Organic Reagents
By James Ashenhurst
Reagent Friday: OsO4 (Osmium Tetroxide)
Last updated: February 27th, 2016
In a blatant plug for the Reagent Guide, each Friday I profile a different reagent that is commonly encountered in Org 1/ Org 2.
Today’s reagent is among one of the best and most useful at what it does in all of organic chemistry. It’s blindingly good, in fact. So blinding, I don’t know if I’ve ever seen an example of it being used in an undergraduate teaching lab. It’s not a reagent for rookies: it’s genuinely dangerous, and best handled with extreme care.
Osmium tetroxide (OsO4) is a volatile liquid that is most useful for the synthesis of 1,2 diols from alkenes. (Side note: another name for 1,2 diols is vicinal diols, or vic-diols). The reaction is very mild, and usefully leads to the formation of syn diols. Another side note: this reaction doesn’t work with alkynes.
The reaction works through a concerted process whereby two oxygens from the osmium interact with one face of the double bond. This results in a 5-membered ring (called an osmate ester) and generates the syn stereochemistry. The osmate ester is broken up into the 1,2-diol by use of a reducing agent such as potassium bisulfite, KHSO3. This is frequently omitted in textbooks, but is worth mentioning just in case.
By the way, dihydroxylation of alkenes can also be performed with cold, dilute potassium permanganate (KMnO4). One advantage of OsO4 is that it is much more compatible with other functional groups than KMnO4, which is kind of a ravenous beast.
Why is osmium “blindingly good”? One of the molecules required for vision is retinol:
What do you think would happen if the vapors from OsO4 reached your eyes? Everything would go dark, let me tell you.
The good news is that apparently the blindness wears off after several months.
P.S. You can read about the chemistry of OsO4 and more than 80 other reagents in undergraduate organic chemistry in the “Organic Chemistry Reagent Guide”, available here as a downloadable PDF.
P.P.S. One preparation in Woodward’s synthesis of cortisone (subscription req’d) calls for Osmium tetroxide (68.48 g) . Damn!!!
Related Posts:
00 General Chemistry Review
- Gen Chem and Organic Chem: How are they different?
- How Gen Chem Relates to Organic Chem, Pt. 1 - The Atom
- From Gen Chem to Organic Chem, Pt. 2 - Electrons and Orbitals
- From Gen Chem to Organic Chem, Pt. 3 - Effective Nuclear Charge
- From Gen Chem to Organic Chem, Pt. 4 - Chemical Bonding
- From Gen Chem to Organic Chem, Pt. 5 - Understanding Periodic Trends
- From Gen Chem to Org Chem, Pt. 6 - Lewis Structures, A Parable
- From Gen Chem to Org Chem, Pt. 7 - Lewis Structures
- From Gen Chem to Org Chem, Pt. 8 - Ionic and Covalent Bonding
- From Gen Chem to Org Chem, Pt. 9 - Acids and Bases
- From Gen Chem to Organic Chem, Pt. 10 - Hess' Law
- From Gen Chem to Organic Chem, Pt. 11 - The Second Law
- From Gen Chem to Org Chem Pt. 12 - Kinetics
- From Gen Chem to Organic Chem, Pt. 13 - Equilibria
- From Gen Chem to Organic Chem, Part 14: Wrapup
01 Bonding, Structure, and Resonance
- How Concepts Build Up In Org 1 ("The Pyramid")
- Review of Atomic Orbitals for Organic Chemistry
- How Do We Know Methane Is Tetrahedral?
- Hybrid Orbitals
- A Hybridization Shortcut
- Hybridization And Bond Strengths
- Sigma bonds come in six varieties: Pi bonds come in one
- A Key Skill: How to Calculate Formal Charge
- Partial Charges Give Clues About Electron Flow
- The Four Intermolecular Forces and How They Affect Boiling Points
- 3 Trends That Affect Boiling Points
- How To Use Electronegativity To Determine Electron Density (and why NOT to trust formal charge)
- Introduction to Resonance
- How To Use Curved Arrows To Interchange Resonance Forms
- Evaluating Resonance Forms (1) - The Rule of Least Charges
- Evaluating Resonance Forms (2): Applying Electronegativity
- Evaluating Resonance Forms: Factors That Stabilize Negative Charges
- Evaluating Resonance Forms (4): Positive Charges
- Exploring Resonance: Pi-Donation
- Exploring Resonance: Pi-acceptors
- In Summary: Resonance
- Drawing Resonance Structures: 3 Common Mistakes To Avoid
- How to apply electronegativity and resonance to understand reactivity
02 Acid Base Reactions
- Introduction to Acid-Base Reactions
- Walkthrough of Acid Base Reactions (1)
- Walkthrough of Acid Base Reactions (2): Basicity
- Walkthrough of Acid-Base Reactions (3) - Acidity Trends
- Five Key Factors That Influence Acidity
- Walkthrough of Acid-Base reactions (4) - pKa
- How to Use a pKa Table
- The pKa Table Is Your Friend
- A Handy Rule of Thumb for Acid-Base Reactions
- Acid Base Reactions Are Fast
- Putting Acidity In Perspective
- Acid Base Reactions: What's the Point?
