A guide to organic chemistry mechanisms

academics organic chemistry premed
By Gift

The dreaded weed-out class. A pre-med’s worst nightmare. Students often approach organic chemistry with apprehension, and a particularly sore spot in the class is mechanisms. Arrows, electrons, charges, and structures all drawn out like a map. Now, make that 10 maps – or 20! What’s a pre-med to do? 

A student once said to me, “I have to memorize all of these?”

While it may seem like memorization is the only option, organic chemistry mechanisms can become quite intuitive if you follow 3 rules:


Mechanisms are used to show the process of chemical synthesis! Instead of being in the lab, you’re forming new molecules on paper. A big part of this is understanding the motion of electrons: which electrons are attacking, stealing, or leaving. 

Identifying nucleophiles and electrophiles and/or atoms with nucleophilic or electrophilic properties is the key to understanding which electrons are acting and how they’re acting. 

Brush up on these definitions. Remember that nucleophiles (electron abundant and where your arrow starts) often attack other compounds and atoms with nucleophilic properties like to steal protons. Electrophiles (electron poor and where your arrow sinks) often receive electrons and atoms with electrophilic properties like to accept bonds. 


What does that even mean? Simply put, if you’re in base, avoid forming acids. If you’re in acid, avoid forming bases.

An easy way to implement this is to identify your solution early on. Then, if you’re in an acidic solution or using an acidic workup, you should only ever have neutral or positive species in your mechanism. If you’re in a basic solution or using a basic workup, you should only ever have neutral or negative species in your mechanism. Any crossover is volatile IRL and is an immediate red flag to any TA or professor grading your work. 

Watch those charges! 


Often, not following this seemingly simple rule is the reason many students find themselves going in circles on their mechanism sheets. 

If you’ve just added a proton to your main compound in the previous step, make sure you don’t remove that proton in the next step - you’re undoing all of your hard work. Similarly, if you’ve just made a bond, don’t break that same bond.

You should always move forward in mechanisms. 

Hint: This is aided by a strong understanding of what your end-product should look like. If you can start a mechanism by drawing out what your product should look like (something you can memorize), you’re halfway there. At each step, just check to make sure that you’re one step closer to that final product. 

Gift graduated with a 4.0/4.0 GPA from the University of Texas at Austin, where she majored in Honors Biology and obtained a certificate in creative writing. Toting a Dean’s Distinction in research and multiple recognitions in academics, Gift is now an MD candidate at Columbia University Vagelos College of Physicians and Surgeons.


academics study skills MCAT medical school admissions SAT college admissions expository writing English MD/PhD admissions writing LSAT GMAT strategy GRE physics chemistry math biology graduate admissions ACT law school admissions interview prep test anxiety language learning academic advice MBA admissions premed personal statements homework help career advice AP exams creative writing MD study schedules Common Application summer activities test prep history computer science philosophy organic chemistry secondary applications supplements economics PSAT admissions coaching grammar mathematics research law statistics & probability psychology 1L ESL CARS SSAT covid-19 dental admissions legal studies logic games reading comprehension USMLE engineering Spanish calculus parents Latin verbal reasoning DAT PhD admissions case coaching excel mentorship political science AMCAS French Linguistics MBA coursework Tutoring Approaches academic integrity chinese medical school Anki DO English literature Social Advocacy admissions advice algebra astrophysics biochemistry business classics diversity statement genetics geometry kinematics mental health presentations quantitative reasoning skills study abroad time management work and activities IB exams ISEE MD/PhD programs STEM adjusting to college algorithms art history artificial intelligence athletics business skills careers cold emails data science functions gap year international students internships letters of recommendation logic mechanical engineering poetry resume revising science social sciences software engineering tech industry technical interviews trigonometry 2L 3L AAMC Academic Interest DMD EMT FlexMed Fourier Series Greek Health Professional Shortage Area Italian Lagrange multipliers London MD vs PhD MMI Montessori National Health Service Corps Pythagorean Theorem Python Sentence Correction Step 2 TMDSAS Taylor Series Zoom acids and bases amino acids analysis essay architecture argumentative writing art art and design schools art portfolios biomedicine brain teaser campus visits cantonese capacitors capital markets cell biology central limit theorem centrifugal force chemical engineering chess chromatography class participation climate change clinical experience community service constitutional law consulting cover letters curriculum dementia demonstrated interest dental school dimensional analysis distance learning electric engineering electricity and magnetism enrichment escape velocity european history executive function finance first generation student freewriting fun facts genomics graphing harmonics health policy history of medicine history of science hybrid vehicles hydrophobic effect ideal gas law induction infinite information sessions institutional actions integrated reasoning intern investing investment banking lab reports linear algebra linear maps mandarin chinese matrices mba medical physics meiosis microeconomics mitosis music music theory neurology neuroscience office hours operating systems organization pedagogy phrase structure rules plagiarism potential energy pre-dental proofs pseudocode psych/soc qualifying exams quantum mechanics