1. Chapter 11 Alcohols and phenols

2. IUPAC Substitutive Nomenclature
An IUPAC name may have up to 4 features: locants, prefixes, parent compound and suffixes
Numbering generally starts from the end of the chain which is closest to the group named in the suffix
IUPAC Nomenclature of Alcohols
Select the longest chain containing the hydroxyl and change the suffix name of the corresponding parent alkane from -ane to -ol
Number the parent to give the hydroxyl the lowest possible number
The other substituents take their locations accordingly
Chapter 4

3. Examples
Common Names of simple alcohols are still often used and are approved by IUPAC
Chapter 4

4. Alcohols with two hydroxyls are called diols in IUPAC nomenclature and glycols in common nomenclature
Chapter 4

5. Physical Properties of Alcohols.
Alcohols have considerably higher boiling points
Molecules of alcohols hydrogen bond to each other
alcohols can hydrogen bond to water and have similar solubilities in water
1-butanol have solubilites of about 8 g per 100 mL in water
Chapter 11

6. Synthesis of Alcohols from Alkenes
Acid-Catalyzed Hydration of Alkenes
This is a reversible reaction with Markovnikov regioselectivity
Oxymercuration-demercuration
This is a Markovnikov addition which occurs without rearrangement
Chapter 11

7. Hydroboration-Oxidation
This addition reaction occurs with anti-Markovnikov regiochemistry and syn stereochemistry
Chapter 11

8. Alcohols by Reduction of Carbonyl Compounds
A variety of carbonyl compounds can be reduced to alcohols
Carboxylic acids can be reduced to primary alcohols
These are difficult reductions and require the use of powerful reducing agents such as lithium aluminum hydride (LiAlH4 also abbreviated LAH)
Chapter 12

9. Esters are also reduced to primary alcohols
LAH or high pressure hydrogenation can accomplish this transformation
Aldehydes and ketones are reduced to 1o and 2o alcohols respectively
Aldehydes and ketones are reduced relatively easily; the mild reducing agent sodium borohydride (NaBH4) is typically used
LAH and hydrogenation with a metal catalyst can also be used
Chapter 12

10. The key step in the reduction is reaction of hydride with the carbonyl carbon
Carboxylic acids and esters are considerably less reactive to reduction than aldehydes and ketones and require the use of LAH
Lithium aluminium hydride is very reactive with water and must be used in an anhydrous solvent such as ether
Sodium borohydride is considerably less reactive and can be used in solvents such as water or an alcohol
Chapter 12

11. Reaction of Grignard Reagents with Carbonyl Compounds
Nucleophilic attack of Grignard reagents at carbonyl carbons is the most important reaction of Grignard reagents
Reaction of Grignard reagents with aldehydes and ketones yields a new carbon-carbon bond and an alcohol
Chapter 12

12. Alcohols from Grignard Reagents
Aldehydes and ketones react with Grignard reagents to yield different classes of alcohols depending on the starting carbonyl compound
Chapter 12

13. Esters react with two molar equivalents of a Grignard reagent to yield a tertiary alcohol
A ketone is formed by the first molar equivalent of Grignard reagent and this immediately reacts with a second equivalent to produce the alcohol
The final product contains two identical groups at the alcohol carbon that are both derived from the Grignard reagent
Chapter 12

14. Chapter 12

15. Alcohols as Acids Alcohols have acidities similar to water
Sterically hindered alcohols such as tert-butyl alcohol are less acidic (have higher pKa values)
Why?: The conjugate base is not well solvated and so is not as stable
Alcohols are stronger acids than terminal alkynes and primary or secondary amines
An alkoxide can be prepared by the reaction of an alcohol with sodium or potassium metal
Chapter 11

16. Conversion of Alcohols into Alkyl Halides
Hydroxyl groups are poor leaving groups, and as such, are often converted to alkyl halides when a good leaving group is needed
Three general methods exist for conversion of alcohols to alkyl halides, depending on the classification of the alcohol and the halogen desired
Reaction can occur with phosphorus tribromide, thionyl chloride or hydrogen halides
Chapter 11

17. Alkyl Halides from the Reaction of Alcohols with Hydrogen Halides
The order of reactivity is as follows
Hydrogen halide HI > HBr > HCl > HF
Type of alcohol 3o > 2o > 1o < methyl
Mechanism of the Reaction of Alcohols with HX
SN1 mechanism for 3o, 2o, allylic and benzylic alcohols
These reactions are prone to carbocation rearrangements
In step 1 the hydroxyl is converted to a good leaving group
In step 2 the leaving group departs as a water molecule, leaving behind a carbocation
Chapter 11

18. Primary and methyl alcohols undergo substitution by an SN2 mechanism
In step 3 the halide, a good nucleophile, reacts with the carbocation
Primary and methyl alcohols undergo substitution by an SN2 mechanism
Primary and secondary chlorides can only be made with the assistance of a Lewis acid such as zinc chloride
Chapter 11

