Oxidation Flashcards
What does a secondary alcohol oxidise to?
Ketone
What is the colour change when a secondary alcohol is oxidised?
Orange to green
What oxidising agent is used for alcohols?
a chromium (6+ ) reagent Na2Cr2O7
Why is the oxidation of secondary alcohols a bad process?
Lots of Cr waste is generated
What alternative name does the oxidation of a secondary alcohol have?
Jones oxidation
How many chromate molecules are used in the Cr(VI) oxidation ?
2
What is the order of the oxidation states for the Cr(VI) oxidation mechanism?
Cr (VI)
Cr (IV)
Cr (III)
In the mechanism for the Cr (VI) oxidation, what is the key oxidising agent?
CrO3
What does a primary alcohol oxidise to initially?
Aldehyde
How does a primary alcohol oxidise to a carboxylic acid (final oxidation state)?
First it is oxidised to an aldehyde, then a water molecule is added which forms a hydrate (two OH), then the hydrate is oxidised to form the carboxylic acid
What is a jones reagent?
Reagent involved in the oxidation of primary and secondary alcohols
What type of reagent oxidises hydrates?
Jones reagents
Alcohols can be oxidised to aldehydes under basic conditions, what reagent would be used in this instance?
Pyridinium chlorochromate
PCC
Apart from basic, what other conditions would you need to use when using PCC?
Anhydrous
How are alkenes oxidised?
Through epoxidation
uses peracid RCO3H
C-O bonds form through syn addition
What type of reaction is synaddition, what does this mean?
Sn2
there will be an inversion of stereochemistry
What are the issues with using Osmium Tetroxide?
Rare
Expensive
Sublimes straight to gas
What are the issues with using Osmium Tetroxide for oxidation of alkene?
Rare
Expensive
Sublimes straight to gas
What happens when osmium tetroxide is used for oxidation of alkene?
C-O bonds are formed in syn addition
Forms cyclic osmate ester through hydrolysis of the ester
What is the product when you use osmium tetroxide to oxidise an alkene?
syn-1,2-diol
What issues can Os (VI) cause?
Reduced to a metal so it forms a metal sheen across the eyeball if it comes close
What type of osmium is needed for the catalytic version of oxidation of the alkene?
Only catalytic OsO4 is needed
In the catalytic version using osmium tetroxide, what is the oxidising agent?
NMO
In the catalytic version, what oxidation happens inside of the reaction?
Oxidation of Os (VI) back to Os (VIII)
When using ozone to oxidise alkenes, what do you need to avoid using?
Oxidising agent as O3 is susceptible to oxidation
When ozone is used to oxidise alkenes, which bond is formed?
C=O formed from C=C
When ozone is used to oxidise alkenes, which bonds of the alkene are cleaved?
Pi and sigma bonds
When ozone is used to oxidise alkenes, what reducing agent is used?
Dimelthylsulfide
What is the product of oxidisation with ozone?
Aldehydes
When ozone reacts with the alkene, what type of reaction is it?
concerted
as pi bond broken at the same time as its added
When ozone reacts with the alkene, what type of addition is it?
Syn
What cyclic product can be formed from ozone reacting with the alkene?
Ozonide
What is formed when Me2S reacts with the cyclic ozonide?
It generates Me2SO and also 2 aldehydes
Because Me2S is a mild reducing agent, what does it prevent?
Prevent the reduction of RCHO to alcohol and prevents the oxidation of RCHO to acid
When oxidising alkenes with ozone, how do you make an alcohol your product instead of an aldehyde?
Use a stronger reducing agent
NaBH4
When oxidising alkenes with ozone, how do you make an acid your product instead of an aldehyde?
Use an oxidising agent
H2O2
