Question

Based on your knowledge of functional group solubility (polar vs. non-polar) and the golden rule of solubility – “like dissolves like” predict the solubility of fentanyl (Recall that each polar functional group affects about 5-6 carbons). Determine if the molecule fentanyl is soluble in water (polar) use a reference. Compare your prediction to a reference value (anything over 1 g/100 ml or 10 mg/ml is soluble). (Do not simply give solubility information from one of your references.)

Answer 1

The structure of fentanyl is given below:

Here, there is one polar group i.e. carbonyl group. But the molecule is not considered as polar because there are total 22 carbons.

Nitrogen is also electronegative but both nitrogens are surrounded by bulky groups.

Hence, from the structure it is predicted that fentanyl is lipophilic. It means it is non polar and is soluble in non polar solvent. There is no difference of 1g/100ml or 10 mg/ ml.

Because, carbonyl group is not so much influential as non polar chain is comparatively very longer than carbonyl.