methyl shifts?

[SunnyD0119]

hey for orgo...i know about methyl shifts and hydride shifts in E1....but i was thinkin that they can happen in Sn1 too...anyone have any examples that can help me out w/ this?
also for those who have taken the dat have you seen any really complicated reactions on the test??

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[dexadental]

This is all fair game for the DAT...but methyl shifts do occur during Sn1 reactions, infact, any reaction that allows for rearrangements through formation of a carbocation can allow for this. Goodluck.

 

[Joeybag]

This is all fair game for the DAT...but methyl shifts do occur during Sn1 reactions, infact, any reaction that allows for rearrangements through formation of a carbocation can allow for this. Goodluck.

Yeah, like dexa said, any reaction that forms a carbocation (like E1 or SN1) as well as like adding HBr or H20 to an alkene are capable of rearranging via hydride or methyl shifts. I dont remember any super complex reactions, but maybe ones involving benzene rings and then adding like Br2/FeBr3 and then adding say CH3CH2Cl/AlCl3-- just testing if you know that Br2 would be a 1,2 or 1,4 substituent. Also they may do the reverse and show the reactant and product and expect you to come up w/ what the reactants would require to get to that product, like get from benzene to 4-methyl-bezoic acid (I'd say 2 but maybe 3 max steps for these types of problems). I found that flat out knowing these omp directors/activators and deactivators (like that br is a deactivator but actually ortho/para) was super helpful.

 

[mochafreak]

Yeah, like dexa said, any reaction that forms a carbocation (like E1 or SN1) as well as like adding HBr or H20 to an alkene are capable of rearranging via hydride or methyl shifts. I dont remember any super complex reactions, but maybe ones involving benzene rings and then adding like Br2/FeBr3 and then adding say CH3CH2Cl/AlCl3-- just testing if you know that Br2 would be a 1,2 or 1,4 substituent. Also they may do the reverse and show the reactant and product and expect you to come up w/ what the reactants would require to get to that product, like get from benzene to 4-methyl-bezoic acid (I'd say 2 but maybe 3 max steps for these types of problems). I found that flat out knowing these omp directors/activators and deactivators (like that br is a deactivator but actually ortho/para) was super helpful.

Did you find that you needed to know the order of strength of the activators/deactivators? Obviously NH2 is stronger activator than CH3, but others are not so obvious, would you recommend memorizing the order?

 

[Joeybag]

Did you find that you needed to know the order of strength of the activators/deactivators? Obviously NH2 is stronger activator than CH3, but others are not so obvious, would you recommend memorizing the order?

I don't recall that being an issue, but I couldn't promise what the testmakers might do either. Obviously if there's two possible choices that could be or seemed correct, I would try and sort out the strong from the weak, but if you had to just remember the strongest and weakest activators/deactivators and that probably would be enough( i.e you probably dont want to start try and and add nitro first and then OH.) In terms of if a ketone or aldehyde are stronger deactivators, I highly doubt the testmakers would be so anal.