Organic Chemistry - Alcohols

1. Presented by:
Nousheen Hayat

2. 1. Introduction to Alcohols
2. Naming Alcohols
3. Types of Alcohols
4. Preparation of Alcohols
5. Physical Properties
6. Chemical Properties
7. Applications of Alcohols

3. Definition:
An alcohol is any organic compound in which a
hydroxyl functional group (-OH) is bound to a carbon
atom, usually connected to other carbon or
hydrogen atoms.
-Alcohols are organic derivatives of water H-O-H in
which one of the hydrogen atoms (H) is replaced by an
alkyl group (R) R-O-H
-The word alcohol appeared in English in the 16th
century originating from the Arabic word
Introduction

4. Naming Alcohols
• IUPAC name: We replace the -e in alkane name with -ol.
• Common name: As simple alcohols using the name of the
alkyl group followed by alcohol.
 CH4 methane CH3─OH (methanol)or(methyl alcohol)
 CH3─CH3 ethane CH3─CH2─OH (ethanol)or(ethyl
alcohol)

5. Naming Alcohols in Steps (IUPAC)
Step 1
Select the longest carbon chain
that contains the -OH group.
Step 2
Number from the end nearest -OH group.
Step 3
Change the ending of parent alkane from -e to -ol.
Use the number to show the location of -OH.
Step 4
Give the location and name of each substituent
(alphabetical order) as a prefix to the name of the
main chain.

6. CH3─CH2─CH2─OH 1-propanol
OH
│
CH3─CH─CH3 2-propanol
CH3
│
OH
│
CH3─CH─CH2─CH2─CH─CH3
6 5 4 3 2 1
5-methyl-2-hexanol
Naming Alcohols
Examples
2 1
3
2 1
3

7. Methanol Ethanol Propanol Butanol
CH3OH C2H5OH C3H7OH C4H9OH
Common Name :
Wood alcohol Grain alcohol rubbing alcohol

8. Depending on the position of -OH group:
The -OH group of alkyl alcohols can be positioned on
different carbon atoms of the carbon chain and are
classified as
Primary (1º) Secondary (2º ) Tertiary (3º)
H CH3 CH3
│ │ │
CH3─C─OH CH3─C─OH CH3─C─OH
│ │ │
H H CH3
1 C 2 C 3 C
attached attached attached
to C-OH to C-OH to C-OH
Different Types of Alcohols

9. Diols & Triols
Depending on the number of –OH groups :
Diol: a compound containing two –OH (Hydroxyl groups).
Triol: a compound containing three –OH (Hydroxyl groups).
CH1 – CH2
OH OH
CH3 – CH2 – CH1 CH3 – CH2 – CH1
OH OH OH OH
OH
1,2-Ethanediol
(Ethylene glycol)
1,2-Propanediol
(Propylene glycol)
1,2,3-Propanetriol
(glycerol, glycerin)
Note: that the -OH groups must be placed in neighboring
carbon atoms to name them glycols & glycerols

10. Preparation of Alcohol
Secondary (2º)
Alcohols
-SN1
-SN2
-Reduction
-Grignard
Tertiary (3º)
Alcohols
-SN1
-Grignard
Type
Primary (1º)
Alcohol
Reaction -SN2
-Reduction
-Grignard
1) Reduction of an aldehyde, ketone, or carboxylic acid with the appropriate
reducing agent.
2)Substitution The SN1 & SN2 reactions are substitution reactions . “SN” stands for
nucleophilic substitution and “1” stands for unimolecular & “2” for bimolecular SN1
has two steps & SN2 has one step for reaction
3)Grignard is an organometallic chemical reaction in which alkyl or aryl magnesium
halide RMgX is used

11. Reactions That Give
Alcohols
Primary (1º) Alcohols

12. Secondary (2º) Alcohols

13. Tertiary (3º) Alcohols

14. Physical Properties of Alcohols
1. Alcohols are polar molecules (because of O-H and C-O).
Electro-negativity: C-O: (3.5 – 2.5 = 1.0)
O-H : (3.5 – 2.1 = 1.4)
2. Hydrogen bonding occurs between alcohols molecules.
relatively weak bond
( represented by dots)
O has a partially negative
charge δ-
& H has a partially positive
charge δ+.
3. Have higher boiling point than Alkanes, Alkenes &
Alkynes & Alkyl-Halides :
due to the Oxygen presence forming polar bonding between C-O
& O-H.

15. 4. They are weak acids (alkyl alcohols weaker than Phenol):
Although alkyl alcohols have an -OH group, they do not ionize in water,
whereas phenols ionize like acids (donating a proton to water).
5. Solubility in water (Molecular weight ↑ : solubility ↓)
-As the chain of the R group increases the hydrocarbon (non- polar)
character of the compound overshadows the (polar) character of the
OH group. Consequently, the solubility and boiling point of an alcohol
are affected by the 1) length of the carbon chain and 2) the shape of the
molecule .
-The short chain alcohols are soluble in water, whereas the longer chain
alcohols are insoluble in water.

