Reef Chemistry Question of the Day #223 Hydrophobic Molecule

[Randy Holmes-Farley]

Reef Chemistry Question of the Day #223

The drawing below is a molecule of domoic acid, a toxin that is synthesized by marine algae.

Which part of the molecule would be considered hydrophobic?

A
B
C
D

Good luck!

































.

 

[beaslbob]

pure guess

B

(it's afraid of h and o's)

 

[MnFish1]

B

 

[SaltEverywhere]

B. Looks like the fatty end of a fatty acid.

 

[Randy Holmes-Farley]

And the answer is...

B

Hydrophilic (water loving) parts of molecules include those that are charged (positive or negative, any charge is loved by water) or which can hydrogen bond to water.

Functional groups that can hydrogen bond include most chemicals that contain O (with a few exceptions such as O2) and many that contain N (and a small number of others). The sections A, C, and D all are good at hydrogen bonding to water and water wants to interact with them strongly. Hydrophilic molecules, or parts of molecules, make them more soluble in water.

Hydrophobic molecules often contain just carbon and hydrogen, but some other atoms can also be present. These oily sorts of structures do not interact much at all with water. Section B has just C and H. Hydrophobic molecules or parts of molecules make them less soluble in water.