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ALCOHOLS� PHENOLS

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OBJECTIVES

• Methods of preparation
• Physical properties
• Identification test
• Pharmaceutical use

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ALCOHOL

• DEFINITION:�� “Those organic compound which containing –OH group, is said to be an alcohol.”� They are generally represented by R–OH.� These are derivatives of H₂O in which hydrogen atom of water is replaced by R group �
• Examples: �� · CH₃OH (methanol)� · CH₃CH₂OH (ethanol)� · CH₃CH₂CH₂OH (propanol)

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Monohydric:

“Those alcohol which contain only one –OH group, called as monohydric alcohol”� e.g. CH₃OH, CH₃CH₂OH

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They are further classified as:

· primary alcohol � ( -OH group is attached with pri. C-atom)

· secondary alcohol� ( -OH group is attached with sec. C-atom)

· tertiary alcohol � ( -OH group is attached with ter. C-atom)

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Dihydric:

those alcohol which contain two –OH group �e.g.

Polyhydric:

those alcohol which contain more than 2 –OH group

e.g.

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PREPARATION OF ALCOHOLS

• Hydrolysis of alkyl halides�� alkyl halides react with aqueous NaOH to form alcohols�� RX + NaOH → ROH + NaX
• Hydration of alkenes�� alkene reaction with sulphuric acid to produce alkyl hydrogen sulphates ( markonikov’s rule followed) alkyl hydrogen sulphates on hydrolysis gives alcohol��

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H₂O

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PREPARATION OF ALCOHOLS

• Hydroboration oxidation of alkene�� alkenes reduce with diborane B2H6. Diborane add as borane BH₃. The positive part of BH₃ is the boron the neg part is the hydrogen�� R-CH=CH₂ + BH₃ → RCH₂CH₂BH₂ → RCH₂CH₂OH
• Reduction of aldehydes & ketones�� ketones can be reduced with H₂/Ni to form corresponding alcohols. Aldehydes give primary alcohol while ketones give sec alcohol�� RCOH + H₂ → RCH₂OH

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H₂O/OH

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PREPARATION OF ALCOHOLS

• Fermentation�� also prepared by fermentation of starch & sugars under the influence of suitable microorganisms �� C₆H₁₂O₆ + yeast → 2CH₃CH₂OH + 2CO₂
• From Grignard reagent�� it react with aldehyde & ketones to form an addition compound which on hydrolysis with dil. Acid gives the corresponding alcohols�� CH₃OCH + RMgX → CH₃CROMgXH → CH₃CROH₂ + MgOHX

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CHEMICAL REACTION OF ALCOHOL

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Alcohol underdo following reactions:

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CHEMICAL REACTION OF ALCOHOL

• Reaction in which C-O bond break� 3° > 2° > 1°� Nu attack
• Reaction in which O-H bond break� 1° > 2° > 3°� Electrophile attack
• Reactions:�

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CHEMICAL REACTION OF ALCOHOL

• With acid metal:� � alcohol react with Na or K to form alkoxide with liberation of H₂ gas�� 2 R-OH + 2Na →2 R-ONa + H₂ � 2 CH₃CH₂-OH + 2Na →2 CH₃CH₂ONa + H₂
• With phosphorus halide:�� alcohol react with phosphorus pentahalide (PX₅) and phosphorus trihalide (PX₅) to form alkyl halide��

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CHEMICAL REACTION OF ALCOHOL

• With thionyl chloride �� alcohol react with thionyl chloride (SOCl₂) to form alkyl chloride�� ���
• With hydrogen halide �� alcohol react with hydrogen halide to form corresponding alkyl halide�� R-OH + HX → R-X +H₂O� CH₃CH₂OH + HBr → CH₃CH₂X +H₂O�

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CHEMICAL REACTION OF ALCOHOL

• Oxidation�� alcohol is converted into aldehyde or ketone by using reagent potassium dichromate (K₂Cr₂O₇)

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CHEMICAL REACTION OF ALCOHOL

• With Grignard reagent �� alcohol react with Grignard reagent (RMgX) to form alkanes�

