have a UV chromophore. In that case it is useful to 'derivatize' or add something that has a UV chromophore to the base structure to aid in its visualization using UV light. A benzyl ester would be a useful derivative for a carboxylic acid that otherwise has no chromophore at long enough UV wavelength, for example. In other cases, derivatization is used to make a compound more mobile on a gas chromatograph or HPLC. Sometimes alcohols, especially polyols are derivatized with the trimethylsilyl group to make them easier to chromatograph. Carboxylic groups are notoriously difficult to elute with a good peak shape and in a reasonably short time. They are often converted into their methyl esters prior to analysis.
     
    Last edited by a moderator: May 4, 2017
  4. Apr 16, 2009 #3

    ~christina~

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    I understand now, but it confuses me because based on what you said, the compounds structure I think is correct, but after each compound why is there is the...simplified formula? in brackets? [ex. 11-hydroxy- 9-THC (11-OH-THC) ] Is it there just for reference purposes? (It reminds me of something like Ca(NO3)2)

    Ah, okay. I understand why derivatization is needed with some compounds.
     
    Last edited by a moderator: May 4, 2017
  5. Apr 18, 2009 #4

    chemisttree

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    Yes, it is an ad hoc abbreviation.
     
  6. Apr 19, 2009 #5

    ~christina~

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    Thanks for your help,
    chemisttree :smile:
     
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