Chemietu

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[see especially, lecture supplements, tutorials, glossary] Some further advice later in the quarter: Late in the quarter in Chem 109A and in Chem 109B students often start to get overwhelmed by the sheer number of reactions and mechanisms to learn.  There is no easy answer other than hard work and 15+ hrs/week of study time, but I have some  suggestions that expand on advice in the syllabus.  Flashcards, or something equivalent, should be a big help, but require that  you be regularly organizing new reactions by entering examples of reactions on the flash cards as you work the problems in  the book.  For mechanisms, you are responsible for a lot of mechanisms and will be hard put to memorize them all.  You need  to know the basics of writing Lewis structures and resonance forms and arrow pushing, and the logic of the breaking and  making of the bonds that change in a reaction.  See, for example, in Chap 16 [17(6 th  Ed.)] (2 nd  C=O chapter), the general  patterns in the reactions of a particular type below. Try to be active in your studying.  From the lectures from Chap 16 [Chap 17(6 th  Ed. Carbonyl I)] and comments made in class  and review sessions, you  ideally will have distilled out important points, like I've done for you below: Some basic rules/patterns of mechanisms that come out of  Chap 16 [Chap 17], for example: 1) The weak nucleophiles, water and alcohols, usually need for the C=O to be activated by protonation(except for the most  reactive C=O compounds, like acid chlorides)  2) Amines and hydroxide ion and stronger bases Ch 20 [Ch. 18 6 th  Ed] are strong enough bases that they don't need acid to  activate the C=O toward addition, though acid is needed later in some mechanisms to make an OH, OR, or NR2 a better  leaving group. 3) many reaction in Chap 16 [17] can be catalyzed by acid or base and have somewhat different mechanisms, though most all  those mechanisms have and addition to the C=O step followed by an elimination step that regenerates a C=O pi bond.   4) The rate-determining step for most of these reactions of carbonyl compounds is the addition step, not the elimination, or  loss of leaving group step.  So the reasons for why rates differ for various carbonyl compounds in this chapter are not based on leaving group ability, even though they may appear to be.  Instead, factors like starting material stability, based upon  resonance stabilization (in the starting ester or amide, for example) are the determining factors.
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