This is our presentation for organic chemistry (group 2)

1. STRUCTURES, NAMES &
PHYSICAL PROPERTIES OF
ALCOHOL
• Structure of Alcohol
• Nomenclature
• Physical Properties

2. STRUCTURE OF ALCOHOL

3. WHAT DO WE KNOW ABOUT ALCOHOLS?
• An organic compound with a functional group (-OH) (hydroxyl group)
• Has 3 classifications: primary(1°), secondary(2°) and tertiary(3°)
• Saturated Alcohols – single bonds (alkane)
• Unsaturated Alcohols – double/triple bonds (alkene/alkyne)

4. • We also know alcohols are found in
disinfectant spray or in some
beverages
• To truly understand the
STRUCTURE of an Alcohol, let’s
take a look at water structure
(H2O), then if we replace (1) one
hydrogen with alkyl group, then
we have an alcohol.

5. But why is it bent structure?
That is because of the concept behind Shells,
Subshells and Orbitals.

6. ORBITAL SHAPES

7. Key points:
• Electrons move around the nucleus in “a cloud” not orbits.
• Orbital – the region with a high probability of containing electrons.
• Shell (energy level) – Subshells – Orbitals
Example: 2nd Shell has (2) Subshells (SP) and 4 Orbitals (1 S orbital & 3 P
orbitals) (2s, 2px , 2py, 2pz)
• These electron clouds repel each other, they are like magnets with same charge. (closer
together = more potential energy, far away with each other = less potential energy)

8. ORBITAL HYBRIDISATION & VSEPR THEORY

9. Example: H2O
To get the hybridization, we will just count the atoms to bond and lone pairs
Solution: 2 atom
2 lone pairs__
4 orbitals ( s, p, p, p )
So it is sp3 hybridized (109.5° tetrahedral) / VSEPR (bent)
Example: CH3OH
Solution: 4 atoms
0 lone pairs__
4 orbitals ( s, p, p, p )
sp3 hybridized (109.5° tetrahedral) / VSEPR (tetrahedral)

10. Example: C2H4
Solution: 3 atoms
0 lone pairs__
3 orbitals ( s, p, p, p )
sp2 hybridized (120° planar triangular) / VSEPR (trigonal planar)
Example: C2H2
Solution: 2 atoms
0 lone pairs__
2 orbitals ( s, p, p, p )
sp hybridized (180° linear) / VSEPR (linear)

11. Summarize :
• Structure of an alcohol is similar to water, having sp3 hybridized tetrahedral oxygen
atom with nonbonding pairs of electrons occupying two of the sp3 hybrid orbitals.

12. NOMENCLATURE

13. NOMENCLATURE
Common Name and (IUPAC) naming system
Common Name
• the name we use in our regular life (e.g. isopropyl & ethyl alcohol)
• There are also unusual common names based on the person who discover, shapes,
places etc. (e.g. megaphone, moronic acid, traumatic acid)

14. Common name:
Prefix “n-” (normal) n-pentane
n-pentanol
Prefix “iso” isopentane
isopentyl alcohol
Prefix “neo” neopentane
neopentyl alcohol

15. Common name:
Prefix “sec” or ”s” sec-butanol
(functional group bonded
to secondary carbon)
Prefix “tert” or ”t” tert-butanol
(functional group bonded
to tertiary carbon)

16. IUPAC system
• The name for an alcohol uses the “-ol” suffix with the name of the parent alkane,
together with a number to give the location of the hydroxyl group.
3 Steps
1. Name the longest carbon chain that contains the –OH group then drop the “-
e” (alkane name) and add “-ol”
2. Number the longest carbon chain nearest to –OH group and use appropriate
number to indicate the position of –OH group.
3. Name the substituents

18. Other examples:
2-butanol
2-chloro-3-methyl-3-hexanol
2-methyl-2-butanol

19. Other examples:
3-penten-2-ol
1,2-propanediol
2,2-propanediol

20. PHYSICAL PROPERTIES OF
ALCOHOLS

21. PHYSICAL PROPERTIES
• Alcohols are polar compounds
• Both the C – O and O – H bonds are polar covalent
• Alcohols associate in the liquid state by hydrogen bonding.
• Hydrogen Bonding the attractive force between a partial positive charge on
hydrogen and partial negative charge on a nearby oxygen, nitrogen, or fluorine
atom.
• The strength of hydrogen bonding in alcohols is approximately 2 to 5 kcal/mol.

