Links to download Zoom Lecture Videos and PDF files
- Lecture Date: Tuesday, January 26, 2021
Welcome all to the first meeting of the spring semester of Chem 12B. This class was mainly in introduction to me and overview of the course and course resources. We did manage to start the alkyne chapter with a look at alkyne structure and acidity of alkynyl protons. It was a good start today with lots more to come.
- Lecture Date: Thursday, January 28, 2021
Well, we started with electrophilic addition to alkynes with addition of acids and hydration, but somehow we also got side tracked into Hammond Postulate, molecular orbital theory vs. natural bonding theory, and transition state theory. All excellent and relavent concepts that we will make good use of throughout the semester. We also hit enol-keto tautomerization, and a little bit of hydroboration of both alkenes and alkynes and how they are similar, and how they are different. We may not have covered as much of the alkyne chapter as I had planned, but we did good work that will support the concepts to come.
- Lecture Date: Tuesday, February 2, 2021
Lots of good questions in today's lecture. Keep those questions coming, you guys are doing great. We covered the rest of the reaction in the alkyne chapter today. We covered catalytic hydrogenation, dissolving metals hydrogenation, and Lindlar type poisoned catalytic hydrolysis. As a wrap up we built a star chart of all the reactions in the alkyne chapter.
- Lecture Date: Thursday, February 4, 2021
Today was an introduction to free radical chemistry. While we only just started the first free radical halogenations, most of this lecture was correlating free radical structure with that of carbocations, and linking free radical stability to carbocation stability. In addition, we introduced common free radical mechanistic steps. We closed the lecture with a look at the origen of the difference in regioselectivity between free radical chlorination and bromination with a strong reminder of the importance of the Hammond Postulate.
- Lecture Date: Tuesday, February 9, 2021
Today we dug deeper into the free radical chapter we were actually able to finish the chapter. We focused on the stereochemistry of the free radical halogenation, allylic halogenation with N-bromosuccinimide, and we talked quite a bit about kinetic vs. thermodynamic and radical resonance. I think that hits all the notes.
- Lecture Date: Thursday, February 11, 2021
We started Chapter 11 Synthesis today. This seemed like a more challenging set of material for people as we started the synthesis chapter today. We looked at the process of retrosynthetic analysis to find constructive ways to break down a product that allow for using know reactions to put it back together. The process calls for breaking the target into synthons and then finding synthetic equivalents for those synthons. The process can seem abstract and intangible. Give it some time. These problems are new, and like any new concept it takes practice. Start with the book problems, they are fantastic. The synthesis problems from the alkyne chapter are also good. I'll provide more problems here for this chapter shortly. Hang in there and don't lose focus! Stay on target.
- Lecture Date: Tuesday, February 16, 2021
While we spent Thursday last week introducing retrosynthetic analysis, I realized that we didn't do any demonstration problems. Today we utilized some of the practice problems that posted in Canvas as demonstration problems and looked at some of the most common themes or patterns you'll encounter.
- Lecture Date: Thursday, February 18, 2021
We opened chapter 13 today and our look at alcohols and phenols. We start off looking at nomenclature of alcohols. We hit classification, physical properties, acidity, some review of reactions that form alcohols, and finally spent quite a bit of time on reduction. We discussed oxidation and reduction and looked at several reducing agents in detail.
- Lecture Date: Tuesday, February 23, 2021
We are now deep in chapter 13 and our look at alcohol reactions. Today we continued to look at reactions that produce diols. We launched into reactions of carbonyls with organometallics, both alkyl lithiums and Grignard reagents, to form primary, secondary and tertiary alcohols. We also started our look at protecting group strategies. Today we focused on the silyl ether type protecting groups and started the introduction of acetyl type protecting groups. We left off with a bit of a cliff hanger on the acetal cleavage mechanism, which we said was very similar and critical to carbohydrate chemistry.
- Lecture Date: Thursday, February 25, 2021
Today we finished up our look at the different protecting groups commonly seen that are used to protect hydroxyl groups. From there we moved into part 2 of this chapter that deals with reaction of alcohols. We started with a quick review of SN1/SN2/E1/E2 reactions. We added to these the formation of good leaving groups from alcohols, namely converstion to tosylates, bromides and chlorides. When we pick it up on Tuesday we'll look at oxidations and the different oxidizing agents.
- Lecture Date: Tuesday, March 2, 2021
We closed out chapter 13 with a look at oxidizing reagents. We looked at Jones, pyridinium chlorochromate (PCC), pyridinium dichromate (PDC), and the Swern oxidation. We reviewed the mechanism and specificity of each reagent. From there we jumped into chapter 14 ethers and thiols. This chapter has a lot of review. Today we nomenclature, crown ethers, and Williamson ether synthesis. We've got another half lecture to go on this chapter, and before we close things out for the first exam.
- Lecture Date: Thursday, March 4, 2021
Today we covered just a little bit in the ethers and moved into epoxides. We looked at a couple of ways to make epoxides, both MCPBA and utilizing SN2 reactions. We looked at enantioselective Sharpless epoxidation utilizing titanium tetraisopropoxide and DET. Finally, we closed out the chapter by creating a star chart of the various reactions that epoxides can undergo. And that's a wrap. That is all of the information that will be on exam 1. In addition to what we did in lecture today, we utilized lab time to review for the exam. Please don't forget to check out the lab videos from today as they are very relavent to lecture.
