[vayden]

Lately, I've been confused on the solvent effects concerning wether it would be classified as elimination over substitution.

I understand SN2 and E2 reactions favor aprotic solvents such as DMSO with fluorine being considered the best nucleophile and going down the periodic  table to iodine being the worst nucleophile.

the opposite would hold true in a polar protic solvent such as water with iodine being the best neculeophile.

my question I need help in understanding if lets  say we have a reaction consisting  of  a reactant such as   2-bromobutane reacting with NaNH3 which would yield a SN2 reaction under aprotic solvent conditions such as DMSO, as it is a secondary site reacting with a moderate nucleophile, but what would happen if same reaction conditions were used but a water solvent was used?

my best guess would be that the reaction would not take place? as it would be endothermic rather than exothermic.. is this guess on a right path?

[wildfyr]

I assume you mean NaNH₂ (sodium amide). Considering that it reacts explosively with water to give ammonia, then your proposed reaction would not occur. But it sure would be exothermic!

Generally though, 2 bromo butane in the presence of a powerful base like :NH2, could both substitute or eliminate depending on temperature, even if solvent is held constant. Considering that :NH2 is SUCH a strong base, I would expect elimination to be prevalent unless things are done very cold. I can't remember ever seeing a literature example of nucleophilic substitution using sodium amide.

Secondary alkyl halides are always the bane of this (common) question. The answer is that they can do both SN1/2 and E1/2. It truly depends on the specifics of the sterics, leaving group, solvent, and temperature to push it in one direction. You seldom attain perfect fidelity.

[Babcock_Hall]

@OP,  Did you perhaps mean sodium azide, NaN₃?