Question

Question: THC is the active component in marijuana, and ethanol is the alcohol in alcoholic beverages. Explain why drug screenings are able to detect the presence of THC but not ethanol weeks after these substances have been introduced into the body.

Short answer

Answer

Due to the less solubility of tetrahydrocannabinol (THC) in water but more in the organic solvent, it can be detected after a few weeks.

Step-by-step solution

Solubility of compounds in water

The solubility of substances (compounds) in water is highly dependent on the polarity of the bonds. The more the polar bond in a compound, the stronger will be the dipole-dipole attraction. This in turn results in high solubility.

Step 2:Solubility of compounds in organic solvents

The non-polar compounds (having no dipole or few dipoles) are soluble in organic solvents.

Explanation

The THC molecule is a larger molecule than ethanol. It has a greater number of non-polar bonds (C-C bonding, C-H bonding) and only one polar bond that forms hydrogen bonding with water molecules (O-H bond). Therefore, THC is slightly soluble in water and highly soluble in an organic solvent, such as the fatty tissues in the body. When THC is introduced into the body, it is not excreted in the urine due to less solubility in water. However, THC is soluble in fatty tissues and therefore is retained for a few weeks. Ethanol forms hydrogen bonding with water molecules due to its smaller molecular structure and greater polarity. Therefore, it is more soluble in water. Hence, ethanol is excreted from the body more readily in urine.