e-content of oxidation for M.pharm students.

1. OXIDATION
Presenting by:
Mr. Purushotham KN
Assistant Professor
Department Of Pharmaceutical Chemistry
Sri Adichunchanagiri College Of Pharmacy,
B G Nagar
2022-2023
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2. • Oxidation is loss of electrons
• Reduction is gain of electrons
–Oxidation is always accompanied by reduction
• The total number of electrons is kept constant
• Oxidizing agents oxidize and are themselves reduced
• Reducing agents reduce and are themselves oxidized
• Oxidation constitutes one of the most powerful tools used in the synthesis of chemical
compounds. The oxidation processes are many and varied.
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3. Oxidizing Agents:
• Permanganates
• Dichromates
• Hypochlorous Acid and Salts
• Sodium Chlorite and Chlorine Dioxide
• Chlorates (HCI03)
• Peroxides
• Nitrogen Tetroxide
• Copper Salts
• Alkali Fusion
• Fuming Sulfuric Acid (Oleum)
• Ozone
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4. Permanganates
• Solid salts of permanganic acid are powerful oxidizing agents.
–Calcium permanganate induces rapid oxidation of ethanol that may result acetic acid.
• Aqueous solutions of the permanganates also possess powerful oxidizing properties.
• These are common and most useful agents employed to oxidize a wide range of organic
molecules.
• It functions as an oxidizing agent of different strengths in alkaline, neutral, and acid
solutions.
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5. • KMnO₄, is probably the most common, and also the most applicable.
• KMnO₄ can be utilized to oxidize a wide range of organic molecules.
• The products that are obtained can vary depending on the conditions, but because KMnO₄ is
such a strong oxidizing agent, the final products are often carboxylic acids.
• KMnO₄ is able to oxidize carbon atoms if they contain sufficiently weak bonds, including:
1. Carbon atoms with π-bonds, as in alkenes and alkynes
2. Carbon atoms with weak C-H bonds, such as
–C-H bonds in the alpha-positions of substituted aromatic rings
–C-H bonds in carbon atoms containing C-O bonds, including alcohols and aldehydes
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6. 3. Carbons with exceptionally weak C-C bonds such as
–C-C bonds in a glycol
–C-C bonds next to an aromatic ring and an oxygen.
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7. Fuming Sulfuric Acid (Oleum):
• Fuming sulfuric acid, H₂SO₄ + SO₂, in the Presence of mercury salts is a powerful
oxidizing agent.
• It was formerly used extensively in the oxidation of
–naphthalene to phthalic anhydride
–piperidine(tetrahydropyridine) may be oxidized to pyridine.
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8. Sodium Chlorite and Chlorine Dioxide
• When reacted with chlorine, sodium chlorite (NaClO3)releases Chlorine dioxide (ClO2),
is a powerful oxidizing and bleaching agent; but because of its instability, it cannot be
produced and stored.
• Chlorine dioxide has also been found to have utility in bleaching and maturing flour,
treating water, checking blue mold in fruits, and bleaching textiles.
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9. Chlorates:
• Chloric acid, HCIO3, is a powerful oxidizing agent. Oxidation of
–ethanol / ethyl ether to acetic acid,
–ethylene to glycol,
–allyl alcohol to glycerine,
–fumaric acid to racemic acid effected with Chloric acid
• However, since its aqueous solutions must be obtained by double decomposition from its
salts, its industrial usefulness is very limited, and it is more often used in the form of the
soluble salts.
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10. Ozone (O3):
• Ozone is being promoted for use in the conversion of
–Tertiary amines to amine oxides
–α-pinene to pinonic and pinic acids.
• The powerful oxidizing potential of ozone has been made use
–in textile bleaching
–paper bleaching
–in limited ways for water purification.
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11. Liquid-phase Oxidation with Oxidizing Compounds
• Oxidation in the gas/liquid phase often occurs in the production of basic and fine
chemicals.