- Lecture Date: Tuesday, March 9, 2021
Today we went over a sort of review for exam 1. In this review we look at the major synthesis patterns for making carbon-carbon bonds. We break down the patterns into adding 1, 2, or 3 or more carbons and how these have similarities that can be recognized if you know how to look at it. So this isn't a full review on it's own, but together with the reviews done in lab that demonstrated the other problem types (see the lab lectures from the March 4), these lectures together form a solid review of the material for the exam.
- Lecture Date: Thursday, March 11, 2021
We counted today as an exam day and gave everyone a break, including me so that I could rest my back. No lecture today.
- Lecture Date: Tuesday, March 16, 2021
I generally think of the lecture course in the spring as broken into three parts, functional groups and reactions, spectroscopy, aromatic/pericyclic reactions/carbonyl chemistry. Having completed the first part we now move into spectroscpy. This lecture presents an introduction to NMR. We look at the origin of the NMR spectroscopy signal, experiment design, a little bit about instrument design and the relationship between magnetic field strength and signal strength, and just the beginning of how to interpret NMR spectroscopy.
- Lecture Date: Thursday, March 18, 2021
Second day on NMR. Today we cover spin-spin coupling. We take a look at how neighboring protons cause splitting of signals in their near neighbors and how this information can be used to rebuild connectivity within the molecule. We also take a look at where different chemical environments show up in the proton and carbon spectrum and start analyzing some simple example spectra.
- Lecture Date: Tuesday, March 30, 2021
Today we worked a single problem, #64 on the Organic Structure Elucidation website. Additionally, we covered roofing in the 1H-NMR, and proton coupled 13C-NMR. I also introduced a good basic 1H-NMR table and a good basic 13C-NMR table that I have linked to inline here, and also below.
- Lecture Date: Thursday, April 1, 2021
Third day on NMR. We ran a bit long on this video, but we presented two good problems (albeit the second one ran a little short on time from what I like to do. - Sorry)
- Lecture Date: Tuesday, April 6, 2021
We started Mass Spectrometry today. We introduced Mass spec and how it works. We looked at different techniques of ionization. We described the formation of the molecular ion, fragmentations, and looked at a couple of isotope effects. We also explored the difference between high resolution mass spec and low resolution and how the two can be used to determine the molecular formula from the mass to charge ratio of the molecular ion peak.
- Lecture Date: Thursday, April 8, 2021
Second day on mass spectrometry. Today we looked at how to use the relative percent abundance of the 13C isotope peak to calculate the number of carbons in the molecule. We further explored α-cleavage, both homolytic and heterolytic, for carbonyl compounds, and McLafferty cleavage as well. We ended by looking at numerous examples of α-cleavage.
- Lecture Date: Tuesday, April 13, 2021
Today we started looking at how to bring all the different types of spectroscopy together to solve a complete unknown. In these problems you are given the IR, 1HNMR, 13CNMR, and the Mass Spectrometry. No molecular formula is provided for these problems. The structural elucidation is performed from the four forms of spectroscopy. We managed to get through two complete examples that illustrated the process.
- Lecture Date: Thursday, April 15, 2021
Last day on spectroscopy. Today I picked a hard all-in-one problem for us to look at. This was a challenging problem that afforded the opportunity to really see how we use all the different forms of spectroscopy in concert together. This lecture, together with the lecture from the lab this moring, are two very important lectures as they show how this is a non-linear process that really relies on correlating many types of data. Each spectroscopy technique brings knowns and unknows (questions), and only together do they allow you to arrive at the whole picture. Make sure you watch that lab video from this morning as well.
- Lecture Date: Tuesday, April 20, 2021
First day on aromaticity. Today we explore what it means to be aromatic. We compare what we know of VSEPR theory, Resonance theory, Natural Bonding Theory and finally Molecular Orbital Theory. We devine what it is to be aromatic and look at using Frost's circle as a means to obtain the relative energies of the valence molecular orbitals and a foundation for explaining what makes an aromatic system.
- Lecture Date: Thursday, April 22, 2021
Having spent our first lecture describing what aromaticity is, in this lecture we start to tackle the reactions of aromatic compounds. We focus first on the reactions of the benzylic position. Most of these reactions are review. New reactions that we covered are the Birch Reduction and Electrophilic Aromatic Substitution (EAS). Most of our time was laying the foundation for EAS reactions by looking at the reaction mechanism. Next week we'll do a deeper dive into the selectivity of these reactions and how to apply the principles to synthesis problems.
- Lecture Date: Tuesday, April 27, 2021
Today we finished up electrophilic aromatic substitution with a look at Friedle-Crafts alkylations and Friedle-Crafts acylations. There was a good bit of chemistry covered today, despite the short description here.
- Lecture Date: Thursday, April 29, 2021
So it seems that I've gone a little out of order with the third edition of the Kline textbook. Aromaticity was chapter 17, Electrophilic Aromatic Substitution was 18, and Conjugated systems was chapter 16. Today we back-track to conjugated systems and look at reactions of these conjugated systems, including Diels-Alder reaction and some other pericyclic reactions.
- Lecture Date: Tuesday, May 4, 2021
The main topic for discussion was Diels-Alder reactions. We looked at the general reaction mechanism, the origin of stereoselectivity for the endo position, and we discussed regioselectivity.
- Lecture Date: Thursday, May 6, 2021
We dived in to chapter 19 today with a look at carbonyl chemistry. We touched on nomenclature of aldehydes and ketones. We looked at reactivity rates and the effects of electronics and sterics. And finally we examined acetal and ketal formation.