1. BY
VANA JAGAN MOHAN RAO M.S.Pharm, MED.CHEM
NIPER-KOLKATA
Asst.Professor, MIPER-KURNOOL
Email: jaganvana6@gmail.com
2. ALCOHOLS
Alcohols: Organic compounds containing
hydroxyl (-OH) functional groups.
R OH
Phenols: Compounds with hydroxyl group bonded
directly to an aromatic (benzene) ring.
OH
3.
4. IUPAC RULES
1. Select the longest continuous chain of carbon atoms
containing the hydroxyl group.
2. Number the carbon atoms in this chain so that the
one bonded to the –OH group has the lowest
possible number.
3. Form the parent alcohol name by replacing the final
–e of the corresponding alkane name by –ol. When
isomers are possible, locate the position of the –OH
by placing the number (hyphenated) of the carbon
atom to which the –OH is bonded immediately before
the parent alcohol name.
4. Name each alkyl branch chain (or other group) and
designate its position by number.
5. Select this chain as the parent compound.
This is the longest continuous chain
that contains an hydroxyl group.
6. 4
3
2 1
This end of the chain is closest to the
OH. Begin numbering here.
12. NOMENCLATURE OFALCOHOLS
CONTAINING TWO DIFFERENT
FUNCTIONAL GROUPS
Alcohol containing double and triple bonds:
- use the –ol suffix after the alkene or alkyne name.
The alcohol functional group takes precedence over
double and triple bonds, so the chain is numbered in
order to give the lowest possible number to the carbon
atom bonded to the hydroxyl group.
The position of the –OH group is given by putting its
number before the –ol suffix.
Numbers for the multiple bonds were once given early in
the name.
13. 1) Longest carbon chain that contains –OH group
- 5 carbon
2) Position of –OH group
- Carbon-2
3) Position of C=C
- Carbon-4
COMPLETE NAME = 4-penten-2-ol
EXAMPL
E
14. Some consideration:
- OH functional group is named as a hydroxy
substituent when it appears on a structure with a
higher priority functional group such as acids, esters,
aldehydes and ketones.
- Examples:
16. Alcohols with two –OH groups diols or lycols.
Naming of diols is like other alcohols except that the
suffix diol is used and two numbers are needed to tell
where the two hydroxyl groups are located.
NOMENCLATURE OF DIOLS
17. NOMENCLATURE OF PHENOLS
The terms ortho (1,2-disubstituted), meta (1,3-
disubstituted) and para (1,4-disubstituted) are often
used in the common names.
18. Phenols may be monohydric, dihydric or
trihydric - (number of hydroxyl groups) in the
benzene ring.
19. COMMON NAMES
Derived from the common name of the alkyl group
and the word alcohol.
For example:
20.
21. According to the type of carbinol carbon atom (C bonded to the –
OH group).
C O H
Classes:
i) Primary alcohol
- -OH group attached to a primary carbon atom
- one alkyl group attached
ii) Secondary alcohol
- -OH group attached to a secondary carbon atom
- two alkyl group attached
iii) Tertiary alcohol
- -OH group attached to a tertiary carbon atom
- three alkyl group attached
CLASSIFICATION
22.
23. • Alcohols that contain more than one OH group -
polyhydroxy alcohols.
• Monohydroxy: one OH group.
• Dihydroxy: two OH groups.
• Trihydroxy: three OH groups.
Polyhydroxy Alcohols
24.
25. PHYSICAL PROPERTIES
PHYSICAL STATES OF ALCOHOLS
- aliphatic alcohols and lower aromatic alcohols
liquids at room temperature.
-highly branched alcohols and alcohols with twelve
or more carbon atoms solids.
26. BOILING POINTS
i)Boiling points of alcohols are higher > alkanes and
chloroalkanes of similar relative molecular mass.
- For example:
C2H5OH CH3CH2CH3 CH3Cl
Relative molecular mass: 46 44 50.5
Boiling point: 78 C -42 C -24 C
- Reason:
* intermolecular hydrogen bonds
27. SOLUBILITY OF ALCOHOLS IN WATER
i)Alcohols with short carbon chains (i.e. methanol, ethanol) -
dissolve in water.
- dissolve in water (hydrogen bonds are formed).
ii)Solubility decreases sharply with the increasing length of
the carbon chain.
iii) Higher alcohols are insoluble in water.
- alcohol contains a polar end (-OH group) called ‘hydrophilic’
and a non-polar end (the alkyl group) called ‘hydrophobic’.
