for the SN1 rx. ,i want to know why the nucleophile is H2O instead of OH^-,
after the attach of H2O, a proton leaves. why not add directly the OH^-?
thx
unimolecular substitution
2008-04-13 10:39 pm
回答 (2)
2008-04-13 11:44 pm
✔ 最佳答案
This is because of the concentration effect.SN1 reaction is a two-stage reaction. In the first step, a carboncation (R+) is formed.
In the second step, the carbocations attract both the hydroxide ions and the lone pairs of electrons on water molecules. The concentration of water molecules is much higher than that of hydroxide ions because water is the solvent of the solution. Therefore, the carbocations attract mainly water molecules, although the hydroxide ions have formal negative charges on them.
2008-04-14 3:39 pm
because in the SN1 reaction, the carbocation is firstly formed which is very stable.
a simple weak nucleophile such as water can finish the job very easily.
that is why a strong nucleophile such as OH- is not necessary at all.
a simple weak nucleophile such as water can finish the job very easily.
that is why a strong nucleophile such as OH- is not necessary at all.
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