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Hemiacetal and hemiketal formation
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Brigida_2130
#1 Posted : Sunday, June 28, 2020 6:59:34 PM
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Why is this considered a Sn1 reaction?
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INSTR_Charanpreet_99
#2 Posted : Wednesday, July 01, 2020 2:17:12 AM
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Not sure what you are referring to - is there an attachment or figure? Please send a screenshot of your question to the instructor and they will get back to you.
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INSTR_Katerina_102
#3 Posted : Thursday, July 02, 2020 1:43:13 PM
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Hi,

I think I understand what you are asking, correct me if you are wrong.

This is a common misconception - In Sn1 reactions are that you get a 50/50 mix of R and S because a carbocation is sp2 and planar.

Because of this, the nucleophile has an equal likelihood of attacking either side, resulting in this mixture.

For hemiacetals and ketals, the carbonyl is also planar, and because of this, you get a 50/50 mix of R and S in the same way. This does not mean that hemiacetals and hemiketals undergo Sn1 reactions. This is a distinct mechanism that happens to have the same ramifications due to the sp2 hybridization and therefore planarity of the carbonyl.

Please let me know if this is unclear or unrelated, and I can draw a picture or clarify.
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