dr. shatha alaqeel. roh aroh alcohol phenol classification and nomenclature of alcohols
TRANSCRIPT
Dr. Shatha Alaqeel
ROH ArOHAlcohol Phenol OH SP2
OR HC
SP3
Classification and Nomenclature of alcohols
CH3 OH CH2R OH CHR OH
R'
CR OH
R'
R''
Carbinol Primary alcohol Secondary alcohol Tertiary alcohol
Nomenclature1) Common Nomenclature
Alkyl + alcohol
CH3CH2OH CH2=CHOH CH2=CHCH2OH
Ethyl alcohol Vinyl alcohol Allyl alcohol
2 )IUPAC Nomenclature1) Select the longest continuous
carbon chain to which the hydroxyl is directly attached.
2) Change the name of the alkane corresponding to this chain by dropping the final -e and adding the suffix –ol
3) Number the longest continuous carbon chain so as to give the carbon atom bearing the hydroxyl group the lower number.
CH3CH3
OHCH3
CH3OH
CH3Cl
OH
CH3
4-Ethyl-2-hexanol 5-Chloro-3-methyl-1-heptanol 3-Methyl-1-cyclohexanol
Primary alcohol CH3OH CH3CH2OH
CH2=CHCH2OHCommon Methyl alcohol Ethyl alcohol Allyl
alcoholIUPAC Methanol Ethanol 2-
Propen-1-olSecondary and tertiary alcohol
Isopropyl alcohol Cyclopentyl alcohol
Methylcyclohexyl alcohol 2-Propanol Cyclopentanol 1-Methyl-1-cyclohexanol
CH3 CH CH3
OH
OHCH3
OH
4) OH group is preferred over the double or triple bond in numbering.OH
5-Hepten-2-ol
notice the removal of the (e)
CH3CHC=CH2
CH2CH3
OH
3-Ethyl-3-buten-2-ol
5) If a compound contains both OH and a double or triple bond, choose the chain that include them both even if this is not the longest chain
CH2CH3
OH
CHOH CH3
CH2
CH3OH
3-buten-2-ol 4-Pentyn-1-ol5-Ethyl-5-hexen-3-ol
8
2-Cyclohexenol
4-Chloro-3-methyl-3-octen-1-ol
OH
ClHO
Alcohols containing two hydroxyl groups are commonly called gylcols. In the IUPAC system, the suffix diol is added to the name of the parent hydrocarbon when two hydroxyl groups are present, and the suffix triol is added when there are three OH groups.
OH OH CH3
OHOH
OH
OH
OH
1,2-Ethanediol
Ethylene glycol
1,2-Propanediol
Propylene glycol
1,2,3-Propanetriol
Glycerol or Glycerin
Nomenclature of Phenols2) Compounds that have a hydroxyl group
attached directly to a benzene ring are called phenolsOH OH
NH2
OH
NO2
Br
OH
NO2
NO2
O2N Cl
Cl
ClCl
Cl
OH
Phenol p-Aminophenol 4-Bromo-2-nitrophenol 2,4,6-Trinitrophenol Pentachlorophenol
OH
CH3
OH
CH3
OH
CH3o-Cresol m-Cresol p-Cresol
OH
OH
OH
OH OH
OH OH
OH
OH
Catechol Resorcinol
PyrogallolHydroquinone
Physical Properties of Alcohols & PhenolsSolubility of alcohols The first three members
are completely miscible with water. The solubility rapidly decreases with increase in molecular mass. The higher members are almost insoluble in water but are soluble in organic solvents like benzene, ether etc.
The solubility of lower alcohols is due to the existence of hydrogen bonds between water and polar -OH group of alcohol molecules. Phenols too are sparingly soluble in water. The -OH group in alcohols and phenols contain a hydrogen bonded to an electronegative oxygen atom. Thus they form hydrogen bonds with water molecules.
The solubility increases with branching of chain.
Phenols are sparingly soluble in water but readily soluble in organic solvents such as alcohol and ether.
•Boiling points of alcohols Boiling point of alcohols are much higher than those of alkenes, halo alkenes or ethers of comparable molecular masses. This is because in alcohols intermolecular hydrogen bonding exists due to which a large amount of energy is required to break these bonds.•Among isomeric alcohols, the boiling point
decreases with increase in branching in the alkyl groupBoiling points of 1o alcohol < 2o alcohol < 3o alcohol•As number of hydroxyl groups increase the solubility and boiling points increase.
Alcohols have weak acidic properties.Phenol is a strong acid than alcohols
because the negative charge in oxygen is dispersed by resonance through the benzene ring.
