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A GC & Orgo Q :) Diagrams included.

Discussion in 'DAT Discussions' started by predentlove, Aug 5, 2011.

  1. predentlove

    5+ Year Member

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    *QR & Orgo Q

    1. [​IMG]

    I keep getting around $66.. It might be a problem error?


    2. [​IMG]

    For the last step, why does the Br add to that side?

    3. [​IMG]

    Why would you call this a 1,2 addition if you were adding to the carbonyl...? and why is it a (1,4 addition) if you were adding to the Beta Carbon?

    I am confused at the numbering .. What would we use as the # 1 C?



    As always,

    huge thanks :) :idea:




    Disclaimer: I do not own any of the images.
     
    #1 predentlove, Aug 5, 2011
    Last edited: Aug 5, 2011
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  3. FROGGBUSTER

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    #1. I got C.

    Let x = Sum of 3 items + 0.065 * (Sum of 3 Items)

    Then you apply the discount = x - 0.25x = 0.75x = your answer.

    My guess is you probably applied the discount before the tax? Never do that, always apply the discount at the end after tax.

    #2. This has to do with mechanism. HBr + peroxides forms the Br radical, which attacks at carbon 1 of the 1-Bromo-1-alkene and forms the secondary radical, which is pretty stable. Just memorize it.

    #3. Yes I think so.
     
  4. indigenoustw

    indigenoustw Am I picking my nose or showing my shaka?
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    #1: ($ sum of all the items)*0.75*1.065 = 94.97*0.75*1.065 = 75.857

    *0.75 = 25% off
    *1.065 = 1 + 0.065 = $ of all items + tax

    #2: what Froggie said. Involves secondary radical formation

    #3: Hmm. for this, I recall that a "simple addition" to alpha, beta-unsaturated aldehydes/ketones resembles a 1,2-addition because a Hydrogen atom adds to the oxygen atom and the Nu: adds to the carbon. Then for "conjugate addition", hydrogen again adds to the oxygen and the Nu: adds to the beta carbon (two carbons from carbonyl carbon) in the enol form, which can undergo tautomerization.

    As far as numbering goes, that's really not how you number the atoms unless you use it to fit your observation of the addition into 1,2 and 1,4 additions. I would rather use simple addition and conjugate addition to describe the reaction because these are more accurate.
     
  5. predentlove

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    Thanks guys! Is it always true to take the state tax before the discount?
     
  6. rmm30

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    The rxn is HBr addition to an alkyne then an alken. The rxn proceeds with anti-markovnikov regioselectivity. That means the electrophile (H in this case) adds to the more substituted side of the double bond while the nucleophile (Br) adds to the less substituted side. Since there is excess HBr it adds twice ( once to triple bond, and once to the dbl) in anti-markovnikov fashion. You might keep in mind that HBr is the only hydrohalic acid that adds anit-markovnikov.

    It's worth noting that this rxn is not that same as HBr (HI, HCl) addition without peroxide. That reaction is a markovnikov addition and proceeds through a carbocation intermediate.


    I think the term 1,4 refers to regioselectivity and the rxn mechanism. You don't have to know it. In fact, scrap it from your brain and just stick with calling it Beta addition. It won't confuse you and you'll remember it better.
     
  7. indigenoustw

    indigenoustw Am I picking my nose or showing my shaka?
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    uhh....i don't think so. How do you buy clothes that's 50% off?

    You take 50% off the ticketed price and then apply state tax to the discounted price, otherwise you would be paying extra tax to those $ shed off your original price. State govn't will love it tho.
     
  8. predentlove

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    oh ok. so how can we assume what to do in this case?... in order to get the right answer?

    thanks :D
     
  9. FROGGBUSTER

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    Actually, it may be the same either way, lol.
     
  10. indigenoustw

    indigenoustw Am I picking my nose or showing my shaka?
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    I don't know. Let say you have a $10 item. 50% off = $5.
    State tax = 5%.

    If you apply state tax first, 10*0.05 = $0.5 tax
    If you apply state tax to final price, 5*0.05 = $0.25 tax

    In conclusion, state tax applies to the final price you are buying the item for. In other words, you don't pay tax on the $ that you don't spend. Govn't won't be in debt if you do.
     
  11. FROGGBUSTER

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    I'm getting that it's the same either way.

    $10 item, 50% off, 5% state tax.

    1. Discount first, then tax.

    $10 - .5*10 = $5.

    $5 + .05*5 = $5.25

    2. Tax first, then discount.

    $10 + 0.05*10 = $10.5.

    $10.5 - .5*10.5 = $5.25.
     
  12. jorourk1

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    yeah it all evens out either way im pretty sure
     
  13. predentlove

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    OHhh okay! So both ways work.

    All right thanks all! ;)
     
  14. indigenoustw

    indigenoustw Am I picking my nose or showing my shaka?
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    yea lol it's even reflected by my very own answer to the original post. (shame on me)

    It's proportionate so order doesn't matter. I guess that just reflects how my brain works when I buy stuff and how I dislike govn't taxes.

    So yeah, predentlove, both ways work.
     
  15. predentlove

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    you're still awesome!! :)

    at least you got the answer!
     

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