In April of this year, Braves reliever Luis Avilan came in with a 5-1 lead in the 8th inning. Eight batters later, he’d given up five runs, blowing the lead. Thankfully for him, the Braves came back in the top of the 9th and reliever David Carpenter nailed down the save. The result: Avilan got … [Read more...]
Curved Arrows (2): Initial Tails and Final Heads
Here's a handy little trick for accounting for charges when you draw curved arrows. You know by now that curved arrows are our accounting system for showing how electrons move, from the tail (electron donor, source of electrons) to the head (electron accepting, destination of electrons). There … [Read more...]
7 Factors that stabilize negative charge in organic chemistry
Like I wrote about last time, it's good - but not enough - to recognize partial charges and to figure out where they interact. Since reactions involve processes that lead to the gain or loss of charges, understanding the factors that stabilize (or destabilize) charge have a tremendous impact on … [Read more...]
Common Mistakes: Formal Charges Can Mislead
Formal charges have their plusses and minuses. Har har. One one hand, they're an indispensable accounting tool. If a molecule bears a charge, it would drive us nuts (for nomenclature reasons) if we didn't adopt some kind of system where a charge was unambiguously assigned to one atom. In many … [Read more...]
The Third Most Important Question to Ask When Learning A New Reaction
When learning any new reaction, I think you always have to start with the "what". What bonds are forming, and what bonds are breaking. After you answer "what", then you can start asking "where" - as in , "where are the electrons of the reactants?" What areas are electron rich? What areas are … [Read more...]
Curved Arrows (for reactions)
If you think of electrons as the currency of chemistry, reactions are transactions of electrons between atoms. Just like double entry book keeping was developed to formalize how financial transactions are recorded, chemists have developed their own convention for showing transactions of electrons … [Read more...]
How to apply electronegativity and resonance to understand reactivity
One thing has been missing from the discussion of resonance. What's the point? Who cares if we can write out resonance structures? What does it matter if we can figure out the two or three most stable resonance structures? So what? Here's the point: we can apply resonance (and … [Read more...]
Evaluating Resonance Forms (1) – The Rule of Least Charges
So far I've talked about resonance, and introduced the curved arrow formalism to show the movement of electrons. Importantly, we've talked about how the "true" picture of a molecule is a hybrid of its resonance forms (and not an equilibrium between forms). Here's a recap of the different "moves" … [Read more...]