Phenol is a valuable industrial commodity for the synthesis of various materials and compounds with — Physical Chemistry — Thermodynamics Chemistry Question
Chemistry of phenol
Phenol is a valuable industrial commodity for the synthesis of various materials and compounds with useful properties. Therefore, its annual production totals several million tons. The classical industrial method of phenol production is a two-stage process developed by the Soviet chemist R. Udris in 1942. First, the mixture of benzene A and propene B is compressed under heating in the presence of an acid as a catalyst. Interaction of equal amounts of A and B leads to compound C which is then oxidized with air followed by acidification, which finally results in two products: phenol and compound D also widely used in industry.
High potential of phenol in the synthesis of polymers, drugs, and dyes can be illustrated by the hereunder examples.
The reaction of phenol with D in the presence of an acid gives bisphenol A, which was for the first time synthesized by the Russian chemist A. Dianin in 1891. The treatment of bisphenol A with NaOH leads to E, which reacts with phosgene affording polycarbonate with a monomeric unit F.
The treatment of phenol with diluted nitric acid results in isomeric compounds G and H, which can be separated by steam distillation. The molecule of G has two planes of symmetry (that of the molecule and an orthogonal one), while the plane of the molecule is the only element of symmetry for H. Starting with G, one can obtain paracetamol J via a two-stage process.
Aspirin M can be obtained from phenol in three steps. First, phenol is treated with NaOH and CO2 under heating and high pressure. This reaction gives compound K, which has only one element of symmetry (plane of the molecule). Two equivalents of an acid are required for acidification of K to form compound L. Further acetylation of L affords aspirin M.
Moreover, L is a precursor of a dye Aluminon used for quantitative determination of aluminum and some other metals. Reaction of two equivalents of L with formaldehyde under acidic conditions affords N. Addition of one more equivalent of L to N in the presence of NaNO2 and sulfuric acid yields O, which finally gives Aluminon upon treatment with ammonia.
[VISUAL]
18.1 Write down the structural formulae of A – E and G – O.
Write down the structure of monomeric unit F.
Model Answer
A: Benzene
B: Propene
C: Isopropylbenzene (cumene)
D: Acetone
E: Sodium bis-phenolate (disodium salt of bisphenol A)
F: Polycarbonate monomeric unit (derived from phosgene and bisphenol A)
G: para-Nitrophenol
H: ortho-Nitrophenol
I: para-Aminophenol
J: Paracetamol (N-(4-hydroxyphenyl)acetamide)
K: Disodium salicylate
L: Salicylic acid (2-hydroxybenzoic acid)
M: Aspirin (acetylsalicylic acid)
N: Bis(3-carboxy-4-hydroxyphenyl)methane (an analogue of bisphenol A)
O: Aurintricarboxylic acid (tri-acid, the direct precursor of Aluminon)
Explanation of synthetic pathways:
- The interaction of equal amounts of benzene (A) and propene (B) yields isopropylbenzene or cumene (C) via Friedel-Crafts alkylation. Oxidation and acidification yield phenol and acetone (D).
- Reaction of phenol with acetone (D) under acidic conditions gives bisphenol A. Treating bisphenol A with NaOH yields disodium salt (E). Reaction of (E) with phosgene gives polycarbonate with monomeric unit (F).
- Nitration of phenol with dilute nitric acid gives G (para-nitrophenol) and H (ortho-nitrophenol). Reduction of G (para-nitrophenol) gives para-aminophenol (I). Subsequent acetylation of the amino group of I gives paracetamol (J).
- Reaction of phenol with CO2 in the presence of NaOH under heat and high pressure (Kolbe-Schmitt reaction) yields disodium salicylate (K). Acidification with two equivalents of acid gives salicylic acid (L). Acetylation of L yields aspirin (M).
- Reaction of two equivalents of salicylic acid (L) with formaldehyde under acidic conditions yields N (an analogue of bisphenol A). Reaction of N with a third equivalent of salicylic acid (L) under oxidative conditions (NaNO2/H2SO4) gives tri-acid O (aurintricarboxylic acid), which produces Aluminon upon treatment with ammonia.