So now that we kind of understand the definition of pKa and how it has to do with some molecules being better acids and some molecules being worse acids, we're going to have to go over our pKa values now. Okay? Now I don't like to give you guys a lot of stuff to memorize in organic chemistry. I like for you guys to understand it versus memorize it. But it turns out that pKa values are just one of those things that it's maybe just better for you to memorize it. If you can understand it, great. But even if you don't understand it, I think it's worth your time just to memorize them because they're going to continue to help you with Orgo 1 and in Orgo. They're that important. So let's go ahead and get started. So here I've given you a basic spectrum of some common molecules that you're going to need to know for your test, for Orgo 2, etcetera, MCAT, whatever you're taking. And, I'm starting off with the worst acids. Not worst, worst. And then I'm going to go all the way to the best at the end. Are you guys cool with that? So I'm going to start with the worst. And if I'm starting off with the worst, that means these are going to have the highest or the lowest values. What do you think? These are going to have the highest values because they're the worst acids. Remember, these are I'm going to start off with, like, the acids. Okay? So let's go ahead and start off with, basically, sp3 hybridized CH. Okay? I know that sounds really complicated, but all that is is that's just another way for me to say alkane. Remember that alkanes are sp3 hybridized because you basically have a carbon with maybe another carbon on it and a bunch of H's. And what that means is it has 4 groups. And if it's 4 groups, then it's sp3 hybridized. Well, these alkanes are not acidic at all. Think about it. It's because they're not reactive. Remember that I told you guys that what makes molecules reactive? Dipoles, charges, strain, double bonds. Alkane doesn't have any of that. So it doesn't want to be an acid at all. So that means that it's going to have the worst pKa of around 50. So it really doesn't get worse than an alkane. An alkane is the worst acid. Then from there, these start to get a little bit better. So let's talk about sp2 hybridized CH. Sounds complicated, but that's just another way of saying alkene. Remember what an alkene is? It's a double bond. So that would be an H coming off of a double bond. Now is this going to be a little bit more reactive than a single bond? Yes. Because remember I told you guys that double bonds are sources of reactivity. So this is going to be a little bit better. And it turns out that this one is going to have a pKa of 44. Okay? So it's still high, but at least it's a little bit better than the alkane. So we're just going to keep going in order. We're just going to keep going up. So now we have amines. Anytime that you have an H coming off directly of a nitrogen with a single bond. And anytime you have an amine, that's going to have a pKa of 38. So it's still really high. Remember that I said 16 is your middle point. Right? So we're still really far away from that. These are still bad acids, but they're getting a little bit better. Then we get to H2. H2 is a really important molecule that you're going to need for some reactions. It's just diatomic hydrogen. This one's going to have a pKa of 35. This one, honestly, there's not a lot to understand. It's just to memorize it. You just need to know that H2 has a pKa of 35. That's going to help you a lot. Then we get all the way down to sp hybridized CH. sp would be an alkyne. Because remember that sp means that it only has 2 groups or 2 bond sites. So that means it would literally be a triple bond with a hydrogen coming off of it. Now that triple bond is even more reactive, so it's going to be a little bit better at donating protons. This one has a pKa of 25. So I made a really big jump. That