03 Alkanes and Nomenclature
- Summary Sheet - Alkane Nomenclature
- Meet the (Most Important) Functional Groups
- Condensed Formulas: Deciphering What the Brackets Mean
- Hidden Hydrogens, Hidden Lone Pairs, Hidden Counterions
- Don't Be Futyl, Learn The Butyls
- Primary, Secondary, Tertiary, Quaternary In Organic Chemistry
- Branching, and Its Affect On Melting and Boiling Points
- The Many, Many Ways of Drawing Butane
- Common Mistakes: Drawing Tetrahedral Carbons
- Common Mistakes in Organic Chemistry: Pentavalent Carbon
- Table of Functional Group Priorities for Nomenclature
- Organic Chemistry IUPAC Nomenclature Demystified With A Simple Puzzle Piece Approach
04 Conformations and Cycloalkanes
- Conformations
- Newman Projections
- Putting the Newman into ACTION
- Introduction to Cycloalkanes (1)
- Cis And Trans Cycloalkanes
- Cycloalkanes - How To Calculate Ring Strain
- Cycloalkanes - Ring Strain In Cyclopropane And Cyclobutane
- Ring Strain in Cyclopentane and Cyclohexane
- An Aerial Tour Of The Cyclohexane Chair
- How To Draw A Cyclohexane Chair
- The Cyclohexane Chair Flip
- The Cyclohexane Chair Flip - Energy Diagram
- Substituted Cyclohexanes - Equatorial vs Axial
- Substituted Cyclohexanes: "A Values"
- The Ups and Downs of Cyclohexanes
- Which Cyclohexane Chair Is Of Lower Energy?
- Fused Rings
- Bridged Bicyclic Rings (And How To Name Them)
- Bredt's Rule (And Summary of Cycloalkanes)
05 A Primer On Organic Reactions
- The Most Important Question To Ask When Learning a New Reaction
- The 4 Major Classes of Reactions in Org 1
- Learning New Reactions: How Do The Electrons Move?
- How (and why) electrons flow
- The Third Most Important Question to Ask When Learning A New Reaction
- 7 Factors that stabilize negative charge in organic chemistry
- 7 Factors That Stabilize Positive Charge in Organic Chemistry
- Common Mistakes: Formal Charges Can Mislead
- Nucleophiles and Electrophiles
- Curved Arrows (for reactions)
- Curved Arrows (2): Initial Tails and Final Heads
- Nucleophilicity vs. Basicity
- The Three Classes of Nucleophiles
- What Makes A Good Nucleophile?
- Leaving Groups Are Nucleophiles Acting In Reverse
- What makes a good leaving group?
- 3 Factors That Stabilize Carbocations
- Three Factors that Destabilize Carbocations
- What's a Transition State?
- Hammond's Postulate
- Grossman's Rule
- Draw The Ugly Version First
- Learning Reactions: A Checklist (PDF)
- Introduction to Addition Reactions
- Introduction to Elimination Reactions
- Introduction to Free Radical Substitution Reactions
- Introduction to Oxidative Cleavage Reactions
06 Free Radical Reactions
- Bond Dissociation Energies = Homolytic Cleavage
- Free Radical Reactions
- 3 Factors That Stabilize Free Radicals
- What Factors Destabilize Free Radicals?
- Bond Strengths And Radical Stability
- Free Radical Initiation: Why Is "Light" Or "Heat" Required?
