Achiever - OMG

[dat_student]

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Test #2, natural sciences, Q77
My chemistry book** says E is the right answer. Achiever says B is the right answer.

Are achiever questions written by PhDs or students like us????

Not sure if I can totally trust all their answers.

**McMurry, Chemistry Professor @ Cornell, 4th edition, page 393

 

[mochafreak]

Is McMurry basic or advanced Ochem? I'm not sure if that would change this one or not, but I think if you're studying advanced Ochem it might make the answers the DAT is looking for harder to find. Anyhow, we were definitely taught that benzylic carbocations and radicals are more stable and react faster than tertiary. Pg. 445 of Carey Ochem says that benzylic chloride reacts in aqueous acetone more than 600X faster than t-butyl chloride.

I think your too smart...your researching basic topics too in-depth because you're bored. Just remember to pick the answer they think is right on your DAT. 🙂

 

[dat_student]

...Anyhow, we were definitely taught that benzylic carbocations and radicals are more stable and react faster than tertiary. Pg. 445 of Carey Ochem says that benzylic chloride reacts in aqueous acetone more than 600X faster than t-butyl chloride.

I think your too smart...your researching basic topics too in-depth because you're bored. Just remember to pick the answer they think is right on your DAT. 🙂

No, it's not about being smart. I just remembered that my book says something different. Some of achiever questions have wrong answers. In the case of carbocations, my book says "a primary benzylic carbocation is more stable than a secondary carbocation; secondary benzylic carbocations are more stable than tertiary carbocations." It looks like radicals are a different story altogether. Benzylic chloride reacts faster than t-butyl chloride because it's an SN2 rxn which favors less hindered nuceophilic attacks.

 

[mochafreak]

My book says those rxn rates are for an SN1 hydrolysis rxn (for the carbocations that is)...if textbooks can't figure out what's what, how are we? I wish there was a DAT review book that says "this is the answer for the DAT" like Examkrackers does for the MCAT. 😡

 

[dat_student]

My book says those rxn rates are for an SN1 hydrolysis rxn (for the carbocations that is)...if textbooks can't figure out what's what, how are we? I wish there was a DAT review book that says "this is the answer for the DAT" like Examkrackers does for the MCAT. 😡

I sent a message to some of my online friends. They know much more about chemistry. One of them is a chemistry professor @Berkeley. If I hear something conclusive I'll let you know. Now, I gotta work on my finances. bb in 4-5 hours.

 

[heshyn2000]

Test #2, natural sciences, Q77
My chemistry book** says E is the right answer. Achiever says B is the right answer.

Are achiever questions written by PhDs or students like us????

Not sure if I can totally trust all their answers.

**McMurry, Chemistry Professor @ Cornell, 4th edition, page 393

I asked my orgo prof. he agrees that B is the correct answer.

 

[dat_student]

I asked my orgo prof. he agrees that B is the correct answer.

My books have the same carbocations and very clearly give stability order that is NOT B.

I consulted with some chemists. The following reply best summerizes my finding:

"It varies. I've seen books with one or another of the orders you give,
each with data to support it. (And some avoid the explicit comparison
of, say, benzylic and tert.) I presume it varies with the specific
reactants and reaction conditions.

3 deg > 2 deg etc is fairly simple, because the only variable is
number of alkyl groups. But when one starts changing the type of
group, it is reasonable that effects vary.

The main effect, which I think all your sources (and mine) would agree
on is that allylic and benzylic primary cations are stable compared to
primary cations without the conjugated double bonds. Again, only one
variable... consider only primary, and the difference is presence of
conjugation." **

**Chemist @ Berkeley

 

[gould409]

Barron's DAT says that B would be the correct answer......

 

[Richnator]

Test #2, natural sciences, Q77
My chemistry book** says E is the right answer. Achiever says B is the right answer.

Are achiever questions written by PhDs or students like us????

Not sure if I can totally trust all their answers.

**McMurry, Chemistry Professor @ Cornell, 4th edition, page 393

When are you going to take your DAT dat student. I am sure you will do well, you seem to know a lot. I am slacking off the studying recently though 🙁 I hope to pick up my studying soon though since my test is in 3 weeks.

 

[dat_student]

When are you going to take your DAT dat student. I am sure you will do well, you seem to know a lot. I am slacking off the studying recently though 🙁 I hope to pick up my studying soon though since my test is in 3 weeks.

I am a slacker too. I don't feel like studying anymore. I'll be lucky if I get 10 across the board. I have scheduled it for early Aug.

 

[dat_student]

Barron's DAT says that B would be the correct answer......

Barron is not very reliable. If @ 8 am Barron tells me it's morning I begin to suspect it's probably night.

Rich: see my other post right above this one