First, the experimental principle
Benzyl alcohol and benzoic acid were prepared from benzaldehyde by Cannizzaro reaction.
Canizaro reaction refers to the disproportionation reaction of aldehyde without α -active hydrogen under the action of concentrated NaOH or KOH water or alcohol solution. This reaction is characterized by simultaneous oxidation and reduction of aldehydes. One molecule of aldehyde is oxidized to carboxylic acid (which becomes carboxylate in alkaline solution) and the other molecule is reduced to alcohol.
Main reaction:
Mechanism: Aldehyde first undergoes nucleophilic addition reaction with hydroxyl anion to obtain anion, and then hydrogen on carbon is transferred to carbonyl group of another molecule with a pair of electrons in the form of hydrogen anion.
Second, the physical constants of reaction reagents, products and by-products
name
molecular weight
Character; Role; letter
melting point
boiling point
density
refractive index
solubility
water
ethanol
ether
Phenylaldehyde
phenyl aldehyde
106. 13
Colorless liquid bitter almond flavor
-26
178. 1
1.04 15
1.5463
slight soluble
∞
∞
benzoic acid
benzoic acid
122. 12
White flake or needle crystal
122.4
248
1.26594 15
1.504
slight soluble
solvable
solvable
benzyl alcohol
benzyl alcohol
108. 15
Colorless liquid with fragrance.
- 15.3
205.35
1.04 19
1.5396
slight soluble
dissolve
dissolve
Third, drugs.
name
actual amount
Theoretical dose
Excess percentage
theoretical yield
Phenylaldehyde
14g (13.5ml, 0.13mol)
14g (13.5ml, 0.13mol)
potassium hydroxide
12g(0.2 1 mol)
3.7 1 g (0.065 mol)
223%
concentrated hydrochloric acid
17.5ml (0.2 1 mol)
ether
45 ml
benzoic acid
7.94 g (0.065 mol)
benzyl alcohol
7.03 g (6.74 ml, 0.065 mol)