help! grignard reagent with epoxide on a ring

[enamel88]

I was going through the road maps in DAT destroyer 2010 version and in road map 6, why does the grignard reagent attacke the least substituted side? BTW there is a ring attached tot he epoxide...does that have anything to do with it? The reagents are 1)CH3MgCl 2)H3O+

Is this not done in acid, thus attacking the most substituted side? any help would be appreciated. Thanks

---

Members don't see this ad.

 

[NDPitch]

Ahhh, don't be fooled!

The gringard itself attacks in the FIRST step. What is a gringard? It's a strong BASE. Thus, it will attack the least substituted side. Then the acid comes in at the SECOND step, after the main event has already happened.

The trap is to see H3O+ and assume this is occurring in acid, but that's not the case! If you were to put a gringard in acid, it would immediately destroy your gringard.

 

[baseness]

I was going through the road maps in DAT destroyer 2010 version and in road map 6, why does the grignard reagent attacke the least substituted side? BTW there is a ring attached tot he epoxide...does that have anything to do with it? The reagents are 1)CH3MgCl 2)H3O+

Is this not done in acid, thus attacking the most substituted side? any help would be appreciated. Thanks

Grignard is never done in acid. Grignard is so basic it would deprotonate an alcohol and be wasted. Such reactions are always done in non protic solvents. When we did a grignard reaction in ochem we had to heat up the reaction vessel with a blowtorch to remove even the smallest amount of water that might have been adsorbed to the glass.

 

[lutopie0730]

I was going through the road maps in DAT destroyer 2010 version and in road map 6, why does the grignard reagent attacke the least substituted side? BTW there is a ring attached tot he epoxide...does that have anything to do with it? The reagents are 1)CH3MgCl 2)H3O+

Is this not done in acid, thus attacking the most substituted side? any help would be appreciated. Thanks

I don't have 2010 version, but i think i can help you here
Grignard is basic.
For example, CH3MgBr has a partial negative charge on the carbon while it has a partial positive charge on the Mg. So it reacts like CH3-, which is a strong base
H3O+ is just a make up step(protonation step) after the reaction.
Therefore, grignard attacks the less substituted side of the epoxide