Direct contradiction in EK/Princeton - Branching, boiling pt & melting pt

[holler01]

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On page 28 of the exam crackers organic chem book, it says increased branching = decrease in BP and increase in MP.

However on page 582 of PR Biological Sciences Book (2008 edition) it says increased branching = decrease in MP and BP

can anyone verify which is correct?

 

[olemissbabydoc]

Moved this to the study q & a for an answer... I have a thought, but I"m not sure of myself 🙂

 

[not respect]

pr is right

 

[AZFutureDoc]

Increased branching lowers boiling point because it changes intermolecular interactions. It lowers the melting point because the branching prevents lattices from forming easy.

So, INCREASED branching => LOWER=BP, LOWER=MP

But, you won't see a melting point question. The trends are too messy and it is not plain and simple, with much more going into it than just branching.

 

[holler01]

but wait melting is solid to liquid so with your reasoning, if increased branching made it harder for a solid to melt wouldnt it increase the melting point?