• Very often, molecular oxygen is used here in the form of process air.
• The oxidation of aniline furnishes an example for comparison of a number of oxidizing
agents.
• Results obtained under conditions best suited for the particular agent are shown below:
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12. The action of oxidizing agents on organic compounds depends not only upon the nature of
the agent or the compound but also upon such factors:
–Concentration of the reactants
–Temperature
–Hydrogen-ion concentration and
–Method of mixing
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14. Aniline to Quinone
• Sodium or potassium dichromate may be used to oxidize aniline to quinone, but a low
temperature and slow addition of the oxidizing agent must be employed in order to
restrict the action.
• Although the high stability of the quinone structure toward further oxidation makes
possible the use of so powerful an oxidizing agent as sodium dichromate in acid solution,
care must still be exercised in order to prevent destructive reaction.
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15. Oxidation of Toluene:
• The use of manganese dioxide for the oxidation of toluene to benzaldehyde and
benzoic acid was formerly extensive.
• With manganese dioxide, the principal product is benzaldehyde; for high yields of
benzoic acid, a stronger oxidizing agent such as chromic acid is required.
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16. Liquid-phase Oxidation with Oxygen:
•The oxygen of the air is the cheapest available oxidizing agent but, at the same time it is
most difficult to control.
•Although atmospheric oxygen is constantly reacted with organic substances at ordinary
temperature, the rates of the reactions are too slow, generally, to be of any significance
(usefulness in chemical synthesis).
•To induce molecular oxygen to react at commercially useful rates, it is necessary to
provide a catalyst, to elevate the temperature, or to use a catalyst in conjunction with
elevated temperatures.
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17. • In liquid-phase processes, catalysts may be either dissolved or suspended in finely
divided form to ensure contact with bubbles of gas containing oxygen which may be
caused to pass through the liquid undergoing oxidation.
• To speed up production, means must be provided for initially raising the temperature
and for later removing reaction heat.
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18. Acetaldehyde to Acetic Acid
• The formation of acetic acid furnishes an excellent example of liquid-phase oxidation with
molecular oxygen.
• Acetic acid may be obtained by the direct oxidation of ethanol,
• but the concentrated acid is generally obtained by oxidation methods from acetaldehyde
that may have been formed by the hydration of acetylene or the oxidation of ethanol.
• The oxidation usually occurs in acetic acid solution in the presence of a catalyst and at
atmospheric or elevated pressures.
• Temperatures may range up to 100°C, depending upon conditions, but are usually lower.
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19. • Ozonolysis has been used frequently in major drug synthesis such as indolizine 251F
and D,L-camptothecin, as well as in fine chemical synthesis such as L-
isoxazolylalanine and prostaglandin endoperoxides.
• Hydrogen peroxide in the presence of catalysts of the oxides of Cr or Mo also
oxidizes organic unsaturated compounds to glycols.
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20. • Isoborneol to camphor: Nitric acid has been widely used in production of
synthetic camphor from turpentine. the commonly accepted general practice for
this manufacture involves the following steps:
• 1) Distillation of turpentine to obtain pinene,
• 2)Saturation with HCl gas to obtain bornyl chloride,
• 3) Hydrolyzing this to obtain camphene
• 4)Esterifying camphene to isobornyl acetate
• 5) Saponification to isoborneol
• 6)Oxidation to camphor.
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21. Oxidizing agents Products
• Sodium chlorate in neutral solution with V₂O catalyst.........fumaric acid.
• Sodium chlorate in dilute acid with OsO₄ catalyst ……… mesotartaric acid.
• Caro’s acid, HO.O.SO₃H, a strong oxidizing agent………….succinic acid.
• Hydrogen peroxide in presence of ferrous salts………….hydroxy furfural.
• Bromine water at (100°C)………………………………….Mucobromic acid.
• Potassium permanganate(diluted solution)……………….Pyromucic acid.
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22. THANKYOU
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