Organic II

[DiverDoc]

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😡 I didnt have a problom in O chem I. But were going over H NMR spectra and having to propose structures for a given spectra... Am I alone or did anybody else struggle with this. This is a hard thing to study because its like either you get it or you dont. Please tell me the whole semester of O chem II isnt based off of this. Also Is C 13 NMR easier to intrepret? thanks

 

[DrBowtie]

Be methodical. First look for benzene and try to figure out if it is mono, di, tri substituted. Then assuming you have the formula, subtract the carbons and protons. Then work with whats left.

C13 is good for symmetry.

 

[Jamers]

😡 I didnt have a problom in O chem I. But were going over H NMR spectra and having to propose structures for a given spectra... Am I alone or did anybody else struggle with this. This is a hard thing to study because its like either you get it or you dont. Please tell me the whole semester of O chem II isnt based off of this. Also Is C 13 NMR easier to intrepret? thanks

Holy crap, my head...it hurts...I hated OCHEM. The whole year is not, however, spectra. It's alot of learning where certain things occur. However, I have pushed all of that information far from my brain and would be of NO help to you

 

[Dr Trek 1]

Yeah it's confusing. However, the EK orgo book does a really good job of explaining it and provides you with a tried and true method to figure it out. I would strongly recommend ignoring every other method and using the EK method. And at most you'll have 1 passage on it on the MCAT, and none in med school.

Just get the EK book and you'll be fine.

 

[scpod]

😡 I didnt have a problom in O chem I. But were going over H NMR spectra and having to propose structures for a given spectra... Am I alone or did anybody else struggle with this. This is a hard thing to study because its like either you get it or you dont. Please tell me the whole semester of O chem II isnt based off of this. Also Is C 13 NMR easier to intrepret? thanks

Only 4 things to look at:

1) Number of absorptions- Gives you the number of different types of protons. For example, 3 absorptions means 3 different types.

2) Size of absorptions- Use the built in integration to tell you the ratio of the numbers of protons. Use that example of 3 absorptions in number 1; 8.8:3.8:2.9 would mean 9 of one type, 4 of another, 3 of the last.

3) Position of Absorptions- H's bonded to a carbon attached to an electronegative (or electron withdrawing like C=O or aromatic rings) group will shift left. CH3Cl (more electronegative) is farther left than CH3Br.

4) Shape of Absorptions- Use the n+1 rule for splits.

 

[MikeyLu2010]

i thought ochem II was definately way harder than ochem I...just the scope of the material..and the amount of mechanisms that our school made us memorize...in retrospect i viewed the NMR spec C or HNMR was the easiest part..i guess our teacher just taught it well ..i had worked about 10x harder for Ochem 2..and still got the same grade i got in ochem I...(B)...i think im just dumb🙁

 

[scpod]

i thought ochem II was definately way harder than ochem I...just the scope of the material..and the amount of mechanisms that our school made us memorize.(

Therein lies the problem. The old way to learn Orgo was simply by memorization, which only works well for the first few hundred reactions. The key to "learning" Orgo is in arrow pushing. Learn that and the concepts of Ph, electronegativity, and steric hindrance; 90% of it is a breeze after that. The thing about arrow pushing is that if you really understand electrons, then you will never have to remember things like which groups are donors or withdrawers or the differences between SN1, SN2, E1, and E2, for instance. It will actually make sense. Of course, the most important thing can be in the professor who's teaching it. He or she can make it very easy or very difficult.

 

[supersash]

i had NMR in orgo 1 last semester, and spring semester hasnt started yet. i too hate NMR, but found that my teacher did an amazing job of explaining. (im still on break, so i remember nothing at this current moment).

what kind of NMR is on the MCAT?

 

[HunterGatherer]

It seems that are always a couple IR, H NMR and C13 spectra problems on the MCAT. It's an easy way to get points if you nail this concept now.

Spectra is something that can be learned with repition just like anything else. I did not perform well in Orgo but managed to bring it together come MCAT time.

I have some websites that may help.

 

[Duchess]

dIvErDoC,

I hated O-chem, both I and II. The whole semester isn't NMR, so don't freak out. However, I would DEFINATELY make an effort to go to your teachers office hours for help or to get a tutor because NMR is almost always on the MCAT. Also, if your teacher is anything like how mine was they'll throw in a random NMR problem on future tests, especially on your final. I am not sure how your Organic Chem Lab is at your school, but we had to make an NMR and IR spectra and analyze it (label stuff, etc.) for the product of almost every experiment. It sucks, but it's important to know. Best of luck to you!