- Initiation, Propagation, Termination
- Isomers From Free Radical Reactions
- Selectivity In Free Radical Reactions
- Selectivity in Free Radical Reactions: Bromine vs. Chlorine
- Halogenation At Tiffany's
- Allylic Bromination
- Bonus Topic: Allylic Rearrangements
- In Summary: Free Radicals
- Synthesis (2) - Reactions of Alkanes
07 Stereochemistry and Chirality
- On Cats, Part 4: Enantiocats
- On Cats, Part 6: Stereocenters
- The Single Swap Rule
- Introduction to Assigning (R) and (S): The Cahn-Ingold-Prelog Rules
- Determining R/S (2) - The Method of Dots
- Types of Isomers: Constitutional Isomers, Stereoisomers, Enantiomers, and Diastereomers
- Enantiomers vs Diastereomers vs The Same? Two Methods For Solving Problems
- Assigning R/S To Newman Projections (And Converting Newman To Line Diagrams)
- The Meso Trap
- Optical Rotation, Optical Activity, and Specific Rotation
- Optical Purity and Enantiomeric Excess
- What's a Racemic Mixture?
- Chiral Allenes And Chiral Axes
08 Substitution Reactions
- Introduction to Nucleophilic Substitution Reactions
- Walkthrough of Substitution Reactions (1) - Introduction
- Two Types of Substitution Reactions
- The SN2 Mechanism
- Why the SN2 Reaction Is Powerful
- The SN1 Mechanism
- The Conjugate Acid Is A Better Leaving Group
- Comparing the SN1 and SN2 Reactions
- Polar Protic? Polar Aprotic? Nonpolar? All About Solvents
- Steric Hindrance is Like a Fat Goalie
- Common Blind Spot: Intramolecular Reactions
- The Conjugate Base is Always a Stronger Nucleophile
09 Elimination Reactions
- Walkthrough of Elimination Reactions (1)
- Elimination Reactions (2): Zaitsev's Rule
- Elimination Reactions Are Favored By Heat
- Two Types of Elimination Reactions
- The E1 Reaction
- The E2 Mechanism
- Comparing the E1 and E2 Reactions
- The E2 Reaction and Cyclohexane Rings
- Bulky Bases in Elimination Reactions
- Comparing the E1 and SN1 Reactions
- Elimination (E1) Reactions With Rearrangements
10 Rearrangements
11 SN1/SN2/E1/E2 Decision
12 Alkene Reactions
- Alkene Nomenclature: Cis and Trans and E and Z
- Addition Reactions: Elimination's Opposite
- Selective vs. Specific
- Addition Reactions: Regioselectivity
- Addition Reactions: Stereochemistry
- Markovnikov's Rule (1)
- Markovnikov's Rule (2) - Why It Works
- Curved Arrows and Addition Reactions
- Addition Pattern #1: The "Carbocation Pathway"
- Rearrangements in Alkene Addition Reactions
- Bromination of Alkenes - How Does It Work?
- Bromination of Alkenes: The Mechanism
- Alkene Addition Pattern #2: The "Three-Membered Ring" Pathway
- Hydroboration of Alkenes
- Hydroboration of Alkenes: The Mechanism
- Alkene Addition Pattern #3: The "Concerted" Pathway
- An Arrow-Pushing Dilemma In Concerted Reactions
- A Fourth Alkene Addition Pattern - Free Radical Addition
- Alkene Reactions: Ozonolysis
- Summary: Alkene Reaction Pathways
- Synthesis (4) - Reactions of Alkenes
13 Alkyne Reactions
- The 2 Most Important Reactions of Alkynes
- Partial Reduction of Alkynes To Obtain Cis or Trans Alkenes
- Hydroboration and Oxymercuration of Alkynes
- Alkyne Reaction Patterns - The Carbocation Pathway
- Alkyne Addition Reactions: The 3-Membered Ring Pathway
- Alkyne Addition Reactions - The "Concerted" Pathway
- Alkynes Via Elimination Reactions
- Alkynes Are A Blank Canvas
- Synthesis (5) - Reactions of Alkynes
14 Alcohols, Epoxides and Ethers
- Alcohols (1) - Nomenclature and Properties
- How To Make Alcohols More Reactive
- Alcohols (3) - Acidity and Basicity
- The Williamson Ether Synthesis
- Williamson Ether Synthesis: Planning
- Synthesis of Ethers (2) - Back To The Future
- Ether Synthesis Via Alcohols And Acid
- Cleavage Of Ethers With Acid
- Epoxides - The Outlier Of The Ether Family
- Opening Of Epoxide With Base
- Opening of Epoxides With Acid
- Making Alkyl Halides From Alcohols
- Tosylates And Mesylates
- PBr3 and SOCl2
- Elimination Reactions of Alcohols
- Elimination of Alcohols To Alkenes With POCl3
- Alcohol Oxidation: "Strong" and "Weak" Oxidants
- Demystifying Alcohol Oxidations
- Intramolecular Reactions of Alcohols and Ethers
- Protecting Groups For Alcohols
- Thiols And Thioethers
- Calculating the oxidation state of a carbon
- Oxidation and Reduction in Organic Chemistry
- Oxidation Ladders
- SOCl2 and the SNi Mechanism
- Synthesis (6) - Reactions of Alcohols
15 Organometallics
- What's An Organometallic?
