Note on Physical property of phenol.

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A physical property of phenol.

The physical property of phenol is as described as below.

  1. Solubility.
  2. Boiling point.

1. Solubility.

The presence of -OH group in phenol permits the formation of intermolecular H-bond with water molecule whereas hydrophobic phenyl group tends to decrease the solubility. The net results are that phenol is slightly soluble in water.

2. Boiling point.

Since phenols can form intermolecular H-bond among themselves, they boil at a higher temperature than the corresponding haloarenes aromatic hydrocarbon. etc.

Important question.

P-nitro phenol boils at higher temperature than its isomer O-nitrophenol Why?.

Image result for O-nitrophenol

O-nitro Phenol

Image result for P-nitrophenol

P-nitro phenol

In O-nitro phenol, intramolecular H- bond is formed between H of -OH group and O of an NO2 group as shown but in P-nitro phenol, no intermolecular H-bond is formed. So, in P-nitrophenol intermolecular h bond is formed which increase its boiling point.

Some commercial important alcohol and phenol.

1) methanol or methyl alcohol

It occurs in nature in the form of esters. For example, oil of wintergreen is known to contain methyl salicylate. Since it was formerly prepared chiefly from wood by a process known as destructive distillation. It is also called wood spirit or wood naphtha.

It can be prepared by any of the general methods of preparation of alcohols. On a commercial scale, it is manufactured from water gas is mixed with half of its volume of hydrogen in ratio 1:1 . To manufacture methanol , water gas is mixed with half of its volume of hydrogen and is compressed to 200-atmosphere pressure. The compressed gaseous mixture is then passed over a Zno-Cr2o3 catalyst at 3000C.

$$\underbrace{CO+H_2}_{Water\,gas}+H_2\xrightarrow{ZnO-Cr_2O_3\,200\,atm\,300^0C}\underbrace{CH_3-OH}_{Methanol}$$

Properties:

Methyl alcohol is a colourless mobile liquid having a specific gravity 0.793 and boiling point 650C. It has a sharp wine like odour and a burning taste. It is miscible with water in all proportions, the mixing being attended by a contraction in volume. It is an excellent solvent for several organic substances such as oils, fats, etc. Methyl alcohol is poisonous and when taken internally it causes blindness or even death . It gives most of the general reactions of alcohols.

Uses:

Methanol is used

(a) As a solvent for nitrocellulose , resins , dyes , plastics, paints, varnishes etc.

(b) As an antifreeze for automobile radiators.

(c) for denaturing ethanol.

(d) as a motor fuel

(e) as the dehydrator for nature gas.

(f) in the manufacture of perfumes, drugs , formaldehyde, and dimethyl terephthalate

Tests

(a) about 1 ml of methyl alcohol is taken in a test tube and, a pinch of salicylic acid and few drops of coneH2SO4 are added. The contents are the warmed bath for a few minutes . Methyl salicylate is produced which is recognised by characteristic fragrant smell.

(b) Few drops of methyl alcohol are taken in a wide mouth test tube . a piece of copper gauze is heated to redness and s dropped into the rest tube. methyl alcohol is oxidised to formaldehyde which is at once recognised by its characteristics pungent odour.

(c) A small quantity of methyl alcohol is added to some water contained in a test tube. A spiral copper wire is heated to redness in the flame of bunsen burner and is plunged into the solution. The process is repeated for several times and the solution is cooled. Now , few drops of a dilute solution of resorcinol are added and cone . H2SO4 is poured along the side of the inclined test tube so as to form a lower layer. At the junction of the liquid , a pink ring appears with a thick white precipitate above it.

Reference.

Bahl, B S, Bahl, and Arun.Advanced Organic chemistry.S. Chand and company Ltd., n.d.

Sthapit, M K, R R Pradhananga, and K B Bajracharya.Foundations of chemistry.Taleju Prakashan, n.d.

Tewari, K S, S N Mehrotra, and N K Vishnoi.A textbook of organic chemistry.Vikash publishing House Pvt. ltd., n.d.

Verma, N K and S K Khanna.Compressive chemistry.8th edition. Laxmi publications P. Ltd., 1999.

  1. The presence of -OH group in phenol permits the formation of intermolecular H-bond with water molecule whereas hydrophobic phenyl group tends to decrease the solubility. The net results are that phenol is slightly soluble in water.
  2. Since phenols can form intermolecular H-bond among themselves, they boil at a higher temperature than the corresponding haloarenes aromatic hydrocarbon. etc.

  3. It occurs in nature in the form of esters. For example, oil of wintergreen is known to contain methyl salicylate. Since it was formerly prepared chiefly from wood by a process known as destructive distillation. It is also called wood spirit or wood naphtha

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