What are the functional groups?

Organic Chemistry: What makes unpolar functional groups "hydrophobic"?

• Are they intrinsically hydrophobic, or are they simply less hydrophilic in comparison to other groups?

• Answer:

  Yeah, it basically means that they're just less hydrophilic than other groups. However, this has very real effects in solution. When a hydrophilic molecule is dissolved in solution, it is surrounded by a shell of water molecules that are attracted to the partial charge on the polar group. This is energetically favorable, which is why it's so easy to dissolve things like salt. For a hydrophobic molecule, it's entropically unfavorable for the water to form a shell around the molecule. This is because the water molecules around the hydrophobic molecule are less able to move around. Now, you might be thinking, doesn't the same apply to hydrophilic molecules? And yes, it does, but the electrostatic interactions that the water has with the polar groups is favorable enough enthalpy-wise that it outweighs the unfavorable entropy change. For hydrophobic molecules, though, the water doesn't get to participate in any significant electrostatic interactions, so it simply isn't favorable for water to be in contact with a hydrophobic molecule. In fact, it's less favorable than the hydrophobic molecule just being associated with other hydrophobic molecules, which is why fats and lipids tend to aggregate in solution. Most of this answer can be found in any chemistry textbook, but I would recommend Chemical Principles by Atkins, Organic Chemistry by Clayden and Greaves, or Fundamentals of Biochemistry by Voet, Voet, and Pratt.