Illegal Parkinson - 24-5-2015 at 13:28
Hello, i'm not very good with calculators.
I understand that pKa Butane ~ 50 whereas acetylene ~25.
In reaction BuLi + HCCH -> BuH + LiCCH
what do pKa numbers actually mean exactly?
How many time more strongly acidic are ethyne protons relative to butane (sp v sp3)?
Based on numbers it looks like two times the amount but it is log scale etc i forgot it.
clearly_not_atara - 24-5-2015 at 13:48
It's logarithmic: a difference of 25 means that acetylene is 10^25 = 10000000000000000000000000 times as acidic as butane. However since n-BuLi has
some covalent character and the reaction occurs in a nonpolar solvent the effect isn't quite as dramatic.