Khan Academy Videos for Organic Chemistry
Unless you’ve been hiding under a rock for the past two years, you’ve heard about Khan Academy. And if you haven’t – geez, where have you been? Here is the relevant Ted talk to give you an idea. So just in case you’re one of those few who isn’t in the know, the Khan Academy is a website with over 3000 free videos (about 10 mins each) on a diverse range of topics from economics to arithmetic to organic chemistry (among many others).
With a few exceptions (mostly Renaissance art), all the videos are made by one individual: Salman Khan, who makes them in a closet in his home with a drawing tablet and his computer. That’s it. What’s his educational background? He has degrees in math and computer science from MIT. So in other words, on most of the topics, he’s teaching himself something first and then making a video.
How big a deal is Khan Academy? As of last viewing on his website, 189 million videos have been watched. So it’s a pretty big deal.
As previously mentioned, Khan has made videos on organic chemistry. Since I write this blog for students who are taking introductory organic chemistry, the big question I want to answer is this:
Q., How useful is Khan Academy for teaching organic chemistry to a “typical” college student taking an introductory organic chemistry course?
In other words, if you watch all 72 videos, what skills, facts, and concepts can you expect to learn? Just as important, what are some of the most important points that you’ll miss?
You can think of a series of smaller questions that will help in trying to answer the big question:
- What topics are covered?
- How accurately are they taught?
- Where are the gaps? What’s missing?
- How could the videos be improved?
Over the past month and a half I’ve managed to find time to watch all 72 videos. So over the next little while I’ll be writing a guide to Organic Chemistry videos offered by Khan Academy. This is the first part.
The Khan Academy is intended to be a free, accessible resource for learning about a diverse range of topics. Khan isn’t a trained organic chemist. So when evaluating these videos my expectations will not be particularly high. I don’t mean that in a derogatory sense; it’s just that he’s had less experience with the subject than your typical instructor, and this is not an easy subject to teach. That’s also part of Khan’s appeal for a lot of people – that he’s this guy who’s taught himself all these subjects, and he gives the impression of being able to meet the audience more at their level relative to someone who’s done a Ph.D. and taught at the university level for ten years. Having low expectations means I would hold Khan to a more forgiving standard than someone who has been teaching the subject for a long time and is trained in it.
The main thing I will want to evaluate is if there are any major errors – howlers – things that are red flags and would lead to serious confusion to a college student supplementing their studying with Khan videos. Someone who’s planning on studying organic chemistry from Khan Academy should know what to expect.
And with that, here’s Part 1, covering the first 12 videos, mostly on nomenclature.
Title: Representing Structures of Organic Molecules
Summary: Starting with the Lewis dot diagram of methane, Khan introduces line notation for bonds, and extends it to propane. The condensed formula (CH3CH2CH3) is introduced, followed by the line diagram for propane.
Key concepts: Understanding chemical drawings, including condensed formula and line notation.
Nitpicky criticisms: When Khan draws the hydrogens in his line diagrams, he places them at 180 degrees to each other. This is not advised, as it will be problematic later on when the wedge-dash notation is introduced.
Red flags: None
Title: Naming Simple Alkanes
Summary: Using the examples of octane and cyclononane, Khan demonstrates how to identify the longest carbon chain, and introduces the terms meth- eth- prop- and so forth. Also names simple rings.
Key concepts/skills: Identifying and naming the longest carbon chain.
Nitpicky criticisms: None
Red Flags: None
Title: Naming Alkanes with Alkyl Groups
Summary: Naming of substituted alkanes, as demonstrated by 4-methyl nonane (erroneously done here as 2-propyl heptane) and 6-butyl tetradecane.
Key concepts/skills: Identifying longest carbon chain, introduction of “yl” for naming substitutents, how to properly number the carbon chain.
Nitpicky criticisms: None
Red Flags: Naming of 2-propylheptane should be 4-methyl nonane. This is corrected in the next video.
Title: Correction – 2-Propylheptane should never be the name!
Summary: Video correcting error in previous video where wrong name was given to 4-methylnonane.
Title: Common and Systematic Naming – Iso, Sec and Tert Prefixes
Summary: The prefixes iso-, sec- and tert- are shown on cyclohexane rings, with the examples butylcyclopentane, s-butylcyclopentane, isobutylcyclopentane, and tert-butylcyclopentane (their proper names are also given).