19. Alkyl Halides from the Reaction of Alcohols with PBr3 and SOCl2
These reagents only react with 1o and 2o alcohols in SN2 reactions
In each case the reagent converts the hydroxyl to an excellent leaving group
No rearrangements are seen
Reaction of phosphorous tribromide to give alkyl bromides
Chapter 11

20. Oxidation of Alcohols Oxidation of Primary Alcohols to Aldehydes
A primary alcohol can be oxidized to an aldehyde or a carboxylic acid
The oxidation is difficult to stop at the aldehyde stage and usually proceeds to the carboxylic acid
A reagent which stops the oxidation at the aldehyde stage is pyridinium chlorochromate (PCC)
PCC is made from chromium trioxide under acidic conditions
It is used in organic solvents such as methylene chloride (CH2Cl2)
Chapter 12

21. Oxidation of Primary Alcohols to Carboxylic Acids
Potassium permanganate (KMnO4) is a typical reagent used for oxidation of a primary alcohol to a carboxylic acid
The reaction is generally carried out in aqueous solution; a brown precipitate of MnO2 indicates that oxidation has taken place
Oxidation of Secondary Alcohols to Ketones
Oxidation of a secondary alcohol stops at the ketone
Many oxidizing agents can be used, including chromic acid (H2CrO4) and Jones reagent (CrO3 in acetone)
Chapter 12

22. Structure and Nomenclature of Phenols
Phenols have hydroxyl groups bonded directly to a benzene ring
Naphthols and phenanthrols have a hydroxyl group bonded to a polycyclic benzenoid ring
Chapter 21

23. Nomenclature of Phenols
Phenol is the parent name for the family of hydroxybenzenes
Methylphenols are called cresols
Chapter 21

24. Synthesis of Phenols Laboratory Synthesis
Phenols can be made by hydrolysis of arenediazonium salts
Chapter 21

25. Industrial Syntheses 1. Hydrolysis of Chlorobenzene (Dow Process)
Chlorobenzene is heated with sodium hydroxide under high pressure
The reaction probably proceeds through a benzyne intermediate (Section 21.11B)
2. Alkali Fusion of Sodium Benzenesulfonate
Sodium benzenesulfonate is melted with sodium hydroxide
Chapter 21

26. Reactions of Phenols as Acids
Strength of Phenols as Acids
Phenols are much stronger acids than alcohols
Chapter 21

27. Phenol is much more acidic than cyclohexanol
Experimental results show that the oxygen of a phenol is more positive and this makes the attached hydrogen more acidic
The oxygen of phenol is more positive because it is attached to an electronegative sp2 carbon of the benzene ring
Resonance contributors to the phenol molecule also make the oxygen more positive
Chapter 21

28. Distinguishing and Separating Phenols from Alcohols and Carboxylic Acids
Phenols are soluble in aqueous sodium hydroxide because of their relatively high acidity
Most alcohols are not soluble in aqueous sodium hydroxide
A water-insoluble alcohol can be separated from a phenol by extracting the phenol into aqueous sodium hydroxide
Phenols are not acidic enough to be soluble in aqueous sodium bicarbonate (NaHCO3)
Carboxylic acids are soluble in aqueous sodium bicarbonate
Carboxylic acids can be separated from phenols by extracting the carboxylic acid into aqueous sodium bicarbonate
Chapter 21

29. Other Reactions of the O-H Group of Phenols
Phenols can be acylated with acid chlorides and anhydrides
Chapter 21

30. Phenols in the Williamson Ether Synthesis
Phenoxides (phenol anions) react with primary alkyl halides to form ethers by an SN2 mechanism
Chapter 21

31. Cleavage of Alkyl Aryl Ethers
Reaction of alkyl aryl ethers with HI or HBr leads to an alkyl halide and a phenol
Recall that when a dialkyl ether is reacted, two alkyl halides are produced
Chapter 21

32. Reaction of the Benzene Ring of Phenols
Bromination
The hydroxyl group is a powerful ortho, meta director and usually the tribromide is obtained
Monobromination can be achieved in the presence of carbon disulfide at low temperature
Nitration
Nitration produces o- and p-nitrophenol
Low yields occur because of competing oxidation of the ring
Chapter 21

33. Sulfonation
Sulfonation gives mainly the the ortho (kinetic) product at low temperature and the para (thermodynamic) product at high temperature
Chapter 21

34. The Kolbe Reaction
Carbon dioxide is the electrophile for an electrophilic aromatic substitution with phenoxide anion
The phenoxide anion reacts as an enolate
The initial keto intermediate undergoes tautomerization to the phenol product
Kolbe reaction of sodium phenoxide results in salicyclic acid, a synthetic precursor to acetylsalicylic acid (aspirin)
Chapter 21