- Synthesis of Grignard and Organolithium Reagents
- Organometallics Are Strong Bases
- Reactions of Grignard Reagents
- Protecting Groups In Grignard Reactions
- Synthesis Using Grignard Reagents (1)
- Grignard Reactions And Synthesis (2)
- Gilman Reagents (Organocuprates): How They're Made
- Gilman Reagents (Organocuprates): What They're Used For
- Common Mistakes with Carbonyls: Carboxylic Acids... Are Acids!
- The Heck, Suzuki, and Olefin Metathesis Reactions (And Why They Don't Belong In Most Introductory Organic Chemistry Courses)
- Reaction Map: Reactions of Organometallics
16 Spectroscopy
- Degrees of Unsaturation (Index of Hydrogen Deficiency)
- How Bleach Works: Understanding Colors From Nature
- Introduction To UV-Vis Spectroscopy
- UV-Vis Spectroscopy: Absorbance of Carbonyls
- UV-Vis Spectroscopy: Some Practice Questions
- Bond Vibrations, IR Spectroscopy, and the "Ball and Spring" Model
- Infrared Spectroscopy: A Quick Primer On Interpreting Spectra
- IR Spectroscopy: Some Simple Practice Problems
- Homotopic, Enantiotopic, Diastereotopic
- Liquid Gold: Pheromones In Doe Urine
- Natural Product Isolation (1) - Extraction
- Natural Product Isolation (2) - Purification of Crude Mixtures Overview
- Structure Determination Case Study: Deer Tarsal Gland Pheromone
17 Dienes and MO Theory
- What To Expect In Organic Chemistry 2
- How Concepts Build Up In Org 2
- Are these molecules conjugated?
- Conjugation and Resonance
- Molecular Orbital Diagram For A Simple Pi Bond - Bonding And Antibonding
- Molecular Orbitals of The Allyl Cation, Allyl Radical, and Allyl Anion
- Pi Molecular Orbitals of Butadiene
- Reactions of Dienes: 1,2 and 1,4 Addition
- Thermodynamic and Kinetic Control
- More On 1,2 and 1,4 Additions To Dienes
- s-cis and s-trans
- The Diels-Alder Reaction
- Cyclic Dienes and Dienophiles in the Diels-Alder Reaction
- Stereochemistry of the Diels-Alder Reaction
- Exo vs Endo Products In The Diels Alder: How To Tell Them Apart
- Molecular Orbitals in the Diels Alder Reaction
- Why Are Endo vs Exo Products Favored in the Diels-Alder Reaction?
- Diels-Alder Reaction: Kinetic and Thermodynamic Control
- The Retro Diels-Alder Reaction
- Regiochemistry In The Diels-Alder Reaction
18 Aromaticity
19 Reactions of Aromatic Molecules
- Electrophilic Aromatic Substitution: Introduction
- Activating and Deactivating Groups In Electrophilic Aromatic Substitution
- Electrophilic Aromatic Substitution - The Mechanism
- Ortho-, Para- and Meta- Directors in Electrophilic Aromatic Substitution
- Understanding Ortho, Para, and Meta Directors
- Why are halogens ortho- para- directors?
