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anybody having trouble with ochem?

Discussion in 'Pre-Pharmacy' started by jlee8023, Nov 22, 2005.

  1. jlee8023

    jlee8023 Junior Member
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    i dont know how other professors in other schools teach it to you guys...but anyone have to know the relative boiling points and stabilities of compounds for organic I??? is it just me or is it damn hard.. i swear it cant be this hard ..can it? i mean i know im not dumb..but its something about this class that makes me think otherwise
     
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  3. ndearwater

    ndearwater SDN Donor
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    Things like boiling points and stabilities can be understood if you think of it logically. Then you don't have to try and memorize random numbers.
    I took OChem last year so I couldn't say exact numbers but basically the heavier a compound and the less hindrance there is, the higher the boiling point. That's because the intermolecular forces are strong.
    The more O's and halogens on a compound the more hydrogen bonding which raises the boiling point as well.
    I know it's hard :( Thanksgiving break is here at least! And it's all on the downswing from there.
     
  4. Pharmwannab

    Pharmwannab Senior Member
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    Taking it now myself. If you have any specific questions, shoot me a private message.

    My best advice is to focus more on trends and the underlying concepts than memorization. If your professor is actually having you memorize numbers for bps and mps, well that's kinda messed up heh, but then I guess you have to do it. As said above, the longer the chain, the higher the mp and bp because of increased van der waal's forces (London dispersion forces). More branching in a molecule means a lower mp and bp because there is less surface area on the molecule and less chance for it to interract with other molecules. I wouldn't say the intermolecular forces are "strong" with less branching and longer chains, but definitely "stronger", because van der waal's forces really are actually pretty weak.

    When you get into reactions, study those mechanisms in detail. You may not be able to memorize all the reactions and what product you get, but if you know those mechanisms and how organic rxns work, you can figure out what the product will be. Flash cards are definitely your friend and lots and lots of practice problems too. I've been doing upwards of 40 questions per chapter, and managing to set the curve in my class so far. It's all about how much you put into it. Good luck.
     
  5. Swenis

    Swenis Member
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    Uggh, don't remind me! I just had my last organic test yesterday, focusing on reaction mechanisms. I think I did OK, and the professor usually curves a little bit, which would be nice! :p My grade is borderline B/C right now and is stressing me out somethin' fierce. We only have one lab report, a spectroscopy test, and the final left. How do I learn spectroscopy in less than a week? :)
     
  6. beccala33

    beccala33 Senior Member
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    For any of you having trouble with Ochm, I tutor for it. Please don't hesitate to ask me something. If you have a specific question, just PM it to me!!!
     
  7. anxietypeaker

    anxietypeaker Senior Member
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    boiling points and trends???? you gotta be kidding me...if you think THATs hard, wait until you get to synthesis and mechanisms (these get crazy later on, even if youve already been exposed to a little bit).

    Im telling you this not to scare you but to be realistic. Ochem is hard. The bp trends is NOTHING compared to what youll learn later. However, realize its hard for most everyone else too. Take comfort in that and pray. My ochem is based off of 2 midterms and a final. Lab is separate so theres NO cusion.

    Seriously though, the best thing to do is accept that ochem is DAMN hard. Then study like crazy for that year of ochem. THats the only thing i can really tell you. Dont forget, its hard for everyone else too.
     
  8. starrfishes

    starrfishes Member
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    That's so awesome you tutor o-chem!! One general thing I hate is NMR spectroscopy and never seem to get pass. Any tips? :D
     
  9. starrfishes

    starrfishes Member
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    I definately agree with anxietypeaker that o-chem is hard. It's meant to be challenging and o-chem can get challenging as you want it to be.
     
  10. starrfishes

    starrfishes Member
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    I agree. If professors are making you memorize numbers upon numbers, I think that would do students no good. In fact, it can be a huge waste of your time, because anyone could just look information and facts just as b.p. and m.p.'s. However, what's most important is to understand concepts and trends and mechanisms and such, so that you can apply it to new problems you've never seen before. i.e. synthesizing rxns are hard! Plus, students tend to forget what they memorize, so learning how to work something with your logics will help you very much, on the long-run. Memorization can only go so far and o-chem should never be looked at as a memorization course. :D
     
  11. jlee8023

    jlee8023 Junior Member
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    i just had my test on sn1/e1 sn2/e2 all that dumb crap yesterday..and i sucked on it
     
  12. beccala33

    beccala33 Senior Member
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    I do actually have some tips...
    Always remember that there are 2 different types of NMR spectroscopy, proton NMR (for the hydrogens) and carbon NMR. The purpose for the most part is to tell the structure of your molecule.
    For proton NMR, always remember that the peaks that are furthest to the left are the hydrogens that are the most "deshielded", for example in something like methanol, CH3OH, the hydrogen on the oxygen would be the most deshielded. In methanol's proton NMR you would expect to get 2 peaks, because there are 2 types of hydrogens, the ones on the carbon and the one on the oxygen, and the one on the oxygen would be further to the left. There's also the splitting thing to worry about with proton NMRs. This part is easier... all you need to know here is the amount of hydrogens on neighboring carbons, and add 1 to this number. What I mean is, say you have CH3CH2Br - you would have 2 peaks because there are 2 different types of hydrogens (some on one C, and some on another with a Br.) Now the peak that would be further to the left would be the hydrogens with the C bonded to the Br. This peak would also be split into 4 peaks, because the neighboring C has 3 hydrogens (so you do 3 + 1 = 4 peaks) The peak to the right would 3 peaks, because the neighboring C only has 2 hydrogens (2 + 1 = 3 peaks)
    Wow, this is really long and not really related that much to the topic, but if you have any more questions about this stuff (this really is just a VERY brief overview) just PM me!
     
  13. Stephie

    Stephie Senior Member
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    I just had a an OChem test on the same topics and I also screwed up really bad! Hang in there and know that there are others in your position. The thing is, I'm usually a good student- I think I'm starting to get burnout...
     
  14. Smilescali

    Smilescali Almost there...
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    Another helpful hint regarding mechanisms (especially if you don't know where to start) is to identify the nucleophile (donator of electrons and is often O) and then the electrophile (wanting electrons and is often a positive charge or partial positive charge). Draw an arrow from the nucleophile to the electrophle and that is your first bond.

    I understand O-chem when my professor is doing these reaction mechanisms on the board, but when it comes time for the test I have a hard time organizing what does what and when.

    I have found that making headings for each class of reaction on a separate sheet of paper and writing down examples, common solvent natures and important rules (Markovnikov and Zaitsef's) is helpful. Then just practice, practice and practice.
     
  15. starrfishes

    starrfishes Member
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    Hi beccala33, thanks for your response! I always get stuck when trying to come up with a complicated structure (given the molecular formula) when looking at a sorta-not-clearly defined splitting of peaks in an NMR graph. When the splitting is not clear, they still at least specify the number of protons on each splitted or not-splitted peak. I never seem to get pass the second quarter of o-chem to learn more about mechanisms of rxns, because our very first midterm is always on Proton NMR. I'll definately have more questions during mid-December. :scared:
     
  16. beccala33

    beccala33 Senior Member
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    No problem, the rxns are my specialty area. Just let me know whenever you have any questions at all!
     

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