Chapter:11

What are Alcohol Phenol and Ether ?

Alcohols

Alcohol contains one or more hydroxy (OH) group(s) directly attached to a carbon atom.

$$(\text{Methane})\space\text{CH}_4\space{\xrightarrow[\text{-OH}]{\text{-H}}}\text{CH}_3\text{OH}(\text{Methyl alcohol})\space\space\space\space\space\space\space\text{R-H}{\xrightarrow[\text{-OH}]{\text{-H}}}\text{R}-\text{OH}(\text{alcohol})$$

Classification Of Alcohols

  • C2H5OH : Monohydric alcohol
  • CH2OH-CH2OH : Dihydric alcohol
  • HOH2C-CHOH-CH2OH : Trihydric alcohol

Nomenclature Of Alcohols

Common and IUPAC Names of Some Alcohols

Cyclic alcohols are named using the prefix cyclo and considering the -OH group attached to C-1

NOMENCLATURE OF ALCOHOLS
Cyclic alcohols

Preparation Of Alcohols

  • By Hydrolysis of Haloalkanes :
    R-X + aq.KOH → ROH + KX
  • By Reduction of Carbonyl Compounds :
    4RCOOH + 3LiAlH4 → 4RCH2OH (1°alcohol)
  • Hydroboration-Oxidation :
Hydroboration-Oxidation

Hydroxylation of Alkenes :

Hydroxylation of Alkenes :

Physical Properties Of Alcohol

  • Lower alcohols are liquid at room temperature while higher ones are solid.
  • High boiling point due to presence of intermolecular hydrogen bonding. Order of Boiling Point : primary > secondary > tertiary
  • Solubility in water decreases with increase in molecular mass due to decrease in extent of intermolecular hydrogen bonding.

Chemical Properties Of Alcohol

  • Alcohol’s Reaction with Metal :
    ROH + Na 2RO+Na– + H2
  • Formation of Halides : 3ROH + P+l2→3Rl + H3PO3
  • Reaction with HNO3: R-OH + HO-NO2→R-O-NO2
  • Reaction with Carboxylic Acid (Esterification)
    : R-OH + R’-COOH + H+ ↔ R’ - COOR
  • Reaction with Grignard Reagent :
    R’OH + RMgX→RH + R’OMgX
  • Reduction of Alcohol:
    ROH + 2HI + Red P→RH + I2 + H2O
  • Dehydration of Alcohol : Dehydration of alcohols takes place in acidic medium. Intramolecular dehydration leads to the formation of alkene while inter molecular dehydration which forms ether. Ease of dehydration: 3° > 2° > 1°
  • Satyzeff’s Rule : Elimination through b carbon containing minimum b hydrogen.
Satyzeff’s Rule
  • Oxidation of Alcohol: RCH2–OH + [O] → RCHO → RCOOH RCH2 + OH + [O] + PCC → RCHO
  • Haloform Reaction: Compound containing CH3CO–group (or compound on oxidation gives CH3CO–group) which is attached with a C or H, in presence of halogen and mild alkali gives haloform. CH3-CH2-COCH2-CH3, CH3-CO-Cl. CH3COOH will not respond to haloform reaction while CH3CH2OH will respond to haloform Reaction.
Haloform Reaction:

Test for Alcohols

  • Lucas Test
  • Victor Meyer test

Uses Of Alcohol

  • Denatured alcohol : A toxic alcohol used as a fuel or solvent.
  • Rubbing alcohol : A denatured alcohol used in topical applications.
  • Propanol : Used to sterilize
  • Alcoholic beverages : Any drink containing ethanol.
  • Alcohol fuel: An alternative fuel

Phenols

  • A Phenol contains one or more hydroxyl group (OH) attached to a carbon atom (s) of the benzene ring.

$$\text{C}_6\text{H}_5-\text{H}\space{\xrightarrow[\text{+OH}]{\text{-H}}}\space\text{C}_6\text{H}_5\text{OH}\space(\text{Phenol})$$

  • The simplest hydroxy derivative of benzene is phenol, it is its common name and also an accepted IUPAC name. As the structure of phenol involves a benzene ring, in its substituted compounds the terms ortho (1,2-disubstituted), meta (1,3-disubstituted) and para (1,4-disubstituted) are often used in the common names.
PHENOLS

Common Name: Phenol o-Cresol m-Cresol p-Cresol

IUPAC Name: Phenol 2-Methyl phenol 3-Methyl phenol 4-Methyl phenol

  • Dihydroxy derivatives of benzene are known as 1, 2-, 1, 3- and 1, 4-benzenediol.
PHENOLS

Common Name: Catechol Resorcinol Quinol Hydroquinone

IUPAC Name: Benzene-1, 2-diol Benzene-1, 3-diol Benzene-1, 4-diol

Preparation Of Phenol

  • Hydrolysis of chlorobenzene: (Dow’s process)
PREPARATION OF PHENOL
  • Alkali fusion of Sodium benzene sulfonate
PREPARATION OF PHENOL
  • Aromatic Nucleophilic Substitution of Nitro Aryl Halides
PREPARATION OF PHENOL
  • Distillation of phenolic acids with soda-lime produces phenols, e.g. sodium salicylate gives phenol.
PREPARATION OF PHENOL

Physical Properties Of Phenols

  • Phenol is a colorless, toxic, corrosive, needle shaped solid.
  • Phenol liquifies easily due to high hygroscopic nature.
  • Phenol is less soluble in water, but readily soluble in organic solvents.
  • Simplest phenols, because of hydrogen bonding have quite high boiling points.
  • o-nitrophenol is, steam volatile and also is less soluble in water because of intramolecular hydrogen bonding.

