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I wanted to figure out a way to compare volatility in organic compounds, so I read on many forums on the differing ways to measure volatility, which included enthalpy of vaporization and melting/boiling points.

I am planning on using melting/boiling point to prove that branching of chains in organic compounds causes weaker volatility.

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According to this Wikipedia page:

In chemistry and physics, volatility is the tendency of a substance to vaporize. Volatility is directly related to a substance's vapor pressure. At a given temperature, a substance with higher vapor pressure vaporizes more readily than a substance with a lower vapor pressure.

So, I'm not sure how much information on volatility you will get from melting point measurements. Ideally, the enthalpy of vaporization would be the best measurement, but, if it fits your needs, the boiling point at ambient pressure is a simple way to determine whether there is a significant difference in the volatility of various compounds.

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  • $\begingroup$ If I use enthalpy of vaporization, what temperature $\endgroup$
    – idk wat else
    Commented Mar 16, 2017 at 3:04
  • $\begingroup$ Enthalpy of vaporization values are usually given either at their boiling point or 298C. Sometimes these values, particularly the value at 298C, are not within the range of temperatures used to calculate the enthalpy, but are extrapolated assuming negligible change in enthalpy values over some range of temperature. I don't know if being able to compare your enthalpy of vaporization values to published values is important, if so I would try to make the measurements close to 298C. $\endgroup$
    – airhuff
    Commented Mar 16, 2017 at 3:19
  • $\begingroup$ After reading through your question again, I'm not sure that just measuring the vapor pressure at 20 or 25C might not be the best and simplest way to go. I just don't know for your experiments whether the extra effort of determining enthalpies of vaporization is worth it or not. That has to be your call I guess. $\endgroup$
    – airhuff
    Commented Mar 16, 2017 at 3:31

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