This document summarizes key information about alcohols and phenols. It discusses their structures, properties, synthesis methods, and reactions. Alcohols contain an OH group bonded to a saturated carbon. They are important solvents and intermediates. Phenol has diverse uses and gives its name to phenolic compounds. The document describes methods for synthesizing alcohols from alkenes, carbonyls, carboxylic acids, and Grignard reagents. It also outlines reactions of alcohols including dehydration, oxidation, conversion to halides, and incorporation into esters. Phenol is produced industrially from benzene sulfonic acid or chlorobenzene. Its hydroxyl group

1. Alcohols and Phenols
Pradeep Kumar L.B
Lecturer in Chemistry
S.C.I.M Govt College

2. • Alcohols contain an OH group connected to a
saturated C (sp3)
• They are important solvents and synthesis
intermediates
• Methanol, CH3OH, called methyl alcohol, is a
common solvent, a fuel additive, produced in
large quantities
• Ethanol, CH3CH2OH, called ethyl alcohol, is a
solvent, fuel, beverage
• Phenol, C6H5OH (“phenyl alcohol”) has diverse
uses - it gives its name to the general class of
compounds

3. • OH groups bonded to vinylic sp2-hybridized
carbons are called enols
OH
CH3CH2OH CH3CHCH3
OH
C
OH
CH3
H3C
CH3
C C
OH
1o
2o
3o
Phenol enol

4. Classification of alcohols
Naming of alcohols

5. Physical Properties
1) Boiling point:
• Depends on the strength of the attractive
forces between the molecules
• The stronger the forces the higher the boiling
point
• Hydrogen bonding: is the attraction that
results from the association of the H atom
with a more electronegative atom such as O, N
and F. Hydrogen bonded molecules have a
greater bp

6. • Van der Waals dispersion forces: attractive
forces within the molecules
• The longer the molecule the higher the boiling
point
• More extended, less spherical the greater the
boiling point
Intermolecular Hydrogen Bonding

7. • Dipole-dipole interaction: molecules with
permanent dipole moments have a higher
boiling point
• Thus alcohols and phenols have a higher bp
than alkane, alkyl halides and ethers of similar
molecular weight

8. 2) Solubility in water
• whereas the hydrocarbons are insoluble in
water, alcohols with one to three carbon
atoms are completely soluble
• As the length of the chain increases, however,
the solubility of alcohols in water decreases;
the molecules become more like
hydrocarbons and less like water

10. 3) Acidity
• Alcohols are weakly basic and weakly acidic
• They are weak Brønsted bases because they
are protonated by strong acids to yield
oxonium ions, ROH2
+

11. • They are weak acid because they can transfer
a proton to water to a very small extent
• Produces H3O+ and an alkoxide ion, RO-, or a
phenoxide ion, ArO-

12. • The acidity constant, Ka, measures the extent
to which a Brønsted acid transfers a proton to
water
[A] [H3O+]
Ka = ————— and pKa = log Ka
[HA]
• Relative acidities are more conveniently
presented on a logarithmic scale, pKa, which is
directly proportional to the free energy of the
equilibrium
• Differences in pKa correspond to differences in
free energy

15. • Simple alcohols are about as acidic as water
• Alkyl groups make an alcohol a weaker acid
• The more easily the alkoxide ion is solvated by
water the more its formation is energetically
favored
• Electron-withdrawing groups make an alcohol
a stronger acid by stabilizing the conjugate
base (alkoxide)
• Alcohols are weak acids – requires a strong
base to form an alkoxide such as NaH, sodium
amide NaNH2, and Grignard reagents (RMgX)

16. • Alkoxides are bases used as reagents in
organic chemistry

17. Acidity of phenol
• Phenols (pKa ~10) are much more acidic than
alcohols (pKa ~ 16) because of resonance
stabilization of the phenoxide ion
• Phenols react with NaOH solutions (but
alcohols do not), forming salts that are soluble
in dilute aqueous solution and isolated after
acid is added to the solution

18. • Phenols with nitro groups at the ortho and
para positions are much stronger acids

20. Synthesis of alcohols

21. Hydration of alkenes
• When treated with aq. acid, most commonly
H2SO4, alkenes form alcohols.
• Regioselectivitypredicted by Markovnikov's
rule
• Reaction proceeds via protonation to give the
morestable carbocation intermediate

22. Mechanism

23. Regiospecific Hydration of Alkenes
• Hydroboration/oxidation: syn, anti-Markovnikov
hydration
• Oxymercuration/reduction: Markovnikov hydration

24. • Cis-1,2-diols from hydroxylation of an alkene
with OsO4 followed by reduction with NaHSO3
• Trans-1,2-diols from acid-catalyzed hydrolysis
of epoxides

25. Reduction of a carbonyl compound
• Aldehydes gives primary alcohols
• Ketones gives secondary alcohols
• NaBH4 is not sensitive to moisture and it does
not reduce other common functional groups
• Lithium aluminum hydride (LiAlH4) is more
powerful, less specific, and very reactive with
water
• Both add the equivalent of “H-”

