Why do the predicted values from Y-MB, S-P, Hoy etc. sometimes differ significantly?
Group contribution methods can never be perfect. They depend both on the quality of the data fed to them and on the choice of subgroups and subgroup interactions. We never tire of saying that ultimately you must be the judge of what constitutes a reasonable HSP set for a particular molecule. Use all the tools in DIY and, above all, try to pin down the δTot from enthalpy of vapourisation so you can at least be sure that your overall HSP values fit, even if the internal balance might be questionable. The more we can get independently measured values (e.g. by IGC) the better we can revise/update group contribution methods. Behind the scenes we’re also working on objective molecular dynamics methods – but don’t expect results any time soon! 7 We sometimes get strange results from the Polymer HSP predictions. Why? Yes, we get them too – just look at the last example in the Polymer video. As we said, this is early days with this new technique. We could have waited to improve it, but we wante
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