- Disubstituted Benzenes: The Strongest Electron-Donor "Wins"
- Electrophilic Aromatic Substitutions (1) - Halogenation
- Electrophilic Aromatic Substitutions (2) - Nitration and Sulfonation
- EAS Reactions (3) - Friedel-Crafts Acylation and Friedel-Crafts Alkylation
- Intramolecular Friedel-Crafts Reactions
- Nucleophilic Aromatic Substitution (NAS)
- Nucleophilic Aromatic Substitution (2) - The Benzyne Mechanism
- Reactions of Diazonium Salts: Sandmeyer and Related Reactions
- Reactions on the "Benzylic" Carbon: Bromination And Oxidation
- The Wolff-Kishner, Clemmensen, And Other Carbonyl Reductions
- More Reactions on the Aromatic Sidechain: Reduction of Nitro Groups and the Baeyer Villiger
- Aromatic Synthesis (1) - "Order Of Operations"
- Aromatic Synthesis (2) - Polarity Reversal
- Aromatic Synthesis (3) - Sulfonyl Blocking Groups
- Synthesis (7): Reaction Map of Benzene and Related Aromatic Compounds
20 Aldehydes and Ketones
- Weird Nomenclature In Carbonyl Chemistry
- The Simple Two-Step Pattern For Seven Key Reactions of Aldehydes and Ketones
- Wittig Reaction
- Imines and Enamines
- Acid Catalysis Of Carbonyl Addition Reactions: Too Much Of A Good Thing?
- On Acetals and Hemiacetals
- Carbonyl Chemistry: 10 Key Concepts (Part 1)
- Carbonyls: 10 key concepts (Part 2)
- Breaking Down Carbonyl Reaction Mechanisms: Anionic Nucleophiles (Part 1)
- Breaking Down Carbonyl Reaction Mechanisms: Reactions of Anionic Nucleophiles (Part 2)
21 Carboxylic Acid Derivatives
- Simplifying the reactions of carboxylic acid derivatives (part 1)
- Carbonyl Mechanisms: Neutral Nucleophiles, Part 1
- Carbonyl chemistry: Anionic versus Neutral Nucleophiles
- Proton Transfers Can Be Tricky
- Let's Talk About the [1,2] Elimination
- Carbonyl Chemistry: Learn Six Mechanisms For the Price Of One
- Summary Sheet #5 - 9 Key Mechanisms in Carbonyl Chemistry
- Summary Sheet #7 - 21 Carbonyl Mechanisms on 1 page
- How Reactions Are Like Music
- Making Music With Mechanisms
- The Magic Wand of Proton Transfer
- The Power of Acid Catalysis
22 Enols and Enolates
23 Amines
- Amides: Properties, Synthesis, and Nomenclature
- Basicity of Amines And pKaH
- 5 Factors That Affect Basicity of Amines
- The Mesomeric Effect And Aromatic Amines
- Nucleophilicity of Amines
- Alkylation of Amines (Sucks)
- Reductive Amination
- The Gabriel Synthesis
- Some Reactions of Azides
- The Hofmann Elimination
- The Hofmann and Curtius Rearrangements
- The Cope Elimination
- Protecting Groups for Amines - Carbamates
- Introduction to Peptide Synthesis
- The Strecker Synthesis of Amino Acids
24 Carbohydrates
- D and L Sugars
- What is Mutarotation?
- Reducing Sugars
- Pyranoses and Furanoses: Ring-Chain Tautomerism In Sugars
- The Big Damn Post Of Sugar Nomenclature
- The Haworth Projection
- Converting a Fischer Projection To A Haworth (And Vice Versa)
- Reactions of Sugars: Glycosylation and Protection
- The Ruff Degradation and Kiliani-Fischer Synthesis
25 Fun and Miscellaneous
- Organic Chemistry and the New MCAT
- A Gallery of Some Interesting Molecules From Nature
- The Organic Chemistry Behind "The Pill"
- Maybe they should call them, "Formal Wins" ?
- Introduction To Synthesis
- Organic Chemistry Is Shit
- The 8 Types of Arrows In Organic Chemistry, Explained
- The Most Annoying Exceptions in Org 1 (Part 1)
- The Most Annoying Exceptions in Org 1 (Part 2)
- Org 1 Review Quizzes
- Screw Organic Chemistry, I'm Just Going To Write About Cats
- On Cats, Part 1: Conformations and Configurations
- On Cats, Part 2: Cat Line Diagrams
- The Marriage May Be Bad, But the Divorce Still Costs Money
- Why Do Organic Chemists Use Kilocalories?
- What Holds The Nucleus Together?
- 9 Nomenclature Conventions To Know
You can make the use of OsO4 catalytic if you throw in a sacrificial oxidant, N-morpholine oxide (NMO). I’ve had several lab mates use catalytic NMO without incident.
Oh yeah. My point (perhaps not so well made) was that undergraduate teaching laboratories are unlikely places to learn how to use OsO4. But maybe there are places out there who do?
