Laboratory
Several methods exist for the preparation of alcohols in the laboratory.
Primary alkyl halides react with aqueous NaOH or KOH mainly to primary alcohols in nucleophilic aliphatic substitution. (Secondary and especially tertiary alkyl halides will give the elimination (alkene) product instead).
Aldehydes or ketones are reduced with sodium borohydride or lithium aluminium hydride (after an acidic workup). Another reduction by aluminumisopropylates is the Meerwein-Ponndorf-Verley reduction.
Alkenes engage in an acid catalysed hydration reaction using concentrated sulfuric acid as a catalyst which gives usually secondary or tertiary alcohols.
The hydroboration-oxidation and oxymercuration-reduction of alkenes are more reliable in organic synthesis.
Grignard reagents react with carbonyl groups to secondary and tertiary alcohols
Noyori asymmetric hydrogenation is the asymmetric reduction of β-keto-esters
The formation of a secondary alcohol via reduction and hydration is shown:
Industrial
Industrially alcohols are produced in several ways:
By fermentation using glucose produced from sugar from the hydrolysis of starch, in the presence of yeast and temperature of less than 37°C to produce ethanol. For instance the conversion of invertase to glucose and fructose or the conversion of glucose to zymase and ethanol.
By direct hydration using ethane or other alkenes from cracking of fractions of distilled crude oil. Uses a catalyst of phosphoric acid under high temperature and pressure of 50-120.
Methanol is produced from water gas: It is manufactured from synthesis gas, where carbon monoxide and 2 equivalents of hydrogen gas are combined to produce methanol using a copper, zinc oxide and aluminum oxide catalyst at 250°C and a pressure of 50-100 atm.
Several methods exist for the preparation of alcohols in the laboratory.
Primary alkyl halides react with aqueous NaOH or KOH mainly to primary alcohols in nucleophilic aliphatic substitution. (Secondary and especially tertiary alkyl halides will give the elimination (alkene) product instead).
Aldehydes or ketones are reduced with sodium borohydride or lithium aluminium hydride (after an acidic workup). Another reduction by aluminumisopropylates is the Meerwein-Ponndorf-Verley reduction.
Alkenes engage in an acid catalysed hydration reaction using concentrated sulfuric acid as a catalyst which gives usually secondary or tertiary alcohols.
The hydroboration-oxidation and oxymercuration-reduction of alkenes are more reliable in organic synthesis.
Grignard reagents react with carbonyl groups to secondary and tertiary alcohols
Noyori asymmetric hydrogenation is the asymmetric reduction of β-keto-esters
The formation of a secondary alcohol via reduction and hydration is shown:
Industrial
Industrially alcohols are produced in several ways:
By fermentation using glucose produced from sugar from the hydrolysis of starch, in the presence of yeast and temperature of less than 37°C to produce ethanol. For instance the conversion of invertase to glucose and fructose or the conversion of glucose to zymase and ethanol.
By direct hydration using ethane or other alkenes from cracking of fractions of distilled crude oil. Uses a catalyst of phosphoric acid under high temperature and pressure of 50-120.
Methanol is produced from water gas: It is manufactured from synthesis gas, where carbon monoxide and 2 equivalents of hydrogen gas are combined to produce methanol using a copper, zinc oxide and aluminum oxide catalyst at 250°C and a pressure of 50-100 atm.
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