Slide 11

Phenols

• Reactions of Phenols (Due to aryl Nucleus)
• Electrophilic substitution reactions

Slide 12

Electrophilic substitution reactions:

• Reactions with halogens
• Reactions with nitric acid
• Reactions with sulfuric acid
• Reactions with concentrated nitric acid and sulfuric acid mixture

Slide 13

Examples of electrophilic substitution reactions:

• Bromination of phenol
  • Equation: C6H5OH + Br2 -> C6H5Br + HBr
  • Explanation: Phenol reacts with bromine to form bromophenol and hydrogen bromide gas.

Slide 14

Examples of electrophilic substitution reactions (cont.):

• Nitration of phenol
  • Equation: C6H5OH + HNO3 -> C6H4(NO2)OH + H2O
  • Explanation: Phenol reacts with nitric acid to form nitrophenol and water.

Slide 15

Examples of electrophilic substitution reactions (cont.):

• Sulfonation of phenol
  • Equation: C6H5OH + SO3 -> C6H4(SO3H)OH
  • Explanation: Phenol reacts with sulfur trioxide to form sulfonated phenol.

Slide 16

Examples of electrophilic substitution reactions (cont.):

• Formation of a picric acid
  • Equation: C6H5OH + HNO3 -> C6H2(NO2)3OH + H2O
  • Explanation: Phenol reacts with nitric acid to form picric acid and water.

Slide 17

Mechanism of electrophilic substitution reactions:

• Introduction to the mechanism
• Step-by-step explanation
• Role of the aryl group in the mechanism

Slide 18

Effect of substituents on the reactivity of phenols:

• Explanation of the effect
• Electron-donating groups
• Electron-withdrawing groups
• Ortho-para directing and meta directing groups

Slide 19

Evidence for the mechanism:

• Experimental observations
• Spectroscopic evidence
• Confirmation of the mechanism through isotopic labeling experiments

Slide 20

Comparison with benzene:

• Differences between the reactivity of phenols and benzene
• Unique properties of phenols

Slide 21

Evidence for the mechanism (cont.):

• Experimental observations
  • Formation of colored products
  • Formation of by-products
• Spectroscopic evidence
  • IR spectroscopy
  • NMR spectroscopy
  • UV-Vis spectroscopy
• Confirmation of the mechanism through isotopic labeling experiments
  • Incorporation of labeled atoms into the product
  • Analysis of isotopic distribution in the product

Slide 22

Comparison with benzene (cont.):

• Differences between the reactivity of phenols and benzene
  • Phenol is more reactive than benzene due to the presence of the hydroxyl group
  • Electrophilic substitution reactions in phenols occur at the ortho and para positions
  • Benzene undergoes electrophilic substitution reactions predominantly at the meta position
• Unique properties of phenols
  • Phenols have higher boiling points compared to hydrocarbons of similar molecular weight
  • Phenols are acidic in nature due to the presence of the hydroxyl group
  • Phenols can form hydrogen bonds with other molecules, leading to higher intermolecular forces

Slide 23

Industrial applications of phenols:

• Use of phenols in the production of plastics and resins
  • Phenol-formaldehyde resin (Bakelite) - used in electrical insulators and molding compounds
  • Phenol-acrylic resin (Coating resin) - used as a protective coating for metal surfaces
• Use of phenols in the synthesis of pharmaceuticals
  • Phenol derivatives are used as intermediates in the synthesis of various drugs
  • Salicylic acid, derived from phenol, is the precursor for aspirin

Slide 24

Summary and conclusion:

• Recap of key points discussed
  • Phenols are compounds with a hydroxyl group attached to an aromatic ring
  • Phenols undergo electrophilic substitution reactions due to the aryl nucleus
  • The reactivity of phenols can be influenced by substituents and their positions
  • Evidence such as experimental observations and spectroscopic analysis support the proposed mechanism
  • Phenols have unique properties and find applications in various industries
• Importance of understanding the reactions of phenols
  • Phenols play a significant role in organic synthesis and have important applications in diverse fields

Slide 25

References:

1. Morrison, R. T., & Boyd, R. N. (1999). Organic Chemistry. Prentice Hall.

2. Carey, F. A., & Atkins, R. C. (2012). Organic Chemistry. McGraw-Hill.

3. March, J. (2001). Advanced Organic Chemistry, Reactions, Mechanisms, and Structure. Wiley.

4. Vollhardt, K. P. C., & Schore, N. E. (2014). Organic Chemistry: Structure and Function. W.H. Freeman and Company.