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• Reduction �� alc. Undergo reduction with conc. Hydroiodic acid to produce alkanes �� ROH + 2 HI → RH + I₂ +H₂O�

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CHEMICAL REACTION OF ALCOHOL

• With nitric acid�� alc. React with nitric acid to form alkyl nitrates� � CH₃CH₂OH + HNO₃ → CH₃CH₂ONO₂ + H₂O
• With carboxylic acid � � alcohol react with carboxylic acid to form esters conc. Sulphuric acid is used as catalyst. The reaction is reversible & can be shifted in the forward direction by removing water � C₂H₅OH + CH₃COOH → CH₃CH₂COOCH₃ + H₂O
• With acid halides / acid anhydrides�� alc. React to form esters ��

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PHARMACEUTICAL APPLICATIONS OF ALCOHOL

• 1. Use in preservatives for biological specimens
• 2. Use in fermentation of yeast ,sugars and starches
• 3. Alcohol are plenty in a diverse range of applications from medicine to cooking
• 4. Methylated spirits used to remove ink from various surface such as metal and plastics
• 5. Use in different cosmetics
• 6. e.g removal of finger nails polish and used in perfumes
• 7. Alcohol used in laboratory industry
• 8. Used as a disinfectant such as phenyl and sanitizer
• 9. Used as a antiseptic like clean needles injection ,surgical blades and forceps
• 10. Used as a pain reliever to subsidise acute pain

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PHYSICAL PROPERTIES

• Alcohols are colorless
• They generally give a sweet smell except for glycerol and a few lower alcohols
• They are flammable and produce a blue flame
• They don’t produce any smoke while burning
• They are generally liquid at room temperature
• They have high boiling point

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IDENTIFICATION TEST

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LUCAS TEST

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IDENTIFICATION TEST

• Iodoform test�� used to determine the presence of methyl group on the adjacent carbon of func. Group attached to the carbon atom

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• Sodium metal test�� it is based on the appearance of brisk effervescence due to liberation of hydrogen gas when alcohol reacts with active metal like sodium�� 2 ROH + 2 Na → 2RONa + H₂

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IDENTIFICATION TEST

• Ester test�� carboxylic acid react with alcohols forming a fruity smell ester. The reaction between an alcohol & a carboxylic acid is called esterification. This reaction is slow due to catalyzed by conc. Sulphuric acid�� ROH + RCOOH → RCOOR + H₂O
• Acetyl chloride test �� alcohol react with acetyl chloride result in the formation of ester & HCl. The resulting HCl on contact with ammonium hydroxide forms a white fumes of ammonium chloride and water�� ROH + CH₃COCl → CH₃COOR + HCl� HCl + NH₄OH → NH₄Cl + H₂O

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PHENOLS

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WHAT IS A PHENOL?�

• An organic compound is aromatic in nature with the structural formula C₆H₅OH. The molecule has a phenyl group (−C₆H₅) attached to a hydroxyl group (−OH). It is slightly acidic and needs careful handling due to its tendency for causing chemical burns.�� It was first obtained from coaltar by Runge in 1834. Phenol is also known as Carbolic acid. Phenols are very commonly present in nature.
• Classification�� phenols are classified as:�� > monohydric phenols� > dihydric phenols� > trihydric phenols

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PHYSICAL PROPERTIES OF PHENOLS

• Colorless, phenolic odor, crystalline
• Melting point 41°C & boiling point 182°C
• Sparingly soluble in water but they are more soluble in water than are alcohols 
• Completely soluble above 68.5°C
• Phenol being an acidic causes blister on skin
• Used as disinfectant
•  in phenols the hydroxyl group is attached to an unsaturated aromatic (alternating double and single bond) hydrocarbon ring such as benzene.
• Phenol (also known as carbolic acid, phenolic acid, or benzenol) is an aromatic organic compound with the molecular formula C ₆H ₅OH

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PREPARATION OF PHENOL

• Dow’s method / from chlorobenzene �� In this method chlorobenzene is treated with 10% NaOH at 360°C and 150 atm, sodium phenoxide on treating wit HCl produces phenol

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• From Sodium Salt of Benzene Sulphonic Acid�� Sodium salt of benzene sulphonic acid reacts with NaOH at 320°C tc give sodium phenoxide which cn treatment with HC1 gives phenol.

