Organic gets easier when you stop seeing the reaction as arrows and figures on the page and start to consider what is actually going on. Everything we see and touch is composed of atoms that have positively charged nuclei and negatively charged electrons orbiting around them. Positives and negatives interacting with positives and negatives. What does this remind you of? Magnets.
Atoms Act Like Magnets
We know that the positive and negative ends of magnets attract, while like charges repel one another. It is no different when considering atoms. Why do we see steric hindrance? Because the negative charges of electrons on two groups repel each other. Why do nucleophiles attack electrophiles? Because the nucleophile is rich in negative charge, while the electrophile is deficient (giving it a partial positive charge). Why is hydrofluoric acid not a strong acid? It has a densely positively charged nucleus in close proximity to the valence shell that hangs on tight to the electrons shared by hydrogen. It's all the push and pull of electrical attraction, the same push and pull you feel with magnets.
Watch It Work: One Reaction, Start to Finish
Let's take one of the first mechanisms you will learn, an SN2 reaction, and explain every arrow with nothing but charge.
The reaction: hydroxide (OH⁻) reacts with bromomethane (CH₃Br) to make methanol (CH₃OH) and bromide (Br⁻).
- Find the negative. Hydroxide carries a full negative charge and lone pairs of electrons. It is the nucleophile, the "negative magnet" looking for something positive.
- Find the positive. Bromine is more electronegative than carbon, so it pulls the shared electrons in the C–Br bond toward itself. That leaves the carbon with a partial positive charge. That carbon is the electrophile.
- Draw the arrow from negative to positive. The first curved arrow starts at a lone pair on oxygen and points at the carbon. That is all a curved arrow is: electrons moving toward positive charge.
- Come in from the back. Hydroxide approaches from the side opposite the bromine. Why? The bromine side is crowded with electrons, and negative repels negative.
- Something has to leave. Carbon cannot hold five bonds, so as the new O–C bond forms, the C–Br bond breaks. The second arrow goes from that bond to bromine, which leaves with the electrons it was already pulling on.
Now swap bromomethane for a tertiary halide like 2-bromo-2-methylpropane, where the carbon is surrounded by three bulky methyl groups. The SN2 reaction barely happens. You do not need to memorize that rule. The back of the carbon is now walled off by electron clouds, and the incoming negative charge is repelled before it can get close. That is steric hindrance, and you just predicted it from scratch.
This is the shift. Every mechanism you will see this semester comes down to a few questions: where is the electron density, where is it lacking, and what is in the way?
Gen Chem Is Your Foundation
The list goes on and on. The base concepts are effective nuclear charge, electronegativity, polarity, etc., which were taught in General Chemistry. There's a common misconception that if you are good at Gen Chem you will be bad at O-Chem, which is unequivocally false. O-Chem really does build on the foundation of Gen Chem. If you want an intuitive understanding of Organic but have a shaky foundation in Gen Chem, go back and review it! There are plenty of resources on YouTube, like The Organic Chemistry Tutor, Khan Academy, and Professor Dave Explains. Or pull up your favorite AI tool, and when you get a problem wrong, ask why. Then ask why again. Do this over and over until you get to the fundamentals of the concept. Or simply ask it to explain it to you like it would to a 5th grader (one of my favorite prompts).
Ask Why Until You Hit Bedrock
Here is what that chain of "why" looks like in practice:
- Why did bromide leave instead of hydroxide? Because bromide is a better leaving group.
- Why is bromide a better leaving group? Because it is more stable on its own with that negative charge.
- Why is it more stable? Because bromine is a large atom, and the charge is spread over a big electron cloud instead of crammed into a small one.
- Why does spreading out charge make it stable? Because like charges repel. Packed tightly, they push on each other. Spread out, they don't.
Four questions in, you are back at Gen Chem. You did not memorize a list of leaving groups. You learned why some atoms hold a negative charge better than others, and you can start to intuitively understand the periodic trends that govern nucleophilicity and leaving group strength.
Memorize or Understand?
The real key here is this: you can spend a massive amount of time memorizing mechanisms or understanding fundamental concepts. It's still the same amount of sacrifice, but the former runs out as soon as a reaction you've never seen shows up on the test. The latter makes you a problem solver.
Frequently Asked Questions
Do I still need to memorize anything in Organic Chemistry? Yes. Reagents, functional group names, and nomenclature rules are vocabulary, and vocabulary has to be memorized. The goal is to memorize the language and understand the grammar, so you can read a mechanism you have never seen.
Is Organic Chemistry harder than General Chemistry? It is different. Gen Chem leans on math and conversions, and Organic leans on visualizing structures and electron movement. But Organic is built on Gen Chem concepts, so a strong Gen Chem foundation makes Organic much more manageable.
What is the fastest way to get better at mechanisms? Practice drawing them from a blank page. For every arrow, say out loud where the electrons are coming from and why they are attracted to where they are going. If you can't explain an arrow, that is the concept to go back and review.
Want Help Building the Foundation?
I tutor Organic Chemistry I and II, along with General Chemistry, in person in Johnson City and online. We work from your syllabus and your professor's problems, and every new student starts with a free intro session. Learn more about chemistry tutoring.