 

[JohnUC33]

O-chem II is not all NMR, but the stuff does peak its head in every now in then throughout the course. Mainly, get ready to memorize a butt-load of reactions. Mainly try to understand the themes, and then the reactions are a little bit easier to memorize. You will want to try to get a grasp on the NMR stuff though. Once you understand it, those will be easy points on the MCAT because a little bit of it will show up on it. Like a previous poster said, EK does a good job of covering the NMR you will need for the MCAT. Just take it one step at a time. Try grasping one topic at a time, and then adding something else. If you put the study time in O-chem II, you will do fine.

 

[stacyij]

😡 I didnt have a problom in O chem I. But were going over H NMR spectra and having to propose structures for a given spectra... Am I alone or did anybody else struggle with this. This is a hard thing to study because its like either you get it or you dont. Please tell me the whole semester of O chem II isnt based off of this. Also Is C 13 NMR easier to intrepret? thanks

It is only in the beginning. Or at least it was in my o-chem 2 class.

 

[PlasticMan]

Therein lies the problem. The old way to learn Orgo was simply by memorization, which only works well for the first few hundred reactions. The key to "learning" Orgo is in arrow pushing. Learn that and the concepts of Ph, electronegativity, and steric hindrance; 90% of it is a breeze after that. The thing about arrow pushing is that if you really understand electrons, then you will never have to remember things like which groups are donors or withdrawers or the differences between SN1, SN2, E1, and E2, for instance. It will actually make sense. Of course, the most important thing can be in the professor who's teaching it. He or she can make it very easy or very difficult.

👍 Understand how things really work at the molecular level and when you get stuck on a problem and can't remember what reaction takes place, you'll be able to figure it out on the fly.

 

[jellibelli]

I LOVED OChem II way more than OChem I. 😀
My advice for spectra (after you understand it a bit) is to practice, practice, practice! Do problems... TONS of problems. You'll learn a lot while you're doing them. Sometimes it's really helpful to sit down with the prof and go over it, too.

Good luck! 😛

 

[MikeyLu2010]

Therein lies the problem. The old way to learn Orgo was simply by memorization, which only works well for the first few hundred reactions. The key to "learning" Orgo is in arrow pushing. Learn that and the concepts of Ph, electronegativity, and steric hindrance; 90% of it is a breeze after that. The thing about arrow pushing is that if you really understand electrons, then you will never have to remember things like which groups are donors or withdrawers or the differences between SN1, SN2, E1, and E2, for instance. It will actually make sense. Of course, the most important thing can be in the professor who's teaching it. He or she can make it very easy or very difficult.

Our school made us memorize the electron pushing..and i still found it hard...for our school..orgo 1 consisted of the basics and maybe 5-10 reactions....Orgo 2 on the other hand had about 20-30 reactions on the first test alone...so yea..i think i had a lot of trouble in the chemistry of ring forming/breaking...never really got the hang of that...good thing i wont need that in med school !! whew

 

[scpod]

Our school made us memorize the electron pushing..and i still found it hard...for our school..

Arrow pushing really isn't something that you can memorize. Memorizing all the tetrahedral intermediates in a reaction, for every reaction, would be incredibly hard (next to impossible), but if you understand the way electrons flow and react, then you can draw them all out for yourself. There's no need to memorize a thing. You don't have to memorize whether a C=O or an aromatic ring is an electron donor or withdrawer, for example, if you understand what the pi and sigma bonds really mean and do, and how they are influenced by surrounding groups. Few professors, however, will be able to explain all that in lecture.

In all honesty, you really don't need to know things on that kind of level, but if you do, your life will be incredibly easy. Perhaps it came easy to me because I am a visual learner. Give me a pencil and piece of paper and I can draw any reaction for you just by pushing those little electrons around. Organic Chemistry ended up being my favorite subject. I know that makes me sound weird, especially for a Biology major, but it's true.

 

[DiverDoc]

Thanks for all the replys guys, I had a better go at it today though and the more I look at it, the more successful I am at proposing a correct structure. 😎

 

[JimmyG]

..i had worked about 10x harder for Ochem 2..and still got the same grade i got in ochem I...(B)...i think im just dumb🙁

You are definitely NOT dumb. I am only 2 weeks into Orgo II and no matter how much I study, I still come out of every class dazed and confused. I just tell myself I have to get through it... I'm praying for your B... 😀