Recent content by Miffymycat

Dipole moment explains boiling point but not the contrary melting point and density trend!

Boiling points differ as expected - the more polar molecule (cis) is higher

Quoted data for cis and trans 1,2 dichloroethenes shows cis has higher density but lower melting point than trans. How can this be explained? Packing arguments are clearly unable to rationalise these observations. Other 1,2 disubstituted ethenes show similar pattern. Thank you.

Thanks Dr Du yes this makes more sense. I hope there are others who would agree with this to provide confirmation / reassurance!

No - it's a different question. I understand that the energy gap increases with deshielding : my query is I am missing the point as to why we say downfield implying a weaker field if the larger gap needs a stronger applied field?!

In CW or FT pmr, as chemical shift increases, why do we say "downfield" implying a lower magnetic field strength, when deshielded protons need a higher flip energy requiring a higher magnetic field strength and / or higher radio frequency radiation? Am I having a senior moment - apologies if so ...

In 2-aminobutane, C3 resonates at lower field (ca 33ppm) compared to C1 (ca 23ppm). Is there a simple rationale for this? The extra inductive effect from C4 should increase electron density around C3 and so shift it upfield compared to C2? Any thoughts/answers greatly appreciated.

OK - a bit weird though, that it fits precisely to polynomial order 6! Coincidence?

Agreed, and seems to support the idea that conductivity data from "ion-exchanges" can't be used to investigate reaction kinetics. Any ideas on the significance of the slope for the linear plot?

Thanks Perok ... I was sending mine while yours was arriving - I was close! So does the function fit one of those categories?

... building on micromass's reply ... something like y = 2a -(a/2^x)? where a is an arbitrary constant. Is it a hyperbolic function??! Or a hyperbolic polynomial! does that exist?

Thanks both! I'm not a mathematician ... just a chemist struggling to make sense of some data! So Hallsofivy, is a "second order difference equation" the same thing as a second order polynomial? I tried to fit the data to a polynomial and it required 6th order before R2= 1 in Excel! (And not...

Calling kinetics experts: rate law from conductivity isn't possible!? Consider the usual primary halogenoalkane aqueous alkaline hydrolysis reaction RX + OH- --> ROH + X- We know the rate law is first order in RX and OH-. We could separately represent the drop in OH- conductivity as an...

Thanks ... but how would that help, if I've already tried to fit it in Excel?

What is f(x) when eg x = 0, 1, 2, 3, 4, 5, 6, etc y = 0, 8, 12, 14, 15, 15.5, 15.75 etc (the y value at x =1 is arbitrary) ie each successive y value adds half the difference of the preceding 2 values. (It is effectively the inverse of a first order exponential decay where the y...