one's getting a lot better. Okay? So if you could group these together, I would recommend always know that your alkanes, alkenes, and your alkynes are 50, 44, and 25. I'm going to grill you guys on that all semester long. You're going to be like, remember sp2? Remember sp? It was 44, 25. I'm going to ask you these values over and over again because they're that important. Then we've got our alpha hydrogens. What the heck is an alpha hydrogen? An alpha hydrogen is any H that's coming directly off of a carbonyl, off of the carbon next to a carbonyl. So here I have a carbonyl. This carbonyl could be anything. It could be an aldehyde, let's say, where it has an H there. This carbon, if that one has an H on it, that H is going to have a pKa of 20. Now it turns out that you're not really going to understand why this has such a low pKa. Because normally, what would be the pKa of a CH bond that's sp3 hybridized? It would usually be 50. But now, instead, the pKa is actually going to be closer to 20. That's a huge jump. So why is it so much more stable if it's on that alpha carbon? And the reason has to do with a phenomenon called tautomerization. Now it turns out that tautomerization is something that we're going to explore more in Orgo 2. This is one of those rare times that I have to teach you something that you're not going to understand right now. And you just have to accept it. You have to take my word for it. Tautomerization is this thing that makes the carbon next to a carbonyl much more acidic. It only has to do with the carbon that has an H on it. Cool. So then we get to some easy ones. So we have ROH, which is alcohol, and water. These both have about the same pKa. They both have a pKa of about 16. If you just remember I told you as water has a pKa of 16, that's the middle point. So this is like the neutral point right here. It's not really neutral. It just means that I compare all the other acids to it. So remember that I said all the ones before it, these would all be the bad acids. So that means that over here, I'm going to start getting into good acids. Is that cool? Another thing to keep in mind, water actually has a more specific pKa. Your professor might want you to know it. It's 15.7. But that's so close to 16 that I always just round it. I always just say water has a pKa of 16. Cool so far? Now we're going to start getting into the good acids. So what happens if I have a nitrogen with a positive charge? If you have a nitrogen with a positive and at least one H on it, that is going to have a pKa of around 10. Now you could imagine this is a pretty good acid because, look, it has a full positive. Remember that I told you guys that if you have formal charges, that makes something really reactive. So this has a full positive. So that means that that's a very good acid. Then you have all your carboxylic acids. I mean, they have acid in the name. Right? And carboxylic acids are about 5. And you would know that because we just calculated the pKa of a carboxylic acid. Remember, acetic acid, that's a type of carboxylic acid. And that one was remember? It was 4.75. So we just round it up to 5. Is that cool? Awesome. So now we're on the home stretch. So now what if we have an O Positive with 1 H on it? What that is is that now we have an O Positive that's a very good acid. That's going to be around negative 2. So if you see now we're getting into the negative numbers, that means these are going to be strong acids. And then finally we have HX. HX is just going to be your strong acids. So remember that I told you, remember your strong 6? Three of your strong 6 are HCl, HBr, and HI. These are all going to have very acidic pKas. And all in, I'm not going to make you memorize those pKas, because most often, professors don't care about those pKas as much because they're all negative. So I'm just going to group them together and just say they're all negative. If you want to memorize them, if your professor's really picky, maybe he'll make you memorize negative 11 and negative 7 and stuff like that. But most of the time, you're fine as long as you know it's just negative. It just means it's really acidic. Is that cool? So I know that was a ton of information, but thankfully, I'm going to give you lots of practice so that by the end of this page, you're going to be feeling more comfortable.
