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What is the difference in the reaction that proceeds when we use the reagent $\ce{C2H5O- Na+}$ and $\ce{NaOH}$ in $\ce{C2H5OH}$ in with, say ethyl chloride. Is the latter considered to be "alcoholic NaOH"?

$$\ce{CH3-CH2-Cl}$$

As per my understanding, $\ce{OH-}$ in $\ce{C2H5OH}$ exist in an equilibrium with $\ce{C2H5O-}$ and $\ce{H2O}$, with the formation being favoured due to a basic medium provided by $\ce{NaOH}$ $$\ce{C_2H_5OH + OH- <=> C_2H_5O- + H2O}$$ $$\ce{C_2H_5O- + CH_3-CH_2-Cl -> C_2H_5OC_2H_5}$$ $$\ce{C_2H_5O- + CH_3-CH_2-Cl -> CH_2=CH_2}$$ Given that the substrate is a primary chloride, nucleophilic substitution by $\ce{C2H5O-}$ seems to be the most favourable pathway, as compared to E2-elimination. (Williamson synthesis)

However, I have seen in multiple books that both alkenes/ethers are given as products in different instances, with the reagents I mentioned being used interchangeably. What is the difference between them and what is the major product formed?

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    $\begingroup$ With sodium ethoxide, there are no traces of water. $\endgroup$
    – Karsten
    Commented Mar 24 at 18:31
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    $\begingroup$ @Karsten what are the implications of that? $\endgroup$
    – mark
    Commented Mar 25 at 5:57
  • $\begingroup$ Depends on the specifics of the reaction. $\endgroup$
    – Karsten
    Commented Mar 25 at 10:04
  • $\begingroup$ @Karsten Could you give some examples of the variables that would decide the major product in the two cases? $\endgroup$
    – mark
    Commented Mar 25 at 14:26
  • $\begingroup$ Temperature, solvent, nucleophilicity/basicity of reagents, steric hindrance of the base are some examples. $\endgroup$
    – Karsten
    Commented Mar 26 at 17:12

1 Answer 1

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NaOH dissolved in ethanol gives a mix of hydroxide and ethoxide depending on how much water is present. To run a reaction with a pure alkoxide the procedure is to dry the alcohol and to generate the alkoxide by careful reaction of the alcohol with the appropriate metal preferably under an N2 atmosphere. Alkoxide solutions can be purchased.

The balance of E2-SN2, E1-SN1 can be complicated and is best investigated on an individual basis. If interested in the Williamson synthesis check here: https://en.wikipedia.org/wiki/Williamson_ether_synthesis

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    $\begingroup$ And how does that affect their reactivity towards ethyl chloride? $\endgroup$
    – mark
    Commented Mar 25 at 5:57

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