✔ 最佳答案
that's obvious.
on the right ring of the lactose molecule, there're 2 hydroxyl groups pointing downward in B, while one of them points upward in A.
in B, the two hydroxyls pointing downward have intramolecular H-bonding, which reduces the extent of intermolecular H-bond between lactose and water.
thus, water solubility of B is lower than A's.
do you need a picture of the model? I've built one using ball-and-stick.
2010-09-27 22:37:45 補充：
B's model. orange lines shows possible intramolecular H-bond.
http://monitorb.pixa.us/images/19054484/DSCN6769
2010-09-27 22:39:54 補充：
A's model. red balls are oxygen; blue balls are also oxygen, just to emphasize the position of 6th-carbon. intramolecular H-bond due to that 2 hydroxyl is not possible.
http://monitorb.pixa.us/images/19054485/DSCN6770
2010-09-27 22:39:57 補充：
if can't see, please suggest hosts other than tinypic and photobucket -- i've difficulties using them.
