Chemistry Exam 2

Lindlar’s catalyst does not work when you start with an alkene

determining whether syn or anti dihydroxylation

Syn products (cis-diols) are formed with OsO₄ or KMnO₄ , while anti products (trans-diols) arise from peroxyacids (RCO₃H) followed by acid hydrolysis (H₃O+)

O-O oxidizing agents go…

Anti (add the OHs on opposite sides)

Metal-O oxidizing agents (KMnO₄ and OsO₄) for dihydroxylations go…

syn (add the OHs on the same side)

Examples of O-O oxidizing agents

O₂, O₃, H₂O₂, peroxyacids such as m-CPBA

Examples of Metal-O oxidizing agents

NaCr₂O₇, CrO₃, PCC, KMnO₄, OsO₄, Ag₂O

In dihydroxylation, KMnO₄ and OsO₄ will go…

syn

In dihydroxylation, peroxyacids (RCO₃H) will go

anti

KMnO₄ in NaOH/H₂O with heat is great for synthesizing…

ketones, acids, and CO₂

this is called oxidative cleavage of alkenes

any singular hydrogen will be turned into an alcohol

if one side of the alkene has two hydrogens on it, it results in CO₂

KMnO₄ in NaOH/H₂O (has water) when the reaction is cold will get you…

Syn dihydroxylation (just like OsO₄)

remember plus enantiomer

A STRONG oxidizing agent in water (both have to be in the same step for the reagents) will lead to oxidative cleavage. you also need heat.

strong oxidizing agents include…

OsO₄, KMnO₄, Ag₂O

Cleaving alkynes always yields…

carboxylic acids and CO₂ EVEN when you use O₃

A terminal alkyne is what would make CO₂

Oxidations of alcohols can only go…

on primary or secondary alcohols (because tertiary has no H to remove)

primary alcohols will yield a carboxylic acid

secondary alcohols will yield a ketone

The reagents you need to oxidize an alcohol are…

NaCr₂O₇ or CrO₃ with aq H₂SO₄

it will yield ketones and acids

if you want an aldehyde instead of an acid when oxidizing a primary alcohol, go with milder conditions such as…

PCC in CH₂Cl₂

Tollen’s reagent (Ag₂O / NH₄OH) can only oxidize…

pi bonds… not alcohols. So NR in terms of oxidation of an alcohol

Swern Oxidation is just like…

PCC, it is mild and can yield aldehydes

when you have a strong oxidizer then acid on an aromatic compound, you will always make…

benzoic acid with the side chain NO MATTER what the side chain is (it gets cleaved down to benzoic acid)

A good Nu will attack a neutral C=O, but a poor Nu can’t so you must…

protonate the O

(because of resonance, the positive charge can be on the carbon. all of this is in terms of the Nu wanting to attack a positive (or partially positive) carbon because that means it is a good electrophile)

Reduction of aldehydes and ketones requires…

a strong reducing agent (H:) which comes from NaBH₄ or LAH