How to explain mesylate structural homologues (e.g., "esylate") being weaker leaving groups than mesylate itself?

I came across a piece of scientific literature (<https://patents.google.com/patent/US20080045602A1/en>) that would seem to imply leaving groups formed by reacting hydroxy groups with, e.g., ethanesulfonyl chloride (EsCl) or 1-propanesulfonyl chloride (PsCl) are, or at the very least *can* be, weaker than -OMs (from mesyl chloride). This has me wondering: How should I rationalize these longer-alkyl-chained leaving groups being weaker? Due to their structural similarity, would a comparison of estimated p*K*a values suffice, or would, for instance, a ranking of their leaving group abilities be more situational (e.g., solvent-dependent)? When I run estimated p*K*a calculations in MarvinSketch, the p*K*a goes up with increasing linear alkyl chain length (indicating that they would be "stronger" weak bases) in the homologous series starting from mesylate. However, I am also wondering if I should consider that, just as trifluoromethyl acts to stabilize the triflate leaving group through acting as a strong EWG, an extended (compared to the methyl portion of mesylate) alkyl EDG chain would have a destabilizing effect on leaving group ability.


Here are two quotations of note from the citation I linked above:



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> Although more reactive esters such as toluenesulfonyloxy or methylsulfonyloxy provide for quicker reaction times..., the use of less reactive esters such as benzenesulfonyloxy or ethylsulfonyloxy is advantageous because less and lower amounts of side products are formed.
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> Compounds of Formula III may be upon isolation and purification used in the next step. Alternatively compounds of Formula III can be used in [the] next step without purification i.e. a single pot synthesis from compounds of Formula II to V or from III to V is envisaged. In case those and/or subsequent intermediates are not isolated and purified, it is advantageous to make and use less reactive compounds, such as benzenesulfonyloxy or ethanesulfonyloxy or propanesulfonyloxy or butanesulfonyloxy.
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Do note that the "compounds of Formula III" are the ones that contain sulfonate ester leaving groups. Additionally, page 17 of a thesis ([https://irep.ntu.ac.uk/id/eprint/13/1/211217\_ISMAIL'S%20thesis.pdf](https://irep.ntu.ac.uk/id/eprint/13/1/211217_ISMAIL%27S%20thesis.pdf)) mentions that in SN2 substitution reactions *t*-butylsulfonates (which could visually be thought of as mesylate but with three methyl groups in place of the C-atom's three H-atoms) have been found to be weak nucleofuges compared to mesylates.


