Quick revision of Alcohol ICSE 2014

Alcohols

General Formula:       C_nH_{2n +1} OH

Functional Group:       OH

IUPAC Name :             Prefix + Wordroot +primary suffix + secondary suffix (‘ol’)

Methyl Alcohol:           Meth + ane + ol = Methanol.

Laboratory preparation:

·         By reaction of methyl chloride with aq.KOH

CH₃Cl + KOH(aq)               ^Boil            CH₃OH + KCl

·         By reaction of methyl bromide with aq.KOH

CH₃Br + KOH(aq)           ^Boil         CH₃OH + KBr

The same method can be used to prepare ethanol also-

CH₃CH₂Cl + KOH(aq)                  ^Boil         CH₃CH₂OH + KCl

CH₃CH₂Br + KOH(aq)                  ^Boil         CH₃CH₂OH + KBr

Industrial preparation:

·         By catalytic reduction of water gas-

CO + H₂ + H₂     ^{Cr2O3 +ZnO, 350 C, 200Atm}           CH₃OH

·         Industrial preparation of ethyl alcohol-

By hydration of Alkenes-

CH₂=CH₂ + H₂SO₄       ^{80 C/ 30atm}                 CH₃CH₂HSO₄

                                                        ^{Ethyl Hydrogen sulphate}

CH₃CH₂HSO₄   + H₂O                               CH₃CH₂OH + H₂SO₄

^{Ethyl Hydrogen sulphate}

By fermentation of carbohydrates-

(Fermentation- Anaerobic breakdown of carbohydrates into alcohol and carbon di oxide)

(C₆H₁₀O₅)_Starch + H₂O     ^diastase                                          C₁₂ H₂₂O₁₁

C₁₂ H₂₂O₁₁        + H₂O      ^hydrolysis                                    2C₆H₁₂O₆

C₆H₁₂O₆         ^Zymase            2C₂H₅OH + 2CO₂

Properties-

Physical

Methanol                                                                     Ethanol

Colour                                     Colourless                                                                     Colourless

Taste                                       Burning, poisonous                                                         Burning

Smell                                       Sweet                                                                           Sweet

Solubility                                 Soluble in water                                                             Soluble in water

Boiling point                            64.5^oC                                                                           78.3^oC

Flammability                           Inflammable                                                                  Inflammable

Chemical

Methanol                                                         Ethanol

With Na metal 2CH₃OH + 2Naà2CH₃ONa + H₂               2CH₃ CH₂OH + Naà2CH₃CH₂ONa + H₂

With PCl₅                     CH₃OH + PCl₅ à CH₃Cl + POCl₃ + HCl      CH₃ CH₂OH + PCl₅ àCH₃CH₂Cl + POCl₃ + HCl