Key concepts/skills: Understanding iso, sec- and tert- prefixes in nomenclature. Avoid using “1” to refer to a substituent if it’s unambiguous
Nitpicky criticisms: None
Red Flags: None
Title: More Organic Chemistry Naming Examples 1
Summary: More examples of naming substituted alkanes, using the examples 5-ethyldecane, 5,6-diethyldecane, 5,6-diethyl-6-isopropyldecane.
Key concepts/skills: introduction to prefixes such as “di”, also alphabetization of substituents (ethyl comes before isopropyl).
Title: Organic Chemistry Naming Examples 2
Summary: Examples with substituted rings, including 1,3-dicyclobutyl cyclohexane, cyclopentyl cyclohexane, 4,5-diisopropyl-2-2-dimethyloctane (alternatively: 2,2-dimethyl-4,5-bis(1-methylethyl) octane)
Key concepts/skills: Further application of proper alphabetization and numbering, as well as introduction of “bis” notation.
Title: Organic chemistry naming examples 3
Summary: More rules for identifying the longest chain on substituted alkanes and cycloalkanes, with the examples 3-methyl-4-propyl-tridecane. 1-tert-butyl-5-heptyl-2-propylcyclononane.
Key concepts/skills: When presented with two chains of equal length, choose the more substituted one as the parent chain. Ignore “tert” and “s” prefixes for alphabetization.
Title: Organic Chemistry Naming Examples 4
Summary: Naming rings attached to complex substituents, using the example 1,6-dicyclobutyl-7-cyclopropyl-2,4-diisobutylcyclooctane. Alternative name: 1,6-dicyclobutyl-7-cyclopropyl-2,4-bis(2-methylpropyl)cyclooctane.
Key concepts/skills: Mostly application of previous concepts, but in more complex setting. Extension of rules of how to number carbon chain/ring properly.
Title: Organic chemistry nomenclature examples 5
Summary: In contrast to previous, here we start with name and draw structure, using the examples 1-cycloentyl-6-ethyl-2,9-diisopropylcyclohexadecane. Also, 3,6,9,9-tetramethyldodecane. Also: 1,3-bis(1,1-dimethylethyl)cyclopentane, which could be alternatively named 1,3-bis-tert-butylcyclopentane.
Key concepts/skills: Going from name to structure
Title: Naming alkenes
Summary: First example of naming simple alkenes, with the examples heptene, hept-2-ene, 2-methyl-hept-2-ene, hept-2-4-diene [here misnamed as hept-2,4-ene]. Cyclohexene, 1,4,6-trimethylcyclohexene.
Key concepts/skills: Use of “ene” suffix, takes preference over “ane”. Number alkene so as to put lowest number on alkene carbon. Also, in the 1,4,6-trimethyl cyclohexene example, note that carbon #2 must be the second carbon in the alkene even though this ends up making the methyl group carbon #6.
Criticisms: small error re: hept-2,4-ene. It should be hept-2,4-diene. This is mentioned in the subsequent video. Also, alkene is trans (E), but this is not mentioned at this point.
Title: Naming Alkyl Halides
Summary: How to name simple alkyl halides, with the examples 4-bromo-2-chloro-5-methyl-octane, 5-bromo-7-chloro-oct-2-ene, 1,1,1-trifluoro-2-bromo-2-chloroethane.
Key concepts/skills: Alphabetization also applies to halides. Alkenes have higher priority over alkanes/halides. Also, extension of principle of giving molecule lowest numbering (1,1,1-trifluoro example).
Overall impression of videos 1-12:
These first 12 videos cover the naming of alkanes, alkenes, and alkyl halides. Overall I think these are a fine introduction to nomenclature, especially if done in concert with further examples from a textbook. They contain most of the key principles.
A few small things that would be good to include would be the following:
- an example of bracket notation for alkane naming. For instance, explain how a molecule like CH3CH(CH3)CH2CH3 is drawn out. Many introductory students struggle with this.
- in the alkyl halide example, mention the fact that the lone pairs on the halogens are “implied” (they’re there, but we don’t draw them). Similar to how hydrogens are “implied”. Being able to “see” the implied hydrogens and lone pairs will be an extremely important skill going forward in the course.
- Some mention during the nomenclature series of the terms “primary, secondary, tertiary, and quaternary” which are commonly encountered throughout the course.