[xxangelxwingsxx]

A tertiary carbocation is more stable than a primary one, but the 13-C NMR shift for a tertiary carbon is more for tertiary than primary suggesting a carbon atom with more carbons attached is less shielded? Why do extra carbons have this deshielding effect, but then also stabilise positive charges?

[xxangelxwingsxx]

Is it to do with there being less diamagnetic shielding as there are less adjacent H atoms? If so why are C-C bonds less efficient at shielding than C-H bonds or is it just that C is more electronegative than H so can withdraw electon density from it more efficiently?

And if this is the case then why in a simple molecule such as pentane why does the middle carbon have the highest chemical shift even though both C(3) and C(2)/(4) are both secondary C atoms?

[xxangelxwingsxx]

*Ignore me, I am impatient*