28. iii) Polyhydroxy alcohols are more soluble than monohydroxy
form more hydrogen bonds with water
molecule.
iv)Branched hydrocarbon increases the solubility of alcohol
in water branched hydrocarbon cause the
hydrophobic region becomes compact.
29. Alcohol weakly acidic.
In aqueous solution, alcohol will donated its proton to
water molecule to give an alkoxide ion (R-O-).
ACIDITY OF ALCOHOLS AND PHENOLS
The acid-dissociation constant, Ka, of an alcohol is defined
by the equilibrium
31. Phenol is more acidic than alcohols by considering
the resonance effect.
i) 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.
32. ii) The phenoxide ion
- one of the lone pairs of electrons on the oxygen atom is
delocalised into the benzene ring.
-the phenoxide ion is more stable because the negative
charge is not confined to the oxygen atom but
delocalised into the benzene ring.
-the phenoxide ion is resonance stabilised by the
benzene ring and this decreases the tendency for the
phenoxide ion to react with H3O+.
33. 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.
The present of electron-withdrawing atoms enhances the acidity of
alcohols.
- The electron withdrawing atom helps to stabilize 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:
Halogen atoms and NO2.
EFFECTS OF Acidity
34. IMPORTANT OF ALCOHOL
Ethanol - solvent for varnishes, perfumes and
flavorings, medium for chemical reactions and in
recrystallization. Also is an important raw material
for synthesis.
Medically, ethanol is classified as a hypnotic (sleep
producer), it is less toxic than other alcohol.
35. Ethanol is prepared both by hydration of ethylene and
by fermentation of sugars. It is the alcohol of alcoholic
beverages.
36. Grignard synthesis
Hydrolysis of alkyl halides
Industrial and laboratory preparations of
ethanol
PREPARATION OF ALCOHOLS
37. GRIGNARD SYNTHESIS
The grignard reagent (RMgX) is prepared by the reaction of
metallic magnesium with the appropriate organic halide.
This reaction is always carried out in an ether solvent,
which is needed to solvate and stabilize the Grignard
reagent as it forms.
Grignard reagents may be made from primary, secondary,
and tertiary alkyl halides, as well as from vinyl and aryl
halides.
Alkyl iodides are the most reactive halides, followed by
bromides and chlorides. Alkyl fluorides generally do not
react.
41. Ketones reacts with Grignard reagents giving
tertiary alcohols.
42. Hydrolysis of alkyl halides is severely limited as a
method of synthesizing alcohol, since alcohol are
usually more available than the corresponding
halides;indeed, the best general preparation of halides
is from alcohols.
For those halides that can undergo elimination, the
formation of alkene must always be considered a
possible side reaction.
HYDROLYSIS OF ALKYL HALIDES
43. 2) First-order substitution: tertiary (and some secondary)
halides
Example:
1) Second-order substitution: primary (and some
secondary halides)
44. There are three principle ways to get the simple alcohols that
are the backbone of aliphatic organic synthesis. These
methods are:
a)hydration of alkenes obtained from the cracking of
petroleum
b)the oxo process from alkenes, carbon monoxide and
hydrogen
c) fermentation of carbohydrate
INDUSTRIAL AND LABORATORY
PREPARATION OF ETHANOL
45. Aldehydes and ketones can be reduced to alcohols
using:
a) lithium aluminium hydride (LiAlH4)
b) sodium borohydride (NaBH4)
c) catalytic hydrogenation
REDUCTION OF ALDEHYDES, KETONES AND
CARBOXYLIC ACIDS
48. Benzoic acid can be reduced to phenylmethanol by using LiAlH4
in ether at low temperatures.
An alkoxide intermediate is formed first.
On adding water, hydrolysis of the intermediate yields the
primary alcohols.
LiAlH4 has no effect on the benzene ring or the double bond.
-COOH is reduced to –CH2OH but the C=C bonds remains
unchanged.
49. Question:
i) Give the structural formulae of L, M and N
ii) How to prepare alcohol A from the
reduction process?
50.
51. Reaction with sodium
Oxidation
Esterification
Halogenation and haloform reactions
Dehydration
Formation of ether (Williamson ether
synthesis)
REACTIONS OF ALCOHOLS
52. Reaction with sodium
Alcohols reacts with Na at room temperature to
form salts (sodium alkoxides) and hydrogen.
For example:
Reactivity of alcohols towards the reactions with
sodium:
CH3 > 1 > 2 > 3
56. Esterification:
- the reaction between an alcohol and a carboxylic acid to
form an ester and H2O.
