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Topic: melting point  (Read 3042 times)

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Offline nikita88

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melting point
« on: April 04, 2011, 11:15:10 AM »
List compounds in increasing order of melting point:
1-hexanol, heptane, and dipropyl ether
and why?

Offline Honclbrif

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Re: melting point
« Reply #1 on: April 04, 2011, 11:50:18 AM »
Do your own damn homework
Individual results may vary

Offline nikita88

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Re: melting point
« Reply #2 on: April 04, 2011, 01:27:33 PM »
there are no organic chem tutors at my college and i have a baby so i cant make study groups. this just looked like a good resource. at a glance though, it seems that those who habituate this forum are more serious chemists then I, so I understand how you might get tired of rudimentary questions.

Offline Honclbrif

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Re: melting point
« Reply #3 on: April 04, 2011, 02:00:22 PM »
I don't mind answering rudimentary questions. In fact, I like helping people out with the basics. Not enough people work on them. What I took issue with was how you asked the question: all you did was post a homework problem. I can't speak for everyone here but I have no interest in just giving away answers. It does you no benefit to just be spoon fed answers without understanding where those answers came from. You can use this forum as a tutoring source, but if you want some help around here, you have to demonstrate that you're not just fishing for answers without any interest in learning.

First, tell us what you know about the problem, and what your reasoning is behind your best guess, or where you are having trouble. From there we might be able to help you better learn the concept instead of handing you an answer for this question and hanging you out to dry the next time you have to answer the same one.
Individual results may vary

Offline Enthalpy

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Re: melting point
« Reply #4 on: April 05, 2011, 09:04:51 AM »
These compounds have been chosen with similar masses, to let you decide from their organisation.

You're supposed to look at effects that let molecules stick together more strongly, like electric dipole moments, or hydrogen bonds.

Though... Such reasons work not too badly for boiling points. As opposed, melting points are very hard to predict and depend hugely (100K differences) on tiny changes in the shape, so I'd tend to answer "found measurements, this is the order" and "because of experimental evidence" but this is probably not the desired answer.

This reflects in prediction software, that use sets of rules to estimate melting and boiling points of compounds. They are often 5-10K accurate on boiling points and 100K false on melting points.

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