[carotis]

I am referrinmg to this source: http://www.masterorganicchemistry.com/2012/11/30/deciding-sn1sn2e1e2-2-the-nucleophilebase/

In example 3 of reactions there is a tertiary OH leaving group which reacts with H2So4 under heat circumstances. The author ruled out E2 elimination, but hence E2 mechanism undergoes a differernt principle than Sn2 substitution I think that it is a mishap.. the circumstance for an E2 reaction I thought was first a rather strong bulky base, but also there must be stereochemically speaking a anti peri planar H atom on one of the beta- Carbons, or is it wrong? Even when H2SO4 is not a common reagent for E2 reactions, I doubt that under these circumstances ANY substitution will occur, rather it will be a mixture of E1 and E2 reactions, in which the Sajzef product will be favoured, would you attest to that?

And there is a case, where a reaction of a halide alkane such as chloride and NaOEt there are predominantely two concurence reactions, one of which is the ether synthesis and thus Substitution and elimination? In case of a tertiary halide no SN2 reaction will occur and because NaOet is a rather strong nucelophile no Sn1 reaction, but what will happen most likely, a E1 or E2 elimination and what role has the HOEt in the mixture with NaOEt ?

I am really looking forward for answers, for I need to be prepared for my final exam, so thanks in advance

[orgopete]

This question aims to split hairs in a certain manner. Let me try to explain how this might be the case.

When referring to the kinetics of a reaction, E1, E2, SN1, or SN2, we are referring to the factors that initiate the reaction or cause it to occur. Therefore, we should not normally have a mixture of E1 and E2 or SN1 and SN2 mechanisms. That is, you wouldn't try to get an E2 reaction using E1 conditions (unless you didn't know better). This can become cloudy with some reactions as concentration can be a factor for which we do not have any practical expectations. I always suggest that if a textbook lists a reagent, base, nucleophile, etc., it is referring to the reagent as kinetically important to the reaction.

That should be sufficient to answer the question. If sulfuric acid were used, could the initiating step be base/nucleophile attack? If tertiary, no because the C-O bond will break faster, i.e., rate limiting reaction. If an alkoxide or halide were the base/nucleophile, could the rate limiting step be a unimolecular breakage of the C-X bond? That is, the rate depends only on the concentration of the halide and independent of the nucleophile. This should again be a "no" if we mean the base/nucleophile is being used as a kinetically important reagent.

Practically, one may find themselves in a situation in which the concentrations are too low to initiate an E2/SN2 reaction. I discovered this in a practical laboratory experiment in which NaOH was used as base with an indicator dye to detect its excess. In a solvolysis of a t-buyl halide, the rate limiting step was actually solvolysis of the C-X bond. The released HX neutralized the NaOH and the reaction was an E1/SN1 reaction. What was missing was the intent of the reaction. It could or should have been an E2 reaction if NaOH were a kinetically important reagent. However, I do not know of any practical way that students could anticipate when a kinetically important concentration is being used. Hence, I refer to the intent of a question. If NaOH were listed as a reagent, it is intended to be kinetically important, hence E2.