Friday, July 10, 2009
Thursday, July 9, 2009
Ethanol
Halogenation
Ethanol reacts with hydrogen halides to produce ethyl halides such as ethyl chloride and ethyl bromide:
CH3CH2OH + HCl → CH3CH2Cl + H2O
HCl reaction requires a catalyst such as zinc chloride. Hydrogen chloride in the presence of their respective zinc chloride is known as Lucas reagent.
CH3CH2OH + HBr → CH3CH2Br + H2O
HBr requires refluxing with a sulfuric acid catalyst.
Ethyl halides can also be produced by reacting ethanol with more specialized halogenating agents, such as thionyl chloride for preparing ethyl chloride, or phosphorus tribromide for preparing ethyl bromide.
CH3CH2OH + SOCl2 → CH3CH2Cl + SO2 + HCl
Haloform reaction
"The haloform reaction is a chemical reaction where a haloform (CHX3, where X is a halogen) is produced by the exhaustive halogenation of a methyl ketone (a molecule containing the R-CO-CH3 group) in the presence of a base.[20]" See main "Haloform reaction" article.
Ester formation
Under acid-catalyzed conditions, ethanol reacts with carboxylic acids to produce ethyl esters and water:
RCOOH + HOCH2CH3 → RCOOCH2CH3 + H2O.
For this reaction to produce useful yields it is necessary to remove water from the reaction mixture as it is formed.
Ethanol can also form esters with inorganic acids. Diethyl sulfate and triethyl phosphate, prepared by reacting ethanol with sulfuric and phosphoric acid respectively, are both useful ethylating agents in organic synthesis. Ethyl nitrite, prepared from the reaction of ethanol with sodium nitrite and sulfuric acid, was formerly a widely-used diuretic.
Dehydration
Strong acid desiccants, such as sulfuric acid, cause ethanol's dehydration to form either diethyl ether or ethylene:
2 CH3CH2OH → CH3CH2OCH2CH3 + H2O (on 120'C)
CH3CH2OH → H2C=CH2 + H2O (on 180'C)
Which product, diethyl ether or ethylene, predominates depends on the precise reaction conditions
Oxidation
Ethanol can be oxidized to acetaldehyde, and further oxidized to acetic acid. In the human body, these oxidation reactions are catalyzed by enzymes. In the laboratory, aqueous solutions of strong oxidizing agents, such as chromic acid or potassium permanganate, oxidize ethanol to acetic acid, and it is difficult to stop the reaction at acetaldehyde at high yield. Ethanol can be oxidized to acetaldehyde, without over oxidation to acetic acid, by reacting it with pyridinium chromic chloride.
The direct oxidation of ethanol to acetic acid using chromic acid is given below.
C2H5OH + 2[O] → CH3COOH + H2O
The oxidation product of ethanol, acetic acid, is spent as nutrient by the human body as acetyl CoA, where the acetyl group can be spent as energy or used for biosynthesis.
Chlorination
When exposed to chlorine, ethanol is both oxidized and its alpha carbon chlorinated to form the compound, chloral.
4Cl2 + C2H5OH → CCl3CHO + 5HCl
Combustion
Combustion of ethanol forms carbon dioxide and water:
C2H5OH(g) + 3 O2(g) → 2 CO2(g) + 3 H2O(l);(ΔHr = −1409 kJ/mol[21])
Specific Heat = 2.44 KJ/KgK
Ethanol reacts with hydrogen halides to produce ethyl halides such as ethyl chloride and ethyl bromide:
CH3CH2OH + HCl → CH3CH2Cl + H2O
HCl reaction requires a catalyst such as zinc chloride. Hydrogen chloride in the presence of their respective zinc chloride is known as Lucas reagent.
CH3CH2OH + HBr → CH3CH2Br + H2O
HBr requires refluxing with a sulfuric acid catalyst.
Ethyl halides can also be produced by reacting ethanol with more specialized halogenating agents, such as thionyl chloride for preparing ethyl chloride, or phosphorus tribromide for preparing ethyl bromide.
CH3CH2OH + SOCl2 → CH3CH2Cl + SO2 + HCl
Haloform reaction
"The haloform reaction is a chemical reaction where a haloform (CHX3, where X is a halogen) is produced by the exhaustive halogenation of a methyl ketone (a molecule containing the R-CO-CH3 group) in the presence of a base.[20]" See main "Haloform reaction" article.
Ester formation
Under acid-catalyzed conditions, ethanol reacts with carboxylic acids to produce ethyl esters and water:
RCOOH + HOCH2CH3 → RCOOCH2CH3 + H2O.
For this reaction to produce useful yields it is necessary to remove water from the reaction mixture as it is formed.
Ethanol can also form esters with inorganic acids. Diethyl sulfate and triethyl phosphate, prepared by reacting ethanol with sulfuric and phosphoric acid respectively, are both useful ethylating agents in organic synthesis. Ethyl nitrite, prepared from the reaction of ethanol with sodium nitrite and sulfuric acid, was formerly a widely-used diuretic.
Dehydration
Strong acid desiccants, such as sulfuric acid, cause ethanol's dehydration to form either diethyl ether or ethylene:
2 CH3CH2OH → CH3CH2OCH2CH3 + H2O (on 120'C)
CH3CH2OH → H2C=CH2 + H2O (on 180'C)
Which product, diethyl ether or ethylene, predominates depends on the precise reaction conditions
Oxidation
Ethanol can be oxidized to acetaldehyde, and further oxidized to acetic acid. In the human body, these oxidation reactions are catalyzed by enzymes. In the laboratory, aqueous solutions of strong oxidizing agents, such as chromic acid or potassium permanganate, oxidize ethanol to acetic acid, and it is difficult to stop the reaction at acetaldehyde at high yield. Ethanol can be oxidized to acetaldehyde, without over oxidation to acetic acid, by reacting it with pyridinium chromic chloride.
The direct oxidation of ethanol to acetic acid using chromic acid is given below.
C2H5OH + 2[O] → CH3COOH + H2O
The oxidation product of ethanol, acetic acid, is spent as nutrient by the human body as acetyl CoA, where the acetyl group can be spent as energy or used for biosynthesis.
Chlorination
When exposed to chlorine, ethanol is both oxidized and its alpha carbon chlorinated to form the compound, chloral.
4Cl2 + C2H5OH → CCl3CHO + 5HCl
Combustion
Combustion of ethanol forms carbon dioxide and water:
C2H5OH(g) + 3 O2(g) → 2 CO2(g) + 3 H2O(l);(ΔHr = −1409 kJ/mol[21])
Specific Heat = 2.44 KJ/KgK
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