Organic Oxidations and Reductions

what is oxidation

increasing oxygen content/decreasing the hydrogen content of a compounds

what is reduction

decreasing the oxygen content/increasing hydrogen content of a compound

If a reaction occurs in which there is a net addition or net elimination of hydrogen and oxygen

the reaction is not oxidation or reduction

What are examples of reactions involving hydrogen and oxygen that are not oxidation/reduction reactions

dehydration of alcohol, hydration of alkene

Converting ethanol to ethanal is

oxidation

Converting ethanal to ethanoic acid is

oxidation

Hydrogenation of a double or triple bond is

reduction

What are the most widely used types of oxidation reagents?

chromium (VI) and manganese (VII)

What are the chromium oxidation reagents

CrO₃, K₂Cr₂O₇, K₂CrO₄

what are the manganese oxidation reagents

KMnO₄

Chromium reagents for oxidation are normally used under BLANK conditions, where all are converted into the active oxidant BLANK

acidic, H₂CrO₄

Manganese oxidation reagents are used under BLANK conditions

basic

What happens when chromic acid or hot basic permanganate are used in an oxidation reaction

they do not stop until all hydrogen atoms attached to the carbon atoms undergoing oxidation have been removed

What type of reagents allows oxidation to stop at the aldehyde stage in the oxidation primary alcohols

anhydrous chromium (IV) reagents

What are the anhydrous chromium reagents

chromium trioxide-pyridine complex (CrO₃-2 pyridine), pyridinium chlorochromate (PCC), and pyridinium dichromate (PDC)

chromium anhydrous reagents are all soluble in

organic solvents

Hot chromic acid and hot basic permanganate react with BLANK to give oxidative cleavage products

alkenes, alkynes, and alkylbenzenes

Oxidation begins on the BLANK atom of alkylbenzenes, only when is has one or more BLANK, to produce benzoic acids

benzylic carbon, benzylic hydrogen atoms

Cleavage of vicinal diols happens via

periodic acid (HIO₄)

Cleavage of alkenes happens via

ozone

Cleavage of methyl ketones happens via

alkaline solutions of halogens (haloform reaction)

What reagents react with alkenes and alkynes to give oxidative addition products

Cold alkaline permanganate, osmium tetroxide, peroxy acids

Reductions of carbonyl compounds are usually performed with

complex metal hydrides

Reductions of alkenes are performed with

catalytic hydrogenation

Reductions of alkynes are performed with either

catalytic hydrogenation or alkali metals in ammonia

Identify the mechanism

Clemmensen Reduction

Identify the mechanism

Wolff-Kishner Reduction

What type of reagent is LiAlH₄

reducing agent

alkaline oxidizing agents react with secondary alcohols to produce BLANK but also react rapidly with BLANK

ketones, double bonds

when will HIO₄ react with an alcohol to perform oxidative cleavage of a C-C bond

when they are 1,2 diols or alpha to a carbonyl group

What is the structure of PCC?

What does PCC do to primary alcohols?

convert to aldehyde

What does PCC do to secondary alcohols?

convert to ketone

What is not affected by PCC?

C-C double or triple bonds

NaBH₄ is what kind of reagent?

reducing agent

What does K₂Cr₂O₇ and H₂SO₄ do to primary alcohols

convert to carboxylic acid

What does hot KMnO₄ do to primary alcohols

converts to carboxylic acid (via aldehyde intermediate)

Chromic acid does not oxidize BLANK, but can oxidize C-C bonds

ketones

basic KMnO₄ reacts rapidly with C-C double bonds to give what product

vicinal diols or oxidative cleavage products

What type of reaction is polyphosphoric acid (P₂O₅/H₃PO₄) used in?

dehydration

What type of reaction converts methyl ketones to carboxylic acids?

haloform (treated with alkaline I₂, Br₂, or bleach/NaOCl, followed by neutralization)

Identify the mechanism

oxidative cleavage of alkenes with KMnO₄

Identify the mechanism

Syn dihydroxylation of alkenes with cold KMnO₄

Terminal alkenes when oxidized by KMnO₄

=CH₂ group is oxidized to CO₂

Monosubstituted carbon atoms (=CHR) when oxidized by KMnO₄ produce what

carboxylic acid

Disubstituted carbon atoms (=CRR’) produce what when oxidized by KMnO₄?

ketones

If the alkene being oxidized by KMnO₄ is a part of a chain

two separate molecules form

If the alkene being oxidized by KMnO₄ is a part of a ring

the ring is broken

A vinyl carbon atom containing a hydrogen atom will convert to what after oxidation via KMnO₄

carboxylic acid

A vinyl carbon with a methyl group will convert to what when oxidized via KMnO₄

ketone

All C-H bonds are converted into what during alkene oxidative cleavage

carboxylic acid

methyl groups attached to an alkene during oxidative cleavage produce what

ketones

C=C is oxidatively cleaved to what

C=O O=C

What is the best stereochemical arrangement of hydroxyl groups in order for periodic acid to cleave it

cis

What reagent will convert an alkene into a cis 1,2-diol

OsO₄ (and a hydrolyzing agent)

What reagent will convert an alkene into a trans 1,2-diol

Peracid (HCO₃H in acidic conditions)

What reagent can produce a cis 1,2-diol from an alkene but in low yield due to its oxidative cleavage abilities?

cold alkaline KMnO₄

What reagent can be used to reduce an alkyne to a Z-alkene

H₂ and a Lindlar catalyst

What is a Lindar catalyst

Pd and a deactivating agent (BaSO₄, BaCO₃/quinoline)

What reagent can be used to reduce an alkyne to an E-alkene

Na (or Li), NH₃

Hydrogenation of an alkene always happens via

syn addition

What do the reagents H₂, Pd/C do

hydrogenation of an alkene

what reagent can reduce a ketone, but will leave alkenes unaffected

NaBH₄ or LiAlH₄

What reagent can reduce carboxylic acids and ketones?

LiAlH₄

What reagent cannot reduce carboxylic acids but can reduce ketones?

NaBH₄

What does LiAlH₄ reduce carboxylic acids to?

primary alcohols

What reagent reduces ketones to a secondary alcohol?

H₂, Pd

Identify the mechanism

ozonolysis

How do alkylbenzenes (aromatic alkanes) react with KMnO₄

oxidizes benzylic carbon to make benzoic acid

what molecules does K₂Cr₂O₇ oxidize best?

aldehydes and alcohols

what reagent cannot oxidize carboxylic acids

K₂Cr₂O₇

What is the product of the oxidation of primary alcohols with K₂Cr₂O₇

aldehydes => carboxylic acids

what is the product of the oxidations of secondary alcohols with K₂Cr₂O₇

ketones

what is the product of a reduction of a ketone, and the product of reduction of an aldehyde, via NaBH₄

secondary alcohol, primary alcohol

what are the reagents of a clemmenson reduction

Zn(Hg), acidic workup