Esterification
57. Esterification also occurs when alcohols
react with derivatives of carboxylic acids
such as acid chlorides
58. Halogenation and haloform reactions
1) Hydrogen halides (HBr or HCl or HI)
R-OH + H-X → R-X + H2O
Example:
• Reactivity of hydrogen halides decreases in order HI >
HBr > HCl
• Reactivity of alcohols with hydrogen halides:
3 > 2 > 1
59.
60. Dehydration of alcohols will formed alkenes and the
products will followed Saytzeff rules.
Dehydration
Saytzeff rule:
• - A reaction that produces an alkene would favour
the formation of an alkene that has the greatest
number of substituents attached to the C=C group.
61.
62. Involves the SN2 attack of an alkoxide ion on an
unhindered primary alkyl halides.
The alkoxide is made by adding Na, K or NaH to the
alcohol.
R-O- + R’-X → R-O-R’ + X-
alkoxide
(R’ must be primary)
Formation of ether (Williamson ether synthesis)
The alkyl halides (or tosylate) must be primary, so that
a back-side attack is not hindered.
If the alkyl halides is not primary, elimination usually
occurs to form alkenes.
63.
64. Reaction with sodium
Esterification
Halogenation of the ring
Nitration of the ring
REACTIONS OF PHENOLS
71. Question:
Alcohol W is a secondary alcohol with a molecular formula
of C4H10O.
a) Draw and give the IUPAC name for alcohol W.
b) Draw the structural formula for the following
compounds:
i)Compound M
ii)Compound N
iii)Compound O
72. c) Give the correct name for the following:
i) Step 1
ii) Step 2
iii)Reagent A
73.
74. 1) Lucas Test
-The alcohol is shaken with Lucas reagent (a solution
of ZnCl2 in concentratedHCl).
-Tertiary alcohol - Immediate cloudiness (due to the
formation of alkyl chloride).
-Secondary alcohol - Solution turns cloudy within
about 5 minutes.
- Primary alcohol - No cloudiness at room temperature.
TESTS TO DISTINGUISH CLASSES OF
ALCOHOLS
75.
76. 2) Oxidation of alcohols
-only primary and secondary alcohols are oxidised by
hot acidified KMnO4 or hot acidified K2Cr2O7 solution.
-the alcohol is heated with KMnO4 or K2Cr2O7 in the
presence of dilute H2SO4.
- 1o or 2o alcohol:
→ the purple colour of KMnO4 solutiondisappears.
→ the colour of the K2Cr2O7 solution changes from
orange to green.
- 3o alcohol do not react with KMnO4 or K2Cr2O7.
77.
78. HALOFORM TEST TO IDENTIFY METHYL
ALCOHOL GROUP
1) Iodoform:
Ethanol and secondary alcohols containing the group
methyl alcohol group which react with alkaline
solutions of iodine to form triiodomethane (iodoform,
CHI3).
Triiodomethane – a pale yellow solid with a
characteristic smell.
79.
80.
81.
82. Question:
a) Classify each of the following alcohols as
primary, secondary or tertiary.
i) 2-Propanol
ii)4-methylpentanol
iii)2,3-dimethylbutan-2-ol
b) Name a simple test to distinguish 1°, 2°, 3°
alcohol. State the reagents and conditions
required for the test and write down the
expected observations.
83. Answer:
a) i) 2°
ii) 1°
iii) 3°
b) Test: Lucas test
Reagent and conditions : Lucas reagent /
Mixture of HCl and ZnCl2
Observatios:
- Clear homogenous solution change into 2
layers or cloudiness
- Rate of reaction: 3° > 2° > 1° alcohol
88. CHLOROBUTANOL
USES OF CHLOROBUTANOL:
1. It is used as a preservative in injectable, ophthalmic and
intranasal preparations.
2. It can be used as Sedative ,hypnotic and in motion
sickness.
3. Local anesthetic in painful IM injections and dental
preparations.
89. CETOSTERYL ALCOHOL
USES OF CETOSTERYL ALCOHOL:
1. It is used as an emulsion stabilizer, opacifying agent and
boosting surfactant.
2. It acts as an emollient in skin anhydrous formulations.
3. It is commonly used in hair conditioners and other hair
products.
93. PROPYLENE GLYCOL
USES OF PROPYLENE GLYCOL:
1. It is used to make polyester compounds and as a base for
deicing solutions.
2. It is used as an antifreeze in chemical, food and
pharmaceutical industries.
3. It is commonly used as a food additive (to preserve and to
dissolve colors and flavors).
