Shouldn't ethylene should be more acidic? It has a C=C bond, so the density of electron cloud would be higher in the areas of the double bond while the C-H single bond have way less electron density. This, plus the fact that carbon has higher electron negativity than phosphorus should mean ethylene is more acidic as C-H bond will be more weakened than P-H bond and thus, C-H bond will break relatively easily, releasing H+ ions more frequently.

However that seems to be not the case (as discussed in this question Is ethylene more acidic than phosphine?).

Why so? Or am I wrong? Any help or discussion is welcomed. Thanks!


1 Answer 1


Phosphorus, a third-period element, forms a weaker bond to hydrogen than carbon; see for instance https://chem.libretexts.org/Courses/Valley_City_State_University/Chem_121/Chapter_8%3A_Chemical_Bonding_and_Molecular_Structures/8.6%3A_Bond_Enthalpies. Thus even though phosphorus has a relatively low electronegativity, the dissociation of a hydrogen ion costs less energy with phosphorus than with most hydrocarbons.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.