Molecular structure and analysis method

[~christina~]

Homework Statement

$$\Delta$$9-Tetrahydrocannabinol (THC) is the primary psychoactive constituent of marijuana. Its metabolites include 11-hydroxy- $$\Delta$$9-THC (11-OH-THC) and 11-nor-9-carboxy- $$\Delta$$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.

Homework Equations

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"
11-hydroxy- $$\Delta$$9-THC (11-OH-THC) : http://en.wikipedia.org/wiki/11-Hydroxy-THC
11-nor-9-carboxy- $$\Delta$$9-THC (THC-COOH) : http://en.wikipedia.org/wiki/11-nor-9-Carboxy-THC"

What does the, "nor" and the $$\Delta$$ 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.

 

[chemisttree]

What does the, "nor" and the $$\Delta$$ stand for in the notations?

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"

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? [/B]

Thank you and the last question I bolded is something I need help on.

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.

 

[~christina~]

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"

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)

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.

Ah, okay. I understand why derivatization is needed with some compounds.

 

[chemisttree]

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)

Yes, it is an ad hoc abbreviation.

 

[~christina~]

Yes, it is an ad hoc abbreviation.

Thanks for your help,
chemisttree