Table of contents
- 1. A Review of General Chemistry5h 5m
- Summary23m
- Intro to Organic Chemistry5m
- Atomic Structure16m
- Wave Function9m
- Molecular Orbitals17m
- Sigma and Pi Bonds9m
- Octet Rule12m
- Bonding Preferences12m
- Formal Charges6m
- Skeletal Structure14m
- Lewis Structure20m
- Condensed Structural Formula15m
- Degrees of Unsaturation15m
- Constitutional Isomers14m
- Resonance Structures46m
- Hybridization23m
- Molecular Geometry16m
- Electronegativity22m
- 2. Molecular Representations1h 14m
- 3. Acids and Bases2h 46m
- 4. Alkanes and Cycloalkanes4h 19m
- IUPAC Naming29m
- Alkyl Groups13m
- Naming Cycloalkanes10m
- Naming Bicyclic Compounds10m
- Naming Alkyl Halides7m
- Naming Alkenes3m
- Naming Alcohols8m
- Naming Amines15m
- Cis vs Trans21m
- Conformational Isomers13m
- Newman Projections14m
- Drawing Newman Projections16m
- Barrier To Rotation7m
- Ring Strain8m
- Axial vs Equatorial7m
- Cis vs Trans Conformations4m
- Equatorial Preference14m
- Chair Flip9m
- Calculating Energy Difference Between Chair Conformations17m
- A-Values17m
- Decalin7m
- 5. Chirality3h 39m
- Constitutional Isomers vs. Stereoisomers9m
- Chirality12m
- Test 1:Plane of Symmetry7m
- Test 2:Stereocenter Test17m
- R and S Configuration43m
- Enantiomers vs. Diastereomers13m
- Atropisomers9m
- Meso Compound12m
- Test 3:Disubstituted Cycloalkanes13m
- What is the Relationship Between Isomers?16m
- Fischer Projection10m
- R and S of Fischer Projections7m
- Optical Activity5m
- Enantiomeric Excess20m
- Calculations with Enantiomeric Percentages11m
- Non-Carbon Chiral Centers8m
- 6. Thermodynamics and Kinetics1h 22m
- 7. Substitution Reactions1h 48m
- 8. Elimination Reactions2h 30m
- 9. Alkenes and Alkynes2h 9m
- 10. Addition Reactions3h 18m
- Addition Reaction6m
- Markovnikov5m
- Hydrohalogenation6m
- Acid-Catalyzed Hydration17m
- Oxymercuration15m
- Hydroboration26m
- Hydrogenation6m
- Halogenation6m
- Halohydrin12m
- Carbene12m
- Epoxidation8m
- Epoxide Reactions9m
- Dihydroxylation8m
- Ozonolysis7m
- Ozonolysis Full Mechanism24m
- Oxidative Cleavage3m
- Alkyne Oxidative Cleavage6m
- Alkyne Hydrohalogenation3m
- Alkyne Halogenation2m
- Alkyne Hydration6m
- Alkyne Hydroboration2m
- 11. Radical Reactions1h 58m
- 12. Alcohols, Ethers, Epoxides and Thiols2h 42m
- Alcohol Nomenclature4m
- Naming Ethers6m
- Naming Epoxides18m
- Naming Thiols11m
- Alcohol Synthesis7m
- Leaving Group Conversions - Using HX11m
- Leaving Group Conversions - SOCl2 and PBr313m
- Leaving Group Conversions - Sulfonyl Chlorides7m
- Leaving Group Conversions Summary4m
- Williamson Ether Synthesis3m
- Making Ethers - Alkoxymercuration4m
- Making Ethers - Alcohol Condensation4m
- Making Ethers - Acid-Catalyzed Alkoxylation4m
- Making Ethers - Cumulative Practice10m
- Ether Cleavage8m
- Alcohol Protecting Groups3m
- t-Butyl Ether Protecting Groups5m
- Silyl Ether Protecting Groups10m
- Sharpless Epoxidation9m
- Thiol Reactions6m
- Sulfide Oxidation4m
- 13. Alcohols and Carbonyl Compounds2h 17m
- 14. Synthetic Techniques1h 26m
- 15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
- Purpose of Analytical Techniques5m
- Infrared Spectroscopy16m
- Infrared Spectroscopy Table31m
- IR Spect:Drawing Spectra40m
- IR Spect:Extra Practice26m
- NMR Spectroscopy10m
- 1H NMR:Number of Signals26m
- 1H NMR:Q-Test26m
- 1H NMR:E/Z Diastereoisomerism8m
- H NMR Table24m
- 1H NMR:Spin-Splitting (N + 1) Rule22m
- 1H NMR:Spin-Splitting Simple Tree Diagrams11m
