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Dr. Lennox

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Everything posted by Dr. Lennox

  1. What bonding forces are present in benzoic acid? How does benzoic acid interact with water? What bonding forces are present in sodium benzoate? How does the benzoate interact with water? Keep in mind that not all carboxylic acids are alike. Lower molecular weight carboxylic acids such as acetic acid are soluble in water. This solubility begins to decrease drastically after C5. Why would such a pattern exist? What can you say about the carbon/heteroatom ratio in acetic acid? In benzoic acid? Finally, benzoic acid is a solid. What crystal packing forces are involved in such a solid? Why would you expect water to disrupt such crystal packing forces? Good luck!
  2. The Student Resources Section below is a compendium of organic chemistry links for the one stop shopper, http://lennoxtutoring.com/organic-chemistry-tutor-student-resources/ Please use them wisely.
  3. One last thing, if you haven't started O-Chem yet, now's the best time to try an innovation I'm using in conjunction with a neuroscientist colleague. Every one of my students is being encouraged to work Sukoku puzzles daily if possible. Everything you need to know about the strategy is in the article, Sudoku for Organic Chemistry Mastery http://lennoxtutoring.com/2012/08/10/sudoku-for-organic-chemistry-mastery/ I welcome you to try it, and I hope you stay with it. Now I have to find a few profs to help me with an experiment for the fall.
  4. Psychology is a science wherein the "scientists" are mostly ill-equipped to carry out the research. There is research, yes, however just how much of it is important research. The human mind is the Final Frontier, as vastly unexplored in a scientific manner as the known universe. Truly understanding the inner workings of the human mind requires one thing not required of any other science, resolution of one's personal demons to be certain results are purely objective and unaffected by the inner workings of narcissistic deficiency need. The soldier scientists of psychology must first experience "divine madness," then grieve their own deaths as they realize there is nothing in this world that matters except the nurturing relationships we have. And if this is the case, what's the point in doing more scientific research in psychology? It will simply be wasted.
  5. We are witnessing a tremendous upheaval in addition to growing pains in the biopharmaceutical industry. Unfortunately these companies are run by businessmen who either were never scientists, or who were scientists who never understood science. The off-shoring to China and India will continue until there are no more jobs left to off-shore. Organic chemistry is the hardest hit sector in chemistry, and medicinal chemistry has nearly been obliterated in the U.S. Workers in China and India, especially, receive 33% the salary of U.S. workers, zero benefits, and have no rights under the U.S. Constitution. Hence big business can exploit them to their heart's content. It's no coincidence that we now have the lowest drug approval rating since 1986. Chinese and Indian chemists are good chemists, however they lack the experience of their U.S. counterparts. Most big companies don't engage in any real research these days, and hence they buy up the fruit of biotech when ripe enough. Chemotherapeutics are shifting to biologics, and it's anyone's guess as to how long pharmaceuticals as we know it will continue. I'd say medicinal chemistry is the worst field for a graduating organic chemist to consider. Employment in chemistry will be found in biochemistry and clinical chemistry. Med chem is practically dead. ~ RIP ~
  6. When receiving the reviewed paper, it's important to address the questions of the reviewers as informatively and humbly as possible. They're doing you a favor by reviewing your paper, and you'll get that paper published much more quickly if your provide them with sufficient information addressing every point of every question. The time for review does vary. If you work for a big name professor, you'll get a quicker turnaround.
  7. It's important that you demonstrate an earnest attempt at solving this problem before receiving help. Is this problem from a textbook or from your prof? You have a simple redox problem, and yes there are electrons being exchanged. What are your proton sources in this problem? When you combine a strong acid with a weak acid salt, what form predominates at equilibrium?
  8. I have to support RajeshK's response. Chemistry is for the lab, not for home. Even experienced chemists with 20 years of laboratory experience realize this. Your safety comes first.
  9. When recrystallizing a solid, it's best to wash the collected crystals with the solvent system used for the recrystallization. I understand you wanted to remove residual water, however this would best be effected via heating at 50 C under high vaccuum for 24 h.
  10. Your synthesis is OK as written. Realize step 1 will produce regioisomers, however the major product will be the one you've indicated. A better route would utilize benzylic oxidation to the carboxylic acid directly via KMnO4 or H2Cr2O4 (removes two steps). The tert-butyl group will be unaffected by this oxidation since there are no hydrogens to be removed from the benzylic carbon.
  11. Many organics soluble in water are capable of hydrogen bonding at some level (alcohols, carboxylic acids, amines, etc). Lower order aldehydes and ketones are hydrogen bond acceptors. When the carbon to oxygen count exceeds 5:1, oxygen containing organics lose their water solubility quickly. Remaining organic compounds without polar functional groups or with excessive carbon/heteroatom ratios cannot dissolve well in a highly polar medium such as water.
  12. Carbohydrate chemistry is an area of Organic Chemistry that requires extensive protective group manipulation in order to effect desired transformations. Your project involves two oxidations, a Horner-Emmons olefination and a Strecker amino acid synthesis. You'll be unable to do this without protective groups. Choose them wisely. Good luck!
  13. You will certainly proceed through a beta-hydroxy carbonyl intermediate, however if heat is specified for the reaction, the result is beta-elimination affording the enal. Additionally, OH- or EtO- is not always used as there are advantages to using LDA to obtain kinetic control. Please read the articles below: Aldol Condensation Part I: The Basics Aldol Condensation Part II: Kinetic Control Aldol Condensation Part III: Stereochemistry Good luck!
  14. I strongly recommend giving the students a rigorous course in O-Chem I, with an emphasis upon getting to electrophilic addition chemistry if at all possible. I prefer Vollhardt's book, probably because he gave me my first copy of it while I was a postdoc at Berkeley. Solomons & Fryhle is also good, and is now being used at UCSD.
  15. If you want an A+ in Organic Chemistry, then I have a few suggestions for you. (1) Study 20 hours per week, non-negotiable. (2) Be able to draw Lewis structures for every reagent and functional group you encounter. (3) Realize that Organic Chemistry is a course in applied logic and deductive reasoning, not memorization. (4) Read my article, 9 Golden Rules for Success in Organic Chemistry (5) Read my article, Drama of the Alarms - Call for Time Management (6) Work as many problems as humanly possible. When finished, do them again. (7) Make compound flash cards for all functional groups, indicating pKa data, IR bands, 1H NMR chemical shifts. (8) Make reaction flash cards for every reaction class, being certain to understand the mechanisms. (9) Get ready to take exams with problems you've never seen before. Acing O-Chem is all about quick thinking and logic. I wish you the best of luck!
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