Chemical Properties Of Phenols

Formation of Esters : Phenyl esters (RCOOAr) are not formed directly from RCOOH. Instead, acid chlorides or anhydrides are reacted with ArOH in the presence of strong base.

(CH3CO)2O + C6H5OH + NaOH →CH3COOC6H5 + CH3COONa + H2O

  • Displacement of OH group :

$$\text{ArOH + Zn}\space{\xrightarrow{\Delta}}\space\text{ArH + ZnO} \text{(poor yields)}$$

  • Hydrogenation
Hydrogenation
  • Oxidation to Quionones:
Oxidation to Quionones
  • Electrophilic Substitution:

The –OH and even more so the—O(phenoxide) are strongly activating ortho, para-directing.

Electrophilic Substitution

Special mild conditions are needed to achieve electrophilic monosubstitution in phenols because their high reactivity favors both polysubstitution and oxidation.

Uses Of Phenols

  • Several commercial compounds are synthesized from a precursor containing phenol.
  • Phenol is included in the production of plywood, ear and nose drops and disinfectants.
  • Phenol are widely used as an antiseptic and disinfectant in several mouthwash, deodorant, lotion and soap.
  • They also used in manufacturing of drugs like aspirin, salo, phenacetin, salicylic acid etc.
  • Phenol used in manufacturing of resins like bakalite which used in manufacturing of electrical goods like plugs and switches etc.
  • The nitro derivatie of phenol like 2,4,6-trinitrophenol (picric acid) used to make explosives and dyeing wool and silk.
  • Phenols are also used in preparation of other chemicals like; azo dyes, phenolphthalein and Cyclohexane.

Ethers

  • An ether contains an alkoxy/aryloxy group (R-O/Ar-O)in place of the H atom of a hydrocarbon.
ETHERS

$$\text{R—H}\space{\xrightarrow[\text{+RO}^]{\text{-H}}}\space\text{R—O—R}\space (\text{aliphatic ether}) \space\space\space\space\space\text{Ar—H}\space{\xrightarrow[\text{+RO}^-]{\text{-H}}}\space\text{Ar—O—R}\space(\text{Aromatic ether})$$

  • Common names of ethers are derived from the names of alkyl/aryl groups written as separate words in alphabetical order and adding the word `ether’ at the end. For example, CH3OC2H5 is ethyle methyl ether. If both the alkyl groups are the same, the prefix `di’ is added before the alkyl group. For example, C2H5OC2H5 is diethyl ether.
  • Structures of Functional Group-In alcohols, the oxygen of the -OH group is attached by a sigma σ bond formed by the overlap of an sp3 hybridized orbital of carbon with an sp3 hybridized orbital of oxygen.
  • According to the IUPAC system of nomenclature, others are regarded as hydrocarbon derivatives in which a hydrogen atom is replaced by an -OR or -OAr group, where R and Ar represent alkyl and aryl groups, respectively. The larger (R) group being chosen as the parent hydrocarbon. The names of a few ethers are given as examples in the Table below :

Common and IUPAC Names of Some Ethers

Common and IUPAC Names of Some Ethers

Preparation Of Ethers

  • From alcohols :

$$\text{CH}_3\text{CH}_2\text{OH}\space{\xrightarrow[140°C]{\text{H}_2\text{SO}_4}}\space\text{CH}_3\text{CH}_2–\text{O}–\text{CH}_2\text{CH}_3\space (\text{Ether})$$

  • Williamson’s synthesis 
Williamson’s synthesis

$$\text{R-X}+\text{Na}^{+}-O-R'{\xrightarrow[]{}R-O-R’ + Na^+X^-}$$

In case of tertiary substrate elimination occurs giving alkenes.

  • From alkenes

Physical Properties Of Phenols

From alkenes
  • From Grignard reagent : Treating α halo ethers with suitable Grignard reagents.
From Grignard reagent

On standing in contact with air, most aliphatic ethers are converted slowly into unstable peroxides. The presence of peroxides is indicated by formation of a red colour when the ether is shaken with an aqueous solution of ferrous ammonium sulphate and potassium thiocyanate.

  • Halogenation of Ethers :
Halogenation of Ethers :
  • Ethers as base :
Ethers as base
  • Reaction With cold conc. HI/HBr :

R—O—R’ + Cold HI→ R-OH + R’I (R’<R)

  • Hot conc. HI/HBr :
R—O—R’ + Hot HI→ RI + R’I + H2O
  • Electrophilic substitution reactions :
Electrophilic substitution reactions

Uses Of Ethers

  • In the past, ethers were commonly used as a general anaesthetic in surgery. They are no longer a common anaesthetic due to their high flammability.
  • Useful solvents for other organic compounds such as fats and oils.
  • Ethers with higher molecular masses can be used as solvents for varnishes and lacquers.
  • Dimethyl ether is used as a propellant for aerosol sprays.
  • Produces excellent relaxation of the muscles, pulse rate and rate of respiration.