- 1H NMR:Spin-Splitting Complex Tree Diagrams12m
- 1H NMR:Spin-Splitting Patterns8m
- NMR Integration18m
- NMR Practice14m
- Carbon NMR4m
- Structure Determination without Mass Spect47m
- Mass Spectrometry12m
- Mass Spect:Fragmentation28m
- Mass Spect:Isotopes27m
- 16. Conjugated Systems6h 13m
- Conjugation Chemistry13m
- Stability of Conjugated Intermediates4m
- Allylic Halogenation12m
- Reactions at the Allylic Position39m
- Conjugated Hydrohalogenation (1,2 vs 1,4 addition)26m
- Diels-Alder Reaction9m
- Diels-Alder Forming Bridged Products11m
- Diels-Alder Retrosynthesis8m
- Molecular Orbital Theory9m
- Drawing Atomic Orbitals6m
- Drawing Molecular Orbitals17m
- HOMO LUMO4m
- Orbital Diagram:3-atoms- Allylic Ions13m
- Orbital Diagram:4-atoms- 1,3-butadiene11m
- Orbital Diagram:5-atoms- Allylic Ions10m
- Orbital Diagram:6-atoms- 1,3,5-hexatriene13m
- Orbital Diagram:Excited States4m
- Pericyclic Reaction10m
- Thermal Cycloaddition Reactions26m
- Photochemical Cycloaddition Reactions26m
- Thermal Electrocyclic Reactions14m
- Photochemical Electrocyclic Reactions10m
- Cumulative Electrocyclic Problems25m
- Sigmatropic Rearrangement17m
- Cope Rearrangement9m
- Claisen Rearrangement15m
- 17. Ultraviolet Spectroscopy51m
- 18. Aromaticity2h 34m
- 19. Reactions of Aromatics: EAS and Beyond5h 1m
- Electrophilic Aromatic Substitution9m
- Benzene Reactions11m
- EAS:Halogenation Mechanism6m
- EAS:Nitration Mechanism9m
- EAS:Friedel-Crafts Alkylation Mechanism6m
- EAS:Friedel-Crafts Acylation Mechanism5m
- EAS:Any Carbocation Mechanism7m
- Electron Withdrawing Groups22m
- EAS:Ortho vs. Para Positions4m
- Acylation of Aniline9m
- Limitations of Friedel-Crafts Alkyation19m
- Advantages of Friedel-Crafts Acylation6m
- Blocking Groups - Sulfonic Acid12m
- EAS:Synergistic and Competitive Groups13m
- Side-Chain Halogenation6m
- Side-Chain Oxidation4m
- Reactions at Benzylic Positions31m
- Birch Reduction10m
- EAS:Sequence Groups4m
- EAS:Retrosynthesis29m
- Diazo Replacement Reactions6m
- Diazo Sequence Groups5m
- Diazo Retrosynthesis13m
- Nucleophilic Aromatic Substitution28m
- Benzyne16m
- 20. Phenols55m
- 21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
- Naming Aldehydes8m
- Naming Ketones7m
- Oxidizing and Reducing Agents9m
- Oxidation of Alcohols28m
- Ozonolysis7m
- DIBAL5m
- Alkyne Hydration9m
- Nucleophilic Addition8m
- Cyanohydrin11m
- Organometallics on Ketones19m
- Overview of Nucleophilic Addition of Solvents13m
- Hydrates6m
- Hemiacetal9m
- Acetal12m
- Acetal Protecting Group16m
- Thioacetal6m
- Imine vs Enamine15m
- Addition of Amine Derivatives5m
- Wolff Kishner Reduction7m
- Baeyer-Villiger Oxidation39m
- Acid Chloride to Ketone7m
- Nitrile to Ketone9m
- Wittig Reaction18m
- Ketone and Aldehyde Synthesis Reactions14m
- 22. Carboxylic Acid Derivatives: NAS2h 51m
- Carboxylic Acid Derivatives7m
- Naming Carboxylic Acids9m
- Diacid Nomenclature6m
- Naming Esters5m
- Naming Nitriles3m
- Acid Chloride Nomenclature5m
- Naming Anhydrides7m
- Naming Amides5m
- Nucleophilic Acyl Substitution18m
- Carboxylic Acid to Acid Chloride6m
- Fischer Esterification5m
- Acid-Catalyzed Ester Hydrolysis4m
- Saponification3m
- Transesterification5m
- Lactones, Lactams and Cyclization Reactions10m
- Carboxylation5m
- Decarboxylation Mechanism14m
- Review of Nitriles46m
- 23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
- 24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
- Tautomerization9m
- Tautomers of Dicarbonyl Compounds6m
- Enolate4m
- Acid-Catalyzed Alpha-Halogentation4m
- Base-Catalyzed Alpha-Halogentation3m
- Haloform Reaction8m
- Hell-Volhard-Zelinski Reaction3m
- Overview of Alpha-Alkylations and Acylations5m
- Enolate Alkylation and Acylation12m
- Enamine Alkylation and Acylation16m
- Beta-Dicarbonyl Synthesis Pathway7m
- Acetoacetic Ester Synthesis13m
- Malonic Ester Synthesis15m
- 25. Condensation Chemistry2h 9m
- 26. Amines1h 43m
- 27. Heterocycles2h 0m
