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CH10136 > Carbonyl chemistry- oxidation > Flashcards

Carbonyl chemistry- oxidation Flashcards

1
Q

How many oxidation levels are there in the carbonyls

A
  1. 5- number of hetero atoms around carbon
  2. Alkane- 1
  3. Alcohol- 2nd oxidation level
  4. Aldehyde/ketone- 3rd level
  5. Carboxylic acid- 4th level
  6. CO2- 5th level
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2
Q

What is a hetero atom

A
  1. Not carbon or hydrogen
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3
Q

What is a FGI for carbonyls

A
  1. Carbonyl derivatives can be accessed via oxidative or reductive processes
  2. E.g. alcohol->ketone->carboxylic acid
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4
Q

What are the two classic methods of converting a primary alcohol to a carboxylic acid

A
  1. Jones oxidation- CrO3, H2SO4, H2O

2. Potassium permanganate- H+ or OH-

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5
Q

What are the oxidants like for Jones and potassium permanganate oxidation

A
  1. Strong oxidants

2. Don’t stop at aldehyde, they continue to oxidise further to carboxylic acid

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6
Q

What is a problem with Jones oxidation

A
  1. Creates a lot of chromium waste- not green

2. Not chemoselective

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7
Q

What is the structure of CrO3

A
  1. Cr in centre with 3 Cr=O bonds
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8
Q

Describe the steps in a jones oxidation

A
  1. Lone pair on OH group attack Cr forming a bond (positive charge on O) and Cr=O bond breaks forming a Cr-O -
  2. Proton transfer forming Cr-OH
  3. Chromium Cr=O bond attacks C-H and series of arrows results in Aldehyde is formation and chromium waste
  4. Reversible reaction with H2O produces a diol
  5. Diol attacks new CrO3 and process repeats
  6. Forms a carboxylic acid
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9
Q

What is the structure of permanganate ion

A
  1. Mn in centre with 3 Mn=O bonds and one Mn-O- bond
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10
Q

What are the 3 main types of selectivity

A
  1. Chemoselectivity- which functional group will react
  2. Regioselectivity- where it will react
  3. Stereoselectivity- how it will react
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11
Q

How can a primary alcohol be oxidised to a aldehyde

A
  1. E.J. Corey developed an alternative to Jones
  2. Pyridinium chlorochromate (PCC)
  3. It is much easier to handle and much less reactive- only oxidises primary alcohols to aldehyde (and secondary to ketone
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12
Q

What is a problem with E.J Coreys method to produce an aldehyde from primary alcohol

A
  1. Not green

2. Bi-product is chromium waste- toxic

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13
Q

Name 3 methods of converting a primary alcohol to an aldehyde

A
  1. Ley oxidation
  2. Dess Martin oxidation
  3. Swern oxidation
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14
Q

Describe conditions needed for Ley oxidation

A
  1. Tetrapropylammonium perruthenate (TPAP) is used as a mild oxidant
  2. Utilises ruthenium in its +7 oxidation state
  3. Catalytic via use of co-oxidant N-methylmorpholine (NMO)
  4. Replaces Cr or Mn with Ru which is greener
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15
Q

Describe Ruthenium in its +7 oxidation state

A
  1. 4 Ru=O bonds

2. Negative charge

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16
Q

Describe Dess Martin oxidation

A
  1. Developed a hypervalent iodine species- Dess-Martin periodinane (DMP)
  2. Utilises iodine in +5 oxidation state
  3. Very mild stoichiometric oxidant
17
Q

What is a downside to Dess Martin oxidation

A
  1. A lot of stoichiometric waste
18
Q

Describe a Swern oxidation

A
  1. Sulfur based oxidation
  2. Utilises sulfur in +4 oxidation state
  3. Don’t need to know mechanism
  4. Uses oxalyl chloride
  5. -78 degrees
  6. Easy to dispose of waste
19
Q

What are the products of Swern oxidation and how to get rid of them

A
  1. Aldehyde/ketone
  2. Me2S- easy to get rid of
  3. CO + CO2- leaves as gas
  4. HCl - washed away with water
20
Q

What does the sulfur in its +4 oxidation state look like

A
  1. S+ to two carbons and negative O

2. DMSO

21
Q

Write equation to show swern oxidation of primary/secondary alcohol

A
  1. Primary/secondary alcohol + DMSO + Oxalyl chloride –> aldehyde/ketone + Me2S + CO +CO2 + 2HCl
22
Q

How can you get from an aldehyde to a carboxylic acid

A
  1. Pinnick oxidation
  2. Sodium chloride (NaClO2) is the oxidant
  3. 2-methyl-2-butene is utilised as a radical scavenger
  4. pH- around 3.5 less acidic than Jones
  5. Bi product is easy to remove
23
Q

Write equation to show oxidation of aldehyde to carboxylic acid in pinnick oxidation

A
  1. Aldehyde + NaClO2 + 2-methyl-2-butene –> carboxylic acid + CH3COH(CH3)CH2(CH3)Cl
24
Q

State a downside to Jones

A
  1. Uses a strong acid
25
Q

State a downside to Dess Martin

A
  1. A lot of powder handling

CH10136 (30 decks)

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