How Concepts Build Up In Org 1 (The Pyramid)

How Org 1 Builds Up (the Hierarchy of Concepts)One comes into organic chemistry from an introductory course ingeneral chemistry. Starting out, its assumed you have a basic knowledge of chemical bonding, the octet rule, VSEPR (geometry), equilibria, acids and bases, thermodynamics and so on.Concepts build from this base. Ive made a few completely arbitrary levels to describe how concepts progress from there. The general idea is that every level depends on concepts from the levels below it. I wouldnt take these levels too seriously, but they might be helpful to group together certain concepts and see how they build on each other.Level 1 Bonding and Geometry. The first week or two of organic chemistry goes over the key concepts of bonding from general chemistry, and introduceshybridization,bonding(sigma and pi),dipoles, moleculargeometry,molecular orbitals, and other notions like condensed formulae. In other words, weshow howatoms bond together to form small molecules like NH3, H2O, CH4, and so on.Level 2 With the Level 1 concepts under our belt, we can now start to think aboutelectron density and electron flow. We can describefunctional groups, examine their dipoles (unequal sharing of electrons) and learn about the intermolecular forces responsible for physical properties likeboiling points. We also learn aboutresonance(delocalization of electrons), and introduce the use ofcurved arrowsto show electron flow. We can also use the tool of curved arrows to show simple chemical reactions such asacid-base reactions, and our lessons on electron flow help us understand thefactors that influence acidity.Level 3 Building on Level 1 concepts like bonding and geometry, we can start to examine slightly larger molecules, and start with the simplest functional group (if you want to call it that) alkanes. Importantly, line diagrams are introduced to show the structure of alkanes, and we learn about structuralisomers, the energies of different molecular shapes (conformations) and the properties ofcycloalkanes. Reactions are generally limited tofree-radicalhalogenation of alkanes (alkyl halides are important for substitution/elimination in Level 5). The structure, bonding and geometry ofalkenes(but not their reactions) is often covered at this point as well.These (arbitrary) levels 2 and 3 are actually pretty interchangeable in terms of the order in which theyre covered. I chose to put electron flow on the bottom because the conformations/cycloalkanes/alkanes chapters flow naturally into stereochemistry geometric isomers (e.g. cis/trans isomers in cycloalkanes and alkenes) being the prime example.Level 4- Now comes the chapter onstereochemistry, which is, in my opinion, the key theme of Org 1, since so many of the reactions learned in subsequent chapters will use the concepts introduced here. Here, the consequences of the three-dimensional nature of organic molecules are first demonstrated, and we learn about stereoisomers. Seeing molecules in 3 dimensions from their depiction on a 2-dimensional page is a struggle for many introductory students.If you start struggling here as many do get help now, because if you wait, it might be too late.Level 5 Three key classes of reactions are covered at this level reactions ofalkenes, nucleophilic substitution, and elimination. The order in which these topics are covered varies considerably from course to course.This is really the wax on, wax off moment where youll be asked to put together all the concepts youve learned previously and apply them!This is also where many students start to really struggle!Why? Three reasons.1. ALL the concepts in the previous levels will be applied here. Its the point where you finally start to stitch together the somewhat disconnected previous chapters into a coherent whole. To take a specific example, truly mastering the chapter on nucleophilic substitution reactions will require that you be able to apply an understanding of stereochemistry, conformations, cycloalkanes, resonance, curved arrows, and acids/bases to various types of problems, in addition to the bedrock material on chemical bonding.2. There are a lot of reactions presented in rapid sequence and itsvery easy to fall behind.3. This is about 6 weeks into the course, a time where you willlikely have many other obligations(midterms in other courses, lab reports, etc). So this is the real squeeze point.All of these combine to provide a perfect storm that leads many to drop the course at this point.Level 6 More reactions. Alkynes are covered after alkenes, and many important reactions of alcohols are of the substitution/elimination variety.There are two common sequences alkene->alkyne then substitution/elim, or substitution/elim then alkene->alkyne.Alkynes are a blank canvas they can be transformed into essentially any functional group we choose. Once reactions of alkynes are covered, youll start to notice youll get an increasing number of synthesis questions. Synthesis is the art of planning how to build a target molecule from starting materials using a sequence of reactions, and success will require you to master ALL of the skills you gain in levels 1-5, most importantly knowledge of the reactions and their stereochemistry.Alcoholsare awild card. The chapter on alcohols contains many substitution and elimination reactions, and furthermore includes reactions of epoxides (generally built from alkenes). Because Org 1 covers so much ground, alcohols are often pushed back to Org 2, but they really belong in Org 1.Another wild card isSpectroscopy the main tool we use to determine the structures of molecules. This needs to get covered somewhere, so its usually shoved near the end of Org 1 or the beginning of Org 2. Alternatively some instructors stagger it out through the courses of Org 1 and Org 2. Lots of variation on this point.

How Concepts Build Up In Org 2OK. Having looked at theOrg 1 Concept Map, lets ask the next logical question: what does a typical Org 2 course look like?One general observation:the way functional groups are covered in your typical two-semester organic chemistry coursegenerally follows the oxidation ladder. Look at the progression: alkanes (low oxidation state) first, then alkyl halides, alkenes, alcohols (medium oxidation state), then ketones, aldehydes, and carboxylic acid derivatives (higher oxidation state). [Amines break this pattern theyre usually covered near the end, but for reasons Ill describe at the bottom its probably best that amines arent covered in Org 1. ]Org 1 is largely about sp3hybridized (i.e. tetrahedral) carbon. We learn about bonding, geometry, conformations,-> stereochemistry