BR Orgo Mechanisms

[DPTinthemaking15]

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I'm about to pound my head against a wall after looking at all of the mechanisms in the BR Orgo 2 book. Here is my question: Will mechanism/reaction questions be somewhat simple on test day? I will eventually understand all of the mechanisms/reactions (Grignard, Aldol, Transesterification, Witting, etc...), but I am afraid I won't have the time to do certain problems. Also, are these types of reactions common on the MCAT? I don't mind studying extra, because I don't want to be caught with my pants down on test day, but I don't want to study information that is useless.

 

[aldol16]

You want to notice the general trends and how reactions go. Aldols, transesterifications, etc. are all made up of a few discrete steps that are applied in some sequence to get a result. There will come a point where you no longer see reactions as going through "named" mechanisms but rather just as those series of steps (e.g. deprotonation to get a good carbon nucleophile, attack on electrophilic ketone, collapse of ketone and kicking out of a leaving group). These key steps happen in all sorts of biochemical reactions and once you see them as common concepts (nucleophile attacks electrophile), the MCAT chemistry becomes a whole lot easier.

 

[Spr1ngrolls]

You want to notice the general trends and how reactions go. Aldols, transesterifications, etc. are all made up of a few discrete steps that are applied in some sequence to get a result. There will come a point where you no longer see reactions as going through "named" mechanisms but rather just as those series of steps (e.g. deprotonation to get a good carbon nucleophile, attack on electrophilic ketone, collapse of ketone and kicking out of a leaving group). These key steps happen in all sorts of biochemical reactions and once you see them as common concepts (nucleophile attacks electrophile), the MCAT chemistry becomes a whole lot easier.

This^

Memorizing the mechanisms won't help you at all. Every MCAT question is unique, and on top of that, actual questions asking you about them wont ask you specifics of an intermediate reaction.

Example of how I would approach it: know if something is a good/poor LG, nucleophile, and electrophiles; basic carbonyl centers; acidic protons of carbonyls; common factors of all reagents for specific types of reactions (oxidations, reductions, etc). Things like these will get you the most points, aid you in understanding all orgo/basic chem principles, and prevent you from having to overload yourself with "arrow pushing" (aka memorizing) like what was expected of you in Orgo I & II lectures.

 

[BerkReviewTeach]

BR Organic Book 2 has 7 mechanisms total (ketal formation on page 83, aldol on page 104, fatty acid biosynthesis on page 106, transesterification on page 107, Wolff-Kishner on page 110, glycolysis on pages 184 and 186, and Edman's degradation on page 266). It is our belief that if you have a good understanding of the fundamentals associated with these seven reaction pathways, then you'll be able to understand any mechanism they present in a passage. Try to see the recurring themes in these reactions. There are some other reactions presented in the text, but only a few key intermediates have been emphasized. Try not to focus on memorizing these mechanisms but instead see how things work in general.

aldol and spring rolls have made excellent points that hopefully help you to relax and see the bigger picture of mechanisms.

If you want some great advice on studying for the exam, look at this page.