22. PHYSICAL PROPERTIES
Boiling Point
• Alcohols have higher boiling points and are more soluble in water than hydrocarbons.
• Alcohol have higher boiling points than alkanes of similar molecular weight. Alcohol
boiling points increase as carbon-chain length increases.
Structural
Formula Name
Molecular
Weight
(g/mol)
Boiling
Point
(C°)
Solubility
in
Water
CH3OH
CH3CH3
Methanol
Ethane
32
30
65
-89
Infinite
Insoluble
CH3CH2OH
CH3CH2CH3
Ethanol
Propane
46
44
78
-42
Infinite
Insoluble
CH3CH2CH2OH
CH3CH2CH2CH3
1-propanol
Butane
60
58
97
0
Infinite
Insoluble
CH3CH2CH2CH2CH2OH
HOCH2CH2CH2CH2OH
CH2CH2CH2CH2CH2CH3
1-pentanol
1,4-butanediol
Hexane
88
90
86
138
230
69
2.3g/100g
Infinite
Insoluble

23. PHYSICAL PROPERTIES
Solubility
• The solubility of alcohol in water is governed by the hydroxyl group
present.
• The hydroxyl group in alcohol is involved in the formation of
intermolecular hydrogen bonding. Thus, the hydrogen bonds are formed
between water and alcohol molecules which make alcohol soluble in
water.
• However, the alkyl group attached to the hydroxyl group is hydrophobic
in nature. Thus, the solubility of alcohol decreases with the increase in
the size of the alkyl group.

24. PHYSICAL PROPERTIES
Acidity
• Alcohols react with active metals such as sodium, potassium etc. to form
the corresponding alkoxide. These reactions of alcohols indicate their
acidic in nature.
• The acidic nature of alcohol is due to the polarity of –OH bond.
• The acidity of alcohols decreases when the electron-donating group is
attached to the hydroxyl group as it increases the electron density on
the oxygen atom.
• Thus, primary alcohols are generally more acidic than secondary and
tertiary alcohols.

25. CHARACTERISTIC
REACTIONS OF ALCOHOLS
• Acidity of Alcohols
• Acid – Catalyzed Dehydration of Alcohols
• Oxidation of Primary and Secondary Alcohols

26. REACTIONS OF ALCOHOLS

27. REACTIONS OF ALCOHOLS
1. Reaction with Metals to form Salt
• Alcohols react with Li, Na, K to liberate hydrogen and metal oxides.

28. REACTIONS OF ALCOHOLS
2. Formation of alkyl halides
• Alcohols react with HBr or HI to produce alkyl bromides or alkyl
halides.

29. REACTIONS OF ALCOHOLS
2. (A) Action of halogen acids on alcohol
(Formation of alkyl halides)
• Alcohols react with HBr or HI to produce alkyl bromides or alkyl
halides.

30. REACTIONS OF ALCOHOLS
2. (B) Action of Phosphorus halides on alcohol
(Formation of alkyl halides)
• Alcohols react with phosphorus halides to produce alkyl halides.

31. REACTIONS OF ALCOHOLS
2. (C) Action of thionyl chloride on alcohol
(Formation of alkyl halides)
• Alcohols react with thionyl chloride in the presence of pyridine to
produce alkyl halides.

32. REACTIONS OF ALCOHOLS
3. Formation of Ester
• Alcohols react with carboxylic acid in the presence of strong acid to form
esters.

33. REACTIONS OF ALCOHOLS
4. Formation of Carboxylic Acid
Oxidation of primary alcohols and aldehydes: Primary alcohols and
aldehydes on oxidation with sodium or potassium dichromate and
sulphuric acid, or potassium permanganate, give the corresponding
carboxylic acids.

34. REACTIONS OF ALCOHOLS
5. Dehydration of Alcohol
• When alcohol is heated in the presence of sulfuric acid to form alkene by
elimination of water.