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PREPARATION OF PHENOL

• From Benzene Sulphonic Acid�� Benzenesulphonic acid can be obtained from benzene by reacting it with oleum. sodium phenoxide on acidification gives phenol.

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• From cumene �� Cumene, a hydrocarbon, is used to make phenol. Cumene, a hydrocarbon, is used to make phenol. cumene (isopropyl benzene) is oxidized to cumene hydroperoxide. It is converted to phenol and acetone

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PREPARATION OF PHENOL

• From diazonium salts

At 273-278 K, an aromatic primary amine is treated with nitrous acid (NaNO2 + HCl) to form a diazonium salt. Diazonium salts are hydrolyzed to phenols by heating them in water or treating them with dilute acids.

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IDENTIFICATION TEST

• (a) Litmus Test:

Red litmus paper turns blue while blue litmus paper remains unchanged in the presence of a base.

Phenol turns blue litmus paper red. This shows that phenol is acidic in nature. Carboxylic acid also gives this test. Compared to carboxylic acid, phenol is weakly acidic and it does not give an effervescence with aqueous sodium carbonate

• (b) Bromine Water Test:

Phenol undergoes electrophilic substitution reaction with bromine. When bromine water is added to aqueous solution of phenol the brown colour of bromine disappears and a white precipitate of tribromophenol is formed.

The chemical reaction is given below.

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IDENTIFICATION TEST

• (c) Phthalein Dye Test:�� Phenol on heating with phthalic anhydride in the presence of concentrated sulfuric acid forms a colourless condensation compound called phenolphthalein

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• (d) Ferric Chloride Test:

Aqueous solution of phenol reacts with freshly prepared ferric chloride solution gives colored complex (violet colored complex). Most phenols give dark colored solutions.

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IDENTIFICATION TEST

• (e) Libermann’s Test:

Phenol reacts with concentrated sulfuric acid and sodium nitrite forms a yellow colour quinone monoxime complex. With excess of phenol and sulfuric acid a deep blue indophenol complex is formed. On dilution a red colour indophenol is formed which turns to deep blue colour sodium salt solution of indophenol on treatment with sodium hydroxide.

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Blue color

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CHEMICAL REACTIONS OF PHENOL

• Formation of salt�� phenol is acidic, it react with sodium hydroxide or Na metal to form salt

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• Sulphonation �� when phenol is treated with conc. H₂SO₄ at 20°C o-hydroxy benzene sulfonic acid & at 100°C p-hydroxy benzene sulfonic acid is produced

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CHEMICAL REACTIONS OF PHENOL

• With zinc�� phenol is distilled with Zn, low yield of benzene is formed

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• Halogenation�� phenol react with bromine water give 2, 4, 6- tribromophenol. Chlorine is also react in the same way

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CHEMICAL REACTIONS OF PHENOL

• Ester formation�� phenol react with acetyl chloride in the presence of a base to form phenyl esters

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• With formaldehyde�� when phenol is treated with an alkaline solution of formaldehyde a mixture of o & p hydroxybenzyl alcohol is formed

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Con’t

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CHEMICAL REACTIONS OF PHENOL

If the reaction is carried at high temperature and in excess of formaldehyde, plastic (polymer) bakelite is formed

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PHARMACEUTICAL APPLICATIONS OF PHENOL

• In synthesis of many chemicals such as picric acid, pharmaceuticals drugs, plastics, polymers & explosive material
• Used by Hittler in the 2^nd World War
• In manufacturing of mouthwashes & removal of mouth bacteria
• As versatile precursor i.e. aspirin
• As germicide
• Cresol ( methyl phenol ) used as disinfectants, preservatives
• Resorcrinal used as for the treatment of gastric ulcer, analgesic
• Naphthol is used as in Molisch’s test to detect carbohydrates, also arginine in the proteins

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Any question

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