Chapter 11


Oxidation in Organic terms
Oxidation
Reduction
Neither
Oxidation of alcohols
Chromic Acid
1° ROH
RCOOH
2° ROH
Ketone
3° ROH
NR
Addition of O, X2; loss of H2
Addition of H2; loss of O or X2
Anytime you oxidize one carbon but
reduce another (ex. Adding H and OH to
adjacent carbons)
KMnO4
RCOOH
Ketone
NR
PCC
RCHO
Ketone
NR
Swern
RCHO
Ketone
NR
Why don’t you oxidize 3° alcohols?
5 bonds to carbon=crazy talk!
[O]

You won’t need to draw the structure of PCC, but you do need to recognize it.
pyridinium chlorochromate (PCC)



You don’t need to know all the reagents of Swern Oxidation for Mr. Baker’s class.
Tollens Test – Not tested in this course.
o Qualitative test for aldehydes
o Aldehyde + AgNO3 → Carboxylic acid + silver metal
o If you see the silver metal coating the tube, then you know you have an
aldehyde.
+
NAD /NADH
o You need to know the structures of both!
o NAD+ is the oxidized form/oxidizing agent
H2
sugar

o NADH is the reduced form/reducing agent
NH2

sugar

Formation of Tosylates
R
tosyl chloride
(a specific sulfonyl chloride)
a sulfonyl chloride
o Addition of tosyl chloride (TsCl) converts the hydroxyl into a good leaving group
(-OTs) with retention of stereochemistry.
 -OTs is a weak base
OTs
OH
TsCl
o Recognize that any sulfo nyl chloride will do this
o You don’t need to draw out the entire structure when you use tosyl chloride to
make a tosylate
 You do need to draw out the entire structure when you use a different
sulfonyl chloride to form a sulfonate.
OH
F3C
O
o The RSO3- is a very weak base, so it’s an excellent leaving group.
CF3

o That’s it! Don’t stress out over this.
Reacting with HX
o The hydroxyl is protonated. Water falls off, leaving a carbocation intermediate

Carbocations rearrange!
o The halide ion attacks the carbocation.


o With 1° alcohols, this reaction occurs through an SN2 mechanism.
“Specialty Reagents”
o PX3, PX5, and SOCl2 all replaced hydroxyl groups with halogens
 Sometimes you’ll just see phosphorus and bromine (or P/I2) here.
 Think flexibly.
 It makes PBr3 (PI3).
 Don’t worry about mechanism or stereochemistry here.
 SOCl2 works better than PCl3 and PCl5.
o That’s it!
Dehydration of alcohols
o Protonate the hydroxyl, water falls off, leaving a carbocation
H2SO4
H3PO4
o Eliminate in both directions
o Look to see if the original carbocation can rearrange
o Again, eliminate in all directions

Formation of symmetrical ethers – industrial dehydration of alcohols
H+
o
o
o

First, the hydroxyl group is protonated, creating a good leaving group.
Then, another alcohol comes along and kicks off the water in an SN2 mechanism.
The reaction is finished off with the deprotonation of the oxygen.
o Favored at reasonably hot temperatures (140° C), because higher temperatures
would favor elimination
o Works best on primary and methyl alcohols.
 It is an SN2 after all!
o If you try to make asymmetrical ethers this way, you will get a mixture of
products.
 Because you get a mixture of products, you can call this a “low-yield”
reaction.
Pinacol Rearrangement – a reaction of vicinal diols
o First, the hydroxyl group is protonated (see a pattern here?)
H+
o Then water falls off.
o A methyl shift happens because the resulting carbocation is resonancestabilized.
The resonanc e form with the positive oxygen is the most stable because of the
octet rule.
o Finish it off by deprotonating the oxygen!
o This reaction occurs with other vicinal diols as well, so don’t expect it to just be
pinacol on the quiz or test.
 Mr. Baker always gives you symmetrical molecules for this reaction, so it
doesn’t matter which hydroxyl you protonate in the first step. If you
were given an asymmetrical molecule then you would get a mixture of
products.
o To get to the product without thinking about the mechanism:
OH
H+
OH


Make one of the –OH’s into a carbonyl.
Put two methyls where they other hydroxyl was.

Periodic Acid Cleavage of Vicinal Diols
o Just cleave the bond between the two carbons and turn the alcohols into
carbonyls.
HIO4

o Do not further oxidize aldehydes to carboxylic acids.
Fischer Esterification
o This is a big one to know!
 ACS, MCAT, DAT, PCAT, OAT, etc. will expect you to know this!
o Overall: Carboxylic acid + alcohol → ester + water
o Step 1: protonation of carbonyl to “activate” it for attack.
H+
o Step 2: Alcohol attacks carbonyl carbon of the acid
o Step 3: Deprotonation of the oxygen from the alcohol
o Step 4: Protonation of one of the oxygens from the acid
H+
o Step 5: Loss of water, forming a resonance-stabilized carbocation
o Step 6: Deprotonation of carbonyl

Esters of inorganic acids
o Just take an acid that isn’t a carboxylic acid (phosphoric, sulfuric, etc) and add an
alcohol to make a different type of ester.
OH
OH
ONO2
HNO3
OH
ONO2
glycerine

ONO2
nitroglycerine
o Know that DNA and RNA are polymers with a phosphate ester in there.
Williamson Ether Synthesis
o Just an SN2 with an alkoxide as the nucleophile.
o Remember that you want the substrate to be either methyl or primary.
 An alkoxide would abstract a proton from a 2° or 3° substrate, in an E2
mechanism
o Ex. How would you synthesize the following ether from two alcohols?
o Answer:
TsCl
Ts
NaH
OTs