35. REACTIONS OF ALCOHOLS
5. (A) E1 Dehydration of Alcohol
• When alcohol is heated in the presence of sulfuric acid to form alkene by
elimination of water.

36. REACTIONS OF ALCOHOLS
5. (B) E2 Dehydration of Alcohol
• When alcohol is heated in the presence of sulfuric acid to form alkene by
elimination of water.

37. REACTIONS OF ALCOHOLS
6. Oxidation of Alcohol
• Alkyl halide undergo reduction with nascent hydrogen in presence of
reducing agent like Zn/HCl to form alkanes.

38. REACTIONS OF ALCOHOLS
7. Catalytic Dehydrogenation of Alcohol
• Alkyl halide undergo reduction with nascent hydrogen in presence of
reducing agent like Zn/HCl to form alkanes.

39. REACTIONS OF ALCOHOLS
8. Reaction with Grignard Reagents
(Formation of Alkanes)
• Alkyl react with Grignard reagents(R-Mg-X) to form alkanes.

40. REACTIONS OF ALCOHOLS
9. Reduction of alcohol to form alkane
• Alcohol undergo reduction with concentrated hydriodic acid and
phosphorus to form alkanes.

41. ACIDITY OF ALCOHOLS

42. • Alcohol weakly acidic.
• In aqueous solution, alcohol will donated its proton to water
molecule to give an alkoxide ion (R-O-).
• R-OH + H2O R-O- + H3O+ Ka = ~10-16 to 10-
18
Example
CH3CH2-OH + H2O CH3CH2-O- + H3O+

43. • The acid-dissociation constant, Ka, of an alcohol is defined
by the equilibrium
R-OH + H2O R-O- + H3O+
[H3O+][RO-]
[ROH] pKa = - log (K3)
• The more smaller the pKa value, the alcohol is more acidic
Ka
Ka =

44. • Alcohol is weakly acidic.
• In aqueous solution, alcohol will donated its proton to water
molecule to give an alkoxide ion (R-O-).

45. Compound Structural Formula pKa
Hydrogen Chloride HCl -7
Acetic Acid CH3COOH 4.8
Methanol CH3OH 15.5
Water H2O 15.7
Ethanol CH3CH2OH 15.9
2-Propanol (CH3)2CHOH 17
2-Methyl-2-propanol (CH3)3COH 18
STRONGER ACID
WEAKER ACID
*Also given for comparison are pKa values for water, acetic acid, and
hydrogen chloride.

46. H2O
Water
CH3OH
Methanol
CH3CH2OH
Ethanol
CH3CH2(OH)CH3
2-Propanol
pKa = 15.7 pKa = 15.5 pKa = 15.9 pKa = 17
• Acidity depends primarily on the degree of stabilization and
solvation of the alkoxide ion.

47. • The negatively charged oxygens of methanol and ethanol
are about as accessible as hydroxide ion for solvation; these
alcohols are about as acidic as water.
• As the bulk of the alkyl group increases, the ability of water
to solvate the alkoxide decreases, the acidity of the alcohol
decreases, and the basicity of the alkoxide ion increases.
• The Alkoxide ion (RO-)
-the negative charge is confined to the oxygen and is
not spread over the alkyl group.
-this makes the RO- ion less stable and more susceptible
to attack by positive ions such as H+ ions.

48. EFFECTS OF ACIDITY
• The acidity decreases as the substitution on the alkyl group
increase.
-Ethyl group is an electron-donating group strengthens
the –O-H bond harder to release a proton.
i.e.: Methanol is more acidic than t-butyl alcohol

49. The present of electrons-withdrawing atoms enhances the
acidity of alcohols.
• The electron withdrawing atom helps to stabilized the alkoxide ion.
• i.e.: 2-chloroethanol is more acidic than ethanol because the electron-
withdrawing chlorine atom helps to stabilize the 2-chloroethoxide ion.
• Alcohol with more than one electron withdrawing atoms are more
acidic. i.e. 2,2,-dichloroethanol is more acidic than 2-chloroethanol.
• Example of electron-withdrawing atom/groups:
• Halogens atoms and NO2.

