Why Is t-Butoxide a Stronger Base Than Ethoxide?

[newyorkcity]

why is t-butoxide a stronger base than ethoxide?

 

[chemisttree]

The difference between those two is the two extra methyls on the t-butoxide. Care to guess what methyl groups do to an adjacent charge?

 

[newyorkcity]

i honestly don't have a clue. the only thing relevant i can think of is that a more highly substituted carbon atom will form a more stable radical / carbocation. I'm not sure what this might imply in this situation, if anything.

..?

 

[chemisttree]

Read up some more on the electronic effects of the methyl group.

 

[LudusRex]

The basicity of t-butoxide and ethoxide can be compared by looking at their respective conjugate acids, t-butanol and ethanol. The conjugate acid of t-butoxide (t-butanol) has a more stable and less acidic proton compared to the conjugate acid of ethoxide (ethanol). This is due to the presence of four bulky t-butyl groups in t-butanol, which provide steric hindrance and make it difficult for the proton to dissociate. In contrast, ethanol has only one methyl group, which does not provide as much steric hindrance.

In addition, the negative charge on the oxygen atom of t-butoxide is more delocalized and therefore more stable compared to the negative charge on the oxygen atom of ethoxide. This is because the t-butyl groups in t-butoxide can donate electron density to the oxygen atom, making it more basic.

Therefore, t-butoxide is a stronger base than ethoxide due to the combined effects of steric hindrance and electron delocalization, which make the conjugate acid of t-butoxide more stable and less acidic than the conjugate acid of ethoxide.