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Page: Preparation
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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 ?-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 ethene or other alkenes from cracking of fractions of distilled crude oil. Uses a catalyst of phosphoric acid under high temperature and pressure.
* 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 aluminium oxide catalyst at 250°C and a pressure of 50-100 atm.
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Important notice:
The content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other
qualified health provider with any questions you may have regarding a medical condition.
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