Your point brings up another question – I”m wondering how many instructors include NMO when they teach the dihydroxylation reaction.
I do :)
I’ve worked with students from dozens of schools, and I can’t find another of an example of an instructor who does (although Jim Tour teaches cat. OsO4 and H2O2). You, my good man, are one of the very few! Good on you.
They do where I go to college (Uni. of Minnesota). My prof mentioned using NMO because OsO4 is ridiculously expensive, and NMO turns it into a catalyst so you don’t need as much. She failed to mention the burning out the eyes part, though.
Good to know!
A friend of mine once had to do a reaction with 10 mL of OsO4. Insane.
NMO is in McMurray, 8th Edition (used by 1 of 3 sections at SUNY Geneseo).
Very helpful. Thank you!!
Ohio State Organic chem teaches using it and Miami University of Ohio
example problem from class..
an alkene —–OSO4 (cat.), NMO——> enantiomers
(side note: if possible adding an image attachment option to the comments)
Wow, I had no idea it’d ever been used on that scale in a synthesis! Unfortunately for those guys the Upjohn catalytic procedure wasn’t reported until 20 years later. I seem to remember that Kumamoto’s synthesis of methyl-kinamycin C and Corey’s neotripterifordin also use it stoichiometrically, although not on anywhere near that scale. I once saw the selective dihydroxylation of one bond in a 1,4-cyclohexadiene reported in a very old Tet. Lett. using stoichiometric OsO4. When I tried it with NMO as the terminal oxidant aromatisation was a major problem so I changed my route. I never had the courage to try with the 1.1 equiv. reported so I’ll always wonder if it would have worked. If nothing else, OsO4 is also damned expensive (~300$/g from Aldrich).
At the university where I currently am (I can tell you it’s in the UK, if you couldn’t guess from my spelling) 3rd year undergrads get to do Sharpless AD, although obviously that’s with potassium osmate, which is far less volatile/nasty. Still, they do generate OsO4 during the reaction, and they only have to quench it wrong (which is not impossible) for potentially bad things to happen. I get very nervous when this experiment runs.
Wow! Sharpless AD in 3rd year? That’s fantastic. The AD-mix makes it pretty easy I guess. Kudos to your school. In the “advanced organic chemistry” labs I’ve been in or TA’d, there’s always seemed to be a fine, 30-year or more patina of dust on the procedure we were using. Nothing wrong with that per se, but it didn’t give you the exciting feeling of doing something cutting edge.
What happens when diol reacts with OsO4?
Why isn’t the stereoisomer for the cyclo hexene drawn (side question)? I feel like the answer’s at the tip of my tongue but I can’t quite get it.
What’s the definition of an “enantiomer” ? : – )
I’m still not understanding…
It’s a meso compound. It has a plane of symmetry and is thus an achiral molecule.
Well done with Master Organic Chemistry. It is clean, simple, and useful.
Hi, just wondering in what cases does OsO4 fail? Certain alkenes? What about enones (I’ve seen that it does some enones but wondering if some cases would fail)? And how are the reactivities between OsO4 and K2OsO4 differ, besides the latter having hydrates and not useful for moisture sensitive reactions? Thanks!
What is the effect of H2O2 on the action of OSO4?
When the reaction is done, “H2O2” re-oxidizes the OsO2(OH)2 back to OsO4. It’s a reoxidant, which allows OsO4 to be used catalytically. A more common reagent for this purpose is N-methyl morpholine N- oxide (NMO)
Hey thanks for all your help and dedication to furthering education. Really appreciate your help with making these pages. Between this and the people at Clutchprep I’m acing organic chem and can’t wait for orgo II, bio chem, and pharmacy school next august.
Cheers :)
Hi James,
How exactly does the H2O2 hydrolyze the intermediate 5-member ring? Does it donate a proton onto the Oxygen involved in the C-O bond? If so, why would the oxygen want to form that O-H bond instead of remaining with the rest of the ring?
I do not believe that products in Example 1 are meso compounds that result from the syn addition. They certainly look like the products of anti-addition. Both -OH groups should be either wedged or dashed, if added on the same side. Here they are the same but on different sides. If you rotate, they definitely look like the products from anti-addition (the example on hydroxylation of a linear alkene).
Hi, it doesn’t say that they are meso compounds in this specific example, it says they are a mixture of enantiomers.
However, what about example 2?