For MCAT, in orgo do we need to know.....

[mubacalypse]

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I understand dipole moments, do we need to know induced dipoles, instantaneous dipole moment?

Also im having hard time understanding observed rotation, optically inactive, optically active? I know there meanings but to put it in context, i cant seem to understand.

Whats the difference between stereoisomers and diastereomers? Are Enantiomers part of Stereoisomers?

Any sort of examples would be appreciate also, thank you.

 

[PingPongPro]

Those all seem like very fundamental O-chem topics. So yes, you do need to know what those are.

It would probably take a long time to try and explain it clearly, but I suggest you look those topics up in an MCAT o-chem book or textbook.

Yes both enantiomers and diastereomers fall under the "stereoisomer" category.

Simply: Enantiomers are nonsuperimposable mirror images, while diasetereomers are nonsuperimposable and not mirror images.

Or even more simply:
Enantiomers are stereoisomers where all chiral centers differ
Diastereomers are isomers where some, but not all chiral centers differ.

SN1 with chiral center results in a racemic product (pair of enantiomer products) that are not optically active.

There is a lot more, and a lot of the O-chem section requires understanding of those topics you mentioned.

 

[paul411]

Which review book are you using? I found EK explained these concepts very well and Kaplan didn't.

 

[chemistryguy]

You should definitely know what it means for something to be optically active, so make sure you know how to spot a chiral center. Enantionmers and diasteriomers are also a pretty basic concept and you should make sure you can differentiate them. If all else is unclear, wikipedia is often very helpful for these types of things!

 

[BerkReviewTeach]

Which review book are you using?

PingPongPro just quoted a BR shortcut, so I'd guess that's what he or she is using.

 

[PingPongPro]

PingPongPro just quoted a BR shortcut, so I'd guess that's what he or she is using.

I think Paul was asking the OP "mubacalypse" what textbook they were using in order to find out why the OP would not know this information.

But you are right, I am using Berk Review in conjunction with many other companies. I have nothing but good words to say about BR however.

 

[Calvinball]

Not sure if I'm right about this -- and maybe even if I am right, it's just a technicality not worth mentioning -- but I think SN1 with chiral center results in a racemic product only if the reactant has one, and only one, chiral center. If the reactant has multiple chiral centers, then SN1 results in a mixture of diastereoisomers, not a mixture of enantiomers, and therefore, not a racemic mixture. (Technically, racemic mixture = 50/50 mixture of enantiomers.)

Sorta - However, in the case of a particular SN1 reaction, we only consider the effect on one of those chiral centers. So, assuming that we only start with one isomer as a reactant, we would end up with a racemic mixture of enantiomers around the involved chiral center.

It's worth noting that both enantiomers will be optically active, but the mixture won't because the approximately 50/50 ratio will want to bend light equally in both directions.

 

[Calvinball]

Are you saying that the assumption is that the reactant has only one chiral center in the entire molecule? Otherwise, the two optically active products formed from an Sn1 rxn will not be an enantiomeric pair (and the mixture will not be optically inactive), as I understand it (perhaps I am wrong).

That's a good point. Well caught.