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Important Carbon Compounds

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Important Carbon Compounds - Lesson Summary

The two important carbon compounds are Ethanol and Ethanoic acid

Alcohol:
Molecules in which hydroxy group attached to alkyl groups are the alcohols.
The formula of alochols can be written by replacing hydrogen ("H") from alkanes with hydroxy group ("OH").
R - H + OH → R - OH
Alcohols can be named by replacing "e" from alkanes with "ol".
Alkan -e + ol → Alkanol

Some of the important alcohols are:

             Name of the alcohol                  Chemical formula of alcohol       Methanol     CH 3-OH       Ethanol     CH 3-CH 2-OH       Propanol     CH 3-CH 2-CH 2-OH       Butanol     CH 3-CH 2-CH 2-CH 2-OH       Pentanol     CH 3-CH 2-CH 2-CH 2-CH 2-OH


Ethanol: 
Ethanol is considered as one of the important organic compound.
The molecular formula of ethanol is C2H5OH. It is also called as ethyl alcohol.

Preparation of Ethanol:
Ethanol can be manufactured through fermentation of molasses. 
The process involves slow decomposition of a complex organic compound like molasses into simpler compounds including ethanol, by means of microorganisms like yeast.

Physical Properties of ethyl alcohol:
     •  It is a colourless inflammable and sweet smelling liquid
     •  Is miscible with water
     •  It is a good solvent that dissolves most known substances.
     •  Ethanol can cause drunkenness on consumption, even in small quantities of dilute ethanol.
     •  Extremely poisonous when consumed in pure form (absolute alcohol)

Chemical properties of Ethanol:
It involves in different chemical reactions due to the presence of hydroxy group (-OH).

Reaction of ethanol with sodium:
Ethanol readily reacts with sodium to form sodium ethoxide and hydrogen gas.
2Na + 2CH3CH2OH → 2CH3CH2ONa+ + H2         

Reaction with concentrated sulphuric acid:
Ethanol on heating to a temperature of 443 K with excess concentrated sulphuric acid, gives ethene.

CH3-CH2-OH        Hot Conc. H ₂ SO ₄ →         CH2=CH2+H2O

Oxidatation:

Ethanol undergoes oxidation in presence of Potassium dichromate to form intially ethanal and finally formsfurther oxidised ethanoic acid.

CH3-CH2-OH + K2Cr2O7 → CH3-CHO → CH3-COOH

Esterification:
Reaction of ethanol with carboxylic acids is called esterification reaction. The product formed in this reaction is an ester along with water. 
Esters are sweet smelling substances which are used in making perfumes and as flavoring agents.
Example:
CH3-CH2-OH + CH3-COOH → CH3-COOC2H5 + H2

Uses of Ethanol:
     •  Ethanol is used in pharmaceutical preparations like tincture of iodine, cough syrups, and tonics.
     •  Ethanol is used in the manufacture of organic compounds like acetaldehyde, acetic acid and chloroform.
     •  Ethanol is used as a preservative for biological specimen.



Acetic acid:
The molecular formula of acetic acid is CH3COOH.
5-8% solution of acetic acid in water is called vinegar.
 
Preparation of Ethanoic acid:
Ethanoic acid is prepared by the oxidation of ethanol in the presence of oxidising agents like Alkaline KMnO4  or acidified K2Cr2O7.

CH3-CH2-OH    Alkaline   KMnO 4   or Acidified   K 2 Cr 2 O 7 →          CH3-COOH

Physical Properties of Ethanoic acid:

     •  Ethanoic acid is a colourless corrosive liquid with a pungent odour.
     •  The melting point of pure ethanoic acid is 17 0C.
     •  Ethanoic acid freezes during the winter and is known as glacial acetic acid.
     •  Miscible with water, ether and ethyl alcohol.

Chemical Properties of Ethanoic acid:
Reaction with sodium carbonate:
Ethanoic acid reacts with sodium carbonate to give sodium acetate ,carbon dioxide and water

                    2CH3-COOH + Na2CO3 → 2CH3COO-Na+ + CO2 + H2O

Reaction with sodium hydrogen carbonate:
Ethanoic acid reacts with sodium hydrogen carbonate to give sodium acetate ,carbon dioxide and water.
                    CH3-COOH + NaHCO3 → CH3COO-Na+ + CO2 + H2O

Reaction with base:
Ethanoic acid reacts with bases to give salt and water.
Example:
Reaction of ethanoic acid with sodium hydroxide to form sodium acetate and water.
                         CH3-COOH + NaOH → CH3COONa + H2O

Reaction with sodium hydrogen carbonate, sodiumhydrogen carbonate and with bases are the acidic properties of ethanoic acid.

Saponification:
Esters react in the presence of an acid or a base to give back the alcohol and carboxylic acid. This is called saponification reaction. This is reverse reaction of esterification reaction.

CH3COOC2H5       Sodium Hydroxide →      CH3-COOH + CH3-CH2-OH

Reaction with active metals:

Ethanoic acid reacts with active metals to form metal ethanoate and hydrogen gas.
Example:
                      2CH3COOH + 2Na → 2CH3COONa + H
                     2CH3COOH + Ca → (CH3COO)2Ca + H2

Reduction: 
Ethanoic acid is reduced to ethanol in presence of reducing reagnets like LiAlH4 (Lithium aluminum hydrate), NaBH4 (Sodium borohydrate).
CH3COOH + LiAlH4 → CH3-OH

Uses of Ethanoic acid:
     •  Preserve food items
     •  Manufacture of artificial fibres
     •  Ethanoic acid is used for coagulating latex to prepare rubber from it.
     •  It is used as a reagent in the laboratory.
     •  It is used in the preparation of perfumes.

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