[BloodCrisis]

Hi, this is a direct question: what mechanism will be favored for this reaction?

(Tertiary)haloalkane + Ethanol

I know that alcohols are weak bases, but they're still basic... so they will proceed as e1
 or e2 reactions?

Ethanol is a protic solvent, but here it's used as a nucleofile?

[Vidya]

Ethanol is a weak base so  E2 is ruled out and SN2 is also ruled out because tertiary alcohols are bulky substrates.
This will favor E1 and SN1 

[BloodCrisis]

Really? Of course SN2 is out, but i'm confused about ethanol... that OH could work as a base... or the ethanol is the solvent and the nucleofile at the time?

[Vidya]

For E2 we need a strong base like C2H5O- to favor reaction in this bulky tertiary substrates . Ethanol is a weak base do not favor E2 in bulky tertiary substrates .However SN1 and E1 are favored because of the protic nature of the solvent and due to tertiary nature of the substrate.You are right C2H5OH is a weak nucleophile as well as a weak base due to lone pairs on Oxygen. 

[BloodCrisis]

Ok, thanks , too bad I answered e2 in the test...

Now maybe you can help me with this one

NaCC2 (Acetylide) + (secondary)Haloakane . Sn2 vs E2 but... which one dominates?

[Vidya]

acetylide ion is a strong nucleophile because of its sleek nature and negative charge on C (

[BloodCrisis]

Yeah the problem there is that acetylide is both a good base and nucleophile, but my teacher says that only one type of mechanism dominates, she says that e2 will slighty win. Why, I dont know.

[BluePill]

E2 slightly win here because your nucleophile is strongly basic as well.

[BloodCrisis]

So... Acetylide is slightly stronger as a base or nucleophile?

[Vidya]

It is a strong base and a strong nucleophile .It can undergo SN2 with primary alkyl halide .May be your substrate is secondary and hence it is not willing to undergo SN2 so preferred E2 in the presence of strong base .
If you check any book it is a common reaction that all tertiary alkyl halides undergo E2 in the presence of strong base   

[BloodCrisis]

Thanks, so it's a "room" problem.

Seriously, thank you !

PD: I Found this "An acetylide ion is a strong base and a powerful nucleophile. It can displace a halide ion from a suitable substrate, giving a substituted acetylene.
If the alkyl halide used is hindered, the acetylide ion will act as a base abstracting a proton from the substrate and causing an E2 elimination reaction."