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05-15-2015, 06:12 PM | #16 | |
Now you've pissed me off!
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Which one of the following compounds adds twice to this molecule: A. MeMgBr (a Grignard) B. Me2CuLi (an organocuprate) C. DIBAL (a source of hydride) D. LDA (A nitrogen atom with two lone pairs and two isopropyl groups) E. All of them will. I added the info in (). We were told throughout the course that irreversible nucleophiles add twice to carboxylic acid derivatives. Also, LDA isn't technically irreversible, but essentially functions as an irreversible nucleophile. |
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05-15-2015, 06:14 PM | #17 |
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Tough call but probably a statics class I had. The material wasn't terribly difficult but it wasn't as intuitive as one would hope and it was taught by a guy who spoke ridiculously bad English. He was almost completely unintelligible so the entire course had to be self taught.
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05-15-2015, 06:15 PM | #18 | |
Pessimistically optimistic.
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05-15-2015, 06:15 PM | #19 |
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**** you Spanish
Hablo.....habla....hablablahmos
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05-15-2015, 06:16 PM | #20 |
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I had no trouble at all doing the work in Differential Equations, but I stood in awe of the people who actually developed those methodologies.
Then I took a course beyond differential equations, and it was there that I threw up the only white flag of my academic career. It was some class that involved doing discontinuous Laplace Transforms. So if you're keeping the score ... 1. If it's a problem that regular calculus can't deal with, you go to differential equations. 2. Within differential equations, there was a particular methodology for certain problems that was called a Laplace Transform. 3. If Laplace Transforms didn't work because you were dealing with discontinuous equations, you entered the realm of this class. I sat in it for perhaps three weeks and had literally no idea what was going on. Not only could I not understand the coursework, I couldn't even understand the problems that the coursework was trying to solve. It was the only time I ever dropped a course because I was terrified for my grade. I took another course in structural dynamics that was a big game of Russian roulette, and it was terrifying for a while. The entire course was one big concept on how to set up equations to measure structural stresses in a complex structure (e.g., a one-piece car frame). It was kind of weird and mind-twisting, and you either got it or you didn't. The first month of that course was terrifying because it was a required course and I wasn't getting it, but finally the light blinked on right before the first test. A friend of mine had a very high gpa and actually went on academic probation because of that one class. The light never came on and he got a D, despite the fact that he was on track to graduate Magna cum Laude.
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05-15-2015, 06:17 PM | #21 |
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I should add that all of mine have been undergrad courses as well. I'm going back to college after 13 years away from it. I haven't had much trouble aside from a Philosophy teacher that I believe graded toughr if you had an opposing view to him.
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05-15-2015, 06:18 PM | #22 | |
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05-15-2015, 06:19 PM | #23 |
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I loved calculus. Loved it. It was like creating art. Unfortunately 30 years without doing has made my skills a bit rusty. As in, it's like I've never had it and have no idea how to do even the simplest problem now.
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05-15-2015, 06:19 PM | #24 | |
Now you've pissed me off!
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05-15-2015, 06:20 PM | #25 | |
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05-15-2015, 06:22 PM | #26 |
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At the risk of being crass, we knew in my undergrad program that you avoided the Chinese profs and instructors at all costs. You could kind of halfway understand the Indian ones, but with the Chinese you were at risk of literally not understanding a word. It surprised me that some of the students never figured that out.
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05-15-2015, 06:23 PM | #27 | |
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A Grignard functions as a source of anionic carbon, so it is irreversible. Here's where it gets hairy, though: A cuprate is also an irreversible organometallic, but it follows different rules than the others (adds 1,4 rather than 1,2, and adds only once). DIBAL is a hydride source. It's almost impossible to kick a hydride ion off a molecule, so it should add twice...but when added to a ketone it actually makes an aldehyde (which, because of the existing double bond to oxygen and the carbon bond, can't add twice because it would give carbon five bonds). LDA, despite having a ridiculously high pKa still isn't irreversible, even though we treated it as such throughout the whole term. So, despite the fact that all four were irreversible and the rule we were told is that irreversible nucleophiles add twice, only one of the aforementioned really added twice. I was ready to spit fire after reading that question. |
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05-15-2015, 06:23 PM | #28 | |
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05-15-2015, 06:29 PM | #29 | |
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05-15-2015, 06:35 PM | #30 |
pie is never free
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