Question

a) Can riboflavin form a hydrogen bond with water? If so, circle the places on the molecule that could form a hydrogen bond with water. b) Can beta-carotene form a hydrogen bond with water? If so, circle the places on the molecule that could form a hydrogen bond with water. c) Are all of the molecules that dissolved in water able to form hydrogen bonds with water? (riboflavin, betanin)

Answer 1

a)

Note that for Hydrogen bonding, we must have the next conditions:

- Species is polar, i.e. there are dipole-dipole interactions between the molecules

- There must be an acidic Hydrogen bonded directly to either, N,O,F; which are very electronegative species.

Clearly, riboflavin has plenty of OH-; NH groups which can form H-bonds, therefore answer is YES

b)

beta-carotene --> nonpolar, therefore not enough force for N,O, present to form H-bonding

c)

not all molecules dissolved in water will form H-bonds

example:

NaCl --> Na++ Cl- can dissolve, but they do not have either O,N,F in their molecule