Acidity of Alcohols & Phenols
Introduction of electron-withdrawing groups, such as NO2 or CN, on the ring increases the acidity of phenol, introducing EDG decrease the acidity of phenols
OH
NO2
NO2
O2N
OH
NO2
NO2
> >
OH
NO2
OH
> >
OH
CH3
Alcohols react with Na (or K) like water to give the alkoxide
Preparation of alcoholsPreparation of alcohols1- From alkenes
CH3
+CH3
H
OHOH2H2SO4
KMnO4 / OH-
OH
OH
1) RCO3H
2) H3O+
OH
OH
2- From alkyl halide
3- From aldehyde, ketone and carboxylic acid
Cl dil KOHOH
CH3
CH3
CH3BrOH2
CH3
CH3
CH3OH
R C
O
H
1) LiAlH4 0r NaBH4
2) H3O+
R CH2 OH
1) LiAlH4 0r NaBH4
2) H3O+
R CH OH
R'
R C R'
O
R C
O
OH
1) LiAlH4
2) H3O+
R CH2 OH
4- From Grignard reagent
R C
O
H
R CH OH
R'
R C OH
R'
R''
R C R'
O
R C
O
OR'
R C OH
R''
R''
+ R'MgX1) Dry ether
2) H2O
+ R''MgX
+ 2 R''MgX
1) Dry ether
2) H2O
1) Dry ether
2) H2O
CH3 C
O
H
CH3 CH
OH
C2H5+ C2H5MgX1) Dry ether
2) H2O
+ CH3MgX1) Dry ether
2) H2O
OCH3
OH
CH3 C
O
OC2H5
CH3 C OH
CH3
CH3
+ 2 CH3MgX 1) Dry ether
2) H2O
Preparation of Phenols1- Hydrolysis of Diazonium salts
2- Fusion of sodium with benzene-sulfonates:
3- From alkyl halide:
N2+Cl
-
H2SO4 / H2O
Heat
OH
+ N2
SO3H
NaOH / 350
O-Na
+
H3O+
OH
Cl
NaOH / 350
O-Na
+
H3O+
OH
300 atm
Reaction of Alcohols and PhenolsReaction of Alcohols and Phenols1- Salt Formation
R OH + 2 Na R O-Na
+2 + H2
Sodium alkoxideAlcohol as acid
CH3 OH + Na CH3 O-Na
+
Sodium MethoxideMethanol
2
OH
+ Na
O-Na
+
Sodium Phenoxide
2- Dehydration
3- Ester formation
CH3 CH3
OH
CH2CH3
CH3 CH3
+ OH2
+ OH2
1-Butene minor
2-Butene major
R C
O
OHR C
O
OR'
+ R'OHH
+
+ OH2
COOH
+ CH3OHH
+C
O
OCH3
+ OH2
4- Reaction with alkyl halide
R OH + HX or SOX2 , PX3, PX5 Heat
R XZnCl2
H H
R C O + [O] R C O + H2O
H H
H H
R C O + [O] R C O + H2O
R R
R H
R C O + [O]
R
This is possible in 1° and 2° alcohols but not in 3° alcohols.
1°
2°
3°
21
For oxidation to take place easily you must have two hydrogen atoms on adjacent C For oxidation to take place easily you must have two hydrogen atoms on adjacent C and O atoms.and O atoms.
Alcohols can be oxidised depending on their classAlcohols can be oxidised depending on their class5)5) Oxidation Of AlcoholsOxidation Of Alcohols
R CH2 OHCu or CrO3 / pyridine
heat
OR
HPrimary alcohol adehyde
CH3 CH2 OHCu or CrO3 / pyridine
heat
OCH3
H
weak oxidizing reagent
R CH2 OHH2Cr2O7 or K2Cr2O7/ H
+
or KMnO4 / heat
OR
OHPrimary alcohol carboxylic acid
R CH OH
R'
K2Cr2O7 or KMnO4
heat
OR
R'Secondary alcohol ketone
OHOK2Cr2O7 / H
+
R C OH
R'
R''
H2CrO7 / H+
heat
Tertiary alcohol
No reaction
OH
H2CrO7 or Na2CrO7 / H+
or KMnO4 / heat
O
O
OH
OHPhenolp-Benzoquinone Hydroquinone
KMnO4 / heat
6- Reaction of aromatic ring of phenols
OH
Br2 / H2O
OH
Br
BrBr
Br2 / CCl4
Br
OH
+Br
OH
dil HNO3
O2N
OH
+NO2
OH
conc HNO3
OH
NO2
NO2
O2N
conc H2SO4
OH
SO3H
+
OH
SO3H