Simple Tricks in Organic Chemistry_ Figuring Out R_S — Master Organic Chemistry

8/25/2016

Simp imple Trick ricks s in Orga rganic Che Chemist mistry ry:: Fig Figurin ring Out R/S R/S — Mast Maste er Orga rganic Che Chemist mistry ry

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A simpl simplee trick: The (R)-(S) Toggle  by James in Organic Chem Study Tips, Tips, Organic Chemistry 1, 1, Stereochemistry

The difficulty of assigning (R)/ (R)/( S) S) to a stereocenter can be highly dependent on the way the molecule is drawn. For example, assigning the stereochemistry of A should be a cakewalk if you are the least bit familiar with the rules, while B and C are a little more difficult. The thing is, you’re is, you’re not always going to be given a structure with the 4th ranked substituent in the back. One thing I see students do a lot in this situation is try to redraw the structure to make it easier to assign (R)/(S) While (R)/(S) While this can be effective, it can easily lead to mistakes. Furthermore, when you’re dealing with cyclic systems like morphine [C], trying to draw the mirror image in a reasonable time frame might induce brain trauma. [By the way, for B, you remember why the CH2CH2Br  group is ranked 3rd, right? [Note 1]] Instead of redrawing the whole molecule, just leave the hydrogen (or other 4th ranked substituent) in front and http://w ww.m aster or gani cchem i str y.com /2010/03/13/a- si m pl e- tr i ck- the- r - s- toggl e/

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