50. ACID-CATALYZED
DEHYDRATION OF
ALCOHOLS

51. ACID-CATALYZED DEHYDRATION OF ALCOHOLS
• We can convert an alcohol to an alkene by eliminating a molecule of
water from adjacent carbon atoms in a reaction called dehydration.
• Dehydration of alcohols is most often brought by heating with either
85% phosphoric acid or concentrated sulfuric acid.
• Primary alcohols – the most difficult to dehydrate – generally require
heating in concentrated sulfuric acid at temperatures as high as 180°C

52. ACID-CATALYZED DEHYDRATION OF ALCOHOLS
• Secondary alcohols undergo acid-catalyzed dehydration at somewhat
lower temperatures.
• Tertiary alcohols generally undergo acid-catalyzed dehydration at
temperatures only slightly above room temperature.

53. 1° Alcohols, 2° Alcohols, 3° Alcohols
• When the acid-catalyzed dehydration of an alcohol yields isomeric
alkenes, the alkene having the greater number of alkyl groups on the
double bond generally predominates.
• Hydration-dehydration reactions are reversible.
Ease of Dehydration Alcohols

54. • Alkene hydration and alcohol dehydration are competing reactions, and
the following equilibrium exists:

55. In accordance with Le Chatelier’s principle:
• Large amounts of water (using dilute aqueous acid) favor alcohol
formation.
• Scarcity of water (using concentrated acid) or experimental conditions
where water is removed (heating the reaction mixture above 100°C)
favor alkene formation.

56. OXIDATION OF PRIMARY
AND SECONDARY
ALCOHOLS

57. ALCOHOL OXIDATION
• Alcohol oxidation is an important organic reaction. The indirect
oxidation of primary alcohols to carboxylic acids normally proceeds via
the corresponding aldehyde, which is transformed via an aldehyde
hydrate by reaction with water.
• Primary alcohols can be oxidized to form aldehydes and carboxylic
acids
• Secondary alcohols can be oxidized to give ketones
• Tertiary alcohols, in contrast, cannot be oxidized without breaking the
molecule's C–C bonds.

58. OXIDATION REACTIONS
• The oxidation, the orange dichromate ion is reduced to the green Cr3+
ion. This can be used to detect alcohols.

59. REACTIVE C-H BONDS
• ([O] = Oxidizer)

60. REAGENTS FOR ALCOHOL OXIDATION
FOR THE OXIDATION OF PRIMARY ALCOHOLS TO
ALDEHYDES
• Cr2O7
2– (dichromate)
• CrO3/pyridine (Collins reagent)
• Pyridinium chlorochromate (PCC)
• Pyridinium dichromate (PDC, Cornforth reagent)
• Dess–Martin periodinane
• Dimethyl sulfoxide (DMSO)/oxalyl chloride (Swern oxidation)

61. REAGENTS FOR ALCOHOL OXIDATION
FOR THE OXIDATION OF SECONDARY ALCOHOLS TO
KETONES
• Cr2O7
2– (dichromate)
• CrO3/pyridine (Collins reagent)
• Pyridinium chlorochromate (PCC)
• Pyridinium dichromate (PDC, Cornforth reagent)
• Dess–Martin periodinane
• Dimethyl sulfoxide (DMSO)/oxalyl chloride (Swern oxidation)
• Dimethyl sulfoxide (DMSO)/oxalyl chloride (Swern oxidation)
• CrO3/H2SO4/acetone (Jones oxidation)
• Aluminium isopropoxide/acetone (Oppenauer oxidation)

62. REAGENTS FOR ALCOHOL OXIDATION
FOR THE DIRECT OXIDATION OF PRIMARY ALCOHOLS
TO CARBOXYLIC ACIDS
• KMnO4 (potassium permanganate)
• RuO4 (ruthenium tetroxide)
• CrO3/H2SO4/acetone (Jones oxidation)

63. GROUP II MEMBERS
Mr. Jhonel D. Balmas (Leader)(Structure of Alcohol & Nomenclature)
Ms. Mariz Bien (Physical Properties of Alcohols)
Ms. Argelyn Bongalbal (Reactions of Alcohols)
Ms. Roce Shelle Castillo (Acidity of Alcohols)
Ms. Maybel Mata (Dehydration of Alcohol)
Ms. Cenia Romo (Alcohol Oxidation)