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Classification and Identification of Alcohols and Phenols
Types of Alcohols
Alcohols may be classified as either primary, secondary or tertiary depending on the number of carbon-containing groups attached to the
carbon- bearing hydroxyl group.
R CH2 OH
Primary Alcohol
CH R'
OH
Secondary Alcohol
R
R C
R'
R''
OH
Tertiary Alcohol
Examples of Alcohols
CH3CH2 OH
ethanola primary alcohol
H3CHC
CH3
OH
2-propanola secondary alcohol C
CH3
H3C
CH3
OH
2-methyl-2-propanola tertiary alcohol
Phenols
A phenol has a hydroxyl group bonded directly to a carbon that is part of an aromatic ring.
OH
phenol
CH3
OH
CH
CH3H3C
2-isopropyl-5-methylphenol
Properties of Alcohols and Phenols
• Alcohols and phenols are polar because of the hydroxyl group
• The polar side and hydrogen bonding allows them to dissolve in water
• The non-polar side allows them to dissolve in certain organic solvents
• Alcohols are not acidic• Phenols are acidic
OR
H
O H
HHydrogen bonding of the hydroxyl group with water
Chemical Properties
A series of tests can be used to distinguish between alcohol types and phenols:
• Solubility• pH• Lucas Test• Chromic Acid Test• Iodoform Test• Iron(III)chloride Test
Lucas Test
Used to distinguish between a primary, secondary and tertiary alcohol.
CH3CH2 OH + HCl + ZnCl2 No reaction
Primary alcohol
(CH3)2CH OH + HCl + ZnCl2 (CH3)2CH Cl + H2O (10 min. heat)Secondary alcohol Insoluble
(CH3)3C OH + HCl + ZnCl2 (CH3)3C Cl + H2O (< 5 min.)
Tertiary alcohol Insoluble
Chromic Acid Test
Used to distinguish primary and secondary alcohols from tertiary alcohols.
Phenols produce a brown tarry mass when combined with chromic acid.
CH3CH2 OH + 4H2CrO4 + 6H2SO43 H3C C OH
O
+ 2Cr2(SO4)3 + 13H2O3
Primary alcohol Brown-red Carboxylic acid Blue-green
H3C CH
OH
CH3 +3 2H2CrO4 + 3H2SO4 3H3C C CH3
O
+ Cr2(SO4)3 + 8H2O
Secondary alcohol Brown-red Ketone Blue-green
(CH3)3C OH + H2CrO4 + H2SO4 No reaction
Tertiary alcohol Brown-red
Iodoform Test
This test is used to distinguish alcohols with the partial structure R-CH3CH(OH) from other alcohols. Phenols also react.
R CHCH3
OH
+ 4I2 + 6NaOH R C O-Na+
O
+ 5NaI + 5H20 + HCI3 (s)
Iodoformyellow
OH
+ 3I2
I
OH
II
+ 3HI
Triiodophenolyellow precipitate
Acidity of Phenol
Phenols are acidic and dissolve in a basic solution. Alcohols are not acidic and will not dissolve in a basic solution.
OH O-
+ +HO- H2O
Iron(III) Chloride Test
This test distinguishes between alcohols and phenols.
OOHFe
Cl
Cl+ +FeCl3 HCl
Light yellow Violet color
The resulting color change can vary from green to purple.
Alcohols produce no color change.
Caution!
• Chromic acid is very corrosive.
• Phenols are toxic, avoid skin contact.
• Your instructor will dispense all of the chromic acid as well as police the hazardous waste.
DO NOT THROW ANY CHEMICALS DOWN THE DRAIN!!!
EACH HAS AN APPROPRIATE WASTE CONTAINER IN THE HOOD!!
Potential Health Effects
• Inhalation: difficulty breathing, sore throat, coughing, dizziness, dullness, headache, drowsiness, sneezing, wheezing, central nervous system depression, narcosis, unconsciousness, choking, inflammation of the upper respiratory system, pulmonary edema, circulatory failure, coma, increased sweating, pulmonary edema, reduced body temperature, euphoria, cyanosis, tissue necrosis, convulsion, chemical pneumonitis and death
• Ingestion: sore throat, narcosis, abdominal pain, nausea, headache, dizziness, diarrhea, kidney damage, liver damage, hearing damage, burns and inflammation of the mouth, throat, esophagus and stomach, brown stains around the mouth, low blood pressure, tachycardia, vomiting , muscular weakness, increased sweating and death
• Skin contact: sensitization, irritant, redness, pain, drying, cracking, defatting of the skin ulcers, rash and can be absorbed through the skin
• Eye contact: stinging, tearing, redness, pain of the eyes, blurred vision, corneal damage and blindness
• Tumorigens, mutagens, carcinogens and reproductive effectors
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