Boiling point is homologous to melting point as far as I know. So, what you said about branch compound is wrong. I always thought, if more branched then both melting poing and boiling point decreases and also higher m.w, higher mp and bp.
*Someone correct me if I am wrong!
As far as viscosity is concerned:
In general, thick liquids are thick because their molecules have a good grip on each other -- either bonded to each other, or tangled up in each other. Thus, it is harder to pull them away from each other -- and that is, of course, what happens when a liquid boils. So, viscosity and boiling point are related by virtue on molecular interaction. Heating reduces viscosity because heating makes the molecules move faster. Under such conditions of increased molecular motion, their grip on each other weakens.
Therefore, the thicker the solution (higher viscosity, higher the mp)