- Nomenclature of Heterocycles15m
- Acid-Base Properties of Nitrogen Heterocycles10m
- Reactions of Pyrrole, Furan, and Thiophene13m
- Directing Effects in Substituted Pyrroles, Furans, and Thiophenes16m
- Addition Reactions of Furan8m
- EAS Reactions of Pyridine17m
- SNAr Reactions of Pyridine18m
- Side-Chain Reactions of Substituted Pyridines20m
- 28. Carbohydrates5h 53m
- Monosaccharide20m
- Monosaccharides - D and L Isomerism9m
- Monosaccharides - Drawing Fischer Projections18m
- Monosaccharides - Common Structures6m
- Monosaccharides - Forming Cyclic Hemiacetals12m
- Monosaccharides - Cyclization18m
- Monosaccharides - Haworth Projections13m
- Mutarotation11m
- Epimerization9m
- Monosaccharides - Aldose-Ketose Rearrangement8m
- Monosaccharides - Alkylation10m
- Monosaccharides - Acylation7m
- Glycoside6m
- Monosaccharides - N-Glycosides18m
- Monosaccharides - Reduction (Alditols)12m
- Monosaccharides - Weak Oxidation (Aldonic Acid)7m
- Reducing Sugars23m
- Monosaccharides - Strong Oxidation (Aldaric Acid)11m
- Monosaccharides - Oxidative Cleavage27m
- Monosaccharides - Osazones10m
- Monosaccharides - Kiliani-Fischer23m
- Monosaccharides - Wohl Degradation12m
- Monosaccharides - Ruff Degradation12m
- Disaccharide30m
- Polysaccharide11m
- 29. Amino Acids3h 20m
- Proteins and Amino Acids19m
- L and D Amino Acids14m
- Polar Amino Acids14m
- Amino Acid Chart18m
- Acid-Base Properties of Amino Acids33m
- Isoelectric Point14m
- Amino Acid Synthesis: HVZ Method12m
- Synthesis of Amino Acids: Acetamidomalonic Ester Synthesis16m
- Synthesis of Amino Acids: N-Phthalimidomalonic Ester Synthesis13m
- Synthesis of Amino Acids: Strecker Synthesis13m
- Reactions of Amino Acids: Esterification7m
- Reactions of Amino Acids: Acylation3m
- Reactions of Amino Acids: Hydrogenolysis6m
- Reactions of Amino Acids: Ninhydrin Test11m
- 30. Peptides and Proteins2h 42m
- Peptides12m
- Primary Protein Structure4m
- Secondary Protein Structure17m
- Tertiary Protein Structure11m
- Disulfide Bonds17m
- Quaternary Protein Structure10m
- Summary of Protein Structure7m
- Intro to Peptide Sequencing2m
- Peptide Sequencing: Partial Hydrolysis25m
- Peptide Sequencing: Partial Hydrolysis with Cyanogen Bromide7m
- Peptide Sequencing: Edman Degradation28m
- Merrifield Solid-Phase Peptide Synthesis18m
- 31. Catalysis in Organic Reactions1h 30m
- 32. Lipids 2h 50m
- 33. The Organic Chemistry of Metabolic Pathways2h 52m
- Intro to Metabolism6m
- ATP and Energy6m
- Intro to Coenzymes3m
- Coenzymes in Metabolism16m
- Energy Production in Biochemical Pathways5m
- Intro to Glycolysis3m
- Catabolism of Carbohydrates: Glycolysis27m
- Glycolysis Summary15m
- Pyruvate Oxidation (Simplified)4m
- Anaerobic Respiration11m
- Catabolism of Fats: Glycerol Metabolism11m
- Intro to Citric Acid Cycle7m
- Structures of the Citric Acid Cycle19m
- The Citric Acid Cycle35m
- 34. Nucleic Acids1h 32m
- 35. Transition Metals6h 14m
- Electron Configuration of Elements45m
- Coordination Complexes20m
- Ligands24m
- Electron Counting10m
- The 18 and 16 Electron Rule13m
- Cross-Coupling General Reactions40m
- Heck Reaction40m
- Stille Reaction13m
- Suzuki Reaction25m
- Sonogashira Coupling Reaction17m
- Fukuyama Coupling Reaction15m
- Kumada Coupling Reaction13m
- Negishi Coupling Reaction16m
- Buchwald-Hartwig Amination Reaction19m
- Eglinton Reaction17m
- Catalytic Allylic Alkylation18m
- Alkene Metathesis23m
- 36. Synthetic Polymers1h 49m
- Introduction to Polymers6m
- Chain-Growth Polymers10m
- Radical Polymerization15m
- Cationic Polymerization8m
- Anionic Polymerization8m
- Polymer Stereochemistry3m
- Ziegler-Natta Polymerization4m
- Copolymers6m
- Step-Growth Polymers11m
- Step-Growth Polymers: Urethane6m
- Step-Growth Polymers: Polyurethane Mechanism10m
- Step-Growth Polymers: Epoxy Resin8m
- Polymers Structure and Properties8m
3. Acids and Bases
pKa
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