Preparation of phenols?
phenols can be prepared by the following methods.
1) hydrolysis of cholorobenzene:
in this process, chlorobenzene which can be obtained by the cholorinationof benzene, is heated at 350*C under high pressure with aqueous sodium hydroxide to get sodium phenoxide, which on acidification yields phenol.
2) pyrolosis of sodium benzenesulphonate:
this, the first commercial process for industrial synthesizing phenol , was developed in Germany in 1890. sodium benzenesulphonate is melted with sodium hydrooxide at 350*C to produce sodium phenoxide, which on acidification yields phenol.
3) oxidaton of cumene:
benzene is alkylated with propene to produce cumene, which is oxidized with air to produce cumene hydroperoxide, which on treatment with 10% sulfuric acid undergoes a hydrolytic rearrangement to yield phenol and acetone.
Phenols are much more acidic than alcohols. This is indicated in the order of acidity constant: Ka Gernal formula PHENOLS 10-10 Ar-OH ALCOHOLS 10-18 C-OH Phenols are more acidic due to the formation of phenoxide ions & phenoxide ions are stable due to resonance, the negative charge on oxygen is spread throughout the benzene ring & is delocalised. On the other hand no resonance is possible in alkoxide ions derived from alcohol. The negative charge…
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Phenols are ''more acidic'' than alcohol since phenols can delocalize its electrons. Also, phenols can remove its hydrogen to make it more stable. The ion is called the phenolate ion. Acidity depends on the concentration of H+. Due to higher electronegativity of sp2 hybridised carbon of phenol the electron density on the oxygen decreases and hence increases the polarity O-H making the phenol unstable compared to phenolate, so it is more acidic. The C6H5-group is…