Ten weeks ago I walked into a classroom of 180 non-science majors to teach a course in Organic Chemistry. Many of these non-science majors were anxious about the experience to come, knowing only that people taking such a class often fell to repeat it once or twice to obtain a passing grade. Most of them had just completed one quarter of introductory general chemistry, and had no idea exactly how much they were about to learn.
Proton Nuclear Magnetic Resonance (NMR) Spectroscopy is a method of analysis, particularly useful to organic chemists, wherein a compound’s structure may be elucidated utilizing an applied external magnetic field (Bo) in conjunction with an electric field (E = hv). The first generation of NMR spectrometers were called continuous wave (CW) instruments because the electric field component was held constant as the magnetic field was incrementally varied by a small degree. Today’s modern Fourier Transform (FT) instruments utilize a homogeneous magnetic field whilst “pulsing” the sample of organic substance with a broad range of radio frequencies to effect the same results.
Most students of Organic Chemistry are introduced to the carbocation rearrangement when learning the SN1 and E1 processes, as this is their first exposure to carbocations. It’s common to see a 1,2-alkyl shift or a 1,2-hydride shift. Sometimes, depending upon the level of challenge presented by the professor, there will be tandem 1,2-hydride and 1,2-alkyl shifts (Scheme I).
When it comes to studying the reactivity of alkenes and alkynes with various reagents, nothing leads to more confusion than the Markovnikov Rule. Proposed in 1870 to explain a limited finite set of results, the rule persists in Organic Chemistry texts to this day. The source of confusion is not the logic of the rule, but rather the rule itself, as it is used in austerely limited form by most undergraduates to memorize the outcome of electrophilic addition reactions to alkenes and alkynes.