While studying Molecular Orbital Theory, I ran into a comparison of basicity between pyridine and piperidine. The latter was concluded to be more basic because of the sp3 hybridization of the positively charged nitrogen opposed to the sp2 hybridization of the pyridine nitrogen. The p orbitals are higher in energy, hence, the higher the p influence on the final hybrid orbital the bigger it will be in energy. Higher energy orbitals result in higher stability for positive charges.
On another moment, when reading about carbocation stability, it was stated that tertiary carbocations are more stable due to the delocalization of the positive charge.
Both statements regarding the positive charge stabilization makes sense, but here's where I started getting confused:
If positive charge delocalization plays a big role on carbocation stability, wouldn't the π-system of the pyridine help delocalize the positive charge through resonance? Wouldn't that compensate the effect of the orbitals lower energy (due to higher s orbital character)?
Considering the answer to the above question was that the orbital hybridization actually plays a bigger factor in positive charge stabilization than delocalization, then why alkynes like methylacetylene are attacked in the secondary carbon (which are sp hybridized in the carbocation form?) and not in the sp3 hybridized carbon? (Consider R = CH3 in the image below)
Could someone give me a light on those matters? I assume I might be making a confusion regarding the carbocation hybridization of methylacetylene, would the secondary carbon have a sp geometry when it's positively charged?