Organic chemistry question

[Alaa1984]

Hi,
When we have an epoxied ring, where should the attack take place? At the more substituted carbon or the less substituted? Chad says that in acidic conditions, always attack the less sub. Carbon. The destroyer says the opposite, it says in acidic conditions attack the more sub. Carbon??!
I am really confused which one is right? And is it different with gringard reagent?
Thanks, ☺️

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[AGSIII]

Acids attack from the most substituted carbon. Bases do just the opposite. Grinards will attack at the least substituted.

 

[DAT Destroyer]

Hi,
When we have an epoxied ring, where should the attack take place? At the more substituted carbon or the less substituted? Chad says that in acidic conditions, always attack the less sub. Carbon. The destroyer says the opposite, it says in acidic conditions attack the more sub. Carbon??!
I am really confused which one is right? And is it different with gringard reagent?
Thanks, ☺️

As written in every organic text.....attack the more substituted carbon. The mechanism is Sn1-like......and the developing carbocation makes the bond weaker. However, it is not a true carbocation.... In acid, ALWAYS attack the more substituted carbon. In base,,,,,things get a bit trickier, and can vary with reaction conditions. As a general rule, attack the less substituted carbon. The reason here is mainly steric, since we are dealing with an Sn2-like process. The text by Maitland Jones presents this quite clearly as well. A Grignard is a powerful base and will attack the LESS substituted carbon.....acidification is the second step.

Hope this helps.

Dr. Jim Romano

 

[Anthony Bogdan]

Remember BLAM: Basic Less, Acid Most