16. • Alcohol function is an extremely versatile functional group
in organic chemistry
• Reaction of Alcohol involves oxidation, substitution and
eliminations to give a significant advantages in synthesis
and functional group modification
Chemical Properties of Alcohols

17. 1. Acid-Catalyzed Dehydration:
CH3CH2OH CH2 = CH2 + H2O
H2SO4
180°C
2
C = C + H O
Dehydration
Hydration
H- C – C -H
H OH
2. Oxidation of Alcohols: (1º), (2º )&(3º)
Using Potassium DichromateK2Cr2O7 & Sulfuric Acid H2SO4
as catalysts

18. In the oxidation [O] of a primary alcohol 1 , one H is
removed from the –OH group and another H from
the C bonded to the –OH and aldehyde is produced
primary alcohol aldehyde
OH
│
CH3─C─H
│
H
ethanol
(ethyl alcohol)
O
║
CH3─C─H + H2O
ethanal
(acetaldehyde)
Oxidation of 1° Alcohols
K2Cr2O7
H2SO4
[O]

19. The oxidation of 2 alcohols is similar to 1 , except that a
ketone is formed.
secondary alcohol ketone
OH
│
CH3─C─CH3
│
H
2-propanol
O
║
CH3─C─CH3 + H2O
2-propanone
Oxidation of 2° Alcohols
[O]
K2Cr2O7
H SO
2 4

21.  As electrophiles, alcohols are considered weak because the
hydroxyl group is a poor leaving group. As such, the hydroxyl
group must be transformed into a good leaving group prior to
reacting as an electrophile.
148

22.  If the alcohol’s OH group is converted into a group
that is a weaker base (and therefore a better leaving
group), a nucleophilic substitution reaction can
occur. One way to convert an OH group into a
weaker base is to protonate it by adding acid to the
solution.
154

23. Tertiary 3 alcohols do not oxidize.
Tertiary alcohol No reaction
OH
│
CH3─C─CH3 No product
│
CH3 no H on the C-OH to oxidize
2-methyl-2-propanol
Oxidation of 3° Alcohols
K2Cr2O7
H2SO4
[O]

24. 3. Alcohols as Nucleophiles or Electrophiles
Alcohols are highly versatile and can be used as both
electrophile or nucleophile in organic reactions.
Alcohols can be used as a weak or strong
nucleophile. This is the natural reactivity of alcohols.

25. In the body:
• Enzymes in the liver oxidize ethanol.
• Blood alcohol concentration over 0.4% can be fatal.
O
║
O
║
3 2 3
ethanal
CH COH
3
acetic acid
2 2
2CO + H O + Energy
ethanol
CH CH OH
[O]
CH CH
Oxidation of Alcohols in our body
[O] [O]
Oxidation: adding one oxygen atom or removing two hydrogen atoms
Reduction: adding two hydrogen atoms or removing one oxygen atom

26. Applications
Alcohols can be used for many scientific ,medical & industrial Utilities.
As a beverage:
Alcohols can be used as a beverage (ethanol only, when fermented from
sugar), Ethanol in the form of alcoholic beverages has been consumed
by humans since pre-historic times. Alcohol usage especially at a young
age may lead to: depression & addiction, serious liver problems such as
fatty liver which is basically the liver falling apart, illnesses also in the
brain(atrophy), heart, pancreas & stomach ,& ultimately serious
malformation of embryos.

27. As a fuel:
Some alcohols, mainly ethanol and methanol, can be used as an
alcohol Fuel. Performance can be increased in forced induction
internal combustion engines by injecting alcohol into the air
intake after the turbocharger or supercharger has pressurized the
air. This cools the pressurized air, providing a denser air charge,
which allows for more fuel, and therefore more power.

28. In industry:
Alcohols have applications in industry and science as reagents or
solvents. Because of its low toxicity and ability to dissolve non-polar
substances, ethanol can be used as a solvent in medical drugs,
perfumes, and vegetable essences such as vanilla. In organic
synthesis, alcohols serve as versatile intermediates.
Glycerols is non toxic and an excellent humectant(moisture-retaining
agent).it is used in bakery products,vanishing creams,shaving soaps
and toothpastes.

29. In pharmacy
Ethanol can be used as an antiseptic to dis-infect the skin
before injections are given, often along with iodine. Ethanol-
based soaps are becoming common in restaurants and are
convenient because they do not require drying due to
volatility of the compound. Alcohol is also used as a
preservative for specimens. Alcohol
gels have become common as hand sanitizers.

30. THE END