27. Reduction of Carboxylic Acids and
Esters
• Carboxylic acids and esters are reduced to give
primary alcohols
• LiAlH4 is used because NaBH4 is not effective

28. Using the Grignard Reagents
• Alkyl, aryl, and vinylic halides react with
magnesium in ether or tetrahydrofuran to
generate Grignard reagents, RMgX
• Grignard reagents react with carbonyl
compounds to yield alcohols

30. • Esters yield tertiary alcohols in which two of
the carbon substituents come from the
Grignard reagent
• Grignard reagents do not add to carboxylic
acids – they undergo an acid-base reaction,
generating the hydrocarbon of the Grignard
reagent

31. Mechanism
• Grignard reagents act as nucleophilic carbon
anions (carbanions = : R) in adding to a carbonyl
group
• The intermediate alkoxide is then protonated to
produce the alcohol

32. Reactions of Alcohols
Dehydration
• forming an alkene from an alcohol through loss of O-H
and H (hence dehydration) of the neighboring C–H to
give  bond
• Zaitzev’s Rule: when two different alkene products are
possible in an elimination, the most highly substituted
(most stable) alkene will be the major product.
• Tertiary alcohols are readily dehydrated with acid
• Secondary alcohols require severe conditions (75%
H2SO4, 100°C) - sensitive molecules do not survive
• Primary alcohols require very harsh conditions –
impractical
• Reactivity is the result of the nature of the carbocation
intermediate

33. • Phosphorus oxychloride in the amine solvent
pyridine can lead to dehydration of secondary
and tertiary alcohols at low temperatures
OH
CH3 CH3
POCl3
pyridine, 0o
C

34. Primary alcohol dehydrates through the
E2 mechanism

35. Secondary and tertiary alcohols dehydrate through the E1 mechanism

36. Conversion of alcohols into alkyl
halides:
- 3˚ alcohols react with HCl or HBr by SN1 through
carbocation intermediate
- 1˚ and 2˚ alcohols converted into halides by
treatment with SOCl2 or PBr3 via SN2 mechanism
- SN- nucleophilic substitution

38. Oxidation of Alcohols
• Can be accomplished by inorganic reagents,
such as KMnO4, CrO3, and Na2Cr2O7 or by
more selective, expensive reagents

39. Oxidation of Primary Alcohols
• To aldehyde: pyridinium chlorochromate (PCC,
C5H6NCrO3Cl) in dichloromethane
PCC
• Other reagents produce carboxylic acids

40. • PCC
• Other reagents produce carboxylic acids

41. Oxidation of Secondary Alcohols
• Effective with inexpensive reagents such as
Na2Cr2O7 in acetic acid
• PCC is used for sensitive alcohols at lower
temperatures

42. Conversion of Alcohols into Tosylates
• Reaction with p-toluenesulfonyl chloride (tosyl
chloride, p-TosCl) in pyridine yields alkyl tosylates,
ROTos
• Formation of the tosylate does not involve the C–O
bond so configuration at a chirality center is
maintained
• Alkyl tosylates react like alkyl halides

43. Uses of Tosylates
• The SN2 reaction of an alcohol via an alkyl halide
proceeds with two inversions, giving product with
same arrangement as starting alcohol
• The SN2 reaction of an alcohol via a tosylate,
produces inversion at the chirality center

44. Incorporation of Alcohols into Esters

45. Protection of Alcohols
• Hydroxyl groups can easily transfer their
proton to a basic reagent
• This can prevent desired reactions
• Converting the hydroxyl to a (removable)
functional group without an acidic proton
protects the alcohol

46. Methods to Protect Alcohols
• Reaction with chlorotrimethylsilane in the
presence of base yields an unreactive
trimethylsilyl (TMS) ether
• The ether can be cleaved with acid or with
fluoride ion to regenerate the alcohol

48. TMS-alcohol Protection-Deprotection

49. Phenol
Phenols are produced by Reaction of i)
Benzene Sulfonic Acid with Hydroxide, ii) Base
Hydrolysis of Chlorobenzene iii) Acidic
Oxidation of Cumene iv) from Aryl Diazonium
Salts. The first three methods are primarily
industrial methods while the hydrolysis of
diazonium salts is the most important
laboratory method.

50. Phenol

51. Acidic Oxidation of Cumene
• Cumene forms cumene hydroperoxide with
oxygen at high temperature
• Converted into phenol and acetone by acid

52. Mechanism of Formation of Phenol

53. Mechanism of Formation of Phenol

54. Reactions of Phenols
• The hydroxyl group is a strongly activating,
making phenols substrates for electrophilic
halogenation, nitration, sulfonation, and
Friedel–Crafts reactions

55. Friedel–Crafts Alkylation of phenol
Williamson synthesis

56. Carboxylation
Friedel–Crafts Acylation of phenol

57. Electrophilic aromatic substitution

58. Nitration

59. Bromination

60. Sulfonation

61. Oxidation of phenol
• Reaction of a phenol with strong oxidizing
agents yields a quinone
• Fremy's salt [(KSO3)2NO] works under mild
conditions through a radical mechanism