Master Organic Chemistry

Classification of Isomers: Constitutional Isomers, Stereoisomers, Enantiomers, and Diastereomers

September 10, 2018 By James Ashenhurst 2 Comments

"How Are We Related, Again?"  A few weeks ago, at a family reunion in Ontario,  I introduced my relatives to the joy of liquid nitrogen ice cream. My cousins were there, as were many of their children. So were a few of my dads' cousins. Being a family reunion,  they invited their (grown) children, … [Read more...]

Filed Under: Organic Chemistry 1, Stereochemistry Tagged With: atropisomers, conformations, constitutional isomers, diastereomers, enantiomers, Lord Voldemort, meso, stereoisomers, tartaric acid

Stereochemistry of the Diels-Alder Reaction

November 13, 2017 By James Ashenhurst 4 Comments

Here's what we've learned about the Diels Alder reaction so far: [previous post in this series] 3 pi bonds are always broken 2 sigma bonds and a pi bond are always formed, resulting in a new six-membered ring electron withdrawing groups on the dienophile increase the reaction … [Read more...]

Filed Under: Dienes and MO Theory, Stereochemistry Tagged With: diels alder, endo, exo, s-cis, stereochemistry

Optical Purity and Enantiomeric Excess

February 24, 2017 By James Ashenhurst Leave a Comment

In our last post on optical rotation, we saw that when Louis Pasteur crystallized a salt of a compound then known as "racemic acid" he discovered that it formed two different types of crystals. When redissolved in water, one set of crystals rotated plane-polarized light clockwise (dextrorotatory, … [Read more...]

Filed Under: Stereochemistry, Uncategorized Tagged With: enantiomeric excess, optical purity, optical rotation, specific rotation

Optical Rotation, Optical Activity, and Specific Rotation

February 7, 2017 By James Ashenhurst 8 Comments

As the title suggests, today's post is all about optical rotation, optical activity, and specific rotation. This post was co-authored with Matt Pierce of Organic Chemistry Solutions.  Ask Matt about scheduling an online tutoring session here. Here's a quick summary of what we'll cover … [Read more...]

Filed Under: Stereochemistry Tagged With: absolute configuration, cahn-ingold-prelog, d and l, enantiomers, optical isomers, optical rotation, pasteur, polarimetry, R and S, specific rotation, stereochemistry, tartaric acid

Assigning R/S To Newman Projections (And Converting Newman To Line Diagrams)

February 1, 2017 By James Ashenhurst 2 Comments

This post was co-authored with Matt Pierce of Organic Chemistry Solutions.  Ask Matt about scheduling an online tutoring session here. In two recent posts we discussed how to assign (R/S) to configurations of chiral carbons in a variety of situations, both simple and more complex. So far, all … [Read more...]

Filed Under: Conformations, Stereochemistry Tagged With: bond-line, cahn-ingold-prelog, cats, chirality, conformations, eclipsed, newman projection, staggered

Determining R/S (2) – The Method of Dots

January 17, 2017 By James Ashenhurst Leave a Comment

This post was co-authored with Matt Pierce of Organic Chemistry Solutions.  Ask Matt about scheduling an online tutoring session here. In our first post on the Cahn-Ingold-Prelog (CIP) Rules, we gave a broad overview of how to assign R or S to chiral centers in a molecule. We followed this up … [Read more...]

Filed Under: Nomenclature, Stereochemistry Tagged With: chirality, CIP, E/Z, isotopes, nomenclature, phantom atoms, priority, pseudoasymmetric, r/s

Introduction to Assigning (R) and (S): The Cahn-Ingold-Prelog Rules

October 20, 2016 By James Ashenhurst 8 Comments

This post was co-authored by Matt Pierce of Organic Chemistry Solutions.  Ask Matt about scheduling an online tutoring session here. Previously on MOC we've described enantiomers: molecules that are non-superimposable mirror images of each other. Perhaps the most memorable example is these … [Read more...]

Filed Under: Stereochemistry Tagged With: cahn-ingold-prelog, chiral centers, R and S, single swap rule, stereochemistry enantiomers

Chiral Allenes And Chiral Axes

January 13, 2015 By James Ashenhurst 8 Comments

We've met alkenes before - right? Just in case you haven't, let's review the basics, because today's post is going to depend on understanding a few of the most important concepts. Alkenes contain both sigma [ σ]  bonding formed through "head-on" orbital overlap [i.e. "single bonds"] and also pi [ … [Read more...]

Filed Under: Alkenes, Stereochemistry Tagged With: allenes, asymmetry, chiral allenes, chiral axis, chirality, pi bonds

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