How does the structure of heroin allow for more rapid penetration of the blood-brain barrier thatn morphine?

Question

How does the structure of heroin allow for more rapid penetration of the blood-brain barrier thatn morphine?

Answer 1

The two acetyl groups mask the alcohol functional groups of morphine with less polar esters that are incapable of donating hydrogen bonds.

Answer 2

It must be less polar.  Polar substances (or those with a charge) have to be actively transported across the BBB.  Non polar substances can diffuse across.