Butyllithium isomers are all stored in alkane solvents. Theoretically, equilibrium should (given enough time) lead to formation of mostly n-hexyllithium in the case of n-BuLi stored in (mostly) n-hexane, I believe. I understand that the kinetics of deprotonating an alkyl proton are extraordinarily slow, apparently even in the case of the much stronger t-BuLi in pentane (which isn't merely thermodynamically neutral; it should be thermodynamically favorable for the lithium to exchange with the proton of a less substituted carbon).
I was wondering, though, does anyone know of any instance where a significant portion (or any observable portion, really) of something like t-BuLi has been noted to have reacted with alkane solvents?
All searches I've attempted have given me completely unrelated results, and even attempting to sift through them, I have come away with no mention of the idea, even.
Also, would the addition of some kind of lithium-binding reagent such as TMEDA or 15-crown-5 increase or decrease the rate here (assuming no Brønsted reaction between BuLi and the ligand)?
I ask because BuLi will typically deprotonate a heteroatom before doing nucleophilic addition, but will do nucleophilic addition (to a carbonyl) before deprotonating most "softer" carbon acids, suggesting alkyllithiums are pretty hard bases. I'm assuming making a more "naked" carbanion would make a harder base (more charge-driven than "HOMO-LUMO overlap"-driven), and I'm wondering if that could make it slower to react with an alkyl proton (though, an unstabilized carbanion is a fairly hard nucleofuge, so I could see the reaction going faster, too).