Dat destroyer organic questions

[niv3k]

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Hi guys, first post here. I have a few questions on the orgo section of the dat destroyer.



So for this question, I thought amide groups were electron donating groups? I've even read several other sources that say so. Don't electron donating groups make compounds more basic? The correct answer is A btw.



This is the answer to the question. The question asks how many isomers (constitutional and stereoisomers) are available. Aren't several of these compounds the same thing? Such as the meso compounds and two of the other E products.



For a, I thought e2 and sn2 occurred under aprotic solvents. Is methanol not a protic solvent?? Also the c, I thought that I is a better leaving group than Cl, or in other words Cl is a better nucleophile than I, so wouldn't it be no reaction? And for e, the answer states that it becomes a tert butyl compound via sn1 mech. I thought that sn1 and e1 always compete against each other since their required conditions are pretty much the same. Wouldn't an alkene also be a product for this reaction??



Answers for number 74 ^.

Hope someone can clear these questions up for me ><. Thank you much.

 

[aznriptide859]

For #48, #2/3 and #5/6 are not the same - it's weird to think this especially if you're good with 3D mental modeling/visualization, but they're not the same molecule. I didn't wrap this around my head in my orgo course, but after some habitualization (hurrhurr bio term) you pretty much differentiate them from each other. #1/4 are meso since they have an internal line of symmetry.

#74 to me, that's just pure reaction memorization (note I absolutely suck in differentiating between E1/E2 and SN1/SN2). Not sure how to explain the rest, but D is trans-bromination of alkenes (this was a studied reaction for my orgo course).

Also do everyone a favor and rotate your pictures lol.

 

[niv3k]

Haha, I'll make sure to take better pics next time.

Hmm so the meso compounds aren't identical either?? I mean if you flipped them around the methyl bonds would be pretty much pointing the same direction wouldn't they? I guess I'll just have to change my ways of thinking on that question hmm.

Ty though

 

[dienepredent]

For the first one, amines are electron donating and i believe amides are electron withdrawing due to carbonyl group by the ring. Anyway, electron donating groups generally DO make BENZENE rings more basics. However, this is not what you're looking for in this question since you're not simply comparing benzene rings. One of the many things that can make something more acidic is having a resonance stabilized conjugate base. Choice A, seems to be the weakest acid because it lacks this resonance stabilization. THEREFORE, it is the strongest base.

For the second one, if it has an enantiomer then both enantiomers count as separate structures. (like if you had a 1R, 2S it's enantiomer 1S 2R would count as well. If you notice, the two meso structures are two different mesos. you'll notice, the methyls are on adjacent carbons on one and the other has a CH2 group in between. They're not the same.

The third, methanol from my understanding is a protic solvent. But E2 reactions don't have to occur in aprotic solvents that is only characteristic of SN2 reactions. for c, yes cl is a weaker leaving group, however its under polar aprotic conditions and the iodide ion is a strong nucleophile, meaning all the conditions for an sn2 reaction and it'll kick the leaving group right out. For e, is not being reacted with a base but rather a nucleophile. elimination reactions require weak bases(for e1) or strong bases(generally e2). therefore it would be a substitution reaction.

I could be wrong about any of this but that's my understanding on it. anyone correct me so I don't make huge mistakes on my DAT lol. Hope it helped a little 🙂

 

[niv3k]

Ty it helped a lot! I appreciate it. On the stereoisomer question I didn't even notice the ch2 group between the methyls *facepalm*, overlooked that too quickly. Ty much makes sense.