Last week Diana left this comment: I recently had my first orgo exam and one of the concepts that I have trouble visceralizing is Hammond's Postulate. I can follow the explanation in my textbook (L.G. Wade, Jr. 7th edition), but I don't really grasp it. Is there an alternative intuitive … [Read more...]
What To Expect In Organic Chemistry 2
A large part of organic chemistry 1 is devoted to laying the foundations: introducing structural concepts such as bonding, geometry, stereochemistry, conformations, resonance, and steric effects, while introducing concepts in chemical reactivity such as nucleophilicity, electrophilicity, acidity, … [Read more...]
What’s a Transition State?
Here's a question that comes up a lot: What's a transition state? A transition state is a very short-lived configuration of atoms at a local energy maximum in a reaction-energy diagram (aka reaction coordinate). A transition state has partial bonds, an extremely short lifetime (measured in … [Read more...]
The Marriage May Be Bad, But the Divorce Still Costs Money
Common misconception: energy is released through the breaking of bonds. Not correct. Energy is released through the FORMATION of chemical bonds. Formation of a new bond between two atoms results in a net lowering of energy of the atoms involved, corresponding with a release of energy (heat) … [Read more...]
Why Do Organic Chemists Use Kilocalories?
What's the deal with organic chemists using kilocalories (kcal) instead of kilojoules (kJ)? The metric system, of System Internationale (SI) was first adopted in France in 1791 soon after the French Revolution (one of their other innovations adopted by the revolutionaries - the ten-day week - did … [Read more...]
From Gen Chem to Organic Chem, Part 14: Wrapup
So what are the key concepts from General Chemistry that you need to apply to Organic Chemistry, going in? This past summer, I saw people asking this question on places like Yahoo Answers and SDN all the time. So I decided to do something about it. It was embarrassing how much 1st year chemistry I'd … [Read more...]
From Gen Chem to Organic Chem, Pt. 13 – Equilibria
(The last lesson in the series. I wish I had this series done by the time school started for most people, but I initially thought I could cover the basics of Gen Chem in 6 posts and it just kept growing - planning fallacy in action.) Chemical Equilibria In chemistry, irreversible reactions … [Read more...]
From Gen Chem to Org Chem Pt. 12 – Kinetics
Chemical kinetics is the study of reaction rates. It can be really important in figuring out the mechanisms of chemical reactions. Here are the essentials of what you need to remember about chemical kinetics as you go from Gen chem to organic chemistry. 1. Reaction rates are proportional to … [Read more...]
From Gen Chem to Organic Chem, Pt. 11 – The Second Law
From Wikiquote: Zeroth law of thermodynamics: you must play the game 1st law : you can't win 2nd law: on a very cold day, you can break even 3rd law: it never gets that cold The 2nd Law of Thermodynamics: Δ G = Δ H - T Δ S. (I wrote a really long description of this law and realize … [Read more...]
From Gen Chem to Organic Chem, Pt. 10 – Hess’ Law
Probably nowhere else does the contrast between the largely quantitative nature of Gen Chem with (relatively) qualitative nature of Org Chem become more apparent than with the topic of thermodynamics. Whereas you probably spent a lot of time in Gen chem figuring out heats of formation, free energy … [Read more...]